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Details:HeatConductivityMoistureDependent

2009-03-27T11:32:51Z

Barbara: /* Heat Conductivity, Moisture-dependent */

= Heat Conductivity, Moisture-dependent =

The [[Details:BasicMaterialData|heat conductivity of the
dry material]] is a basic material parameter and thus indispensable.
If, in addition, the dependence of the heat conductivity on the
moisture content must be taken into account, WUFI can optionally
employ a table with the relevant data. WUFI interpolates linearly
between table entries.


If a simple linear dependence of the heat conductivity on the
moisture content is sufficient, a two-line table may be
generated by entering the moisture-induced heat conductivity
supplement. The linear interpolation in this table is then
equivalent to evaluating the formula


<TABLE>
<TR><TD COLSPAN="3">λ(w) = λo·(1 + b·w/ρs)</TD></TR>
<TR><TD>λ(w)</TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of moist material</TD></TR>
<TR><TD>λo</TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of dry material</TD></TR>
<TR><TD>ρs</TD><TD ALIGN="RIGHT">[kg/m³]:</TD><TD>bulk density of dry material</TD></TR>
<TR><TD>b</TD><TD ALIGN="RIGHT">[%/m-%]:</TD><TD>moisture-induced heat conductivity supplement</TD></TR>
</TABLE>


The supplement b gives the fractional increase [in %] of the heat
conductivity per mass-% moisture. Its value depends on the material;
in hygroscopic materials, however, it is largely independent of
their bulk density.


Examples:


<TABLE>
<TR ALIGN="CENTER"><TD>Material</TD><TD>Bulk Density</TD><TD>λ</TD><TD>b</TD></TR>
<TR ALIGN="CENTER"><TD> </TD><TD>[kg/m³]  </TD><TD>[W/mK]  </TD><TD>[%/M.-%]  </TD></TR>

<TR ALIGN="CENTER"><TD>cellular concrete</TD><TD>400-800</TD><TD>0.09-0.19</TD><TD>4</TD></TR>

<TR ALIGN="CENTER"><TD>lime silica brick</TD><TD>1800</TD><TD>0.7</TD><TD>8</TD></TR>

<TR ALIGN="CENTER"><TD>expanded clay concrete, pumice concrete</TD><TD>1400-1800</TD><TD>0.5-1.0</TD><TD>4</TD></TR>

<TR ALIGN="CENTER"><TD>light-weight concrete with EPS aggregate</TD><TD>300-900</TD><TD>0.07-0.28</TD><TD>3</TD></TR>

<TR ALIGN="CENTER"><TD>normal concrete</TD><TD>2300</TD><TD>1.3-1.5</TD><TD>8</TD></TR>

<TR ALIGN="CENTER"><TD>wood</TD><TD>400-700</TD><TD>0.08-0.15</TD><TD>1.5</TD></TR>
</TABLE>


In organic insulation materials, there is in general no linear
relationship between the heat conductivity and the moisture content.


In this context, 'heat conductivity of moist materials' means
exclusively the influence of stationary water on heat transport.
Water vapor diffusion with phase change (evaporation and condensation
of water) also contributes to heat transport, but this is allowed
for by separate terms in the transport equations. However, since
in the standard measurement techniques this effect of water vapor
diffusion is usually included, results of measurements in
the plate apparatus for permeable materials (e.g. mineral wool)
have to be regarded with caution.


During the calculation WUFI performs iterations where it samples
small regions of the tabulated curve. Very sharp bends in the curve
may throw the iteration off and thus impede its convergence. In
such a case, the curve should be smoothed by inserting additional
points. A large number of entries may slow the search in the
table, however.


Please note that design values, such as the data given in
German Standard DIN 4108, may already contain the contribution
of a typical water content and, if so, are not strictly dry values. 
If you want to perform the calculation with a constant (i.e. not
moisture-dependent) heat conductivity (for example because you have
no detailed data on the moisture-dependence), you may use these
design values to allow for moisture content at least in a crude
approximation. However, if you explicitly use a table of
moisture-dependent heat conductivities, you should make sure that
the value for moisture content = 0 is really the dry value.


On the other hand, hygrothermal simulations (in particular the
resulting moisture contents and distributions) usually
don't depend very sensitively on the precise values of the heat
conductivities, so the difference may be generally negligible
unless you are specifically interested in heat flows.

Details:HeatConductivityMoistureDependent

2009-03-27T11:29:48Z

Barbara: /* Heat Conductivity, Moisture-dependent */

= Heat Conductivity, Moisture-dependent =

The [[Details:BasicMaterialData|heat conductivity of the
dry material]] is a basic material parameter and thus indispensable.
If, in addition, the dependence of the heat conductivity on the
moisture content must be taken into account, WUFI can optionally
employ a table with the relevant data. WUFI interpolates linearly
between table entries.


If a simple linear dependence of the heat conductivity on the
moisture content is sufficient, a two-line table may be
generated by entering the moisture-induced heat conductivity
supplement. The linear interpolation in this table is then
equivalent to evaluating the formula


<TABLE>
<TR><TD COLSPAN="3">λ(w) = λo·(1 + b·w/ρs)</TD></TR>
<TR><TD>l(w)</TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of moist material</TD></TR>
<TR><TD>lo</TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of dry material</TD></TR>
<TR><TD>r s</TD><TD ALIGN="RIGHT">[kg/m³]:</TD><TD>bulk density of dry material</TD></TR>
<TR><TD>b</TD><TD ALIGN="RIGHT">[%/m-%]:</TD><TD>moisture-induced heat conductivity supplement</TD></TR>
</TABLE>


The supplement b gives the fractional increase [in %] of the heat
conductivity per mass-% moisture. Its value depends on the material;
in hygroscopic materials, however, it is largely independent of
their bulk density.


Examples:


<TABLE>
<TR ALIGN="CENTER"><TD>Material</TD><TD>Bulk Density</TD><TD>l</TD><TD>b</TD></TR>
<TR ALIGN="CENTER"><TD> </TD><TD>[kg/m³]  </TD><TD>[W/mK]  </TD><TD>[%/M.-%]  </TD></TR>

<TR ALIGN="CENTER"><TD>cellular concrete</TD><TD>400-800</TD><TD>0.09-0.19</TD><TD>4</TD></TR>

<TR ALIGN="CENTER"><TD>lime silica brick</TD><TD>1800</TD><TD>0.7</TD><TD>8</TD></TR>

<TR ALIGN="CENTER"><TD>expanded clay concrete, pumice concrete</TD><TD>1400-1800</TD><TD>0.5-1.0</TD><TD>4</TD></TR>

<TR ALIGN="CENTER"><TD>light-weight concrete with EPS aggregate</TD><TD>300-900</TD><TD>0.07-0.28</TD><TD>3</TD></TR>

<TR ALIGN="CENTER"><TD>normal concrete</TD><TD>2300</TD><TD>1.3-1.5</TD><TD>8</TD></TR>

<TR ALIGN="CENTER"><TD>wood</TD><TD>400-700</TD><TD>0.08-0.15</TD><TD>1.5</TD></TR>
</TABLE>


In organic insulation materials, there is in general no linear
relationship between the heat conductivity and the moisture content.


In this context, 'heat conductivity of moist materials' means
exclusively the influence of stationary water on heat transport.
Water vapor diffusion with phase change (evaporation and condensation
of water) also contributes to heat transport, but this is allowed
for by separate terms in the transport equations. However, since
in the standard measurement techniques this effect of water vapor
diffusion is usually included, results of measurements in
the plate apparatus for permeable materials (e.g. mineral wool)
have to be regarded with caution.


During the calculation WUFI performs iterations where it samples
small regions of the tabulated curve. Very sharp bends in the curve
may throw the iteration off and thus impede its convergence. In
such a case, the curve should be smoothed by inserting additional
points. A large number of entries may slow the search in the
table, however.


Please note that design values, such as the data given in
German Standard DIN 4108, may already contain the contribution
of a typical water content and, if so, are not strictly dry values. 
If you want to perform the calculation with a constant (i.e. not
moisture-dependent) heat conductivity (for example because you have
no detailed data on the moisture-dependence), you may use these
design values to allow for moisture content at least in a crude
approximation. However, if you explicitly use a table of
moisture-dependent heat conductivities, you should make sure that
the value for moisture content = 0 is really the dry value.


On the other hand, hygrothermal simulations (in particular the
resulting moisture contents and distributions) usually
don't depend very sensitively on the precise values of the heat
conductivities, so the difference may be generally negligible
unless you are specifically interested in heat flows.

1D:Dialog InfoLastCalculationRun

2009-03-27T08:32:12Z

Barbara: /* "Status of Calculation": */

= Dialog: Status of Last Calculation =

[[Bild:DialogStatusOfLastCalculation_03.gif]]

This dialog displays a short summary of the calculation results.


=== "Water Content" (1): ===


For each layer WUFI displays the initial water content, the final water content, and
the minimum and maximum water contents that occurred during the calculation. 
This allows you a quick first assessment of what happened to the component during the
simulation (e.g., it dried out or accumulated water etc). 
  


=== "Status of Calculation": ===

"Simulation: Time and Date" (2): 
The time and date when the simulation was performed. 
  
"Computing Time" (2): 
The time it took WUFI to perform the calculation. 
  
"No. of Convergence Failures" (3): 
WUFI uses an iterative method for the solution of the transport equations. Sometimes, the convergence is very slow and WUFI reaches the maximum allowed number of iterations without the interim solutions meeting the termination criteria. 
  
In this case, the iteration is stopped and the convergence achieved so far compared to somewhat relaxed criteria. If these are met, WUFI accepts the results and continues with the next time step. If the criteria are not met, WUFI also accepts the result and continues with the calculation, but the number of convergence failures is increased by one. 
  
The total number of convergence failures is a first hint concerning the reliability of the results. The fact that a convergence failure has been registered does not tell, however, how large the remaining error was when the iteration was stopped. 
  
It is quite possible that the termination criteria were missed by a small margin only and the convergence failure is therefore irrelevant; this is usually the case. 
  
Sometimes it is also possible, however, that a numerical instability has developed and the iteration steps drift farther and farther away from the real solution. Then the solution left by the aborted iterations is only a bad (in rare cases very bad) approximation for the solution of the transport equations. This often reveals itself by water appearing or disappearing in the middle of the component, without the boundary conditions having called for such behaviour. The results are sudden jumps in the course of the water content and a bad water balance (see below). 
  
The criteria for a convergence failure have been adjusted to be very sensitive. Experience shows that in general a few convergence failures are harmless. If you have calculated over one year, one or two convergence failures are in general nothing to worry about. 
Numerical instabilities, however, usually announce their arrival by a generally higher number of convergence failures. Fifty convergence failures per year are possibly (but not always) indicating a problem. 
  
A better indicator for the quality of the results is the water balance (see below). 
  
"No. of Rain Absorption Failures" (3): 
WUFI uses an iterative method to determine the amount of water absorbed when rain hits the component surface, because there may be less rain than the component can theoretically absorb during the time step. This limitation imposed by the amount of rain has to be allowed for, but the amount actually absorbed can only be determined iteratively; see the relevant question in the [[FAQ:QuestionsAndAnswers | Questions & Answers]] section). 
  
It is possible although very rare that convergence is too slow and WUFI reaches the maximum allowed number of iterations without the interim solutions meeting the termination criteria. 
  
In this case, the iteration is stopped, WUFI accepts the results and continues with the next time step, but the number of rain absorption failures is increased by one. 
  
This is usually no reason to worry, since a rain absorption failure normally doesn't mean the result of the time step is terribly wrong, it only means that the termination criteria - which are somewhat arbitrary anyway - haven't been met. The result of the time step is usually well acceptable in view of all the simplifications and approximations that go into such a simulation model in the context of building physics. 
  
"Fluxes e (ke, de)",, 
"Fluxes i (ki, di)" (4): 
the total amount of water which flows into or out of the component during the calculation.

<TABLE>
<TR><TD>ke</TD>
<TD>:</TD>
<TD>by capillary transport at the exterior surface,</TD>
</TR>
<TR><TD>de</TD>
<TD>:</TD>
<TD>by vapour transport at the exterior surface,</TD>
</TR>
<TR><TD>ki</TD>
<TD>:</TD>
<TD>by capillary transport at the interior surface,</TD>
</TR>
<TR><TD VALIGN="TOP">di</TD>
<TD VALIGN="TOP">:</TD>
<TD>by vapour transport at the interior surface.(*) 
  
</TD>
</TR>
</TABLE><TABLE>
<TR><TD>positive</TD>
<TD>:</TD>
<TD>indoor direction (positive X-direction),</TD>
</TR>
<TR><TD>negative</TD>
<TD>:</TD>
<TD>outdoor direction (negative X-direction).</TD>
</TR>
</TABLE>


These moisture flows serve to calculate the moisture balance (see below).


Please note: These are not the moisture flows through the surface,
but the flows between the surface and the component. It may happen that
water condenses at a cold surface in such amounts that the absorption capacity
of the building material is surpassed and the water runs off at the surface.
This run-off 'disappears' for the calculation, so that the amount of water
arriving at the surface from the environment may not be identical to the
amount entering into the component from the surface.


Therefore the above moisture flows are not evaluated at the surfaces but at
the boundaries between the first and the second, and between the next-to-last
and the last grid element. This has to be borne in mind if the above numbers
are to be interpreted, especially if the first or last element has some
appreciable thickness. 
  



(*) It is also the reason why the above definition just vaguely says
"at the surface" instead of "through the surface".


So do not wonder, for instance, if you get a non-zero capillary flow ki at
the interior surface, although it certainly never rains there. This is a
capillary flow closely (half an element) below the surface. 
  

"Balance 1 [kg/m²]", 
"Balance 2 [kg/m²]" (4): 
the change in 'total water content' during the calculation, and the sum of the 'surface flows' (ka+da-ki-di, see above). 
  
Ideally, these two numbers should be identical, since any change in the total water content must result from moisture being transported through the surfaces. Rounding errors and convergence problems may cause discrepancies, however. 
If the discrepancies become too large, you should repeat the calculation with appropriate modifications (see below). 
  
Please note: for the reasons discussed above, the first and the last grid element are not allowed for in the determination of this 'total water content' so that it is less than the total water content you get as the official result of the calculation. Therefore, the change in the 'total water content' may also slightly differ from what you infer from the official results, especially if the first or last element has some appreciable thickness. 
  
These numbers are only meant to provide a consistency check on the numerical calculation. Analyses of the water content and the surface flows should be done using the calculation results themselves only. 
  
If you get too many convergence failures or a bad water balance, you should check whether your choice of the numerical grid is indeed appropriate for the project at hand. A typical problem, for instance, are condensation phenomena at a layer boundary or at a surface, so that steep water content gradients occur which can not be represented adequately if the grid is too coarse at that location. You may need to use the fine grid option or to [[1D:Dialog_Assembly | adapt the grid manually]]. 
  
This is further discussed in [[Discussion:WUFI-Pro_PerformanceandLimitations | "WUFI's Performance and Limitations"]], in [[1D:Dialog_Assembly | "Dialog: Assembly / Monitor Positions"]], in [[1D:Dialog_Numerics | "Dialog: Numerics"]] and in the [[FAQ:QuestionsAndAnswers | Questions & Answers section]]. 
  

=== "Calculation locked" (5): ===

If after a calculation you inadvertently restart it, the existing results are
overwritten and lost. There is a security query, but if you want to avoid any risk,
lock the calculation and save the project file once more (to make the lock permanent).


This is especially advisable if the results of long and tedious calculations shall be
demonstrated in a hectic atmosphere...

1D:Dialog RunCalculationWithFilm

2009-03-25T10:31:02Z

Barbara: /* Dialog: Run Calculation with Film */

= Dialog: Run Calculation with Film =

[[Bild:Dialog_FilmAnimation1D_3.gif]]


This full-screen dialog displays the results of the calculation, while in progress, in
the form of a 'film' showing the thermal and hygric processes in the building component
as an animation.


Use the control buttons to 
[[Bild:RunFilm.gif]] start the calculation, 
[[Bild:PauseFilm.gif]] pause and resume the calculation, 
[[Bild:SingleStep.gif]] single-step through the calculation.


After the calculation has finished, you may view the film again: choose
"Outputs | View Film" to start a film viewer which offers additional options
for operation and analysis.



The speed slider allows you to slow the display down (for demonstration purposes).
Drag the slider with the mouse or adjust it with the cursor keys or the PageUp/PageDown
or Home/End keys. 
If the speed is set too high, the film viewer may start to skip 'frames'.


The clock and the calendar show you the current date the film display
has reached. 
  



In the left part of the screen, the temporal sequence of the hourly profiles of
temperature, relative humidity / vapor pressure and water content is displayed as a
film. The selection of the curves to be displayed, the adjustment of the axes
and editing of other settings are done in a subdialog which can be reached by pressing
the button [[1D:Dialog_FilmProperties | "Properties"]].


The temperature (red) is displayed in the upper diagram.
Water content (blue) and relative humidity / vapor pressure
(green) are both displayed in the lower diagram. The left Y-axis corresponds to the
water content, the right Y-axis, to the relative humidity / vapor pressure.


You can zoom into the component by dragging open a zoom frame from upper left
to lower right. To zoom out, drag open a zoom frame from lower right to upper left. 
Point the cursor at one of the curves to see the x-coordinate and the
curve value displayed in the status bar.


The current boundary conditions (air temperatures and relative humidities /
vapor pressures) are indicated by red and green arrows, respectively, at the sides of
the diagrams. The left climate may include radiation and rain whose intensities are
displayed by the respective bar indicators. 
  


Above the diagrams the heat and moisture flows across the two component surfaces
and the inner material interfaces are indicated by arrows whose length depends on the
strength of the respective flow (these arrows are further discussed in the online help
for the subdialog [[1D:Dialog_FilmProperties | "Properties"]]).


Point the cursor at one of the arrows to see the flux value displayed in the status bar.


At the exterior surface, the heat flow indicated by the arrows includes the incident
solar radiation,
<TABLE>
<TR><TD WIDTH="10"> </TD>
<TD>which is what the viewer intuitively expects in general. Note, however, that electromagnetic radiation is not really a heat flow, and in the [[1D:Dialog_ResultGraphs | Result Graphs]] only the proper heat flows are displayed. While incident solar radiation will create a large 'heat flow' arrow in the positive x-direction, what really happens is that the radiation is absorbed in the material and becomes converted to heat, most of which flows as a proper heat flow out of the component, in negative x-direction. This is further discussed in the [[FAQ:QuestionsAndAnswers | Questions & Answers]] section.
</TD>
</TR>
</TABLE>


The moisture flow is the sum of diffusion flow and capillary flow. 
  



You can speed up the calculation by performing it without film. Choose
"Run | Run Calculation" instead of
"Run | Run Calculation with Film". WUFI then only displays a progress bar:

[[Bild:FortschrittsBalken_02.gif]]

1D:Dialog RunCalculationWithFilm

2009-03-25T10:29:31Z

Barbara: /* Dialog: Run Calculation with Film */

= Dialog: Run Calculation with Film =

[[Bild:Dialog_FilmAnimation1D_3.gif]]


This full-screen dialog displays the results of the calculation, while in progress, in
the form of a 'film' showing the thermal and hygric processes in the building component
as an animation.


Use the control buttons to 
[[Bild:RunFilm.gif]] start the calculation, 
[[Bild:PauseFilm.gif]] pause and resume the calculation, 
[[Bild:SingleStep.gif]] single-step through the calculation.


After the calculation has finished, you may view the film again: choose
"Outputs | View Film" to start a film viewer which offers additional options
for operation and analysis.



The speed slider allows you to slow the display down (for demonstration purposes).
Drag the slider with the mouse or adjust it with the cursor keys or the PageUp/PageDown
or Home/End keys. 
If the speed is set too high, the film viewer may start to skip 'frames'.


The clock and the calendar show you the current date the film display
has reached. 
  



In the left part of the screen, the temporal sequence of the hourly profiles of
temperature, relative humidity / vapor pressure and water content is displayed as a
film. The selection of the curves to be displayed, the adjustment of the axes
and editing of other settings are done in a subdialog which can be reached by pressing
the button [[1D:Dialog_FilmProperties | "Properties"]].


The temperature (red) is displayed in the upper diagram.
Water content (blue) and relative humidity / vapor pressure
(green) are both displayed in the lower diagram. The left Y-axis corresponds to the
water content, the right Y-axis, to the relative humidity / vapor pressure.


You can zoom into the component by dragging open a zoom frame from upper left
to lower right. To zoom out, drag open a zoom frame from lower right to upper left. 
Point the cursor at one of the curves to see the x-coordinate and the
curve value displayed in the status bar.


The current boundary conditions (air temperatures and relative humidities /
vapor pressures) are indicated by red and green arrows, respectively, at the sides of
the diagrams. The left climate may include radiation and rain whose intensities are
displayed by the respective bar indicators. 
  


Above the diagrams the heat and moisture flows across the two component surfaces
and the inner material interfaces are indicated by arrows whose length depends on the
strength of the respective flow (these arrows are further discussed in the online help
for the subdialog [[1D:Dialog_FilmProperties | "Properties"]]).


Point the cursor at one of the arrows to see the flux value displayed in the status bar.


At the exterior surface, the heat flow indicated by the arrows includes the incident
solar radiation,
<TABLE>
<TR><TD WIDTH="10"> </TD>
<TD>which is what the viewer intuitively expects in general. Note, however, that electromagnetic radiation is not really a heat flow, and in the [[1D:Dialog_ResultGraphs | Result Graphs]] only the proper heat flows are displayed. While incident solar radiation will create a large 'heat flow' arrow in the positive x-direction, what really happens is that the radiation is absorbed in the material and becomes converted to heat, most of which flows as a proper heat flow out of the component, in negative x-direction. This is further discussed in the [[FAQ:QuestionsAndAnswers | Questions &
Answers]] section.
</TD>
</TR>
</TABLE>


The moisture flow is the sum of diffusion flow and capillary flow. 
  



You can speed up the calculation by performing it without film. Choose
"Run | Run Calculation" instead of
"Run | Run Calculation with Film". WUFI then only displays a progress bar:

[[Bild:FortschrittsBalken_02.gif]]

1D:Dialog SelectClimateFileFromBrowser

2009-03-25T10:23:51Z

Barbara: /* Dialog: Select Climate File (file browser) */

= Dialog: Select Climate File (file browser)=

[[Bild:DialogKlimadateiBenutzerdefiniert_5.gif]]


This dialog serves to select a user-defined climate file for the calculation. 
The files supplied with WUFI can be selected from
[[1D:Dialog_SelectClimateFileFromMap | maps]].


Version note: this dialog is only available in WUFI
Pro.



"Browse...":


This button opens a file dialog in which you can select the desired file. 
  



"Additional Geographic Data":


To be able to convert the solar radiation data contained in the climate files for
receiving surfaces at arbitrary [[1D:Dialog_Orientation | orientation and
inclination]], WUFI needs to compute
the position of the sun in the sky, and for this it must know the geographic coordinates
and the time zone of the climate location. 
Since most climate file formats do not contain these data, they must be provided by some
other means. For the files supplied with WUFI they have been filed in the database.
For each user-defined climate file the user must create an
[[Details:AGD-File | *.AGD]] file with the relevant supplementary data. 
  


Note: We recommend to always specify the climate file with its full path.
Otherwise ambiguities might arise, especially if the climate file is accompanied
by an [[Details:AGD-File | *.AGD]] file.

Details:MoistureStorageFunction

2009-03-25T10:19:21Z

Barbara: /* Approximation of the moisture storage function */

= Moisture Storage Function =

=== The moisture storage function ===

In a porous hygroscopic material, the surfaces of the pore system
accumulate water molecules until a specific equilibrium moisture
content corresponding to the humidity of the ambient
air is reached.
Due to the reduction of the saturation vapor pressure in the smaller
capillaries, there is also some condensation which - at relative
humidities above ca. 0.6 .. 0.8 - results in a marked increase of
the equilibrium moisture.

[[Bild:e_fspfkt_k.gif]]


A capillary-active material in contact with water will take up this
water until it reaches its free saturation wf.
This water content wf corresponds to the moisture
storage function at a relative humidity of 1 (=100%). Because of
air pockets trapped in the pore structure, however, the free
saturation is less than the maximum water content
wmax which is determined by the
[[Details:BasicMaterialData | porosity]]. Moisture
contents exceeding wf may e.g. result from
condensation in a temperature gradient (especially in insulation
materials; these are often not capillary-active and therefore
have wf ~ 0).


The free saturation wf ranks among the standard
material data and is known for most materials. The 'practical
moisture content' w80 that corresponds to the
equilibrium moisture at a RH of 0.8 is another standard quantity.


The dependence of the moisture storage function on the temperature is marginal and is ignored in WUFI.


=== Measurement of the moisture storage function ===

Because of limitations of the respective measuring procedures,
the moisture storage function has to be composed from sorption
isotherms (up to ~ 0.9 RH) and pressure plate measurements
(above 0.95 RH) [1]. The hysteresis between adsorption and
desorption isotherms is usually not very pronounced, so that it
is sufficient to use the adsorption isotherm. Where necessary, a
mean isotherm may be used. Due to the measuring technique, the
pressure plate measurements are 'desorption' measurements.


=== The moisture storage function in WUFI ===

In WUFI, the moisture storage function is described by means of
a table with relative humidities and the corresponding moisture
contents. The table may contain an arbitrary number of entries
between which WUFI interpolates linearly.


Example: Sander sandstone

<CENTER>
<TABLE>
<TR ALIGN="CENTER"><TD>j [-]</TD><TD>w[kg/m³]</TD></TR>
<TR ALIGN="RIGHT"><TD> </TD><TD> </TD></TR>
<TR ALIGN="RIGHT"><TD>0</TD><TD>0</TD></TR>
<TR ALIGN="RIGHT"><TD>0.1</TD><TD>4.4</TD></TR>
<TR ALIGN="RIGHT"><TD>0.3</TD><TD>10.2</TD></TR>
<TR ALIGN="RIGHT"><TD>0.65</TD><TD>15.2</TD></TR>
<TR ALIGN="RIGHT"><TD>0.8</TD><TD>19.0</TD></TR>
<TR ALIGN="RIGHT"><TD>0.91</TD><TD>30.0</TD></TR>
<TR ALIGN="RIGHT"><TD>0.95</TD><TD>45.9</TD></TR>
<TR ALIGN="RIGHT"><TD>0.99</TD><TD>61.7</TD></TR>
<TR ALIGN="RIGHT"><TD>0.995</TD><TD>75.0</TD></TR>
<TR ALIGN="RIGHT"><TD>1.0</TD><TD>130.0</TD></TR>
</TABLE>
</CENTER>

The pressure plate measurements would even allow a still finer
subdivision of the table in the high-moisture region, but then
at φ ~ 1 the curve would approach
the ordinate so closely that its immensely steep slope might cause
numerical problems. If the moisture transport across the interface
between two capillary-active materials in capillary contact is to be
calculated, however, the moisture storage function must be as detailed
as possible in this region [2]. (If the capillary contact is non-ideal,
an additional transfer resistance has to be taken into account [2]).


WUFI allows moisture contents in the supersaturated region, since
these may well occur under condensation conditions. However, in
this region there is no unique functional relation between relative
humidity and moisture content. The relative humidity is always 1,
and the moisture content varies between wf and
wmax. 
The moisture content thus doesn't depend on the relative humidity,
it is determined by the boundary conditions: it increases under
condensation conditions and decreases under evaporation conditions.
In order to treat these moisture contents above wf,
WUFI internally extends the table of each material by introducing
an additional entry:

<CENTER>
<TABLE>
<TR><TD ALIGN="CENTER">φ[-]  </TD><TD ALIGN="CENTER">w[kg/m³]  </TD></TR>
<TR><TD ALIGN="CENTER">...</TD><TD ALIGN="CENTER">...</TD></TR>
<TR><TD ALIGN="CENTER">1.01</TD><TD ALIGN="CENTER">wmax</TD></TR>
</TABLE>
</CENTER>


Relative humidities between 1 and 1.01 are only fictitious,
of course, but they allow WUFI to assign a unique RH to each
water content, as required by the moisture transport equations.


During the calculation WUFI performs iterations where it samples
small regions of the tabulated curve. Very sharp bends in the
curve may throw the iteration off and thus impede its convergence.
In such a case, the curve should be smoothed by inserting
additional points. A large number of entries may slow the search
in the table, however.


=== Approximation of the moisture storage function ===

If the moisture storage function can be adequately described by
the function

<TABLE>
<TR><TD VALIGN="CENTER">w = wf·</TD><TD>(b-1)·φ b-φ</TD><TD> </TD></TR>
<TR><TD COLSPAN="3"> </TD></TR>
<TR><TD>w</TD><TD>[kg/m³]:</TD><TD>moisture content corresponding to relative humidity φ</TD></TR>
<TR><TD>wf</TD><TD>[kg/m³]:</TD><TD>moisture content at free saturation</TD></TR>
<TR><TD>φ</TD><TD>[-]:</TD><TD>relative
humidity</TD></TR>
<TR><TD>b</TD><TD>[-]:</TD><TD>approximation factor,</TD></TR>
</TABLE>


then it is sufficient to specify w80 and
wf, in order to define the moisture storage
function for WUFI (this is called 'approximation of the moisture
storage function'). However, this condition is not met by all
materials (e.g. some kinds of concrete).

[[Bild:E_fspfkt_meas_approx.gif]]

<H3>WUFI's default moisture storage function</H3>

The moisture storage function of non-hygroscopic materials
(essentially insulating materials, but
[[AirLayers|air layers]] as well) is
theoretically more or less zero in the region
φ = 0..1, whereas for
φ = 1 it takes on some indefinite
value between zero and wmax, so that no
well-defined functional relationship exists. Because of numerical
requirements, however, WUFI assigns a (low) artificial moisture
storage function to all materials for which the user did not
define such a function. 
So the results of a WUFI calculation will indicate some (low)
moisture content even in materials for which you did not define
a moisture storage function. These moisture contents are artificial
and should be regarded with caution. Only when the moisture contents
surpass the fictitious free saturation of ca. 0.05·wmax,
they have resulted from condensation phenomena which are independent
from the choice of the moisture storage function. In that case the
excess of the moisture content over wf can with
appropriate caution be regarded as a realistic measure of the
amount of condensed moisture.


For discussion of some specific questions concerning the moisture storage function, see the
[[FAQ:Main|Questions & Answers]] section.


Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Krus, M.: Moisture Transport and
Storage Coefficients of Porous Mineral Building Materials.
Theoretical Principles and New Test Methods 
Fraunhofer IRB Verlag, 1996</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>Holm, A., Krus, M., Künzel, H.M.:
Feuchtetransport über Materialgrenzen im Mauerwerk. 
Bauinstandsetzen 2 (1996), H. 5, 375 - 396.
</TABLE>

Details:MoistureStorageFunction

2009-03-25T10:16:33Z

Barbara: /* The moisture storage function in WUFI */

= Moisture Storage Function =

=== The moisture storage function ===

In a porous hygroscopic material, the surfaces of the pore system
accumulate water molecules until a specific equilibrium moisture
content corresponding to the humidity of the ambient
air is reached.
Due to the reduction of the saturation vapor pressure in the smaller
capillaries, there is also some condensation which - at relative
humidities above ca. 0.6 .. 0.8 - results in a marked increase of
the equilibrium moisture.

[[Bild:e_fspfkt_k.gif]]


A capillary-active material in contact with water will take up this
water until it reaches its free saturation wf.
This water content wf corresponds to the moisture
storage function at a relative humidity of 1 (=100%). Because of
air pockets trapped in the pore structure, however, the free
saturation is less than the maximum water content
wmax which is determined by the
[[Details:BasicMaterialData | porosity]]. Moisture
contents exceeding wf may e.g. result from
condensation in a temperature gradient (especially in insulation
materials; these are often not capillary-active and therefore
have wf ~ 0).


The free saturation wf ranks among the standard
material data and is known for most materials. The 'practical
moisture content' w80 that corresponds to the
equilibrium moisture at a RH of 0.8 is another standard quantity.


The dependence of the moisture storage function on the temperature is marginal and is ignored in WUFI.


=== Measurement of the moisture storage function ===

Because of limitations of the respective measuring procedures,
the moisture storage function has to be composed from sorption
isotherms (up to ~ 0.9 RH) and pressure plate measurements
(above 0.95 RH) [1]. The hysteresis between adsorption and
desorption isotherms is usually not very pronounced, so that it
is sufficient to use the adsorption isotherm. Where necessary, a
mean isotherm may be used. Due to the measuring technique, the
pressure plate measurements are 'desorption' measurements.


=== The moisture storage function in WUFI ===

In WUFI, the moisture storage function is described by means of
a table with relative humidities and the corresponding moisture
contents. The table may contain an arbitrary number of entries
between which WUFI interpolates linearly.


Example: Sander sandstone

<CENTER>
<TABLE>
<TR ALIGN="CENTER"><TD>j [-]</TD><TD>w[kg/m³]</TD></TR>
<TR ALIGN="RIGHT"><TD> </TD><TD> </TD></TR>
<TR ALIGN="RIGHT"><TD>0</TD><TD>0</TD></TR>
<TR ALIGN="RIGHT"><TD>0.1</TD><TD>4.4</TD></TR>
<TR ALIGN="RIGHT"><TD>0.3</TD><TD>10.2</TD></TR>
<TR ALIGN="RIGHT"><TD>0.65</TD><TD>15.2</TD></TR>
<TR ALIGN="RIGHT"><TD>0.8</TD><TD>19.0</TD></TR>
<TR ALIGN="RIGHT"><TD>0.91</TD><TD>30.0</TD></TR>
<TR ALIGN="RIGHT"><TD>0.95</TD><TD>45.9</TD></TR>
<TR ALIGN="RIGHT"><TD>0.99</TD><TD>61.7</TD></TR>
<TR ALIGN="RIGHT"><TD>0.995</TD><TD>75.0</TD></TR>
<TR ALIGN="RIGHT"><TD>1.0</TD><TD>130.0</TD></TR>
</TABLE>
</CENTER>

The pressure plate measurements would even allow a still finer
subdivision of the table in the high-moisture region, but then
at φ ~ 1 the curve would approach
the ordinate so closely that its immensely steep slope might cause
numerical problems. If the moisture transport across the interface
between two capillary-active materials in capillary contact is to be
calculated, however, the moisture storage function must be as detailed
as possible in this region [2]. (If the capillary contact is non-ideal,
an additional transfer resistance has to be taken into account [2]).


WUFI allows moisture contents in the supersaturated region, since
these may well occur under condensation conditions. However, in
this region there is no unique functional relation between relative
humidity and moisture content. The relative humidity is always 1,
and the moisture content varies between wf and
wmax. 
The moisture content thus doesn't depend on the relative humidity,
it is determined by the boundary conditions: it increases under
condensation conditions and decreases under evaporation conditions.
In order to treat these moisture contents above wf,
WUFI internally extends the table of each material by introducing
an additional entry:

<CENTER>
<TABLE>
<TR><TD ALIGN="CENTER">φ[-]  </TD><TD ALIGN="CENTER">w[kg/m³]  </TD></TR>
<TR><TD ALIGN="CENTER">...</TD><TD ALIGN="CENTER">...</TD></TR>
<TR><TD ALIGN="CENTER">1.01</TD><TD ALIGN="CENTER">wmax</TD></TR>
</TABLE>
</CENTER>


Relative humidities between 1 and 1.01 are only fictitious,
of course, but they allow WUFI to assign a unique RH to each
water content, as required by the moisture transport equations.


During the calculation WUFI performs iterations where it samples
small regions of the tabulated curve. Very sharp bends in the
curve may throw the iteration off and thus impede its convergence.
In such a case, the curve should be smoothed by inserting
additional points. A large number of entries may slow the search
in the table, however.


=== Approximation of the moisture storage function ===

If the moisture storage function can be adequately described by
the function

<TABLE>
<TR><TD VALIGN="CENTER">w = wf·</TD><TD>(b-1)·j b-j</TD><TD> </TD></TR>
<TR><TD COLSPAN="3"> </TD></TR>
<TR><TD>w</TD><TD>[kg/m³]:</TD><TD>moisture content corresponding to relative humidity j</TD></TR>
<TR><TD>wf</TD><TD>[kg/m³]:</TD><TD>moisture content at free saturation</TD></TR>
<TR><TD>j</TD><TD>[-]:</TD><TD>relative
humidity</TD></TR>
<TR><TD>b</TD><TD>[-]:</TD><TD>approximation factor,</TD></TR>
</TABLE>


then it is sufficient to specify w80 and
wf, in order to define the moisture storage
function for WUFI (this is called 'approximation of the moisture
storage function'). However, this condition is not met by all
materials (e.g. some kinds of concrete).

[[Bild:E_fspfkt_meas_approx.gif]]

<H3>WUFI's default moisture storage function</H3>

The moisture storage function of non-hygroscopic materials
(essentially insulating materials, but
[[AirLayers|air layers]] as well) is
theoretically more or less zero in the region
j = 0..1, whereas for
j = 1 it takes on some indefinite
value between zero and wmax, so that no
well-defined functional relationship exists. Because of numerical
requirements, however, WUFI assigns a (low) artificial moisture
storage function to all materials for which the user did not
define such a function. 
So the results of a WUFI calculation will indicate some (low)
moisture content even in materials for which you did not define
a moisture storage function. These moisture contents are artificial
and should be regarded with caution. Only when the moisture contents
surpass the fictitious free saturation of ca. 0.05·wmax,
they have resulted from condensation phenomena which are independent
from the choice of the moisture storage function. In that case the
excess of the moisture content over wf can with
appropriate caution be regarded as a realistic measure of the
amount of condensed moisture.


For discussion of some specific questions concerning the moisture storage function, see the
[[FAQ:Main|Questions & Answers]] section.


Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Krus, M.: Moisture Transport and
Storage Coefficients of Porous Mineral Building Materials.
Theoretical Principles and New Test Methods 
Fraunhofer IRB Verlag, 1996</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>Holm, A., Krus, M., Künzel, H.M.:
Feuchtetransport über Materialgrenzen im Mauerwerk. 
Bauinstandsetzen 2 (1996), H. 5, 375 - 396.
</TABLE>

Details:BasicMaterialData

2009-03-25T10:13:04Z

Barbara: /* Basic Material Data */

= Basic Material Data =

These material data constitute an indispensable minimum without
which a calculation is not possible:

<DL>
<DT>• Bulk density [kg/m³],
<DD>
serves to convert the specific heat by mass to the specific heat
by volume. 
  
The bulk density ρbulk
is the ratio of the mass m of the sample and the total volume
Vtot of the sample:
ρbulk = m / Vtot. 
The true density ρtrue, by
contrast, is the ratio of the mass of the sample and the volume taken
up by the material matrix only:
ρtrue = m /
(Vtot - Vpores) = m / Vtrue. 
  
The bulk density should be available for virtually every building
material. If not, it can be measured very easily. Since it only affects
the specific heat value entering into the calculation, and hygrothermal
simulations usually don't depend very sensitively on this value, it need
not be known with great precision. 
 

<DT>• Porosity [m³/m³],
<DD>
determines the
[[Details:MoistureStorageFunction | maximum water content]]
wmax (by
multiplication by ρwater = 1000 kg/m³). 
  
Since most calculations are not sensitive to the exact value of the
maximum water content (you'll rarely encounter water contents above
[[Details:MoistureStorageFunction | free saturation]], it
is usually sufficient to estimate it if no value
is available for the material in question. 
  
The porosity can be estimated from the true density
ρtrue and the bulk
density ρbulk: 
ρbulk = m / Vtot = m / (Vtrue + Vpores) = ρtrue / (1 + Vpores/Vtrue) = ρtrue * Vtrue/Vtot = ρtrue * (1 - Vpores/Vtot) = ρtrue * (1 - porosity), therefore 
  
<CENTER>porosity = 1 - ρbulk / ρtrue.</CENTER>
  
ρtrue can in turn be
estimated from other materials which have the same composition but
different bulk density, if their bulk density and porosity are known.
Example: a cellular concrete brick with ρbulk = 600 kg/m³ and porosity = 0.72 has
ρtrue =
600 / (1 - 0.72) kg/m³ = 2140 kg/m³. The porosity of a
cellular concrete brick with ρbulk = 400 kg/m³ can then be estimated as
porosity = 1 - 400 / 2140 = 0.81. 
  

<DT>• Heat capacity [J/kgK],
<DD>
the specific heat capacity by mass of the dry material. 
  
Using the specific heat capacity by mass has the advantage that this
value only depends on the chemical composition of the material, but
not on its porosity. For example, cellular concrete bricks with
bulk densities of 400 kg/m³ and 600 kg/m³ have the same
specific heat capacity by mass. 
  
To convert into heat capacity by volume (which enters into the
transport equations), WUFI multiplies the mass-specific heat capacity
by the bulk density. 
  
Rough values are 850 J/kgK for mineral materials and 1500 J/kgK for
organic materials. In most cases, these estimates will be sufficient
since hygrothermal simulations usually don't depend very sensitively on
this value.
 

WUFI automatically allows for the additional heat capacity of the
water content, if any. 
  

<DT>• Heat conductivity dry [W/mK],
<DD>
the heat conductivity of the material in dry condition. A
[[Details:HeatConductivityMoistureDependent | moisture-dependent
heat conductivity]] is optional. 
  
Please note that experimentally measured heat conductivities
of vapor-permeable materials may include the effect of vapor
transport with phase change (i.e. water evaporating at one
side of the specimen and condensing at the other side, thus
in effect transporting latent heat without a corresponding
heat flow being conducted across the specimen). Since WUFI
explicitly computes this thermal effect of vapor flow, it
should not be included in the heat conductivity, if possible.
However, it is usually difficult or impossible to separate
this effect out of the measured data. 
  
Furthermore, design values, such as the data given in German
Standard DIN 4108, may already contain the contribution of a
typical water content and, if so, are not strictly dry values. 
If you want to perform the calculation with a constant (i.e. not
moisture-dependent) heat conductivity (for example because you
have no detailed data on the moisture-dependence), you may use
these design values to allow for moisture content at least in
a crude approximation. However, if you explicitly use a table of
[[Details:HeatConductivityMoistureDependent | moisture-dependent]]
heat conductivities, you should make sure
that the value for moisture content = 0 is really the dry value. 
  
On the other hand, hygrothermal simulations (in particular the
resulting moisture contents and distributions) usually don't depend
very sensitively on the precise values of the heat conductivities,
so the difference may be generally negligible unless you are
specifically interested in heat flows. 
  

<DT>• Diffusion resistance factor dry [-]
<DD>the diffusion resistance factor (µ-value) of the
material in dry condition. The µ-value states by how much
the diffusion resistance of the material in question is higher
than that of stagnant air. A
[[Details:DiffusionResistanceFactorMoistureDependent | moisture-dependent µ-value]]
is optional. 
  
The definition of the µ-value and its relation to
permeability are discussed in the topic
[[Details:WaterVaporDiffusion|Water Vapor Diffusion]]. 
  
Please note that even if you do not explicitly use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value, WUFI will treat it as
moisture-dependent for moisture contents above free
saturation wf. WUFI will reduce it in proportion
to the moisture excess over wf, until it reaches
µ=0 at wmax. This reflects - in a first
approximation - the fact that at very high moisture contents
even the larger capillaries become clogged with water and can't
contribute to vapor transport any more.

Details:BasicMaterialData

2009-03-25T10:09:40Z

Barbara: /* Basic Material Data */

= Basic Material Data =

These material data constitute an indispensable minimum without
which a calculation is not possible:

<DL>
<DT>• Bulk density [kg/m³],
<DD>
serves to convert the specific heat by mass to the specific heat
by volume. 
  
The bulk density ρbulk
is the ratio of the mass m of the sample and the total volume
Vtot of the sample:
ρbulk = m / Vtot. 
The true density ρtrue, by
contrast, is the ratio of the mass of the sample and the volume taken
up by the material matrix only:
ρtrue = m /
(Vtot - Vpores) = m / Vtrue. 
  
The bulk density should be available for virtually every building
material. If not, it can be measured very easily. Since it only affects
the specific heat value entering into the calculation, and hygrothermal
simulations usually don't depend very sensitively on this value, it need
not be known with great precision. 
 

<DT>• Porosity [m³/m³],
<DD>
determines the
[[Details:MoistureStorageFunction | maximum water content]]
wmax (by
multiplication by ρwater = 1000 kg/m³). 
  
Since most calculations are not sensitive to the exact value of the
maximum water content (you'll rarely encounter water contents above
[[Details:MoistureStorageFunction | free saturation]], it
is usually sufficient to estimate it if no value
is available for the material in question. 
  
The porosity can be estimated from the true density
ρtrue and the bulk
density ρbulk: 
ρbulk = m / Vtot = m / (Vtrue + Vpores) = ρtrue / (1 + Vpores/Vtrue) = ρtrue * Vtrue/Vtot = ρtrue * (1 - Vpores/Vtot) = ρtrue * (1 - porosity), therefore 
  
<CENTER>porosity = 1 - ρbulk / ρtrue.</CENTER>
  
ρtrue can in turn be
estimated from other materials which have the same composition but
different bulk density, if their bulk density and porosity are known.
Example: a cellular concrete brick with ρbulk = 600 kg/m³ and porosity = 0.72 has
ρtrue =
600 / (1 - 0.72) kg/m³ = 2140 kg/m³. The porosity of a
cellular concrete brick with ρbulk = 400 kg/m³ can then be estimated as
porosity = 1 - 400 / 2140 = 0.81. 
  

<DT>• Heat capacity [J/kgK],
<DD>
the specific heat capacity by mass of the dry material. 
  
Using the specific heat capacity by mass has the advantage that this
value only depends on the chemical composition of the material, but
not on its porosity. For example, cellular concrete bricks with
bulk densities of 400 kg/m³ and 600 kg/m³ have the same
specific heat capacity by mass. 
  
To convert into heat capacity by volume (which enters into the
transport equations), WUFI multiplies the mass-specific heat capacity
by the bulk density. 
  
Rough values are 850 J/kgK for mineral materials and 1500 J/kgK for
organic materials. In most cases, these estimates will be sufficient
since hygrothermal simulations usually don't depend very sensitively on
this value.
 

WUFI automatically allows for the additional heat capacity of the
water content, if any. 
  

<DT>• Heat conductivity dry [W/mK],
<DD>
the heat conductivity of the material in dry condition. A
[[Details:HeatConductivityMoistureDependent | moisture-dependent
heat conductivity]] is optional. 
  
Please note that experimentally measured heat conductivities
of vapor-permeable materials may include the effect of vapor
transport with phase change (i.e. water evaporating at one
side of the specimen and condensing at the other side, thus
in effect transporting latent heat without a corresponding
heat flow being conducted across the specimen). Since WUFI
explicitly computes this thermal effect of vapor flow, it
should not be included in the heat conductivity, if possible.
However, it is usually difficult or impossible to separate
this effect out of the measured data. 
  
Furthermore, design values, such as the data given in German
Standard DIN 4108, may already contain the contribution of a
typical water content and, if so, are not strictly dry values. 
If you want to perform the calculation with a constant (i.e. not
moisture-dependent) heat conductivity (for example because you
have no detailed data on the moisture-dependence), you may use
these design values to allow for moisture content at least in
a crude approximation. However, if you explicitly use a table of
[[Details:HeatConductivityMoistureDependent | moisture-dependent]]
heat conductivities, you should make sure
that the value for moisture content = 0 is really the dry value. 
  
On the other hand, hygrothermal simulations (in particular the
resulting moisture contents and distributions) usually don't depend
very sensitively on the precise values of the heat conductivities,
so the difference may be generally negligible unless you are
specifically interested in heat flows. 
  

<DT>• Diffusion resistance factor dry [-]
<DD>the diffusion resistance factor (µ-value) of the
material in dry condition. The µ-value states by how much
the diffusion resistance of the material in question is higher
than that of stagnant air. A
[[Details:DiffusionResistanceFactorMoistureDependent | moisture-dependent µ-value]]
is optional. 
  
The definition of the µ-value and its relation to
permeability are discussed in the topic
[[Details:WaterVaporDiffusion|Water Vapor Diffusion]]. 
  
Please note that even if you do not explicitly use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value, WUFI will treat it as
moisture-dependent for moisture contents above free
saturation wf. WUFI will reduce it in proportion
to the moisture excess over wf, until it reaches
µ=0 at wmax. This reflects - in a first
approximation - the fact that at very high moisture contents
even the larger capillaries become clogged with water and can't
contribute to vapor transport any more.

Details:BasicMaterialData

2009-03-25T10:08:00Z

Barbara: /* Basic Material Data */

= Basic Material Data =

These material data constitute an indispensable minimum without
which a calculation is not possible:

<DL>
<DT>• Bulk density [kg/m³],
<DD>
serves to convert the specific heat by mass to the specific heat
by volume. 
  
The bulk density ρbulk
is the ratio of the mass m of the sample and the total volume
Vtot of the sample:
ρbulk = m / Vtot. 
The true density ρtrue, by
contrast, is the ratio of the mass of the sample and the volume taken
up by the material matrix only:
ρtrue = m /
(Vtot - Vpores) = m / Vtrue. 
  
The bulk density should be available for virtually every building
material. If not, it can be measured very easily. Since it only affects
the specific heat value entering into the calculation, and hygrothermal
simulations usually don't depend very sensitively on this value, it need
not be known with great precision. 
 

<DT>• Porosity [m³/m³],
<DD>
determines the
[[Details:MoistureStorageFunction | maximum water content]]
wmax (by
multiplication by ρwater = 1000 kg/m³). 
  
Since most calculations are not sensitive to the exact value of the
maximum water content (you'll rarely encounter water contents above
[[Details:MoistureStorageFunction | free saturation]], it
is usually sufficient to estimate it if no value
is available for the material in question. 
  
The porosity can be estimated from the true density
ρtrue and the bulk
density ρbulk: 
ρbulk = m / Vtot = m / (Vtrue + Vpores) = ρtrue / (1 + Vpores/Vtrue) = ρtrue * Vtrue/Vtot = ρtrue * (1 - Vpores/Vtot) = ρtrue * (1 - porosity), therefore 
  
<CENTER>porosity = 1 - ρbulk / ρtrue.</CENTER>
  
ρtrue can in turn be
estimated from other materials which have the same composition but
different bulk density, if their bulk density and porosity are known.
Example: a cellular concrete brick with ρbulk = 600 kg/m³ and porosity = 0.72 has
ρtrue =
600 / (1 - 0.72) kg/m³ = 2140 kg/m³. The porosity of a
cellular concrete brick with ρbulk = 400 kg/m³ can then be estimated as
porosity = 1 - 400 / 2140 = 0.81. 
  

<DT>• Heat capacity [J/kgK],
<DD>
the specific heat capacity by mass of the dry material. 
  
Using the specific heat capacity by mass has the advantage that this
value only depends on the chemical composition of the material, but
not on its porosity. For example, cellular concrete bricks with
bulk densities of 400 kg/m³ and 600 kg/m³ have the same
specific heat capacity by mass. 
  
To convert into heat capacity by volume (which enters into the
transport equations), WUFI multiplies the mass-specific heat capacity
by the bulk density. 
  
Rough values are 850 J/kgK for mineral materials and 1500 J/kgK for
organic materials. In most cases, these estimates will be sufficient
since hygrothermal simulations usually don't depend very sensitively on
this value.
 

WUFI automatically allows for the additional heat capacity of the
water content, if any. 
  

<DT>• Heat conductivity dry [W/mK],
<DD>
the heat conductivity of the material in dry condition. A
[[Details:HeatConductivityMoistureDependent | moisture-dependent
heat conductivity]] is optional. 
  
Please note that experimentally measured heat conductivities
of vapor-permeable materials may include the effect of vapor
transport with phase change (i.e. water evaporating at one
side of the specimen and condensing at the other side, thus
in effect transporting latent heat without a corresponding
heat flow being conducted across the specimen). Since WUFI
explicitly computes this thermal effect of vapor flow, it
should not be included in the heat conductivity, if possible.
However, it is usually difficult or impossible to separate
this effect out of the measured data. 
  
Furthermore, design values, such as the data given in German
Standard DIN 4108, may already contain the contribution of a
typical water content and, if so, are not strictly dry values. 
If you want to perform the calculation with a constant (i.e. not
moisture-dependent) heat conductivity (for example because you
have no detailed data on the moisture-dependence), you may use
these design values to allow for moisture content at least in
a crude approximation. However, if you explicitly use a table of
[[Details:HeatConductivityMoistureDependent | moisture-dependent]]
heat conductivities, you should make sure
that the value for moisture content = 0 is really the dry value. 
  
On the other hand, hygrothermal simulations (in particular the
resulting moisture contents and distributions) usually don't depend
very sensitively on the precise values of the heat conductivities,
so the difference may be generally negligible unless you are
specifically interested in heat flows. 
  

<DT>• Diffusion resistance factor dry [-]
<DD>the diffusion resistance factor (µ-value) of the
material in dry condition. The µ-value states by how much
the diffusion resistance of the material in question is higher
than that of stagnant air. A
[[Details:DiffusionResistanceFactorMoistureDependent | moisture-dependent µ-value]]
is optional. 
  
The definition of the µ-value and its relation to
permeability are discussed in the topic
[[Details:WaterVaporDiffusion|Water Vapor Diffusion]]. 
  
Please note that even if you do not explicitly use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value, WUFI will treat it as
moisture-dependent for moisture contents above free
saturation wf. WUFI will reduce it in proportion
to the moisture excess over wf, until it reaches
µ=0 at wmax. This reflects - in a first
approximation - the fact that at very high moisture contents
even the larger capillaries become clogged with water and can't
contribute to vapor transport any more.

Details:BasicMaterialData

2009-03-25T10:06:30Z

Barbara: /* Basic Material Data */

= Basic Material Data =

These material data constitute an indispensable minimum without
which a calculation is not possible:

<DL>
<DT>• Bulk density [kg/m³],
<DD>
serves to convert the specific heat by mass to the specific heat
by volume. 
  
The bulk density ρbulk
is the ratio of the mass m of the sample and the total volume
Vtot of the sample:
ρbulk = m / Vtot. 
The true density ρtrue, by
contrast, is the ratio of the mass of the sample and the volume taken
up by the material matrix only:
ρtrue = m /
(Vtot - Vpores) = m / Vtrue. 
  
The bulk density should be available for virtually every building
material. If not, it can be measured very easily. Since it only affects
the specific heat value entering into the calculation, and hygrothermal
simulations usually don't depend very sensitively on this value, it need
not be known with great precision. 
 

<DT>• Porosity [m³/m³],
<DD>
determines the
[[Details:MoistureStorageFunction | maximum water content]]
wmax (by
multiplication by ρwater = 1000 kg/m³). 
  
Since most calculations are not sensitive to the exact value of the
maximum water content (you'll rarely encounter water contents above
[[Details:MoistureStorageFunction | free saturation]], it
is usually sufficient to estimate it if no value
is available for the material in question. 
  
The porosity can be estimated from the true density
ρtrue and the bulk
density ρbulk: 
ρbulk = m / Vtot = m / (Vtrue + Vpores) = ρtrue / (1 + Vpores/Vtrue) = ρtrue * Vtrue/Vtot = ρtrue * (1 - Vpores/Vtot) = ρtrue * (1 - porosity), therefore 
  
<CENTER>porosity = 1 - ρbulk / ρtrue.</CENTER>
  
ρtrue can in turn be
estimated from other materials which have the same composition but
different bulk density, if their bulk density and porosity are known.
Example: a cellular concrete brick with ρbulk = 600 kg/m³ and porosity = 0.72 has
ρtrue =
600 / (1 - 0.72) kg/m³ = 2140 kg/m³. The porosity of a
cellular concrete brick with ρbulk = 400 kg/m³ can then be estimated as
porosity = 1 - 400 / 2140 = 0.81. 
  

<DT>• Heat capacity [J/kgK],
<DD>
the specific heat capacity by mass of the dry material. 
  
Using the specific heat capacity by mass has the advantage that this
value only depends on the chemical composition of the material, but
not on its porosity. For example, cellular concrete bricks with
bulk densities of 400 kg/m³ and 600 kg/m³ have the same
specific heat capacity by mass. 
  
To convert into heat capacity by volume (which enters into the
transport equations), WUFI multiplies the mass-specific heat capacity
by the bulk density. 
  
Rough values are 850 J/kgK for mineral materials and 1500 J/kgK for
organic materials. In most cases, these estimates will be sufficient
since hygrothermal simulations usually don't depend very sensitively on
this value. 
 
WUFI automatically allows for the additional heat capacity of the
water content, if any. 
  

<DT>• Heat conductivity dry [W/mK],
<DD>
the heat conductivity of the material in dry condition. A
[[Details:HeatConductivityMoistureDependent | moisture-dependent
heat conductivity]] is optional. 
  
Please note that experimentally measured heat conductivities
of vapor-permeable materials may include the effect of vapor
transport with phase change (i.e. water evaporating at one
side of the specimen and condensing at the other side, thus
in effect transporting latent heat without a corresponding
heat flow being conducted across the specimen). Since WUFI
explicitly computes this thermal effect of vapor flow, it
should not be included in the heat conductivity, if possible.
However, it is usually difficult or impossible to separate
this effect out of the measured data. 
  
Furthermore, design values, such as the data given in German
Standard DIN 4108, may already contain the contribution of a
typical water content and, if so, are not strictly dry values. 
If you want to perform the calculation with a constant (i.e. not
moisture-dependent) heat conductivity (for example because you
have no detailed data on the moisture-dependence), you may use
these design values to allow for moisture content at least in
a crude approximation. However, if you explicitly use a table of
[[Details:HeatConductivityMoistureDependent | moisture-dependent]]
heat conductivities, you should make sure
that the value for moisture content = 0 is really the dry value. 
  
On the other hand, hygrothermal simulations (in particular the
resulting moisture contents and distributions) usually don't depend
very sensitively on the precise values of the heat conductivities,
so the difference may be generally negligible unless you are
specifically interested in heat flows. 
  

<DT>• Diffusion resistance factor dry [-]
<DD>the diffusion resistance factor (µ-value) of the
material in dry condition. The µ-value states by how much
the diffusion resistance of the material in question is higher
than that of stagnant air. A
[[Details:DiffusionResistanceFactorMoistureDependent | moisture-dependent µ-value]]
is optional. 
  
The definition of the µ-value and its relation to
permeability are discussed in the topic
[[Details:WaterVaporDiffusion|Water Vapor Diffusion]]. 
  
Please note that even if you do not explicitly use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value, WUFI will treat it as
moisture-dependent for moisture contents above free
saturation wf. WUFI will reduce it in proportion
to the moisture excess over wf, until it reaches
µ=0 at wmax. This reflects - in a first
approximation - the fact that at very high moisture contents
even the larger capillaries become clogged with water and can't
contribute to vapor transport any more.

Details:BasicMaterialData

2009-03-25T10:05:26Z

Barbara: /* Basic Material Data */

= Basic Material Data =

These material data constitute an indispensable minimum without
which a calculation is not possible:

<DL>
<DT>• Bulk density [kg/m³],
<DD>
serves to convert the specific heat by mass to the specific heat
by volume. 
  
The bulk density ρbulk
is the ratio of the mass m of the sample and the total volume
Vtot of the sample:
ρbulk = m / Vtot. 
The true density ρtrue, by
contrast, is the ratio of the mass of the sample and the volume taken
up by the material matrix only:
ρtrue = m /
(Vtot - Vpores) = m / Vtrue. 
  
The bulk density should be available for virtually every building
material. If not, it can be measured very easily. Since it only affects
the specific heat value entering into the calculation, and hygrothermal
simulations usually don't depend very sensitively on this value, it need
not be known with great precision. 
 

<DT>• Porosity [m³/m³],
<DD>
determines the
[[Details:MoistureStorageFunction | maximum water content]]
wmax (by
multiplication by ρwater = 1000 kg/m³). 
  
Since most calculations are not sensitive to the exact value of the
maximum water content (you'll rarely encounter water contents above
[[Details:MoistureStorageFunction | free saturation]], it
is usually sufficient to estimate it if no value
is available for the material in question. 
  
The porosity can be estimated from the true density
ρtrue and the bulk
density ρbulk: 
ρbulk = m / Vtot = m / (Vtrue + Vpores) = ρtrue / (1 + Vpores/Vtrue) = ρtrue * Vtrue/Vtot = ρtrue * (1 - Vpores/Vtot) = ρtrue * (1 - porosity), therefore 
  
<CENTER>porosity = 1 - ρbulk / ρtrue.</CENTER>
  
ρtrue can in turn be
estimated from other materials which have the same composition but
different bulk density, if their bulk density and porosity are known.
Example: a cellular concrete brick with ρbulk = 600 kg/m³ and porosity = 0.72 has
r true =
600 / (1 - 0.72) kg/m³ = 2140 kg/m³. The porosity of a
cellular concrete brick with r bulk = 400 kg/m³ can then be estimated as
porosity = 1 - 400 / 2140 = 0.81. 
  

<DT>• Heat capacity [J/kgK],
<DD>
the specific heat capacity by mass of the dry material. 
  
Using the specific heat capacity by mass has the advantage that this
value only depends on the chemical composition of the material, but
not on its porosity. For example, cellular concrete bricks with
bulk densities of 400 kg/m³ and 600 kg/m³ have the same
specific heat capacity by mass. 
  
To convert into heat capacity by volume (which enters into the
transport equations), WUFI multiplies the mass-specific heat capacity
by the bulk density. 
  
Rough values are 850 J/kgK for mineral materials and 1500 J/kgK for
organic materials. In most cases, these estimates will be sufficient
since hygrothermal simulations usually don't depend very sensitively on
this value. 
 
WUFI automatically allows for the additional heat capacity of the
water content, if any. 
  

<DT>• Heat conductivity dry [W/mK],
<DD>
the heat conductivity of the material in dry condition. A
[[Details:HeatConductivityMoistureDependent | moisture-dependent
heat conductivity]] is optional. 
  
Please note that experimentally measured heat conductivities
of vapor-permeable materials may include the effect of vapor
transport with phase change (i.e. water evaporating at one
side of the specimen and condensing at the other side, thus
in effect transporting latent heat without a corresponding
heat flow being conducted across the specimen). Since WUFI
explicitly computes this thermal effect of vapor flow, it
should not be included in the heat conductivity, if possible.
However, it is usually difficult or impossible to separate
this effect out of the measured data. 
  
Furthermore, design values, such as the data given in German
Standard DIN 4108, may already contain the contribution of a
typical water content and, if so, are not strictly dry values. 
If you want to perform the calculation with a constant (i.e. not
moisture-dependent) heat conductivity (for example because you
have no detailed data on the moisture-dependence), you may use
these design values to allow for moisture content at least in
a crude approximation. However, if you explicitly use a table of
[[Details:HeatConductivityMoistureDependent | moisture-dependent]]
heat conductivities, you should make sure
that the value for moisture content = 0 is really the dry value. 
  
On the other hand, hygrothermal simulations (in particular the
resulting moisture contents and distributions) usually don't depend
very sensitively on the precise values of the heat conductivities,
so the difference may be generally negligible unless you are
specifically interested in heat flows. 
  

<DT>• Diffusion resistance factor dry [-]
<DD>the diffusion resistance factor (µ-value) of the
material in dry condition. The µ-value states by how much
the diffusion resistance of the material in question is higher
than that of stagnant air. A
[[Details:DiffusionResistanceFactorMoistureDependent | moisture-dependent µ-value]]
is optional. 
  
The definition of the µ-value and its relation to
permeability are discussed in the topic
[[Details:WaterVaporDiffusion|Water Vapor Diffusion]]. 
  
Please note that even if you do not explicitly use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value, WUFI will treat it as
moisture-dependent for moisture contents above free
saturation wf. WUFI will reduce it in proportion
to the moisture excess over wf, until it reaches
µ=0 at wmax. This reflects - in a first
approximation - the fact that at very high moisture contents
even the larger capillaries become clogged with water and can't
contribute to vapor transport any more.

Details:BasicMaterialData

2009-03-25T10:00:34Z

Barbara: /* Basic Material Data */

= Basic Material Data =

These material data constitute an indispensable minimum without
which a calculation is not possible:

<DL>
<DT>• Bulk density [kg/m³],
<DD>
serves to convert the specific heat by mass to the specific heat
by volume. 
  
The bulk density ρbulk
is the ratio of the mass m of the sample and the total volume
Vtot of the sample:
ρbulk = m / Vtot. 
The true density ρtrue, by
contrast, is the ratio of the mass of the sample and the volume taken
up by the material matrix only:
ρtrue = m /
(Vtot - Vpores) = m / Vtrue. 
  
The bulk density should be available for virtually every building
material. If not, it can be measured very easily. Since it only affects
the specific heat value entering into the calculation, and hygrothermal
simulations usually don't depend very sensitively on this value, it need
not be known with great precision. 
 

<DT>• Porosity [m³/m³],
<DD>
determines the
[[Details:MoistureStorageFunction | maximum water content]]
wmax (by
multiplication by ρwater = 1000 kg/m³). 
  
Since most calculations are not sensitive to the exact value of the
maximum water content (you'll rarely encounter water contents above
[[Details:MoistureStorageFunction | free saturation]], it
is usually sufficient to estimate it if no value
is available for the material in question. 
  
The porosity can be estimated from the true density
r true and the bulk
density r bulk: 
r bulk = m / Vtot = m / (Vtrue + Vpores) = r true / (1 + Vpores/Vtrue) = r true * Vtrue/Vtot = r true * (1 - Vpores/Vtot) = r true * (1 - porosity), therefore 
  
<CENTER>porosity = 1 - r bulk / r true.</CENTER>
  
r true can in turn be
estimated from other materials which have the same composition but
different bulk density, if their bulk density and porosity are known.
Example: a cellular concrete brick with r bulk = 600 kg/m³ and porosity = 0.72 has
r true =
600 / (1 - 0.72) kg/m³ = 2140 kg/m³. The porosity of a
cellular concrete brick with r bulk = 400 kg/m³ can then be estimated as
porosity = 1 - 400 / 2140 = 0.81. 
  

<DT>• Heat capacity [J/kgK],
<DD>
the specific heat capacity by mass of the dry material. 
  
Using the specific heat capacity by mass has the advantage that this
value only depends on the chemical composition of the material, but
not on its porosity. For example, cellular concrete bricks with
bulk densities of 400 kg/m³ and 600 kg/m³ have the same
specific heat capacity by mass. 
  
To convert into heat capacity by volume (which enters into the
transport equations), WUFI multiplies the mass-specific heat capacity
by the bulk density. 
  
Rough values are 850 J/kgK for mineral materials and 1500 J/kgK for
organic materials. In most cases, these estimates will be sufficient
since hygrothermal simulations usually don't depend very sensitively on
this value. 
 
WUFI automatically allows for the additional heat capacity of the
water content, if any. 
  

<DT>• Heat conductivity dry [W/mK],
<DD>
the heat conductivity of the material in dry condition. A
[[Details:HeatConductivityMoistureDependent | moisture-dependent
heat conductivity]] is optional. 
  
Please note that experimentally measured heat conductivities
of vapor-permeable materials may include the effect of vapor
transport with phase change (i.e. water evaporating at one
side of the specimen and condensing at the other side, thus
in effect transporting latent heat without a corresponding
heat flow being conducted across the specimen). Since WUFI
explicitly computes this thermal effect of vapor flow, it
should not be included in the heat conductivity, if possible.
However, it is usually difficult or impossible to separate
this effect out of the measured data. 
  
Furthermore, design values, such as the data given in German
Standard DIN 4108, may already contain the contribution of a
typical water content and, if so, are not strictly dry values. 
If you want to perform the calculation with a constant (i.e. not
moisture-dependent) heat conductivity (for example because you
have no detailed data on the moisture-dependence), you may use
these design values to allow for moisture content at least in
a crude approximation. However, if you explicitly use a table of
[[Details:HeatConductivityMoistureDependent | moisture-dependent]]
heat conductivities, you should make sure
that the value for moisture content = 0 is really the dry value. 
  
On the other hand, hygrothermal simulations (in particular the
resulting moisture contents and distributions) usually don't depend
very sensitively on the precise values of the heat conductivities,
so the difference may be generally negligible unless you are
specifically interested in heat flows. 
  

<DT>• Diffusion resistance factor dry [-]
<DD>the diffusion resistance factor (µ-value) of the
material in dry condition. The µ-value states by how much
the diffusion resistance of the material in question is higher
than that of stagnant air. A
[[Details:DiffusionResistanceFactorMoistureDependent | moisture-dependent µ-value]]
is optional. 
  
The definition of the µ-value and its relation to
permeability are discussed in the topic
[[Details:WaterVaporDiffusion|Water Vapor Diffusion]]. 
  
Please note that even if you do not explicitly use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value, WUFI will treat it as
moisture-dependent for moisture contents above free
saturation wf. WUFI will reduce it in proportion
to the moisture excess over wf, until it reaches
µ=0 at wmax. This reflects - in a first
approximation - the fact that at very high moisture contents
even the larger capillaries become clogged with water and can't
contribute to vapor transport any more.

Details:BasicMaterialData

2009-03-25T09:57:15Z

Barbara: /* Basic Material Data */

= Basic Material Data =

These material data constitute an indispensable minimum without
which a calculation is not possible:

<DL>
<DT>• Bulk density [kg/m³],
<DD>
serves to convert the specific heat by mass to the specific heat
by volume. 
  
The bulk density ρbulk
is the ratio of the mass m of the sample and the total volume
Vtot of the sample:
ρbulk = m / Vtot. 
The true density ρbulk, by
contrast, is the ratio of the mass of the sample and the volume taken
up by the material matrix only:
ρbulk = m /
(Vtot - Vpores) = m / Vtrue. 
  
The bulk density should be available for virtually every building
material. If not, it can be measured very easily. Since it only affects
the specific heat value entering into the calculation, and hygrothermal
simulations usually don't depend very sensitively on this value, it need
not be known with great precision. 
 

<DT>• Porosity [m³/m³],
<DD>
determines the
[[Details:MoistureStorageFunction | maximum water content]]
wmax (by
multiplication by rwater = 1000 kg/m³). 
  
Since most calculations are not sensitive to the exact value of the
maximum water content (you'll rarely encounter water contents above
[[Details:MoistureStorageFunction | free saturation]], it
is usually sufficient to estimate it if no value
is available for the material in question. 
  
The porosity can be estimated from the true density
r true and the bulk
density r bulk: 
r bulk = m / Vtot = m / (Vtrue + Vpores) = r true / (1 + Vpores/Vtrue) = r true * Vtrue/Vtot = r true * (1 - Vpores/Vtot) = r true * (1 - porosity), therefore 
  
<CENTER>porosity = 1 - r bulk / r true.</CENTER>
  
r true can in turn be
estimated from other materials which have the same composition but
different bulk density, if their bulk density and porosity are known.
Example: a cellular concrete brick with r bulk = 600 kg/m³ and porosity = 0.72 has
r true =
600 / (1 - 0.72) kg/m³ = 2140 kg/m³. The porosity of a
cellular concrete brick with r bulk = 400 kg/m³ can then be estimated as
porosity = 1 - 400 / 2140 = 0.81. 
  

<DT>• Heat capacity [J/kgK],
<DD>
the specific heat capacity by mass of the dry material. 
  
Using the specific heat capacity by mass has the advantage that this
value only depends on the chemical composition of the material, but
not on its porosity. For example, cellular concrete bricks with
bulk densities of 400 kg/m³ and 600 kg/m³ have the same
specific heat capacity by mass. 
  
To convert into heat capacity by volume (which enters into the
transport equations), WUFI multiplies the mass-specific heat capacity
by the bulk density. 
  
Rough values are 850 J/kgK for mineral materials and 1500 J/kgK for
organic materials. In most cases, these estimates will be sufficient
since hygrothermal simulations usually don't depend very sensitively on
this value. 
 
WUFI automatically allows for the additional heat capacity of the
water content, if any. 
  

<DT>• Heat conductivity dry [W/mK],
<DD>
the heat conductivity of the material in dry condition. A
[[Details:HeatConductivityMoistureDependent | moisture-dependent
heat conductivity]] is optional. 
  
Please note that experimentally measured heat conductivities
of vapor-permeable materials may include the effect of vapor
transport with phase change (i.e. water evaporating at one
side of the specimen and condensing at the other side, thus
in effect transporting latent heat without a corresponding
heat flow being conducted across the specimen). Since WUFI
explicitly computes this thermal effect of vapor flow, it
should not be included in the heat conductivity, if possible.
However, it is usually difficult or impossible to separate
this effect out of the measured data. 
  
Furthermore, design values, such as the data given in German
Standard DIN 4108, may already contain the contribution of a
typical water content and, if so, are not strictly dry values. 
If you want to perform the calculation with a constant (i.e. not
moisture-dependent) heat conductivity (for example because you
have no detailed data on the moisture-dependence), you may use
these design values to allow for moisture content at least in
a crude approximation. However, if you explicitly use a table of
[[Details:HeatConductivityMoistureDependent | moisture-dependent]]
heat conductivities, you should make sure
that the value for moisture content = 0 is really the dry value. 
  
On the other hand, hygrothermal simulations (in particular the
resulting moisture contents and distributions) usually don't depend
very sensitively on the precise values of the heat conductivities,
so the difference may be generally negligible unless you are
specifically interested in heat flows. 
  

<DT>• Diffusion resistance factor dry [-]
<DD>the diffusion resistance factor (µ-value) of the
material in dry condition. The µ-value states by how much
the diffusion resistance of the material in question is higher
than that of stagnant air. A
[[Details:DiffusionResistanceFactorMoistureDependent | moisture-dependent µ-value]]
is optional. 
  
The definition of the µ-value and its relation to
permeability are discussed in the topic
[[Details:WaterVaporDiffusion|Water Vapor Diffusion]]. 
  
Please note that even if you do not explicitly use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value, WUFI will treat it as
moisture-dependent for moisture contents above free
saturation wf. WUFI will reduce it in proportion
to the moisture excess over wf, until it reaches
µ=0 at wmax. This reflects - in a first
approximation - the fact that at very high moisture contents
even the larger capillaries become clogged with water and can't
contribute to vapor transport any more.

Details:BasicMaterialData

2009-03-25T09:56:03Z

Barbara: /* Basic Material Data */

= Basic Material Data =

These material data constitute an indispensable minimum without
which a calculation is not possible:

<DL>
<DT>• Bulk density [kg/m³],
<DD>
serves to convert the specific heat by mass to the specific heat
by volume. 
  
The bulk density ρbulk
is the ratio of the mass m of the sample and the total volume
Vtot of the sample:
ρbulk = m / Vtot. 
The true density r true, by
contrast, is the ratio of the mass of the sample and the volume taken
up by the material matrix only:
r true = m /
(Vtot - Vpores) = m / Vtrue. 
  
The bulk density should be available for virtually every building
material. If not, it can be measured very easily. Since it only affects
the specific heat value entering into the calculation, and hygrothermal
simulations usually don't depend very sensitively on this value, it need
not be known with great precision. 
 

<DT>• Porosity [m³/m³],
<DD>
determines the
[[Details:MoistureStorageFunction | maximum water content]]
wmax (by
multiplication by rwater = 1000 kg/m³). 
  
Since most calculations are not sensitive to the exact value of the
maximum water content (you'll rarely encounter water contents above
[[Details:MoistureStorageFunction | free saturation]], it
is usually sufficient to estimate it if no value
is available for the material in question. 
  
The porosity can be estimated from the true density
r true and the bulk
density r bulk: 
r bulk = m / Vtot = m / (Vtrue + Vpores) = r true / (1 + Vpores/Vtrue) = r true * Vtrue/Vtot = r true * (1 - Vpores/Vtot) = r true * (1 - porosity), therefore 
  
<CENTER>porosity = 1 - r bulk / r true.</CENTER>
  
r true can in turn be
estimated from other materials which have the same composition but
different bulk density, if their bulk density and porosity are known.
Example: a cellular concrete brick with r bulk = 600 kg/m³ and porosity = 0.72 has
r true =
600 / (1 - 0.72) kg/m³ = 2140 kg/m³. The porosity of a
cellular concrete brick with r bulk = 400 kg/m³ can then be estimated as
porosity = 1 - 400 / 2140 = 0.81. 
  

<DT>• Heat capacity [J/kgK],
<DD>
the specific heat capacity by mass of the dry material. 
  
Using the specific heat capacity by mass has the advantage that this
value only depends on the chemical composition of the material, but
not on its porosity. For example, cellular concrete bricks with
bulk densities of 400 kg/m³ and 600 kg/m³ have the same
specific heat capacity by mass. 
  
To convert into heat capacity by volume (which enters into the
transport equations), WUFI multiplies the mass-specific heat capacity
by the bulk density. 
  
Rough values are 850 J/kgK for mineral materials and 1500 J/kgK for
organic materials. In most cases, these estimates will be sufficient
since hygrothermal simulations usually don't depend very sensitively on
this value. 
 
WUFI automatically allows for the additional heat capacity of the
water content, if any. 
  

<DT>• Heat conductivity dry [W/mK],
<DD>
the heat conductivity of the material in dry condition. A
[[Details:HeatConductivityMoistureDependent | moisture-dependent
heat conductivity]] is optional. 
  
Please note that experimentally measured heat conductivities
of vapor-permeable materials may include the effect of vapor
transport with phase change (i.e. water evaporating at one
side of the specimen and condensing at the other side, thus
in effect transporting latent heat without a corresponding
heat flow being conducted across the specimen). Since WUFI
explicitly computes this thermal effect of vapor flow, it
should not be included in the heat conductivity, if possible.
However, it is usually difficult or impossible to separate
this effect out of the measured data. 
  
Furthermore, design values, such as the data given in German
Standard DIN 4108, may already contain the contribution of a
typical water content and, if so, are not strictly dry values. 
If you want to perform the calculation with a constant (i.e. not
moisture-dependent) heat conductivity (for example because you
have no detailed data on the moisture-dependence), you may use
these design values to allow for moisture content at least in
a crude approximation. However, if you explicitly use a table of
[[Details:HeatConductivityMoistureDependent | moisture-dependent]]
heat conductivities, you should make sure
that the value for moisture content = 0 is really the dry value. 
  
On the other hand, hygrothermal simulations (in particular the
resulting moisture contents and distributions) usually don't depend
very sensitively on the precise values of the heat conductivities,
so the difference may be generally negligible unless you are
specifically interested in heat flows. 
  

<DT>• Diffusion resistance factor dry [-]
<DD>the diffusion resistance factor (µ-value) of the
material in dry condition. The µ-value states by how much
the diffusion resistance of the material in question is higher
than that of stagnant air. A
[[Details:DiffusionResistanceFactorMoistureDependent | moisture-dependent µ-value]]
is optional. 
  
The definition of the µ-value and its relation to
permeability are discussed in the topic
[[Details:WaterVaporDiffusion|Water Vapor Diffusion]]. 
  
Please note that even if you do not explicitly use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value, WUFI will treat it as
moisture-dependent for moisture contents above free
saturation wf. WUFI will reduce it in proportion
to the moisture excess over wf, until it reaches
µ=0 at wmax. This reflects - in a first
approximation - the fact that at very high moisture contents
even the larger capillaries become clogged with water and can't
contribute to vapor transport any more.

Details:AirLayers

2009-03-25T09:52:36Z

Barbara: /* Air Layers */

= Air Layers =

WUFI can also include air layers in the building component. It does not simulate the
air convection (which would not make much sense in one dimension anyway), but it allows
for the air layer as a resistance to heat and moisture flows.


In addition to heat conduction, in air layers heat can also be transferred by convection
and radiation. In addition to water vapor diffusion, in air layers water vapor can also
be transferred by convection. Since WUFI is primarily intended for solid materials, it
only allows for heat conduction and water vapor diffusion (plus liquid transport, which
is not relevant here). However, the additional transport phenomena can be included by
adjusting the
[[Details:BasicMaterialData | heat conductivity]] and the
[[Details:BasicMaterialData | diffusion resistance]] so that the correct heat
and vapor flows result from the calculation.


The method is based on the following considerations which are valid for
non-ventilated air layers. (No general treatment is possible for ventilated air
layers; they may even exhibit the same conditions as the exterior air. Building
components outward from the air layer may then be disregarded except for their shielding
of rain and radiation.)


The relative contributions of heat conduction, convection and radiation are dependent on
the thickness and orientation of the air layer, the nature of the two surfaces and the
temperature. Fortunately, the dependence on the temperature may be neglected in building
physics. Furthermore, it suffices to distinguish between metallic and non-metallic
surfaces. So if we restrict ourselves to, say, vertical air layers with non-metallic
surfaces, we can simply determine (e.g. from measurements) a heat resistance
Rnon-met which depends only on the air layer thickness and which comprises
all transport phenomena.


Now, for WUFI the effective heat conductivity λ*
has to be chosen so that for an air layer with a given thickness the heat resistance
Rnon-met as
determined above results. Note: the thickness with wich the air layer is included in the
assembly for calculation need not (but can) be identical with the real thickness, since
the real thickness has already been allowed for in the specific choice of
Rnon-met.


The heat resistance of an air layer with the desired thickness, orientation (vertical,
horizontal) and surfaces (metallic, non-metallic) may be looked up in a relevant table.
Let's choose non-metallic surfaces here, since in building components non-metallic surfaces
are predominant, and call this value Rnon-met. We also choose an arbitrary
thickness Dx*, which shall be the thickness of the
air layer as inserted in WUFI's component assembly. Then 
  
 Rnon-met = Δx* /
λ*, 
  
therefore 
  
 λ* = Δx*
/ Rnon-met. 
  



Since water vapor diffusion and convective water vapor transport are based on analogous
mechanisms as heat conductivity and convective heat transport, the coefficients describing
vapor transport can be derived from the coefficients for heat transport, using similarity
relations. For vapor flow, we have formally: 
  
 -gv = Dc / µ* ·
Δc / Δx*
= Δc / S 
  
<TABLE>
<TR><TD>gv</TD>
<TD>[kg/m²s]</TD>
<TD>:</TD>
<TD>water vapor diffusion flux density</TD>
</TR>
<TR><TD>Dc</TD>
<TD>[m²/s]</TD>
<TD>:</TD>
<TD>concentration-related diffusion coefficient</TD>
</TR>
<TR><TD>µ*</TD>
<TD>[-]</TD>
<TD>:</TD>
<TD>effective water vapor diffusion resistance factor</TD>
</TR>
<TR><TD>c</TD>
<TD>[kg/m³]</TD>
<TD>:</TD>
<TD>water vapor concentration</TD>
</TR>
<TR><TD>Δx*</TD>
<TD>[m]</TD>
<TD>:</TD>
<TD>effective layer thickness</TD>
</TR>
<TR><TD>S</TD>
<TD>[m³/s²Pa]</TD>
<TD>:</TD>
<TD>water vapor diffusion resistance,</TD>
</TABLE>
  therefore 
    
 µ* = Dc · S / Δx* 
  
But we have 
  
 Dc = 0.083 · (T/273)1.81
≈ 0.09   [1], 
  
and, because of similarity relations, 
  
 S ≈ Rmet / 3.5   [2], 
  
where we have to use the heat resistance Rmet of air layers between metallic
surfaces (i.e., without radiation exchange), since we want to estimate the vapor diffusion
resistance and there is no transport mechanism analogous to radiation involved, in
contrast to the above case of heat transport.


Finally, we have the freedom to choose an arbitrary thickness
Δx* with which the layer is included in the component
assembly for calculation, since the real thickness was already allowed for in the choice
of the specific value for Rmet. 
  
 µ* = 0.09 · Rmet / (3.5 · Δx*) = 0.026 · Rmet / Δx* 
  


For vertical air layers, Rnon-met and Rmet may be taken
from this table (interpolated after [3]): 


<TABLE>
<TR><TD WIDTH="20"> </TD>
<TD>thickness</TD>
<TD WIDTH="10"> </TD>
<TD>Rnon-met</TD>
<TD WIDTH="10"> </TD>
<TD>Rmet</TD>
</TR>
<TR><TD> </TD>
<TD>[cm]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
</TR>
<TR><TD> </TD>
<TD COLSPAN="5"> <HR> </TD>
</TR>

<TR><TD> </TD>
<TD> 0</TD>
<TD> </TD>
<TD>0</TD>
<TD> </TD>
<TD>0</TD>
</TR>
<TR><TD> </TD>
<TD> 1</TD>
<TD> </TD>
<TD>0.140</TD>
<TD> </TD>
<TD>0.280</TD>
</TR>
<TR><TD> </TD>
<TD> 2</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
<TR><TD> </TD>
<TD> 3</TD>
<TD> </TD>
<TD>0.171</TD>
<TD> </TD>
<TD>0.526</TD>
</TR>
<TR><TD> </TD>
<TD> 4</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.590</TD>
</TR>
<TR><TD> </TD>
<TD> 5</TD>
<TD> </TD>
<TD>0.180</TD>
<TD> </TD>
<TD>0.620</TD>
</TR>
<TR><TD> </TD>
<TD> 6</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.627</TD>
</TR>
<TR><TD> </TD>
<TD> 7</TD>
<TD> </TD>
<TD>0.176</TD>
<TD> </TD>
<TD>0.623</TD>
</TR>
<TR><TD> </TD>
<TD> 8</TD>
<TD> </TD>
<TD>0.174</TD>
<TD> </TD>
<TD>0.613</TD>
</TR>
<TR><TD> </TD>
<TD> 9</TD>
<TD> </TD>
<TD>0.172</TD>
<TD> </TD>
<TD>0.598</TD>
</TR>
<TR><TD> </TD>
<TD>10</TD>
<TD> </TD>
<TD>0.170</TD>
<TD> </TD>
<TD>0.580</TD>
</TR>
<TR><TD> </TD>
<TD>11</TD>
<TD> </TD>
<TD>0.168</TD>
<TD> </TD>
<TD>0.557</TD>
</TR>
<TR><TD> </TD>
<TD>12</TD>
<TD> </TD>
<TD>0.166</TD>
<TD> </TD>
<TD>0.530</TD>
</TR>
<TR><TD> </TD>
<TD>13</TD>
<TD> </TD>
<TD>0.164</TD>
<TD> </TD>
<TD>0.501</TD>
</TR>
<TR><TD> </TD>
<TD>14</TD>
<TD> </TD>
<TD>0.162</TD>
<TD> </TD>
<TD>0.468</TD>
</TR>
<TR><TD> </TD>
<TD>15</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
</TABLE>

The other [[Details:BasicMaterialData | basic material parameters]] may be determined
according to the following:

* if Δx* was chosen not equal to the real thickness, multiplication of the 'bulk density' 1.29 kg/m³ by (real thickness)/Δx* results in the correct heat capacity;
* the 'porosity' should be chosen very high (e.g. 0.999 m³/m³);
* the specific heat capacity by mass of the air layer is 1 kJ/kgK, even if Δx* is chosen not equal to the real thickness.


For the graphical display of the [[1D:Dialog_Assembly | component assembly]], it
will be advisable to choose Δx* equal to the real
thickness. Note however that if you want to repeat the calculation with an air layer of
a different thickness, it is not sufficient to simply adapt the layer thickness in the
component assembly. Instead, λ* and
µ* have to be newly determined from scratch. 
  


Regarding the 'moisture storage function' of air layers, see the
[[Details:MoistureStorageFunction | reference: Moisture Storage Function]].


The definition of the diffusion resistance factor (µ-value) is discussed in the
[[Details:WaterVaporDiffusion | reference: Water Vapor Diffusion]].


=== Literature: ===
[1] Schirmer, R.: Die Diffusionszahl von Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177. 
  
[2] Illig, W.: Die Größe der Wasserdampfübergangszahl bei Diffusionsvorgängen in Wänden von Wohnungen, Stallungen und Kühlräumen, Gesundheitsingenieur 73 (1952), H. 7/8, p. 124-127. 
  
[3]Gösele, K., Schüle, W.: Schall·Wärme·Feuchte. Bauverlag 1989.

Details:AirLayers

2009-03-25T09:50:38Z

Barbara: /* Air Layers */

= Air Layers =

WUFI can also include air layers in the building component. It does not simulate the
air convection (which would not make much sense in one dimension anyway), but it allows
for the air layer as a resistance to heat and moisture flows.


In addition to heat conduction, in air layers heat can also be transferred by convection
and radiation. In addition to water vapor diffusion, in air layers water vapor can also
be transferred by convection. Since WUFI is primarily intended for solid materials, it
only allows for heat conduction and water vapor diffusion (plus liquid transport, which
is not relevant here). However, the additional transport phenomena can be included by
adjusting the
[[Details:BasicMaterialData | heat conductivity]] and the
[[Details:BasicMaterialData | diffusion resistance]] so that the correct heat
and vapor flows result from the calculation.


The method is based on the following considerations which are valid for
non-ventilated air layers. (No general treatment is possible for ventilated air
layers; they may even exhibit the same conditions as the exterior air. Building
components outward from the air layer may then be disregarded except for their shielding
of rain and radiation.)


The relative contributions of heat conduction, convection and radiation are dependent on
the thickness and orientation of the air layer, the nature of the two surfaces and the
temperature. Fortunately, the dependence on the temperature may be neglected in building
physics. Furthermore, it suffices to distinguish between metallic and non-metallic
surfaces. So if we restrict ourselves to, say, vertical air layers with non-metallic
surfaces, we can simply determine (e.g. from measurements) a heat resistance
Rnon-met which depends only on the air layer thickness and which comprises
all transport phenomena.


Now, for WUFI the effective heat conductivity λ*
has to be chosen so that for an air layer with a given thickness the heat resistance
Rnon-met as
determined above results. Note: the thickness with wich the air layer is included in the
assembly for calculation need not (but can) be identical with the real thickness, since
the real thickness has already been allowed for in the specific choice of
Rnon-met.


The heat resistance of an air layer with the desired thickness, orientation (vertical,
horizontal) and surfaces (metallic, non-metallic) may be looked up in a relevant table.
Let's choose non-metallic surfaces here, since in building components non-metallic surfaces
are predominant, and call this value Rnon-met. We also choose an arbitrary
thickness Dx*, which shall be the thickness of the
air layer as inserted in WUFI's component assembly. Then 
  
 Rnon-met = Δx* /
λ*, 
  
therefore 
  
 λ* = Δx*
/ Rnon-met. 
  



Since water vapor diffusion and convective water vapor transport are based on analogous
mechanisms as heat conductivity and convective heat transport, the coefficients describing
vapor transport can be derived from the coefficients for heat transport, using similarity
relations. For vapor flow, we have formally: 
  
 -gv = Dc / µ* ·
Δc / Δx*
= Δc / S 
  
<TABLE>
<TR><TD>gv</TD>
<TD>[kg/m²s]</TD>
<TD>:</TD>
<TD>water vapor diffusion flux density</TD>
</TR>
<TR><TD>Dc</TD>
<TD>[m²/s]</TD>
<TD>:</TD>
<TD>concentration-related diffusion coefficient</TD>
</TR>
<TR><TD>µ*</TD>
<TD>[-]</TD>
<TD>:</TD>
<TD>effective water vapor diffusion resistance factor</TD>
</TR>
<TR><TD>c</TD>
<TD>[kg/m³]</TD>
<TD>:</TD>
<TD>water vapor concentration</TD>
</TR>
<TR><TD>Δx*</TD>
<TD>[m]</TD>
<TD>:</TD>
<TD>effective layer thickness</TD>
</TR>
<TR><TD>S</TD>
<TD>[m³/s²Pa]</TD>
<TD>:</TD>
<TD>water vapor diffusion resistance,</TD>
</TABLE>
  therefore 
    
 µ* = Dc · S / Δx* 
  
But we have 
  
 Dc = 0.083 · (T/273)1.81
≈ 0.09   [1], 
  
and, because of similarity relations, 
  
 S ≈ Rmet / 3.5   [2], 
  
where we have to use the heat resistance Rmet of air layers between metallic
surfaces (i.e., without radiation exchange), since we want to estimate the vapor diffusion
resistance and there is no transport mechanism analogous to radiation involved, in
contrast to the above case of heat transport.


Finally, we have the freedom to choose an arbitrary thickness
Δx* with which the layer is included in the component
assembly for calculation, since the real thickness was already allowed for in the choice
of the specific value for Rmet. 
  
 µ* = 0.09 · Rmet / (3.5 · Δx*) = 0.026 · Rmet / Δx* 
  


For vertical air layers, Rnon-met and Rmet may be taken
from this table (interpolated after [3]): 


<TABLE>
<TR><TD WIDTH="20"> </TD>
<TD>thickness</TD>
<TD WIDTH="10"> </TD>
<TD>Rnon-met</TD>
<TD WIDTH="10"> </TD>
<TD>Rmet</TD>
</TR>
<TR><TD> </TD>
<TD>[cm]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
</TR>
<TR><TD> </TD>
<TD COLSPAN="5"> <HR> </TD>
</TR>

<TR><TD> </TD>
<TD> 0</TD>
<TD> </TD>
<TD>0</TD>
<TD> </TD>
<TD>0</TD>
</TR>
<TR><TD> </TD>
<TD> 1</TD>
<TD> </TD>
<TD>0.140</TD>
<TD> </TD>
<TD>0.280</TD>
</TR>
<TR><TD> </TD>
<TD> 2</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
<TR><TD> </TD>
<TD> 3</TD>
<TD> </TD>
<TD>0.171</TD>
<TD> </TD>
<TD>0.526</TD>
</TR>
<TR><TD> </TD>
<TD> 4</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.590</TD>
</TR>
<TR><TD> </TD>
<TD> 5</TD>
<TD> </TD>
<TD>0.180</TD>
<TD> </TD>
<TD>0.620</TD>
</TR>
<TR><TD> </TD>
<TD> 6</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.627</TD>
</TR>
<TR><TD> </TD>
<TD> 7</TD>
<TD> </TD>
<TD>0.176</TD>
<TD> </TD>
<TD>0.623</TD>
</TR>
<TR><TD> </TD>
<TD> 8</TD>
<TD> </TD>
<TD>0.174</TD>
<TD> </TD>
<TD>0.613</TD>
</TR>
<TR><TD> </TD>
<TD> 9</TD>
<TD> </TD>
<TD>0.172</TD>
<TD> </TD>
<TD>0.598</TD>
</TR>
<TR><TD> </TD>
<TD>10</TD>
<TD> </TD>
<TD>0.170</TD>
<TD> </TD>
<TD>0.580</TD>
</TR>
<TR><TD> </TD>
<TD>11</TD>
<TD> </TD>
<TD>0.168</TD>
<TD> </TD>
<TD>0.557</TD>
</TR>
<TR><TD> </TD>
<TD>12</TD>
<TD> </TD>
<TD>0.166</TD>
<TD> </TD>
<TD>0.530</TD>
</TR>
<TR><TD> </TD>
<TD>13</TD>
<TD> </TD>
<TD>0.164</TD>
<TD> </TD>
<TD>0.501</TD>
</TR>
<TR><TD> </TD>
<TD>14</TD>
<TD> </TD>
<TD>0.162</TD>
<TD> </TD>
<TD>0.468</TD>
</TR>
<TR><TD> </TD>
<TD>15</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
</TABLE>

The other [[Details:BasicMaterialData | basic material parameters]] may be determined
according to the following:

* if Δx* was chosen not equal to the real thickness, multiplication of the 'bulk density' 1.29 kg/m³ by (real thickness)/Δx* results in the correct heat capacity;
* the 'porosity' should be chosen very high (e.g. 0.999 m³/m³);
* the specific heat capacity by mass of the air layer is 1 kJ/kgK, even if Δx* is chosen not equal to the real thickness.


For the graphical display of the [[1D:Dialog_Assembly | component assembly]], it
will be advisable to choose Dx* equal to the real
thickness. Note however that if you want to repeat the calculation with an air layer of
a different thickness, it is not sufficient to simply adapt the layer thickness in the
component assembly. Instead, l* and
µ* have to be newly determined from scratch. 
  


Regarding the 'moisture storage function' of air layers, see the
[[Details:MoistureStorageFunction | reference: Moisture Storage Function]].


The definition of the diffusion resistance factor (µ-value) is discussed in the
[[Details:WaterVaporDiffusion | reference: Water Vapor Diffusion]].


=== Literature: ===
[1] Schirmer, R.: Die Diffusionszahl von Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177. 
  
[2] Illig, W.: Die Größe der Wasserdampfübergangszahl bei Diffusionsvorgängen in Wänden von Wohnungen, Stallungen und Kühlräumen, Gesundheitsingenieur 73 (1952), H. 7/8, p. 124-127. 
  
[3]Gösele, K., Schüle, W.: Schall·Wärme·Feuchte. Bauverlag 1989.

Details:AirLayers

2009-03-25T09:49:11Z

Barbara: /* Air Layers */

= Air Layers =

WUFI can also include air layers in the building component. It does not simulate the
air convection (which would not make much sense in one dimension anyway), but it allows
for the air layer as a resistance to heat and moisture flows.


In addition to heat conduction, in air layers heat can also be transferred by convection
and radiation. In addition to water vapor diffusion, in air layers water vapor can also
be transferred by convection. Since WUFI is primarily intended for solid materials, it
only allows for heat conduction and water vapor diffusion (plus liquid transport, which
is not relevant here). However, the additional transport phenomena can be included by
adjusting the
[[Details:BasicMaterialData | heat conductivity]] and the
[[Details:BasicMaterialData | diffusion resistance]] so that the correct heat
and vapor flows result from the calculation.


The method is based on the following considerations which are valid for
non-ventilated air layers. (No general treatment is possible for ventilated air
layers; they may even exhibit the same conditions as the exterior air. Building
components outward from the air layer may then be disregarded except for their shielding
of rain and radiation.)


The relative contributions of heat conduction, convection and radiation are dependent on
the thickness and orientation of the air layer, the nature of the two surfaces and the
temperature. Fortunately, the dependence on the temperature may be neglected in building
physics. Furthermore, it suffices to distinguish between metallic and non-metallic
surfaces. So if we restrict ourselves to, say, vertical air layers with non-metallic
surfaces, we can simply determine (e.g. from measurements) a heat resistance
Rnon-met which depends only on the air layer thickness and which comprises
all transport phenomena.


Now, for WUFI the effective heat conductivity λ*
has to be chosen so that for an air layer with a given thickness the heat resistance
Rnon-met as
determined above results. Note: the thickness with wich the air layer is included in the
assembly for calculation need not (but can) be identical with the real thickness, since
the real thickness has already been allowed for in the specific choice of
Rnon-met.


The heat resistance of an air layer with the desired thickness, orientation (vertical,
horizontal) and surfaces (metallic, non-metallic) may be looked up in a relevant table.
Let's choose non-metallic surfaces here, since in building components non-metallic surfaces
are predominant, and call this value Rnon-met. We also choose an arbitrary
thickness Dx*, which shall be the thickness of the
air layer as inserted in WUFI's component assembly. Then 
  
 Rnon-met = Δx* /
λ*, 
  
therefore 
  
 λ* = Δx*
/ Rnon-met. 
  



Since water vapor diffusion and convective water vapor transport are based on analogous
mechanisms as heat conductivity and convective heat transport, the coefficients describing
vapor transport can be derived from the coefficients for heat transport, using similarity
relations. For vapor flow, we have formally: 
  
 -gv = Dc / µ* ·
Δc / Δx*
= Δc / S 
  
<TABLE>
<TR><TD>gv</TD>
<TD>[kg/m²s]</TD>
<TD>:</TD>
<TD>water vapor diffusion flux density</TD>
</TR>
<TR><TD>Dc</TD>
<TD>[m²/s]</TD>
<TD>:</TD>
<TD>concentration-related diffusion coefficient</TD>
</TR>
<TR><TD>µ*</TD>
<TD>[-]</TD>
<TD>:</TD>
<TD>effective water vapor diffusion resistance factor</TD>
</TR>
<TR><TD>c</TD>
<TD>[kg/m³]</TD>
<TD>:</TD>
<TD>water vapor concentration</TD>
</TR>
<TR><TD>Δx*</TD>
<TD>[m]</TD>
<TD>:</TD>
<TD>effective layer thickness</TD>
</TR>
<TR><TD>S</TD>
<TD>[m³/s²Pa]</TD>
<TD>:</TD>
<TD>water vapor diffusion resistance,</TD>
</TABLE>
  therefore 
    
 µ* = Dc · S / Δx* 
  
But we have 
  
 Dc = 0.083 · (T/273)1.81
≈ 0.09   [1], 
  
and, because of similarity relations, 
  
 S ≈ Rmet / 3.5   [2], 
  
where we have to use the heat resistance Rmet of air layers between metallic
surfaces (i.e., without radiation exchange), since we want to estimate the vapor diffusion
resistance and there is no transport mechanism analogous to radiation involved, in
contrast to the above case of heat transport.


Finally, we have the freedom to choose an arbitrary thickness
Δx* with which the layer is included in the component
assembly for calculation, since the real thickness was already allowed for in the choice
of the specific value for Rmet. 
  
 µ* = 0.09 · Rmet / (3.5 · Δx*) = 0.026 · Rmet / Δx* 
  


For vertical air layers, Rnon-met and Rmet may be taken
from this table (interpolated after [3]): 


<TABLE>
<TR><TD WIDTH="20"> </TD>
<TD>thickness</TD>
<TD WIDTH="10"> </TD>
<TD>Rnon-met</TD>
<TD WIDTH="10"> </TD>
<TD>Rmet</TD>
</TR>
<TR><TD> </TD>
<TD>[cm]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
</TR>
<TR><TD> </TD>
<TD COLSPAN="5"> <HR> </TD>
</TR>

<TR><TD> </TD>
<TD> 0</TD>
<TD> </TD>
<TD>0</TD>
<TD> </TD>
<TD>0</TD>
</TR>
<TR><TD> </TD>
<TD> 1</TD>
<TD> </TD>
<TD>0.140</TD>
<TD> </TD>
<TD>0.280</TD>
</TR>
<TR><TD> </TD>
<TD> 2</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
<TR><TD> </TD>
<TD> 3</TD>
<TD> </TD>
<TD>0.171</TD>
<TD> </TD>
<TD>0.526</TD>
</TR>
<TR><TD> </TD>
<TD> 4</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.590</TD>
</TR>
<TR><TD> </TD>
<TD> 5</TD>
<TD> </TD>
<TD>0.180</TD>
<TD> </TD>
<TD>0.620</TD>
</TR>
<TR><TD> </TD>
<TD> 6</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.627</TD>
</TR>
<TR><TD> </TD>
<TD> 7</TD>
<TD> </TD>
<TD>0.176</TD>
<TD> </TD>
<TD>0.623</TD>
</TR>
<TR><TD> </TD>
<TD> 8</TD>
<TD> </TD>
<TD>0.174</TD>
<TD> </TD>
<TD>0.613</TD>
</TR>
<TR><TD> </TD>
<TD> 9</TD>
<TD> </TD>
<TD>0.172</TD>
<TD> </TD>
<TD>0.598</TD>
</TR>
<TR><TD> </TD>
<TD>10</TD>
<TD> </TD>
<TD>0.170</TD>
<TD> </TD>
<TD>0.580</TD>
</TR>
<TR><TD> </TD>
<TD>11</TD>
<TD> </TD>
<TD>0.168</TD>
<TD> </TD>
<TD>0.557</TD>
</TR>
<TR><TD> </TD>
<TD>12</TD>
<TD> </TD>
<TD>0.166</TD>
<TD> </TD>
<TD>0.530</TD>
</TR>
<TR><TD> </TD>
<TD>13</TD>
<TD> </TD>
<TD>0.164</TD>
<TD> </TD>
<TD>0.501</TD>
</TR>
<TR><TD> </TD>
<TD>14</TD>
<TD> </TD>
<TD>0.162</TD>
<TD> </TD>
<TD>0.468</TD>
</TR>
<TR><TD> </TD>
<TD>15</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
</TABLE>

The other [[Details:BasicMaterialData | basic material parameters]] may be determined
according to the following:

* if Dx* was chosen not equal to the real thickness, multiplication of the 'bulk density' 1.29 kg/m³ by (real thickness)/Dx* results in the correct heat capacity;
* the 'porosity' should be chosen very high (e.g. 0.999 m³/m³);
* the specific heat capacity by mass of the air layer is 1 kJ/kgK, even if Dx* is chosen not equal to the real thickness.


For the graphical display of the [[1D:Dialog_Assembly | component assembly]], it
will be advisable to choose Dx* equal to the real
thickness. Note however that if you want to repeat the calculation with an air layer of
a different thickness, it is not sufficient to simply adapt the layer thickness in the
component assembly. Instead, l* and
µ* have to be newly determined from scratch. 
  


Regarding the 'moisture storage function' of air layers, see the
[[Details:MoistureStorageFunction | reference: Moisture Storage Function]].


The definition of the diffusion resistance factor (µ-value) is discussed in the
[[Details:WaterVaporDiffusion | reference: Water Vapor Diffusion]].


=== Literature: ===
[1] Schirmer, R.: Die Diffusionszahl von Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177. 
  
[2] Illig, W.: Die Größe der Wasserdampfübergangszahl bei Diffusionsvorgängen in Wänden von Wohnungen, Stallungen und Kühlräumen, Gesundheitsingenieur 73 (1952), H. 7/8, p. 124-127. 
  
[3]Gösele, K., Schüle, W.: Schall·Wärme·Feuchte. Bauverlag 1989.

Details:AirLayers

2009-03-25T09:46:17Z

Barbara: /* Air Layers */

= Air Layers =

WUFI can also include air layers in the building component. It does not simulate the
air convection (which would not make much sense in one dimension anyway), but it allows
for the air layer as a resistance to heat and moisture flows.


In addition to heat conduction, in air layers heat can also be transferred by convection
and radiation. In addition to water vapor diffusion, in air layers water vapor can also
be transferred by convection. Since WUFI is primarily intended for solid materials, it
only allows for heat conduction and water vapor diffusion (plus liquid transport, which
is not relevant here). However, the additional transport phenomena can be included by
adjusting the
[[Details:BasicMaterialData | heat conductivity]] and the
[[Details:BasicMaterialData | diffusion resistance]] so that the correct heat
and vapor flows result from the calculation.


The method is based on the following considerations which are valid for
non-ventilated air layers. (No general treatment is possible for ventilated air
layers; they may even exhibit the same conditions as the exterior air. Building
components outward from the air layer may then be disregarded except for their shielding
of rain and radiation.)


The relative contributions of heat conduction, convection and radiation are dependent on
the thickness and orientation of the air layer, the nature of the two surfaces and the
temperature. Fortunately, the dependence on the temperature may be neglected in building
physics. Furthermore, it suffices to distinguish between metallic and non-metallic
surfaces. So if we restrict ourselves to, say, vertical air layers with non-metallic
surfaces, we can simply determine (e.g. from measurements) a heat resistance
Rnon-met which depends only on the air layer thickness and which comprises
all transport phenomena.


Now, for WUFI the effective heat conductivity λ*
has to be chosen so that for an air layer with a given thickness the heat resistance
Rnon-met as
determined above results. Note: the thickness with wich the air layer is included in the
assembly for calculation need not (but can) be identical with the real thickness, since
the real thickness has already been allowed for in the specific choice of
Rnon-met.


The heat resistance of an air layer with the desired thickness, orientation (vertical,
horizontal) and surfaces (metallic, non-metallic) may be looked up in a relevant table.
Let's choose non-metallic surfaces here, since in building components non-metallic surfaces
are predominant, and call this value Rnon-met. We also choose an arbitrary
thickness Dx*, which shall be the thickness of the
air layer as inserted in WUFI's component assembly. Then 
  
 Rnon-met = Δx* /
λ*, 
  
therefore 
  
 λ* = Δx*
/ Rnon-met. 
  



Since water vapor diffusion and convective water vapor transport are based on analogous
mechanisms as heat conductivity and convective heat transport, the coefficients describing
vapor transport can be derived from the coefficients for heat transport, using similarity
relations. For vapor flow, we have formally: 
  
 -gv = Dc / µ* ·
Δc / Δx*
= Δc / S 
  
<TABLE>
<TR><TD>gv</TD>
<TD>[kg/m²s]</TD>
<TD>:</TD>
<TD>water vapor diffusion flux density</TD>
</TR>
<TR><TD>Dc</TD>
<TD>[m²/s]</TD>
<TD>:</TD>
<TD>concentration-related diffusion coefficient</TD>
</TR>
<TR><TD>µ*</TD>
<TD>[-]</TD>
<TD>:</TD>
<TD>effective water vapor diffusion resistance factor</TD>
</TR>
<TR><TD>c</TD>
<TD>[kg/m³]</TD>
<TD>:</TD>
<TD>water vapor concentration</TD>
</TR>
<TR><TD>Δx*</TD>
<TD>[m]</TD>
<TD>:</TD>
<TD>effective layer thickness</TD>
</TR>
<TR><TD>S</TD>
<TD>[m³/s²Pa]</TD>
<TD>:</TD>
<TD>water vapor diffusion resistance,</TD>
</TABLE>
  therefore 
    
 µ* = Dc · S / Δx* 
  
But we have 
  
 Dc = 0.083 · (T/273)1.81
≈ 0.09   [1], 
  
and, because of similarity relations, 
  
 S ≈ Rmet / 3.5   [2], 
  
where we have to use the heat resistance Rmet of air layers between metallic
surfaces (i.e., without radiation exchange), since we want to estimate the vapor diffusion
resistance and there is no transport mechanism analogous to radiation involved, in
contrast to the above case of heat transport.


Finally, we have the freedom to choose an arbitrary thickness
Dx* with which the layer is included in the component
assembly for calculation, since the real thickness was already allowed for in the choice
of the specific value for Rmet. 
  
 &micro* = 0.09 · Rmet / (3.5 · Dx*) = 0.026 · Rmet / Dx* 
  


For vertical air layers, Rnon-met and Rmet may be taken
from this table (interpolated after [3]): 


<TABLE>
<TR><TD WIDTH="20"> </TD>
<TD>thickness</TD>
<TD WIDTH="10"> </TD>
<TD>Rnon-met</TD>
<TD WIDTH="10"> </TD>
<TD>Rmet</TD>
</TR>
<TR><TD> </TD>
<TD>[cm]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
</TR>
<TR><TD> </TD>
<TD COLSPAN="5"> <HR> </TD>
</TR>

<TR><TD> </TD>
<TD> 0</TD>
<TD> </TD>
<TD>0</TD>
<TD> </TD>
<TD>0</TD>
</TR>
<TR><TD> </TD>
<TD> 1</TD>
<TD> </TD>
<TD>0.140</TD>
<TD> </TD>
<TD>0.280</TD>
</TR>
<TR><TD> </TD>
<TD> 2</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
<TR><TD> </TD>
<TD> 3</TD>
<TD> </TD>
<TD>0.171</TD>
<TD> </TD>
<TD>0.526</TD>
</TR>
<TR><TD> </TD>
<TD> 4</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.590</TD>
</TR>
<TR><TD> </TD>
<TD> 5</TD>
<TD> </TD>
<TD>0.180</TD>
<TD> </TD>
<TD>0.620</TD>
</TR>
<TR><TD> </TD>
<TD> 6</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.627</TD>
</TR>
<TR><TD> </TD>
<TD> 7</TD>
<TD> </TD>
<TD>0.176</TD>
<TD> </TD>
<TD>0.623</TD>
</TR>
<TR><TD> </TD>
<TD> 8</TD>
<TD> </TD>
<TD>0.174</TD>
<TD> </TD>
<TD>0.613</TD>
</TR>
<TR><TD> </TD>
<TD> 9</TD>
<TD> </TD>
<TD>0.172</TD>
<TD> </TD>
<TD>0.598</TD>
</TR>
<TR><TD> </TD>
<TD>10</TD>
<TD> </TD>
<TD>0.170</TD>
<TD> </TD>
<TD>0.580</TD>
</TR>
<TR><TD> </TD>
<TD>11</TD>
<TD> </TD>
<TD>0.168</TD>
<TD> </TD>
<TD>0.557</TD>
</TR>
<TR><TD> </TD>
<TD>12</TD>
<TD> </TD>
<TD>0.166</TD>
<TD> </TD>
<TD>0.530</TD>
</TR>
<TR><TD> </TD>
<TD>13</TD>
<TD> </TD>
<TD>0.164</TD>
<TD> </TD>
<TD>0.501</TD>
</TR>
<TR><TD> </TD>
<TD>14</TD>
<TD> </TD>
<TD>0.162</TD>
<TD> </TD>
<TD>0.468</TD>
</TR>
<TR><TD> </TD>
<TD>15</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
</TABLE>

The other [[Details:BasicMaterialData | basic material parameters]] may be determined
according to the following:

* if Dx* was chosen not equal to the real thickness, multiplication of the 'bulk density' 1.29 kg/m³ by (real thickness)/Dx* results in the correct heat capacity;
* the 'porosity' should be chosen very high (e.g. 0.999 m³/m³);
* the specific heat capacity by mass of the air layer is 1 kJ/kgK, even if Dx* is chosen not equal to the real thickness.


For the graphical display of the [[1D:Dialog_Assembly | component assembly]], it
will be advisable to choose Dx* equal to the real
thickness. Note however that if you want to repeat the calculation with an air layer of
a different thickness, it is not sufficient to simply adapt the layer thickness in the
component assembly. Instead, l* and
µ* have to be newly determined from scratch. 
  


Regarding the 'moisture storage function' of air layers, see the
[[Details:MoistureStorageFunction | reference: Moisture Storage Function]].


The definition of the diffusion resistance factor (µ-value) is discussed in the
[[Details:WaterVaporDiffusion | reference: Water Vapor Diffusion]].


=== Literature: ===
[1] Schirmer, R.: Die Diffusionszahl von Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177. 
  
[2] Illig, W.: Die Größe der Wasserdampfübergangszahl bei Diffusionsvorgängen in Wänden von Wohnungen, Stallungen und Kühlräumen, Gesundheitsingenieur 73 (1952), H. 7/8, p. 124-127. 
  
[3]Gösele, K., Schüle, W.: Schall·Wärme·Feuchte. Bauverlag 1989.

Details:AirLayers

2009-03-25T09:42:58Z

Barbara: /* Air Layers */

= Air Layers =

WUFI can also include air layers in the building component. It does not simulate the
air convection (which would not make much sense in one dimension anyway), but it allows
for the air layer as a resistance to heat and moisture flows.


In addition to heat conduction, in air layers heat can also be transferred by convection
and radiation. In addition to water vapor diffusion, in air layers water vapor can also
be transferred by convection. Since WUFI is primarily intended for solid materials, it
only allows for heat conduction and water vapor diffusion (plus liquid transport, which
is not relevant here). However, the additional transport phenomena can be included by
adjusting the
[[Details:BasicMaterialData | heat conductivity]] and the
[[Details:BasicMaterialData | diffusion resistance]] so that the correct heat
and vapor flows result from the calculation.


The method is based on the following considerations which are valid for
non-ventilated air layers. (No general treatment is possible for ventilated air
layers; they may even exhibit the same conditions as the exterior air. Building
components outward from the air layer may then be disregarded except for their shielding
of rain and radiation.)


The relative contributions of heat conduction, convection and radiation are dependent on
the thickness and orientation of the air layer, the nature of the two surfaces and the
temperature. Fortunately, the dependence on the temperature may be neglected in building
physics. Furthermore, it suffices to distinguish between metallic and non-metallic
surfaces. So if we restrict ourselves to, say, vertical air layers with non-metallic
surfaces, we can simply determine (e.g. from measurements) a heat resistance
Rnon-met which depends only on the air layer thickness and which comprises
all transport phenomena.


Now, for WUFI the effective heat conductivity λ*
has to be chosen so that for an air layer with a given thickness the heat resistance
Rnon-met as
determined above results. Note: the thickness with wich the air layer is included in the
assembly for calculation need not (but can) be identical with the real thickness, since
the real thickness has already been allowed for in the specific choice of
Rnon-met.


The heat resistance of an air layer with the desired thickness, orientation (vertical,
horizontal) and surfaces (metallic, non-metallic) may be looked up in a relevant table.
Let's choose non-metallic surfaces here, since in building components non-metallic surfaces
are predominant, and call this value Rnon-met. We also choose an arbitrary
thickness Dx*, which shall be the thickness of the
air layer as inserted in WUFI's component assembly. Then 
  
 Rnon-met = Δx* /
λ*, 
  
therefore 
  
 λ* = Δx*
/ Rnon-met. 
  



Since water vapor diffusion and convective water vapor transport are based on analogous
mechanisms as heat conductivity and convective heat transport, the coefficients describing
vapor transport can be derived from the coefficients for heat transport, using similarity
relations. For vapor flow, we have formally: 
  
 -gv = Dc / µ* ·
Δc / Δx*
= Δc / S 
  
<TABLE>
<TR><TD>gv</TD>
<TD>[kg/m²s]</TD>
<TD>:</TD>
<TD>water vapor diffusion flux density</TD>
</TR>
<TR><TD>Dc</TD>
<TD>[m²/s]</TD>
<TD>:</TD>
<TD>concentration-related diffusion coefficient</TD>
</TR>
<TR><TD>µ*</TD>
<TD>[-]</TD>
<TD>:</TD>
<TD>effective water vapor diffusion resistance factor</TD>
</TR>
<TR><TD>c</TD>
<TD>[kg/m³]</TD>
<TD>:</TD>
<TD>water vapor concentration</TD>
</TR>
<TR><TD>Δx*</TD>
<TD>[m]</TD>
<TD>:</TD>
<TD>effective layer thickness</TD>
</TR>
<TR><TD>S</TD>
<TD>[m³/s²Pa]</TD>
<TD>:</TD>
<TD>water vapor diffusion resistance,</TD>
</TABLE>
  
therefore 
  
  
 µ* = Dc · S / Dx* 
  
But we have 
  
 Dc = 0.083 · (T/273)1.81
≈ 0.09   [1], 
  
and, because of similarity relations, 
  
 S ≈ Rmet / 3.5   [2], 
  
where we have to use the heat resistance Rmet of air layers between metallic
surfaces (i.e., without radiation exchange), since we want to estimate the vapor diffusion
resistance and there is no transport mechanism analogous to radiation involved, in
contrast to the above case of heat transport.


Finally, we have the freedom to choose an arbitrary thickness
Dx* with which the layer is included in the component
assembly for calculation, since the real thickness was already allowed for in the choice
of the specific value for Rmet. 
  
 &micro* = 0.09 · Rmet / (3.5 · Dx*) = 0.026 · Rmet / Dx* 
  


For vertical air layers, Rnon-met and Rmet may be taken
from this table (interpolated after [3]): 


<TABLE>
<TR><TD WIDTH="20"> </TD>
<TD>thickness</TD>
<TD WIDTH="10"> </TD>
<TD>Rnon-met</TD>
<TD WIDTH="10"> </TD>
<TD>Rmet</TD>
</TR>
<TR><TD> </TD>
<TD>[cm]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
</TR>
<TR><TD> </TD>
<TD COLSPAN="5"> <HR> </TD>
</TR>

<TR><TD> </TD>
<TD> 0</TD>
<TD> </TD>
<TD>0</TD>
<TD> </TD>
<TD>0</TD>
</TR>
<TR><TD> </TD>
<TD> 1</TD>
<TD> </TD>
<TD>0.140</TD>
<TD> </TD>
<TD>0.280</TD>
</TR>
<TR><TD> </TD>
<TD> 2</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
<TR><TD> </TD>
<TD> 3</TD>
<TD> </TD>
<TD>0.171</TD>
<TD> </TD>
<TD>0.526</TD>
</TR>
<TR><TD> </TD>
<TD> 4</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.590</TD>
</TR>
<TR><TD> </TD>
<TD> 5</TD>
<TD> </TD>
<TD>0.180</TD>
<TD> </TD>
<TD>0.620</TD>
</TR>
<TR><TD> </TD>
<TD> 6</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.627</TD>
</TR>
<TR><TD> </TD>
<TD> 7</TD>
<TD> </TD>
<TD>0.176</TD>
<TD> </TD>
<TD>0.623</TD>
</TR>
<TR><TD> </TD>
<TD> 8</TD>
<TD> </TD>
<TD>0.174</TD>
<TD> </TD>
<TD>0.613</TD>
</TR>
<TR><TD> </TD>
<TD> 9</TD>
<TD> </TD>
<TD>0.172</TD>
<TD> </TD>
<TD>0.598</TD>
</TR>
<TR><TD> </TD>
<TD>10</TD>
<TD> </TD>
<TD>0.170</TD>
<TD> </TD>
<TD>0.580</TD>
</TR>
<TR><TD> </TD>
<TD>11</TD>
<TD> </TD>
<TD>0.168</TD>
<TD> </TD>
<TD>0.557</TD>
</TR>
<TR><TD> </TD>
<TD>12</TD>
<TD> </TD>
<TD>0.166</TD>
<TD> </TD>
<TD>0.530</TD>
</TR>
<TR><TD> </TD>
<TD>13</TD>
<TD> </TD>
<TD>0.164</TD>
<TD> </TD>
<TD>0.501</TD>
</TR>
<TR><TD> </TD>
<TD>14</TD>
<TD> </TD>
<TD>0.162</TD>
<TD> </TD>
<TD>0.468</TD>
</TR>
<TR><TD> </TD>
<TD>15</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
</TABLE>

The other [[Details:BasicMaterialData | basic material parameters]] may be determined
according to the following:

* if Dx* was chosen not equal to the real thickness, multiplication of the 'bulk density' 1.29 kg/m³ by (real thickness)/Dx* results in the correct heat capacity;
* the 'porosity' should be chosen very high (e.g. 0.999 m³/m³);
* the specific heat capacity by mass of the air layer is 1 kJ/kgK, even if Dx* is chosen not equal to the real thickness.


For the graphical display of the [[1D:Dialog_Assembly | component assembly]], it
will be advisable to choose Dx* equal to the real
thickness. Note however that if you want to repeat the calculation with an air layer of
a different thickness, it is not sufficient to simply adapt the layer thickness in the
component assembly. Instead, l* and
µ* have to be newly determined from scratch. 
  


Regarding the 'moisture storage function' of air layers, see the
[[Details:MoistureStorageFunction | reference: Moisture Storage Function]].


The definition of the diffusion resistance factor (µ-value) is discussed in the
[[Details:WaterVaporDiffusion | reference: Water Vapor Diffusion]].


=== Literature: ===
[1] Schirmer, R.: Die Diffusionszahl von Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177. 
  
[2] Illig, W.: Die Größe der Wasserdampfübergangszahl bei Diffusionsvorgängen in Wänden von Wohnungen, Stallungen und Kühlräumen, Gesundheitsingenieur 73 (1952), H. 7/8, p. 124-127. 
  
[3]Gösele, K., Schüle, W.: Schall·Wärme·Feuchte. Bauverlag 1989.

Details:AirLayers

2009-03-25T09:41:00Z

Barbara: /* Air Layers */

= Air Layers =

WUFI can also include air layers in the building component. It does not simulate the
air convection (which would not make much sense in one dimension anyway), but it allows
for the air layer as a resistance to heat and moisture flows.


In addition to heat conduction, in air layers heat can also be transferred by convection
and radiation. In addition to water vapor diffusion, in air layers water vapor can also
be transferred by convection. Since WUFI is primarily intended for solid materials, it
only allows for heat conduction and water vapor diffusion (plus liquid transport, which
is not relevant here). However, the additional transport phenomena can be included by
adjusting the
[[Details:BasicMaterialData | heat conductivity]] and the
[[Details:BasicMaterialData | diffusion resistance]] so that the correct heat
and vapor flows result from the calculation.


The method is based on the following considerations which are valid for
non-ventilated air layers. (No general treatment is possible for ventilated air
layers; they may even exhibit the same conditions as the exterior air. Building
components outward from the air layer may then be disregarded except for their shielding
of rain and radiation.)


The relative contributions of heat conduction, convection and radiation are dependent on
the thickness and orientation of the air layer, the nature of the two surfaces and the
temperature. Fortunately, the dependence on the temperature may be neglected in building
physics. Furthermore, it suffices to distinguish between metallic and non-metallic
surfaces. So if we restrict ourselves to, say, vertical air layers with non-metallic
surfaces, we can simply determine (e.g. from measurements) a heat resistance
Rnon-met which depends only on the air layer thickness and which comprises
all transport phenomena.


Now, for WUFI the effective heat conductivity λ*
has to be chosen so that for an air layer with a given thickness the heat resistance
Rnon-met as
determined above results. Note: the thickness with wich the air layer is included in the
assembly for calculation need not (but can) be identical with the real thickness, since
the real thickness has already been allowed for in the specific choice of
Rnon-met.


The heat resistance of an air layer with the desired thickness, orientation (vertical,
horizontal) and surfaces (metallic, non-metallic) may be looked up in a relevant table.
Let's choose non-metallic surfaces here, since in building components non-metallic surfaces
are predominant, and call this value Rnon-met. We also choose an arbitrary
thickness Dx*, which shall be the thickness of the
air layer as inserted in WUFI's component assembly. Then 
  
 Rnon-met = Δx* /
λ*, 
  
therefore 
  
 λ* = Δx*
/ Rnon-met. 
  



Since water vapor diffusion and convective water vapor transport are based on analogous
mechanisms as heat conductivity and convective heat transport, the coefficients describing
vapor transport can be derived from the coefficients for heat transport, using similarity
relations. For vapor flow, we have formally: 
  
 -gv = Dc / µ* ·
Dc / Dx*
= Dc / S 
  
<TABLE>
<TR><TD>gv</TD>
<TD>[kg/m²s]</TD>
<TD>:</TD>
<TD>water vapor diffusion flux density</TD>
</TR>
<TR><TD>Dc</TD>
<TD>[m²/s]</TD>
<TD>:</TD>
<TD>concentration-related diffusion coefficient</TD>
</TR>
<TR><TD>µ*</TD>
<TD>[-]</TD>
<TD>:</TD>
<TD>effective water vapor diffusion resistance factor</TD>
</TR>
<TR><TD>c</TD>
<TD>[kg/m³]</TD>
<TD>:</TD>
<TD>water vapor concentration</TD>
</TR>
<TR><TD>Dx*</TD>
<TD>[m]</TD>
<TD>:</TD>
<TD>effective layer thickness</TD>
</TR>
<TR><TD>S</TD>
<TD>[m³/s²Pa]</TD>
<TD>:</TD>
<TD>water vapor diffusion resistance,</TD>
</TABLE>
  
therefore 
  
  
 µ* = Dc · S / Dx* 
  
But we have 
  
 Dc = 0.083 · (T/273)1.81
≈ 0.09   [1], 
  
and, because of similarity relations, 
  
 S ≈ Rmet / 3.5   [2], 
  
where we have to use the heat resistance Rmet of air layers between metallic
surfaces (i.e., without radiation exchange), since we want to estimate the vapor diffusion
resistance and there is no transport mechanism analogous to radiation involved, in
contrast to the above case of heat transport.


Finally, we have the freedom to choose an arbitrary thickness
Dx* with which the layer is included in the component
assembly for calculation, since the real thickness was already allowed for in the choice
of the specific value for Rmet. 
  
 &micro* = 0.09 · Rmet / (3.5 · Dx*) = 0.026 · Rmet / Dx* 
  


For vertical air layers, Rnon-met and Rmet may be taken
from this table (interpolated after [3]): 


<TABLE>
<TR><TD WIDTH="20"> </TD>
<TD>thickness</TD>
<TD WIDTH="10"> </TD>
<TD>Rnon-met</TD>
<TD WIDTH="10"> </TD>
<TD>Rmet</TD>
</TR>
<TR><TD> </TD>
<TD>[cm]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
</TR>
<TR><TD> </TD>
<TD COLSPAN="5"> <HR> </TD>
</TR>

<TR><TD> </TD>
<TD> 0</TD>
<TD> </TD>
<TD>0</TD>
<TD> </TD>
<TD>0</TD>
</TR>
<TR><TD> </TD>
<TD> 1</TD>
<TD> </TD>
<TD>0.140</TD>
<TD> </TD>
<TD>0.280</TD>
</TR>
<TR><TD> </TD>
<TD> 2</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
<TR><TD> </TD>
<TD> 3</TD>
<TD> </TD>
<TD>0.171</TD>
<TD> </TD>
<TD>0.526</TD>
</TR>
<TR><TD> </TD>
<TD> 4</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.590</TD>
</TR>
<TR><TD> </TD>
<TD> 5</TD>
<TD> </TD>
<TD>0.180</TD>
<TD> </TD>
<TD>0.620</TD>
</TR>
<TR><TD> </TD>
<TD> 6</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.627</TD>
</TR>
<TR><TD> </TD>
<TD> 7</TD>
<TD> </TD>
<TD>0.176</TD>
<TD> </TD>
<TD>0.623</TD>
</TR>
<TR><TD> </TD>
<TD> 8</TD>
<TD> </TD>
<TD>0.174</TD>
<TD> </TD>
<TD>0.613</TD>
</TR>
<TR><TD> </TD>
<TD> 9</TD>
<TD> </TD>
<TD>0.172</TD>
<TD> </TD>
<TD>0.598</TD>
</TR>
<TR><TD> </TD>
<TD>10</TD>
<TD> </TD>
<TD>0.170</TD>
<TD> </TD>
<TD>0.580</TD>
</TR>
<TR><TD> </TD>
<TD>11</TD>
<TD> </TD>
<TD>0.168</TD>
<TD> </TD>
<TD>0.557</TD>
</TR>
<TR><TD> </TD>
<TD>12</TD>
<TD> </TD>
<TD>0.166</TD>
<TD> </TD>
<TD>0.530</TD>
</TR>
<TR><TD> </TD>
<TD>13</TD>
<TD> </TD>
<TD>0.164</TD>
<TD> </TD>
<TD>0.501</TD>
</TR>
<TR><TD> </TD>
<TD>14</TD>
<TD> </TD>
<TD>0.162</TD>
<TD> </TD>
<TD>0.468</TD>
</TR>
<TR><TD> </TD>
<TD>15</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
</TABLE>

The other [[Details:BasicMaterialData | basic material parameters]] may be determined
according to the following:

* if Dx* was chosen not equal to the real thickness, multiplication of the 'bulk density' 1.29 kg/m³ by (real thickness)/Dx* results in the correct heat capacity;
* the 'porosity' should be chosen very high (e.g. 0.999 m³/m³);
* the specific heat capacity by mass of the air layer is 1 kJ/kgK, even if Dx* is chosen not equal to the real thickness.


For the graphical display of the [[1D:Dialog_Assembly | component assembly]], it
will be advisable to choose Dx* equal to the real
thickness. Note however that if you want to repeat the calculation with an air layer of
a different thickness, it is not sufficient to simply adapt the layer thickness in the
component assembly. Instead, l* and
µ* have to be newly determined from scratch. 
  


Regarding the 'moisture storage function' of air layers, see the
[[Details:MoistureStorageFunction | reference: Moisture Storage Function]].


The definition of the diffusion resistance factor (µ-value) is discussed in the
[[Details:WaterVaporDiffusion | reference: Water Vapor Diffusion]].


=== Literature: ===
[1] Schirmer, R.: Die Diffusionszahl von Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177. 
  
[2] Illig, W.: Die Größe der Wasserdampfübergangszahl bei Diffusionsvorgängen in Wänden von Wohnungen, Stallungen und Kühlräumen, Gesundheitsingenieur 73 (1952), H. 7/8, p. 124-127. 
  
[3]Gösele, K., Schüle, W.: Schall·Wärme·Feuchte. Bauverlag 1989.

Details:AirLayers

2009-03-25T09:38:41Z

Barbara: /* Air Layers */

= Air Layers =

WUFI can also include air layers in the building component. It does not simulate the
air convection (which would not make much sense in one dimension anyway), but it allows
for the air layer as a resistance to heat and moisture flows.


In addition to heat conduction, in air layers heat can also be transferred by convection
and radiation. In addition to water vapor diffusion, in air layers water vapor can also
be transferred by convection. Since WUFI is primarily intended for solid materials, it
only allows for heat conduction and water vapor diffusion (plus liquid transport, which
is not relevant here). However, the additional transport phenomena can be included by
adjusting the
[[Details:BasicMaterialData | heat conductivity]] and the
[[Details:BasicMaterialData | diffusion resistance]] so that the correct heat
and vapor flows result from the calculation.


The method is based on the following considerations which are valid for
non-ventilated air layers. (No general treatment is possible for ventilated air
layers; they may even exhibit the same conditions as the exterior air. Building
components outward from the air layer may then be disregarded except for their shielding
of rain and radiation.)


The relative contributions of heat conduction, convection and radiation are dependent on
the thickness and orientation of the air layer, the nature of the two surfaces and the
temperature. Fortunately, the dependence on the temperature may be neglected in building
physics. Furthermore, it suffices to distinguish between metallic and non-metallic
surfaces. So if we restrict ourselves to, say, vertical air layers with non-metallic
surfaces, we can simply determine (e.g. from measurements) a heat resistance
Rnon-met which depends only on the air layer thickness and which comprises
all transport phenomena.


Now, for WUFI the effective heat conductivity λ*
has to be chosen so that for an air layer with a given thickness the heat resistance
Rnon-met as
determined above results. Note: the thickness with wich the air layer is included in the
assembly for calculation need not (but can) be identical with the real thickness, since
the real thickness has already been allowed for in the specific choice of
Rnon-met.


The heat resistance of an air layer with the desired thickness, orientation (vertical,
horizontal) and surfaces (metallic, non-metallic) may be looked up in a relevant table.
Let's choose non-metallic surfaces here, since in building components non-metallic surfaces
are predominant, and call this value Rnon-met. We also choose an arbitrary
thickness Dx*, which shall be the thickness of the
air layer as inserted in WUFI's component assembly. Then 
  
 Rnon-met = Dx* /
l*, 
  
therefore 
  
 l* = Dx*
/ Rnon-met. 
  



Since water vapor diffusion and convective water vapor transport are based on analogous
mechanisms as heat conductivity and convective heat transport, the coefficients describing
vapor transport can be derived from the coefficients for heat transport, using similarity
relations. For vapor flow, we have formally: 
  
 -gv = Dc / µ* ·
Dc / Dx*
= Dc / S 
  
<TABLE>
<TR><TD>gv</TD>
<TD>[kg/m²s]</TD>
<TD>:</TD>
<TD>water vapor diffusion flux density</TD>
</TR>
<TR><TD>Dc</TD>
<TD>[m²/s]</TD>
<TD>:</TD>
<TD>concentration-related diffusion coefficient</TD>
</TR>
<TR><TD>µ*</TD>
<TD>[-]</TD>
<TD>:</TD>
<TD>effective water vapor diffusion resistance factor</TD>
</TR>
<TR><TD>c</TD>
<TD>[kg/m³]</TD>
<TD>:</TD>
<TD>water vapor concentration</TD>
</TR>
<TR><TD>Dx*</TD>
<TD>[m]</TD>
<TD>:</TD>
<TD>effective layer thickness</TD>
</TR>
<TR><TD>S</TD>
<TD>[m³/s²Pa]</TD>
<TD>:</TD>
<TD>water vapor diffusion resistance,</TD>
</TABLE>
  
therefore 
  
  
 µ* = Dc · S / Dx* 
  
But we have 
  
 Dc = 0.083 · (T/273)1.81
≈ 0.09   [1], 
  
and, because of similarity relations, 
  
 S ≈ Rmet / 3.5   [2], 
  
where we have to use the heat resistance Rmet of air layers between metallic
surfaces (i.e., without radiation exchange), since we want to estimate the vapor diffusion
resistance and there is no transport mechanism analogous to radiation involved, in
contrast to the above case of heat transport.


Finally, we have the freedom to choose an arbitrary thickness
Dx* with which the layer is included in the component
assembly for calculation, since the real thickness was already allowed for in the choice
of the specific value for Rmet. 
  
 &micro* = 0.09 · Rmet / (3.5 · Dx*) = 0.026 · Rmet / Dx* 
  


For vertical air layers, Rnon-met and Rmet may be taken
from this table (interpolated after [3]): 


<TABLE>
<TR><TD WIDTH="20"> </TD>
<TD>thickness</TD>
<TD WIDTH="10"> </TD>
<TD>Rnon-met</TD>
<TD WIDTH="10"> </TD>
<TD>Rmet</TD>
</TR>
<TR><TD> </TD>
<TD>[cm]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
</TR>
<TR><TD> </TD>
<TD COLSPAN="5"> <HR> </TD>
</TR>

<TR><TD> </TD>
<TD> 0</TD>
<TD> </TD>
<TD>0</TD>
<TD> </TD>
<TD>0</TD>
</TR>
<TR><TD> </TD>
<TD> 1</TD>
<TD> </TD>
<TD>0.140</TD>
<TD> </TD>
<TD>0.280</TD>
</TR>
<TR><TD> </TD>
<TD> 2</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
<TR><TD> </TD>
<TD> 3</TD>
<TD> </TD>
<TD>0.171</TD>
<TD> </TD>
<TD>0.526</TD>
</TR>
<TR><TD> </TD>
<TD> 4</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.590</TD>
</TR>
<TR><TD> </TD>
<TD> 5</TD>
<TD> </TD>
<TD>0.180</TD>
<TD> </TD>
<TD>0.620</TD>
</TR>
<TR><TD> </TD>
<TD> 6</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.627</TD>
</TR>
<TR><TD> </TD>
<TD> 7</TD>
<TD> </TD>
<TD>0.176</TD>
<TD> </TD>
<TD>0.623</TD>
</TR>
<TR><TD> </TD>
<TD> 8</TD>
<TD> </TD>
<TD>0.174</TD>
<TD> </TD>
<TD>0.613</TD>
</TR>
<TR><TD> </TD>
<TD> 9</TD>
<TD> </TD>
<TD>0.172</TD>
<TD> </TD>
<TD>0.598</TD>
</TR>
<TR><TD> </TD>
<TD>10</TD>
<TD> </TD>
<TD>0.170</TD>
<TD> </TD>
<TD>0.580</TD>
</TR>
<TR><TD> </TD>
<TD>11</TD>
<TD> </TD>
<TD>0.168</TD>
<TD> </TD>
<TD>0.557</TD>
</TR>
<TR><TD> </TD>
<TD>12</TD>
<TD> </TD>
<TD>0.166</TD>
<TD> </TD>
<TD>0.530</TD>
</TR>
<TR><TD> </TD>
<TD>13</TD>
<TD> </TD>
<TD>0.164</TD>
<TD> </TD>
<TD>0.501</TD>
</TR>
<TR><TD> </TD>
<TD>14</TD>
<TD> </TD>
<TD>0.162</TD>
<TD> </TD>
<TD>0.468</TD>
</TR>
<TR><TD> </TD>
<TD>15</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
</TABLE>

The other [[Details:BasicMaterialData | basic material parameters]] may be determined
according to the following:

* if Dx* was chosen not equal to the real thickness, multiplication of the 'bulk density' 1.29 kg/m³ by (real thickness)/Dx* results in the correct heat capacity;
* the 'porosity' should be chosen very high (e.g. 0.999 m³/m³);
* the specific heat capacity by mass of the air layer is 1 kJ/kgK, even if Dx* is chosen not equal to the real thickness.


For the graphical display of the [[1D:Dialog_Assembly | component assembly]], it
will be advisable to choose Dx* equal to the real
thickness. Note however that if you want to repeat the calculation with an air layer of
a different thickness, it is not sufficient to simply adapt the layer thickness in the
component assembly. Instead, l* and
µ* have to be newly determined from scratch. 
  


Regarding the 'moisture storage function' of air layers, see the
[[Details:MoistureStorageFunction | reference: Moisture Storage Function]].


The definition of the diffusion resistance factor (µ-value) is discussed in the
[[Details:WaterVaporDiffusion | reference: Water Vapor Diffusion]].


=== Literature: ===
[1] Schirmer, R.: Die Diffusionszahl von Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177. 
  
[2] Illig, W.: Die Größe der Wasserdampfübergangszahl bei Diffusionsvorgängen in Wänden von Wohnungen, Stallungen und Kühlräumen, Gesundheitsingenieur 73 (1952), H. 7/8, p. 124-127. 
  
[3]Gösele, K., Schüle, W.: Schall·Wärme·Feuchte. Bauverlag 1989.

Details:AirLayers

2009-03-25T09:37:04Z

Barbara: /* Air Layers */

= Air Layers =

WUFI can also include air layers in the building component. It does not simulate the
air convection (which would not make much sense in one dimension anyway), but it allows
for the air layer as a resistance to heat and moisture flows.


In addition to heat conduction, in air layers heat can also be transferred by convection
and radiation. In addition to water vapor diffusion, in air layers water vapor can also
be transferred by convection. Since WUFI is primarily intended for solid materials, it
only allows for heat conduction and water vapor diffusion (plus liquid transport, which
is not relevant here). However, the additional transport phenomena can be included by
adjusting the
[[Details:BasicMaterialData | heat conductivity]] and the
[[Details:BasicMaterialData | diffusion resistance]] so that the correct heat
and vapor flows result from the calculation.


The method is based on the following considerations which are valid for
non-ventilated air layers. (No general treatment is possible for ventilated air
layers; they may even exhibit the same conditions as the exterior air. Building
components outward from the air layer may then be disregarded except for their shielding
of rain and radiation.)


The relative contributions of heat conduction, convection and radiation are dependent on
the thickness and orientation of the air layer, the nature of the two surfaces and the
temperature. Fortunately, the dependence on the temperature may be neglected in building
physics. Furthermore, it suffices to distinguish between metallic and non-metallic
surfaces. So if we restrict ourselves to, say, vertical air layers with non-metallic
surfaces, we can simply determine (e.g. from measurements) a heat resistance
Rnon-met which depends only on the air layer thickness and which comprises
all transport phenomena.


Now, for WUFI the effective heat conductivity l*
has to be chosen so that for an air layer with a given thickness the heat resistance
Rnon-met as
determined above results. Note: the thickness with wich the air layer is included in the
assembly for calculation need not (but can) be identical with the real thickness, since
the real thickness has already been allowed for in the specific choice of
Rnon-met.


The heat resistance of an air layer with the desired thickness, orientation (vertical,
horizontal) and surfaces (metallic, non-metallic) may be looked up in a relevant table.
Let's choose non-metallic surfaces here, since in building components non-metallic surfaces
are predominant, and call this value Rnon-met. We also choose an arbitrary
thickness Dx*, which shall be the thickness of the
air layer as inserted in WUFI's component assembly. Then 
  
 Rnon-met = Dx* /
l*, 
  
therefore 
  
 l* = Dx*
/ Rnon-met. 
  



Since water vapor diffusion and convective water vapor transport are based on analogous
mechanisms as heat conductivity and convective heat transport, the coefficients describing
vapor transport can be derived from the coefficients for heat transport, using similarity
relations. For vapor flow, we have formally: 
  
 -gv = Dc / µ* ·
Dc / Dx*
= Dc / S 
  
<TABLE>
<TR><TD>gv</TD>
<TD>[kg/m²s]</TD>
<TD>:</TD>
<TD>water vapor diffusion flux density</TD>
</TR>
<TR><TD>Dc</TD>
<TD>[m²/s]</TD>
<TD>:</TD>
<TD>concentration-related diffusion coefficient</TD>
</TR>
<TR><TD>µ*</TD>
<TD>[-]</TD>
<TD>:</TD>
<TD>effective water vapor diffusion resistance factor</TD>
</TR>
<TR><TD>c</TD>
<TD>[kg/m³]</TD>
<TD>:</TD>
<TD>water vapor concentration</TD>
</TR>
<TR><TD>Dx*</TD>
<TD>[m]</TD>
<TD>:</TD>
<TD>effective layer thickness</TD>
</TR>
<TR><TD>S</TD>
<TD>[m³/s²Pa]</TD>
<TD>:</TD>
<TD>water vapor diffusion resistance,</TD>
</TABLE>
  
therefore 
  
  
 µ* = Dc · S / Dx* 
  
But we have 
  
 Dc = 0.083 · (T/273)1.81
≈ 0.09   [1], 
  
and, because of similarity relations, 
  
 S ≈ Rmet / 3.5   [2], 
  
where we have to use the heat resistance Rmet of air layers between metallic
surfaces (i.e., without radiation exchange), since we want to estimate the vapor diffusion
resistance and there is no transport mechanism analogous to radiation involved, in
contrast to the above case of heat transport.


Finally, we have the freedom to choose an arbitrary thickness
Dx* with which the layer is included in the component
assembly for calculation, since the real thickness was already allowed for in the choice
of the specific value for Rmet. 
  
 &micro* = 0.09 · Rmet / (3.5 · Dx*) = 0.026 · Rmet / Dx* 
  


For vertical air layers, Rnon-met and Rmet may be taken
from this table (interpolated after [3]): 


<TABLE>
<TR><TD WIDTH="20"> </TD>
<TD>thickness</TD>
<TD WIDTH="10"> </TD>
<TD>Rnon-met</TD>
<TD WIDTH="10"> </TD>
<TD>Rmet</TD>
</TR>
<TR><TD> </TD>
<TD>[cm]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
</TR>
<TR><TD> </TD>
<TD COLSPAN="5"> <HR> </TD>
</TR>

<TR><TD> </TD>
<TD> 0</TD>
<TD> </TD>
<TD>0</TD>
<TD> </TD>
<TD>0</TD>
</TR>
<TR><TD> </TD>
<TD> 1</TD>
<TD> </TD>
<TD>0.140</TD>
<TD> </TD>
<TD>0.280</TD>
</TR>
<TR><TD> </TD>
<TD> 2</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
<TR><TD> </TD>
<TD> 3</TD>
<TD> </TD>
<TD>0.171</TD>
<TD> </TD>
<TD>0.526</TD>
</TR>
<TR><TD> </TD>
<TD> 4</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.590</TD>
</TR>
<TR><TD> </TD>
<TD> 5</TD>
<TD> </TD>
<TD>0.180</TD>
<TD> </TD>
<TD>0.620</TD>
</TR>
<TR><TD> </TD>
<TD> 6</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.627</TD>
</TR>
<TR><TD> </TD>
<TD> 7</TD>
<TD> </TD>
<TD>0.176</TD>
<TD> </TD>
<TD>0.623</TD>
</TR>
<TR><TD> </TD>
<TD> 8</TD>
<TD> </TD>
<TD>0.174</TD>
<TD> </TD>
<TD>0.613</TD>
</TR>
<TR><TD> </TD>
<TD> 9</TD>
<TD> </TD>
<TD>0.172</TD>
<TD> </TD>
<TD>0.598</TD>
</TR>
<TR><TD> </TD>
<TD>10</TD>
<TD> </TD>
<TD>0.170</TD>
<TD> </TD>
<TD>0.580</TD>
</TR>
<TR><TD> </TD>
<TD>11</TD>
<TD> </TD>
<TD>0.168</TD>
<TD> </TD>
<TD>0.557</TD>
</TR>
<TR><TD> </TD>
<TD>12</TD>
<TD> </TD>
<TD>0.166</TD>
<TD> </TD>
<TD>0.530</TD>
</TR>
<TR><TD> </TD>
<TD>13</TD>
<TD> </TD>
<TD>0.164</TD>
<TD> </TD>
<TD>0.501</TD>
</TR>
<TR><TD> </TD>
<TD>14</TD>
<TD> </TD>
<TD>0.162</TD>
<TD> </TD>
<TD>0.468</TD>
</TR>
<TR><TD> </TD>
<TD>15</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
</TABLE>

The other [[Details:BasicMaterialData | basic material parameters]] may be determined
according to the following:

* if Dx* was chosen not equal to the real thickness, multiplication of the 'bulk density' 1.29 kg/m³ by (real thickness)/Dx* results in the correct heat capacity;
* the 'porosity' should be chosen very high (e.g. 0.999 m³/m³);
* the specific heat capacity by mass of the air layer is 1 kJ/kgK, even if Dx* is chosen not equal to the real thickness.


For the graphical display of the [[1D:Dialog_Assembly | component assembly]], it
will be advisable to choose Dx* equal to the real
thickness. Note however that if you want to repeat the calculation with an air layer of
a different thickness, it is not sufficient to simply adapt the layer thickness in the
component assembly. Instead, l* and
µ* have to be newly determined from scratch. 
  


Regarding the 'moisture storage function' of air layers, see the
[[Details:MoistureStorageFunction | reference: Moisture Storage Function]].


The definition of the diffusion resistance factor (µ-value) is discussed in the
[[Details:WaterVaporDiffusion | reference: Water Vapor Diffusion]].


=== Literature: ===
[1] Schirmer, R.: Die Diffusionszahl von Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177. 
  
[2] Illig, W.: Die Größe der Wasserdampfübergangszahl bei Diffusionsvorgängen in Wänden von Wohnungen, Stallungen und Kühlräumen, Gesundheitsingenieur 73 (1952), H. 7/8, p. 124-127. 
  
[3]Gösele, K., Schüle, W.: Schall·Wärme·Feuchte. Bauverlag 1989.

Details:AirLayers

2009-03-25T09:36:41Z

Barbara: /* Air Layers */

= Air Layers =

WUFI can also include air layers in the building component. It does not simulate the
air convection (which would not make much sense in one dimension anyway), but it allows
for the air layer as a resistance to heat and moisture flows.


In addition to heat conduction, in air layers heat can also be transferred by convection
and radiation. In addition to water vapor diffusion, in air layers water vapor can also
be transferred by convection. Since WUFI is primarily intended for solid materials, it
only allows for heat conduction and water vapor diffusion (plus liquid transport, which
is not relevant here). However, the additional transport phenomena can be included by
adjusting the
[[Details:BasicMaterialData | heat conductivity]] and the
[[Details:BasicMaterialData | diffusion resistance]] so that the correct heat
and vapor flows result from the calculation.


The method is based on the following considerations which are valid for
non-ventilated air layers. (No general treatment is possible for ventilated air
layers; they may even exhibit the same conditions as the exterior air. Building
components outward from the air layer may then be disregarded except for their shielding
of rain and radiation. [##update: air change sources##])


The relative contributions of heat conduction, convection and radiation are dependent on
the thickness and orientation of the air layer, the nature of the two surfaces and the
temperature. Fortunately, the dependence on the temperature may be neglected in building
physics. Furthermore, it suffices to distinguish between metallic and non-metallic
surfaces. So if we restrict ourselves to, say, vertical air layers with non-metallic
surfaces, we can simply determine (e.g. from measurements) a heat resistance
Rnon-met which depends only on the air layer thickness and which comprises
all transport phenomena.


Now, for WUFI the effective heat conductivity l*
has to be chosen so that for an air layer with a given thickness the heat resistance
Rnon-met as
determined above results. Note: the thickness with wich the air layer is included in the
assembly for calculation need not (but can) be identical with the real thickness, since
the real thickness has already been allowed for in the specific choice of
Rnon-met.


The heat resistance of an air layer with the desired thickness, orientation (vertical,
horizontal) and surfaces (metallic, non-metallic) may be looked up in a relevant table.
Let's choose non-metallic surfaces here, since in building components non-metallic surfaces
are predominant, and call this value Rnon-met. We also choose an arbitrary
thickness Dx*, which shall be the thickness of the
air layer as inserted in WUFI's component assembly. Then 
  
 Rnon-met = Dx* /
l*, 
  
therefore 
  
 l* = Dx*
/ Rnon-met. 
  



Since water vapor diffusion and convective water vapor transport are based on analogous
mechanisms as heat conductivity and convective heat transport, the coefficients describing
vapor transport can be derived from the coefficients for heat transport, using similarity
relations. For vapor flow, we have formally: 
  
 -gv = Dc / µ* ·
Dc / Dx*
= Dc / S 
  
<TABLE>
<TR><TD>gv</TD>
<TD>[kg/m²s]</TD>
<TD>:</TD>
<TD>water vapor diffusion flux density</TD>
</TR>
<TR><TD>Dc</TD>
<TD>[m²/s]</TD>
<TD>:</TD>
<TD>concentration-related diffusion coefficient</TD>
</TR>
<TR><TD>µ*</TD>
<TD>[-]</TD>
<TD>:</TD>
<TD>effective water vapor diffusion resistance factor</TD>
</TR>
<TR><TD>c</TD>
<TD>[kg/m³]</TD>
<TD>:</TD>
<TD>water vapor concentration</TD>
</TR>
<TR><TD>Dx*</TD>
<TD>[m]</TD>
<TD>:</TD>
<TD>effective layer thickness</TD>
</TR>
<TR><TD>S</TD>
<TD>[m³/s²Pa]</TD>
<TD>:</TD>
<TD>water vapor diffusion resistance,</TD>
</TABLE>
  
therefore 
  
  
 µ* = Dc · S / Dx* 
  
But we have 
  
 Dc = 0.083 · (T/273)1.81
≈ 0.09   [1], 
  
and, because of similarity relations, 
  
 S ≈ Rmet / 3.5   [2], 
  
where we have to use the heat resistance Rmet of air layers between metallic
surfaces (i.e., without radiation exchange), since we want to estimate the vapor diffusion
resistance and there is no transport mechanism analogous to radiation involved, in
contrast to the above case of heat transport.


Finally, we have the freedom to choose an arbitrary thickness
Dx* with which the layer is included in the component
assembly for calculation, since the real thickness was already allowed for in the choice
of the specific value for Rmet. 
  
 &micro* = 0.09 · Rmet / (3.5 · Dx*) = 0.026 · Rmet / Dx* 
  


For vertical air layers, Rnon-met and Rmet may be taken
from this table (interpolated after [3]): 


<TABLE>
<TR><TD WIDTH="20"> </TD>
<TD>thickness</TD>
<TD WIDTH="10"> </TD>
<TD>Rnon-met</TD>
<TD WIDTH="10"> </TD>
<TD>Rmet</TD>
</TR>
<TR><TD> </TD>
<TD>[cm]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
<TD> </TD>
<TD>[m²K/W]</TD>
</TR>
<TR><TD> </TD>
<TD COLSPAN="5"> <HR> </TD>
</TR>

<TR><TD> </TD>
<TD> 0</TD>
<TD> </TD>
<TD>0</TD>
<TD> </TD>
<TD>0</TD>
</TR>
<TR><TD> </TD>
<TD> 1</TD>
<TD> </TD>
<TD>0.140</TD>
<TD> </TD>
<TD>0.280</TD>
</TR>
<TR><TD> </TD>
<TD> 2</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
<TR><TD> </TD>
<TD> 3</TD>
<TD> </TD>
<TD>0.171</TD>
<TD> </TD>
<TD>0.526</TD>
</TR>
<TR><TD> </TD>
<TD> 4</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.590</TD>
</TR>
<TR><TD> </TD>
<TD> 5</TD>
<TD> </TD>
<TD>0.180</TD>
<TD> </TD>
<TD>0.620</TD>
</TR>
<TR><TD> </TD>
<TD> 6</TD>
<TD> </TD>
<TD>0.178</TD>
<TD> </TD>
<TD>0.627</TD>
</TR>
<TR><TD> </TD>
<TD> 7</TD>
<TD> </TD>
<TD>0.176</TD>
<TD> </TD>
<TD>0.623</TD>
</TR>
<TR><TD> </TD>
<TD> 8</TD>
<TD> </TD>
<TD>0.174</TD>
<TD> </TD>
<TD>0.613</TD>
</TR>
<TR><TD> </TD>
<TD> 9</TD>
<TD> </TD>
<TD>0.172</TD>
<TD> </TD>
<TD>0.598</TD>
</TR>
<TR><TD> </TD>
<TD>10</TD>
<TD> </TD>
<TD>0.170</TD>
<TD> </TD>
<TD>0.580</TD>
</TR>
<TR><TD> </TD>
<TD>11</TD>
<TD> </TD>
<TD>0.168</TD>
<TD> </TD>
<TD>0.557</TD>
</TR>
<TR><TD> </TD>
<TD>12</TD>
<TD> </TD>
<TD>0.166</TD>
<TD> </TD>
<TD>0.530</TD>
</TR>
<TR><TD> </TD>
<TD>13</TD>
<TD> </TD>
<TD>0.164</TD>
<TD> </TD>
<TD>0.501</TD>
</TR>
<TR><TD> </TD>
<TD>14</TD>
<TD> </TD>
<TD>0.162</TD>
<TD> </TD>
<TD>0.468</TD>
</TR>
<TR><TD> </TD>
<TD>15</TD>
<TD> </TD>
<TD>0.160</TD>
<TD> </TD>
<TD>0.430</TD>
</TR>
</TABLE>

The other [[Details:BasicMaterialData | basic material parameters]] may be determined
according to the following:

* if Dx* was chosen not equal to the real thickness, multiplication of the 'bulk density' 1.29 kg/m³ by (real thickness)/Dx* results in the correct heat capacity;
* the 'porosity' should be chosen very high (e.g. 0.999 m³/m³);
* the specific heat capacity by mass of the air layer is 1 kJ/kgK, even if Dx* is chosen not equal to the real thickness.


For the graphical display of the [[1D:Dialog_Assembly | component assembly]], it
will be advisable to choose Dx* equal to the real
thickness. Note however that if you want to repeat the calculation with an air layer of
a different thickness, it is not sufficient to simply adapt the layer thickness in the
component assembly. Instead, l* and
µ* have to be newly determined from scratch. 
  


Regarding the 'moisture storage function' of air layers, see the
[[Details:MoistureStorageFunction | reference: Moisture Storage Function]].


The definition of the diffusion resistance factor (µ-value) is discussed in the
[[Details:WaterVaporDiffusion | reference: Water Vapor Diffusion]].


=== Literature: ===
[1] Schirmer, R.: Die Diffusionszahl von Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177. 
  
[2] Illig, W.: Die Größe der Wasserdampfübergangszahl bei Diffusionsvorgängen in Wänden von Wohnungen, Stallungen und Kühlräumen, Gesundheitsingenieur 73 (1952), H. 7/8, p. 124-127. 
  
[3]Gösele, K., Schüle, W.: Schall·Wärme·Feuchte. Bauverlag 1989.

2D:Dialog ClimateFileDetails

2009-03-25T09:32:12Z

Barbara: /* *.WET files: */

= Dialog: Climate File | Details =


Some climate formats offer additional options:


=== *.WET files: ===

[[Bild:DialogKlimaErweiterteEinstellungenWET_3.gif]]


[[Details:WET-File | *.WET]] files can
contain additional measured data that might be useful for a
hygrothermic simulation:




"Temperature":
WET files may contain several columns with measured temperatures.
WUFI usually reads and uses the air temperature. However, it may
optionally read and use surface temperatures of a white and a
black facade or the ground temperatures at different depths. 
 

"Black surface", 
"White surface":

[[Bild:Oberflaechen_1.gif]]

A *.WET file created for Holzkirchen contains the measured
surface temperatures of a 'white' (
[[Details:ShortWaveRadiationAbsorptivity | as]] ~ 0.4)
and a 'black' (as ~ 0.9) west-facing facade
specimen modeled after an ETICS. If you want to expose your component
to the same surface temperatures, select the respective option and set the
[[2D:Dialog_EditSurfaceCoefficients | heat transfer coefficient]]
for the surface to a large number. WUFI then reads the corresponding
temperature from the file and uses it as the 'air temperature' for
the calculation; the large heat transfer coefficient takes care that
the surface assumes the same temperature. 
Using measured surface temperatures also requires proper
treatment of other climate quantities: 
  
"Relative humidity": 
The relative humidity in the climate file is based on the temperature contained
in the column [[Details:WET-File | 'Exterior air temperature']].
If, instead, one of the surface temperatures is used as the 'air' temperature,
this combination will result in wrong water vapor partial pressures at the component
surface. The option "Adjust relative humidity" adjusts the relative humidity
read from the file so that the correct partial pressures result at the surface. 
  
"Radiation": 
If the surface temperature of the component has been set to assume the measured surface
temperature, "No radiation" must be used for the calculation, since the thermal
effect of the solar radiation is already included in the measured temperature. 
  

"Ground surface":

For calculating heat transport within the ground it may be helpful to use
measured ground surface temperatures as boundary conditions. Select
this option and set the
[[2D:Dialog_EditSurfaceCoefficients | heat transfer coefficient]] for
the surface to a large number. WUFI then reads the corresponding temperature from
the file and uses it as the ambient air temperature for the calculation; the
large heat transfer coefficient takes care that the surface assumes the same
temperature. 
The ground surface temperatures recorded in Holzkirchen are measured a few
centimeters below the actual surface. 
Using measured ground surface temperatures also requires proper treatment of
other climate quantities: 
  
"Relative humidity": 
The relative humidity in the climate file is based on the temperature contained
in the column
[[Details:WET-File | 'Exterior air temperature']]. If,
instead, the ground surface temperature is used as the 'air' temperature, this
combination will result in wrong water vapor partial pressures at the component
surface. The option "Adjust relative humidity" adjusts the relative humidity
read from the file so that the correct partial pressures result at the surface. 
  

"50 cm below ground surface", 
"1 m below ground surface":

For the hygrothermal simulation of a component in contact with the ground (e.g. a
cellar wall) it may be helpful to use measured ground temperatures as
boundary conditions. Select the respective option and set the
[[2D:Dialog_EditSurfaceCoefficients | heat transfer coefficient]]
for the surface to a large number. WUFI then reads the corresponding temperature
from the file and uses it as the ambient air temperature for the calculation;
the large heat transfer coefficient takes care that the surface assumes the same
temperature. 
If you want to allow for the thermal effect which the component has on the
ground temperatures, insert a sufficiently thick layer of soil in front of the
component and set the exterior surface of this layer to the measured temperatures. 

Using measured ground temperatures also requires proper treatment of other
climate quantities:
  
"Relative humidity": 
The soil usually has a fairly "constant relative humidity"; if plant
cover is present, the humidity is at least about 99%, since otherwise the
plants could not overcome the soil's hydraulic tension and were not able to
draw water from the ground. For simulation of components in contact with the
ground, WUFI therefore uses a constant relative humidity as boundary condition
whose value you can enter according to your wishes. 
 
"Radiation": 
Since there is "no radiation" within the ground, the solar radiation
data from the climate file are ignored. 
 
"Rain": 
Since there is "no rain" within the ground, the rain data from the climate
file are ignored. If you want to simulate the uptake of (pressureless) ground
water, it would be preferable to use an appropriately tailored
[[Details:KLI-File | *.KLI file]]. 
  



"Relative humidity":
Depending on the selected temperature option (see above) it may be
necessary to adjust the relative humidity for a different temperature level
or to set it constant. 
  

"Radiation":
Depending on the selected temperature option (see above) it may be necessary to
suppress solar radiation.
Otherwise, you have the option to bypass the usual conversion of solar radiation
for the specific orientation and inclination of your facade, and to directly
read and use radiation data measured on the facade (if available). 
  

"Rain":
Depending on the selected temperature option (see above) it may be necessary to suppress rain. Otherwise, you have the option to bypass the usual conversion from normal rain to driving rain and to directly read and use rain data measured on the facade (if available). 
For this purpose, set the [[1D:Dialog_Orientation | rain coefficients]] to R1=1 and R2=0. 
 

Also, see [[Details:WET-File | The *.WET Format for Climate Data]]
for details.





 


=== *.KLI files: ===

[[Bild:DialogKlimaErweiterteEinstellungenKLI_2.gif]]


[[Details:KLI-File | *.KLI]] files contain data describing
the outdoor climate (rain, radiation, air temperature, relative humidity) and
data describing the indoor climate (air temperature, relative humidity). This
dialog allows you to specify which one of the two shall be applied to the surface
segment under consideration.



 


=== *.TRY, *.DAT, *.WAC, *.IWC, *.WBC files: ===

[[Bild:DialogKlimaErweiterteEinstellungenIWC_3.gif]]


No options are available for these file types.

2D:Dialog ClimateFileDetails

2009-03-25T09:28:58Z

Barbara: /* *.WET files: */

= Dialog: Climate File | Details =


Some climate formats offer additional options:


=== *.WET files: ===

[[Bild:DialogKlimaErweiterteEinstellungenWET_3.gif]]


[[Details:WET-File | *.WET]] files can
contain additional measured data that might be useful for a
hygrothermic simulation:




"Temperature":
WET files may contain several columns with measured temperatures.
WUFI usually reads and uses the air temperature. However, it may
optionally read and use surface temperatures of a white and a
black facade or the ground temperatures at different depths. 
 

"Black surface", 
"White surface":

[[Bild:Oberflaechen_1.gif]]

A *.WET file created for Holzkirchen contains the measured
surface temperatures of a 'white' (
[[Details:ShortWaveRadiationAbsorptivity | as]] ~ 0.4)
and a 'black' (as ~ 0.9) west-facing facade
specimen modeled after an ETICS. If you want to expose your component
to the same surface temperatures, select the respective option and set the
[[2D:Dialog_EditSurfaceCoefficients | heat transfer coefficient]]
for the surface to a large number. WUFI then reads the corresponding
temperature from the file and uses it as the 'air temperature' for
the calculation; the large heat transfer coefficient takes care that
the surface assumes the same temperature. 
Using measured surface temperatures also requires proper
treatment of other climate quantities: 
  
"Relative humidity": 
The relative humidity in the climate file is based on the temperature contained
in the column [[Details:WET-File | 'Exterior air temperature']].
If, instead, one of the surface temperatures is used as the 'air' temperature,
this combination will result in wrong water vapor partial pressures at the component
surface. The option "Adjust relative humidity" adjusts the relative humidity
read from the file so that the correct partial pressures result at the surface. 
  
"Radiation": 
If the surface temperature of the component has been set to assume the measured surface
temperature, "No radiation" must be used for the calculation, since the thermal
effect of the solar radiation is already included in the measured temperature. 
  

"Ground surface":

For calculating heat transport within the ground it may be helpful to use
measured ground surface temperatures as boundary conditions. Select
this option and set the
[[2D:Dialog_EditSurfaceCoefficients | heat transfer coefficient]] for
the surface to a large number. WUFI then reads the corresponding temperature from
the file and uses it as the ambient air temperature for the calculation; the
large heat transfer coefficient takes care that the surface assumes the same
temperature. 
The ground surface temperatures recorded in Holzkirchen are measured a few
centimeters below the actual surface. 
Using measured ground surface temperatures also requires proper treatment of
other climate quantities: 
  
"Relative humidity": 
The relative humidity in the climate file is based on the temperature contained
in the column
[[Details:WET-File | 'Exterior air temperature']]. If,
instead, the ground surface temperature is used as the 'air' temperature, this
combination will result in wrong water vapor partial pressures at the component
surface. The option "Adjust relative humidity" adjusts the relative humidity
read from the file so that the correct partial pressures result at the surface. 
  

"50 cm below ground surface", 
"1 m below ground surface":

For the hygrothermal simulation of a component in contact with the ground (e.g. a
cellar wall) it may be helpful to use measured ground temperatures as
boundary conditions. Select the respective option and set the
[[2D:Dialog_EditSurfaceCoefficients | heat transfer coefficient]]
for the surface to a large number. WUFI then reads the corresponding temperature
from the file and uses it as the ambient air temperature for the calculation;
the large heat transfer coefficient takes care that the surface assumes the same
temperature. 
If you want to allow for the thermal effect which the component has on the
ground temperatures, insert a sufficiently thick layer of soil in front of the
component and set the exterior surface of this layer to the measured temperatures. 

Using measured ground temperatures also requires proper treatment of other
climate quantities:
  
"Relative humidity": 
The soil usually has a fairly "constant relative humidity"; if plant
cover is present, the humidity is at least about 99%, since otherwise the
plants could not overcome the soil's hydraulic tension and were not able to
draw water from the ground. For simulation of components in contact with the
ground, WUFI therefore uses a constant relative humidity as boundary condition
whose value you can enter according to your wishes. 
 
"Radiation": 
Since there is "no radiation" within the ground, the solar radiation
data from the climate file are ignored. 
 
"Rain": 
Since there is "no rain" within the ground, the rain data from the climate
file are ignored. If you want to simulate the uptake of (pressureless) ground
water, it would be preferable to use an appropriately tailored
[[Details:KLI-File | *.KLI file]]. 
  



"Relative humidity":
Depending on the selected temperature option (see above) it may be
necessary to adjust the relative humidity for a different temperature level
or to set it constant. 
  

"Radiation":
Depending on the selected temperature option (see above) it may be necessary to
suppress solar radiation.
Otherwise, you have the option to bypass the usual conversion of solar radiation
for the specific orientation and inclination of your facade, and to directly
read and use radiation data measured on the facade (if available). 
  

"Rain":
Depending on the selected temperature option (see above) it may be necessary to suppress rain. Otherwise, you have the option to bypass the usual conversion from normal rain to driving rain and to directly read and use rain data measured on the facade (if available). 
For this purpose, set the rain coefficients to R1=1 and R2=0. 
 

Also, see [[Details:WET-File | The *.WET Format for Climate Data]]
for details.





 


=== *.KLI files: ===

[[Bild:DialogKlimaErweiterteEinstellungenKLI_2.gif]]


[[Details:KLI-File | *.KLI]] files contain data describing
the outdoor climate (rain, radiation, air temperature, relative humidity) and
data describing the indoor climate (air temperature, relative humidity). This
dialog allows you to specify which one of the two shall be applied to the surface
segment under consideration.



 


=== *.TRY, *.DAT, *.WAC, *.IWC, *.WBC files: ===

[[Bild:DialogKlimaErweiterteEinstellungenIWC_3.gif]]


No options are available for these file types.

2D:Dialog ClimateFileDetails

2009-03-25T09:24:01Z

Barbara: /* *.WET files: */

= Dialog: Climate File | Details =


Some climate formats offer additional options:


=== *.WET files: ===

[[Bild:DialogKlimaErweiterteEinstellungenWET_3.gif]]


[[Details:WET-File | *.WET]] files can
contain additional measured data that might be useful for a
hygrothermic simulation:




"Temperature":
WET files may contain several columns with measured temperatures.
WUFI usually reads and uses the air temperature. However, it may
optionally read and use surface temperatures of a white and a
black facade or the ground temperatures at different depths. 
 

"Black surface", 
"White surface":

[[Bild:Oberflaechen_1.gif]]

A *.WET file created for Holzkirchen contains the measured
surface temperatures of a 'white' (
[[Details:ShortWaveRadiationAbsorptivity | as]] ~ 0.4)
and a 'black' (as ~ 0.9) west-facing facade
specimen modeled after an ETICS. If you want to expose your component
to the same surface temperatures, select the respective option and set the
[[2D:Dialog_EditSurfaceCoefficients | heat transfer coefficient]]
for the surface to a large number. WUFI then reads the corresponding
temperature from the file and uses it as the 'air temperature' for
the calculation; the large heat transfer coefficient takes care that
the surface assumes the same temperature. 
Using measured surface temperatures also requires proper
treatment of other climate quantities: 
  
"Relative humidity": 
The relative humidity in the climate file is based on the temperature contained
in the column [[Details:WET-File | 'Exterior air temperature']].
If, instead, one of the surface temperatures is used as the 'air' temperature,
this combination will result in wrong water vapor partial pressures at the component
surface. The option "Adjust relative humidity" adjusts the relative humidity
read from the file so that the correct partial pressures result at the surface. 
  
"Radiation": 
If the surface temperature of the component has been set to assume the measured surface
temperature, "No radiation" must be used for the calculation, since the thermal
effect of the solar radiation is already included in the measured temperature. 
  

"Ground surface":

For calculating heat transport within the ground it may be helpful to use
measured ground surface temperatures as boundary conditions. Select
this option and set the
[[2D:Dialog_EditSurfaceCoefficients | heat transfer coefficient]] for
the surface to a large number. WUFI then reads the corresponding temperature from
the file and uses it as the ambient air temperature for the calculation; the
large heat transfer coefficient takes care that the surface assumes the same
temperature. 
The ground surface temperatures recorded in Holzkirchen are measured a few
centimeters below the actual surface. 
Using measured ground surface temperatures also requires proper treatment of
other climate quantities: 
  
"Relative humidity": 
The relative humidity in the climate file is based on the temperature contained
in the column
[[Details:WET-File | 'Exterior air temperature']]. If,
instead, the ground surface temperature is used as the 'air' temperature, this
combination will result in wrong water vapor partial pressures at the component
surface. The option "Adjust relative humidity" adjusts the relative humidity
read from the file so that the correct partial pressures result at the surface. 
  

"50 cm below ground surface", 
"1 m below ground surface":

For the hygrothermal simulation of a component in contact with the ground (e.g. a
cellar wall) it may be helpful to use measured ground temperatures as
boundary conditions. Select the respective option and set the
[[2D:Dialog_EditSurfaceCoefficients | heat transfer coefficient]]
for the surface to a large number. WUFI then reads the corresponding temperature
from the file and uses it as the ambient air temperature for the calculation;
the large heat transfer coefficient takes care that the surface assumes the same
temperature. 
If you want to allow for the thermal effect which the component has on the
ground temperatures, insert a sufficiently thick layer of soil in front of the
component and set the exterior surface of this layer to the measured temperatures. 

Using measured ground temperatures also requires proper treatment of other
climate quantities:
  
"Relative humidity": 
The soil usually has a fairly "constant relative humidity"; if plant
cover is present, the humidity is at least about 99%, since otherwise the
plants could not overcome the soil's hydraulic tension and were not able to
draw water from the ground. For simulation of components in contact with the
ground, WUFI therefore uses a constant relative humidity as boundary condition
whose value you can enter according to your wishes. 
 
"Radiation": 
Since there is "no radiation" within the ground, the solar radiation
data from the climate file are ignored. 
 
"Rain": 
Since there is "no rain" within the ground, the rain data from the climate
file are ignored. If you want to simulate the uptake of (pressureless) ground
water, it would be preferable to use an appropriately tailored
[[Details:KLI-File | *.KLI file]]. 
  



"Relative humidity":
Depending on the selected temperature option (see above) it may be
necessary to adjust the relative humidity for a different temperature level
or to set it constant. 
  

"Radiation":
Depending on the selected temperature option (see above) it may be necessary to
suppress solar radiation.
Otherwise, you have the option to bypass the usual conversion of solar radiation
for the specific orientation and inclination of your facade, and to directly
read and use radiation data measured on the facade (if available). 
  

"Rain":
Depending on the selected temperature option (see above) it may be necessary to
suppress rain. 
  
Otherwise, you have the option to bypass the usual conversion from normal
rain to driving rain and to directly read and use rain data measured on the
facade (if available). 
For this purpose, set the rain coefficients to R1=1 and R2=0. 
 

Also, see [[Details:WET-File | The *.WET Format for Climate Data]]
for details.





 


=== *.KLI files: ===

[[Bild:DialogKlimaErweiterteEinstellungenKLI_2.gif]]


[[Details:KLI-File | *.KLI]] files contain data describing
the outdoor climate (rain, radiation, air temperature, relative humidity) and
data describing the indoor climate (air temperature, relative humidity). This
dialog allows you to specify which one of the two shall be applied to the surface
segment under consideration.



 


=== *.TRY, *.DAT, *.WAC, *.IWC, *.WBC files: ===

[[Bild:DialogKlimaErweiterteEinstellungenIWC_3.gif]]


No options are available for these file types.

Details:WET-File

2009-03-25T08:18:08Z

Barbara: /* The *.WET Format for Climate Data */

= The *.WET Format for Climate Data =


You can use existing IBP weather files (file format *.WET) to perform WUFI calculations; you can also convert your own weather data to that format and use them.


IBP weather files contain 21 lines of header which explain the meaning of the different data columns and an arbitrary number of lines with hourly weather data. WUFI skips the header.


Example:


[[Bild:WETexample.gif]]


(for formatting reasons, the data lines cannot be reproduced here in their entirety. Please refer to the file IBP1991.WET you received with WUFI for a complete example).


The format of the numbers is free; the only requirement is that a PASCAL program (like WUFI) must be able to read them. 
The file need not conform to a specific column format (as in FORTRAN), the number of decimal places does not matter, floating point numbers need not be in exponential format etc.


The number type <TT>real</TT>/<TT>integer</TT> has to be adhered to, however. The individual numbers must be separated by blanks, not tabulators.


The fact that the floating point numbers in the example all start with a zero is irrelevant (they were created with a FORTRAN program which likes to write numbers this way).


The data in detail:


* Day, month, year, hour (<TT>integer</TT>):   The IBP files contain hourly mean values of the measured data. These time stamps indicate the point in time when each measuring interval of one hour was finished and the measured mean values recorded. I.e., the data line starting with 01 01 91 04 contains the mean values for the hour from 03:00 to 04:00 on January 1, 1991.   Since its data are real-life data, an IBP weather file may contain an intercalary day (February 29). WUFI however knows nothing about intercalary days (at least in the present version). These must be deleted from files you want to use for WUFI calculations.   The time count always refers to winter time (CET). There is no daylight saving time.  

* Exterior air temperature (<TT>real</TT>):   the temperature of the exterior ambient air in [°C]. It is used without change as the exterior air temperature in the WUFI calculation.   

* Temperature of black surface (<TT>real</TT>):
* Temperature of white surface (<TT>real</TT>):   Surface temperatures of west-facing test facade elements painted black ([[Details:ShortWave |as]] ~ 0.9) and white (as ~ 0.4), respectively. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Temperature of Ground Surface (<TT>real</TT>):
* Temperature 50 cm below Ground Surface (<TT>real</TT>):
* Temperature 1 m below Ground Surface (<TT>real</TT>):   Soil temperatures at various depths in [°C]. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Global radiation (<TT>real</TT>):   the sum of the direct and diffuse components of the solar radiation incident on a horizontal surface; in [W/m²].  

* Diffuse radiation (<TT>real</TT>):   the diffuse component of the solar radiation incident on a horizontal surface; in [W/m²].   Subtracting the diffuse radiation from the global radiation results in the direct radiation. From this, the direct normal radiation can be calculated, i.e., the amount of radiation incident on a surface that is orthogonal to the ray direction. This calculation requires knowledge of the time and geographical location of the measurement, since the corresponding position of the sun has to be determined [2].   The direct normal radiation can then be used to calculate the direct radiation incident on a surface with arbitrary orientation and inclination. Addition of the appropriate fraction of diffuse radiation results in the global radiation incident on the building component.   These calculations are automatically done by WUFI during a simulation run.   WUFI uses a [[FAQ:General | simplified radiation model]] which treats the diffuse radiation as isotropic and ignores the albedo of the ground. If you are more demanding or want to allow for local specifics (like shadows etc.), you can perform the conversion yourself and feed the results to WUFI via a [[Details:KLI-File | *.KLI file]].   

* Western radiation (<TT>real</TT>):   the global radiation measured with a west-facing solarimeter; in [W/m²]. [[2D:Dialog_ClimateFileDetails |Optionally]], the radiation component impinging on a (west-facing) facade may directly be read from this column. No conversion is then necessary as would be the case if global and diffuse radiation were used as data source.   

* Relative humidity (<TT>real</TT>):   the relative humidity of the ambient air (0..1). Used by WUFI without change as the exterior relative humidity.  

* Barometric pressure (<TT>real</TT>):   the ambient air pressure reduced to sea level; in [hPA].   

* Wind velocity (<TT>real</TT>):   the scalar mean of the wind velocity; in [m/s]. It is needed to compute the driving rain from the normal rain.   The scalar mean of the wind velocity is the mean value of the readings of an anemometer without the directions taken into account. For example, if for an hour the wind is blowing at 2 m/s but at the same time steadily travelling through all the direcions, then the scalar mean is 2 m/s, whereas the vectorial mean is 0 m/s.   In the vectorial mean, some vector components may cancel. Thus, the scalar mean is greater than (or at least equal to) the vectorial mean.   The IBP weather files also contain information about the distribution of the wind directions (see below). This allows to ignore components that come from 'behind' (and don't contribute to the rain load) and to weight the remaining directions according to the angle they make with the surface.   

* Normal rain / tipping bucket (<TT>real</TT>):
* Normal rain / droplet counter (<TT>real</TT>):   the normal rain (i.e., the rain incident on a horizontal surface in open area) during one hour, measured with a tipping bucket and a droplet counter rain gauge, respectively; in [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The rain load on a wall is determined by the driving rain rather than the normal rain. The driving rain can be estimated from the normal rain and the wind velocity:   The rain coefficients R1 and R2 in the dialog [[1D:Dialog_Orientation | orientation, inclination and height]] serve to estimate the driving rain load on a surface of arbitrary orientation and inclination from data on normal rain, wind velocity and wind direction distributions, using the relation   <CENTER>rain load = rain · (R1 + R2 · wind velocity),</CENTER>
:where 'rain' is the normal rain and 'wind velocity' is that component of the mean wind velocity (measured at a height of 10 m, in open area), which is orthogonal to the building surface. This component is determined from the scalar mean of the wind velocity (see above) and the wind direction distribution (see below). R1 and R2 are strongly dependent on the specific location on the building facade. If calculations are to be compared to actual measurements, these coefficients should be experimentally determined for that location. If they cannot be measured, only a very rough estimate is possible. For vertical surfaces, R1 is zero. R2 is about 0.2 s/m for free-standing locations without influence from surrounding buildings etc.; it is markedly less in the center of a facade (e.g. 0.07 s/m); it may even be greater at exposed locations of a building (near edges and corners)[1].  

* Driving rain / tipping bucket (<TT>real</TT>):
* Driving rain / droplet counter (<TT>real</TT>):   the driving rain load on a west-facing wall, measured at a height of 1.50 m with a tipping bucket and a droplet counter rain gauge, respectively. In [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The values in this column can [[2D:Dialog_ClimateFileDetails | optionally]] be read and used for the variable 'rain' in the formula for the rain load (see above: normal rain). Set R1 to 1 and R2 to zero; the resulting rain load will then directly be the measured driving rain.   

* Wind direction distribution (17 * <TT>integer</TT>):   the frequency of wind directions, binned into sectors of 22.5° each.   The wind direction is averaged over 2 minutes and the counter of the corresponding sector then increased by one. A special counter is registering calms. The sum of all counts during one hour should thus be 30 if no interruption of the measurements has occured.   The individual counters are assigned to the following directions:   
<CENTER>NNE-NE-ENE-E-ESE-SE-SSE-S-SSW-SW-WSW-W-WNW-NW-NNW-N-calm</CENTER>
:For the calculation of the driving rain load, the contributions of the different directions are determined individually and then summed up. Wind coming 'from behind' does not contribute to the rain load and is ignored. 


A *.WET file supplied by the user must be accompanied by a [[Details:AGD-File | *.AGD file]] which contains geographical information on the climate location.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Künzel, H.M.: Bestimmung der Schlagregenbelastung von Fassadenflächen. IBP-Mitteilung 21 (1994), Nr. 263</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>VDI 3789 Umweltmeteorologie, Blatt 2: Wechselwirkungen zwischen Atmosphäre und Oberflächen; Berechnung der kurz- und der langwelligen Strahlung. Oktober 1994</TD></TR>
</TABLE>

Details:WET-File

2009-03-25T08:15:49Z

Barbara: /* The *.WET Format for Climate Data */

= The *.WET Format for Climate Data =


You can use existing IBP weather files (file format *.WET) to perform WUFI calculations; you can also convert your own weather data to that format and use them.


IBP weather files contain 21 lines of header which explain the meaning of the different data columns and an arbitrary number of lines with hourly weather data. WUFI skips the header.


Example:


[[Bild:WETexample.gif]]


(for formatting reasons, the data lines cannot be reproduced here in their entirety. Please refer to the file IBP1991.WET you received with WUFI for a complete example).


The format of the numbers is free; the only requirement is that a PASCAL program (like WUFI) must be able to read them. 
The file need not conform to a specific column format (as in FORTRAN), the number of decimal places does not matter, floating point numbers need not be in exponential format etc.


The number type <TT>real</TT>/<TT>integer</TT> has to be adhered to, however. The individual numbers must be separated by blanks, not tabulators.


The fact that the floating point numbers in the example all start with a zero is irrelevant (they were created with a FORTRAN program which likes to write numbers this way).


The data in detail:


* Day, month, year, hour (<TT>integer</TT>):   The IBP files contain hourly mean values of the measured data. These time stamps indicate the point in time when each measuring interval of one hour was finished and the measured mean values recorded. I.e., the data line starting with 01 01 91 04 contains the mean values for the hour from 03:00 to 04:00 on January 1, 1991.   Since its data are real-life data, an IBP weather file may contain an intercalary day (February 29). WUFI however knows nothing about intercalary days (at least in the present version). These must be deleted from files you want to use for WUFI calculations.   The time count always refers to winter time (CET). There is no daylight saving time.  

* Exterior air temperature (<TT>real</TT>):   the temperature of the exterior ambient air in [°C]. It is used without change as the exterior air temperature in the WUFI calculation.   

* Temperature of black surface (<TT>real</TT>):
* Temperature of white surface (<TT>real</TT>):   Surface temperatures of west-facing test facade elements painted black ([[Details:ShortWave |as]] ~ 0.9) and white (as ~ 0.4), respectively. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Temperature of Ground Surface (<TT>real</TT>):
* Temperature 50 cm below Ground Surface (<TT>real</TT>):
* Temperature 1 m below Ground Surface (<TT>real</TT>):   Soil temperatures at various depths in [°C]. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Global radiation (<TT>real</TT>):   the sum of the direct and diffuse components of the solar radiation incident on a horizontal surface; in [W/m²].  

* Diffuse radiation (<TT>real</TT>):   the diffuse component of the solar radiation incident on a horizontal surface; in [W/m²].   Subtracting the diffuse radiation from the global radiation results in the direct radiation. From this, the direct normal radiation can be calculated, i.e., the amount of radiation incident on a surface that is orthogonal to the ray direction. This calculation requires knowledge of the time and geographical location of the measurement, since the corresponding position of the sun has to be determined [2].   The direct normal radiation can then be used to calculate the direct radiation incident on a surface with arbitrary orientation and inclination. Addition of the appropriate fraction of diffuse radiation results in the global radiation incident on the building component.   These calculations are automatically done by WUFI during a simulation run.   WUFI uses a [[FAQ:General | simplified radiation model]] which treats the diffuse radiation as isotropic and ignores the albedo of the ground. If you are more demanding or want to allow for local specifics (like shadows etc.), you can perform the conversion yourself and feed the results to WUFI via a [[Details:KLI-File | *.KLI file]].   

* Western radiation (<TT>real</TT>):   the global radiation measured with a west-facing solarimeter; in [W/m²]. [[2D:Dialog_ClimateFileDetails |Optionally]], the radiation component impinging on a (west-facing) facade may directly be read from this column. No conversion is then necessary as would be the case if global and diffuse radiation were used as data source.   

* Relative humidity (<TT>real</TT>):   the relative humidity of the ambient air (0..1). Used by WUFI without change as the exterior relative humidity.  

* Barometric pressure (<TT>real</TT>):   the ambient air pressure reduced to sea level; in [hPA].   

* Wind velocity (<TT>real</TT>):   the scalar mean of the wind velocity; in [m/s]. It is needed to compute the driving rain from the normal rain.   The scalar mean of the wind velocity is the mean value of the readings of an anemometer without the directions taken into account. For example, if for an hour the wind is blowing at 2 m/s but at the same time steadily travelling through all the direcions, then the scalar mean is 2 m/s, whereas the vectorial mean is 0 m/s.   In the vectorial mean, some vector components may cancel. Thus, the scalar mean is greater than (or at least equal to) the vectorial mean.   The IBP weather files also contain information about the distribution of the wind directions (see below). This allows to ignore components that come from 'behind' (and don't contribute to the rain load) and to weight the remaining directions according to the angle they make with the surface.   

* Normal rain / tipping bucket (<TT>real</TT>):
* Normal rain / droplet counter (<TT>real</TT>):   the normal rain (i.e., the rain incident on a horizontal surface in open area) during one hour, measured with a tipping bucket and a droplet counter rain gauge, respectively; in [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The rain load on a wall is determined by the driving rain rather than the normal rain. The driving rain can be estimated from the normal rain and the wind velocity:   The rain coefficients R1 and R2 in the dialog [[1D:Dialog_Orientation | orientation, inclination and height]] serve to estimate the driving rain load on a surface of arbitrary orientation and inclination from data on normal rain, wind velocity and wind direction distributions, using the relation   <CENTER>rain load = rain · (R1 + R2 · wind velocity),</CENTER>
:where 'rain' is the normal rain and 'wind velocity' is that component of the mean wind velocity (measured at a height of 10 m, in open area), which is orthogonal to the building surface. This component is determined from the scalar mean of the wind velocity (see above) and the wind direction distribution (see below). R1 and R2 are strongly dependent on the specific location on the building facade. If calculations are to be compared to actual measurements, these coefficients should be experimentally determined for that location. If they cannot be measured, only a very rough estimate is possible. For vertical surfaces, R1 is zero. R2 is about 0.2 s/m for free-standing locations without influence from surrounding buildings etc.; it is markedly less in the center of a facade (e.g. 0.07 s/m); it may even be greater at exposed locations of a building (near edges and corners)[1].  
* Driving rain / tipping bucket (<TT>real</TT>):
* Driving rain / droplet counter (<TT>real</TT>):   the driving rain load on a west-facing wall, measured at a height of 1.50 m with a tipping bucket and a droplet counter rain gauge, respectively. In [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The values in this column can [[2D:Dialog_ClimateFileDetails | optionally]] be read and used for the variable 'rain' in the formula for the rain load (see above: normal rain). Set R1 to 1 and R2 to zero; the resulting rain load will then directly be the measured driving rain.   
* Wind direction distribution (17 * <TT>integer</TT>):   the frequency of wind directions, binned into sectors of 22.5° each.   The wind direction is averaged over 2 minutes and the counter of the corresponding sector then increased by one. A special counter is registering calms. The sum of all counts during one hour should thus be 30 if no interruption of the measurements has occured.   The individual counters are assigned to the following directions:   
<CENTER>NNE-NE-ENE-E-ESE-SE-SSE-S-SSW-SW-WSW-W-WNW-NW-NNW-N-calm</CENTER>
For the calculation of the driving rain load, the contributions of the different directions are determined individually and then summed up. Wind coming 'from behind' does not contribute to the rain load and is ignored. 


A *.WET file supplied by the user must be accompanied by a [[Details:AGD-File | *.AGD file]] which contains geographical information on the climate location.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Künzel, H.M.: Bestimmung der Schlagregenbelastung von Fassadenflächen. IBP-Mitteilung 21 (1994), Nr. 263</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>VDI 3789 Umweltmeteorologie, Blatt 2: Wechselwirkungen zwischen Atmosphäre und Oberflächen; Berechnung der kurz- und der langwelligen Strahlung. Oktober 1994</TD></TR>
</TABLE>

Details:WET-File

2009-03-25T08:14:35Z

Barbara: /* The *.WET Format for Climate Data */

= The *.WET Format for Climate Data =


You can use existing IBP weather files (file format *.WET) to perform WUFI calculations; you can also convert your own weather data to that format and use them.


IBP weather files contain 21 lines of header which explain the meaning of the different data columns and an arbitrary number of lines with hourly weather data. WUFI skips the header.


Example:


[[Bild:WETexample.gif]]


(for formatting reasons, the data lines cannot be reproduced here in their entirety. Please refer to the file IBP1991.WET you received with WUFI for a complete example).


The format of the numbers is free; the only requirement is that a PASCAL program (like WUFI) must be able to read them. 
The file need not conform to a specific column format (as in FORTRAN), the number of decimal places does not matter, floating point numbers need not be in exponential format etc.


The number type <TT>real</TT>/<TT>integer</TT> has to be adhered to, however. The individual numbers must be separated by blanks, not tabulators.


The fact that the floating point numbers in the example all start with a zero is irrelevant (they were created with a FORTRAN program which likes to write numbers this way).


The data in detail:


* Day, month, year, hour (<TT>integer</TT>):   The IBP files contain hourly mean values of the measured data. These time stamps indicate the point in time when each measuring interval of one hour was finished and the measured mean values recorded. I.e., the data line starting with 01 01 91 04 contains the mean values for the hour from 03:00 to 04:00 on January 1, 1991.   Since its data are real-life data, an IBP weather file may contain an intercalary day (February 29). WUFI however knows nothing about intercalary days (at least in the present version). These must be deleted from files you want to use for WUFI calculations.   The time count always refers to winter time (CET). There is no daylight saving time.  

* Exterior air temperature (<TT>real</TT>):   the temperature of the exterior ambient air in [°C]. It is used without change as the exterior air temperature in the WUFI calculation.   

* Temperature of black surface (<TT>real</TT>):
* Temperature of white surface (<TT>real</TT>):   Surface temperatures of west-facing test facade elements painted black ([[Details:ShortWave |as]] ~ 0.9) and white (as ~ 0.4), respectively. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Temperature of Ground Surface (<TT>real</TT>):
* Temperature 50 cm below Ground Surface (<TT>real</TT>):
* Temperature 1 m below Ground Surface (<TT>real</TT>):   Soil temperatures at various depths in [°C]. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Global radiation (<TT>real</TT>):   the sum of the direct and diffuse components of the solar radiation incident on a horizontal surface; in [W/m²].  

* Diffuse radiation (<TT>real</TT>):   the diffuse component of the solar radiation incident on a horizontal surface; in [W/m²].   Subtracting the diffuse radiation from the global radiation results in the direct radiation. From this, the direct normal radiation can be calculated, i.e., the amount of radiation incident on a surface that is orthogonal to the ray direction. This calculation requires knowledge of the time and geographical location of the measurement, since the corresponding position of the sun has to be determined [2].   The direct normal radiation can then be used to calculate the direct radiation incident on a surface with arbitrary orientation and inclination. Addition of the appropriate fraction of diffuse radiation results in the global radiation incident on the building component.   These calculations are automatically done by WUFI during a simulation run.   WUFI uses a [[FAQ:General | simplified radiation model]] which treats the diffuse radiation as isotropic and ignores the albedo of the ground. If you are more demanding or want to allow for local specifics (like shadows etc.), you can perform the conversion yourself and feed the results to WUFI via a [[Details:KLI-File | *.KLI file]].   

* Western radiation (<TT>real</TT>):   the global radiation measured with a west-facing solarimeter; in [W/m²]. [[2D:Dialog_ClimateFileDetails |Optionally]], the radiation component impinging on a (west-facing) facade may directly be read from this column. No conversion is then necessary as would be the case if global and diffuse radiation were used as data source.   

* Relative humidity (<TT>real</TT>):   the relative humidity of the ambient air (0..1). Used by WUFI without change as the exterior relative humidity.  

* Barometric pressure (<TT>real</TT>):   the ambient air pressure reduced to sea level; in [hPA].   

* Wind velocity (<TT>real</TT>):   the scalar mean of the wind velocity; in [m/s]. It is needed to compute the driving rain from the normal rain.   The scalar mean of the wind velocity is the mean value of the readings of an anemometer without the directions taken into account. For example, if for an hour the wind is blowing at 2 m/s but at the same time steadily travelling through all the direcions, then the scalar mean is 2 m/s, whereas the vectorial mean is 0 m/s.   In the vectorial mean, some vector components may cancel. Thus, the scalar mean is greater than (or at least equal to) the vectorial mean.   The IBP weather files also contain information about the distribution of the wind directions (see below). This allows to ignore components that come from 'behind' (and don't contribute to the rain load) and to weight the remaining directions according to the angle they make with the surface.   

* Normal rain / tipping bucket (<TT>real</TT>):
* Normal rain / droplet counter (<TT>real</TT>):   the normal rain (i.e., the rain incident on a horizontal surface in open area) during one hour, measured with a tipping bucket and a droplet counter rain gauge, respectively; in [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The rain load on a wall is determined by the driving rain rather than the normal rain. The driving rain can be estimated from the normal rain and the wind velocity:   The rain coefficients R1 and R2 in the dialog [[1D:Dialog_Orientation | orientation, inclination and height]] serve to estimate the driving rain load on a surface of arbitrary orientation and inclination from data on normal rain, wind velocity and wind direction distributions, using the relation   <CENTER>rain load = rain · (R1 + R2 · wind velocity),</CENTER>
:where 'rain' is the normal rain and 'wind velocity' is that component of the mean wind velocity (measured at a height of 10 m, in open area), which is orthogonal to the building surface. This component is determined from the scalar mean of the wind velocity (see above) and the wind direction distribution (see below). R1 and R2 are strongly dependent on the specific location on the building facade. If calculations are to be compared to actual measurements, these coefficients should be experimentally determined for that location. If they cannot be measured, only a very rough estimate is possible. For vertical surfaces, R1 is zero. R2 is about 0.2 s/m for free-standing locations without influence from surrounding buildings etc.; it is markedly less in the center of a facade (e.g. 0.07 s/m); it may even be greater at exposed locations of a building (near edges and corners)[1].  
* Driving rain / tipping bucket (<TT>real</TT>):
* Driving rain / droplet counter (<TT>real</TT>):   the driving rain load on a west-facing wall, measured at a height of 1.50 m with a tipping bucket and a droplet counter rain gauge, respectively. In [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The values in this column can [[2D:Dialog_ClimateFileDetails | optionally be read]] and used for the variable 'rain' in the formula for the rain load (see above: normal rain). Set R1 to 1 and R2 to zero; the resulting rain load will then directly be the measured driving rain.   
* Wind direction distribution (17 * <TT>integer</TT>):   the frequency of wind directions, binned into sectors of 22.5° each.   The wind direction is averaged over 2 minutes and the counter of the corresponding sector then increased by one. A special counter is registering calms. The sum of all counts during one hour should thus be 30 if no interruption of the measurements has occured.   The individual counters are assigned to the following directions:   
<CENTER>NNE-NE-ENE-E-ESE-SE-SSE-S-SSW-SW-WSW-W-WNW-NW-NNW-N-calm</CENTER>
For the calculation of the driving rain load, the contributions of the different directions are determined individually and then summed up. Wind coming 'from behind' does not contribute to the rain load and is ignored. 


A *.WET file supplied by the user must be accompanied by a [[Details:AGD-File | *.AGD file]] which contains geographical information on the climate location.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Künzel, H.M.: Bestimmung der Schlagregenbelastung von Fassadenflächen. IBP-Mitteilung 21 (1994), Nr. 263</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>VDI 3789 Umweltmeteorologie, Blatt 2: Wechselwirkungen zwischen Atmosphäre und Oberflächen; Berechnung der kurz- und der langwelligen Strahlung. Oktober 1994</TD></TR>
</TABLE>

Details:WET-File

2009-03-25T08:11:50Z

Barbara: /* The *.WET Format for Climate Data */

= The *.WET Format for Climate Data =


You can use existing IBP weather files (file format *.WET) to perform WUFI calculations; you can also convert your own weather data to that format and use them.


IBP weather files contain 21 lines of header which explain the meaning of the different data columns and an arbitrary number of lines with hourly weather data. WUFI skips the header.


Example:


[[Bild:WETexample.gif]]


(for formatting reasons, the data lines cannot be reproduced here in their entirety. Please refer to the file IBP1991.WET you received with WUFI for a complete example).


The format of the numbers is free; the only requirement is that a PASCAL program (like WUFI) must be able to read them. 
The file need not conform to a specific column format (as in FORTRAN), the number of decimal places does not matter, floating point numbers need not be in exponential format etc.


The number type <TT>real</TT>/<TT>integer</TT> has to be adhered to, however. The individual numbers must be separated by blanks, not tabulators.


The fact that the floating point numbers in the example all start with a zero is irrelevant (they were created with a FORTRAN program which likes to write numbers this way).


The data in detail:


* Day, month, year, hour (<TT>integer</TT>):   The IBP files contain hourly mean values of the measured data. These time stamps indicate the point in time when each measuring interval of one hour was finished and the measured mean values recorded. I.e., the data line starting with 01 01 91 04 contains the mean values for the hour from 03:00 to 04:00 on January 1, 1991.   Since its data are real-life data, an IBP weather file may contain an intercalary day (February 29). WUFI however knows nothing about intercalary days (at least in the present version). These must be deleted from files you want to use for WUFI calculations.   The time count always refers to winter time (CET). There is no daylight saving time.  

* Exterior air temperature (<TT>real</TT>):   the temperature of the exterior ambient air in [°C]. It is used without change as the exterior air temperature in the WUFI calculation.   

* Temperature of black surface (<TT>real</TT>):
* Temperature of white surface (<TT>real</TT>):   Surface temperatures of west-facing test facade elements painted black ([[Details:ShortWave |as]] ~ 0.9) and white (as ~ 0.4), respectively. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Temperature of Ground Surface (<TT>real</TT>):
* Temperature 50 cm below Ground Surface (<TT>real</TT>):
* Temperature 1 m below Ground Surface (<TT>real</TT>):   Soil temperatures at various depths in [°C]. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Global radiation (<TT>real</TT>):   the sum of the direct and diffuse components of the solar radiation incident on a horizontal surface; in [W/m²].  

* Diffuse radiation (<TT>real</TT>):   the diffuse component of the solar radiation incident on a horizontal surface; in [W/m²].   Subtracting the diffuse radiation from the global radiation results in the direct radiation. From this, the direct normal radiation can be calculated, i.e., the amount of radiation incident on a surface that is orthogonal to the ray direction. This calculation requires knowledge of the time and geographical location of the measurement, since the corresponding position of the sun has to be determined [2].   The direct normal radiation can then be used to calculate the direct radiation incident on a surface with arbitrary orientation and inclination. Addition of the appropriate fraction of diffuse radiation results in the global radiation incident on the building component.   These calculations are automatically done by WUFI during a simulation run.   WUFI uses a [[FAQ:General | simplified radiation model]] which treats the diffuse radiation as isotropic and ignores the albedo of the ground. If you are more demanding or want to allow for local specifics (like shadows etc.), you can perform the conversion yourself and feed the results to WUFI via a [[Details:KLI-File | *.KLI file]].   

* Western radiation (<TT>real</TT>):   the global radiation measured with a west-facing solarimeter; in [W/m²]. [[2D:Dialog_ClimateFileDetails |Optionally]], the radiation component impinging on a (west-facing) facade may directly be read from this column. No conversion is then necessary as would be the case if global and diffuse radiation were used as data source.   

* Relative humidity (<TT>real</TT>):   the relative humidity of the ambient air (0..1). Used by WUFI without change as the exterior relative humidity.  

* Barometric pressure (<TT>real</TT>):   the ambient air pressure reduced to sea level; in [hPA].   

* Wind velocity (<TT>real</TT>):   the scalar mean of the wind velocity; in [m/s]. It is needed to compute the driving rain from the normal rain.   The scalar mean of the wind velocity is the mean value of the readings of an anemometer without the directions taken into account. For example, if for an hour the wind is blowing at 2 m/s but at the same time steadily travelling through all the direcions, then the scalar mean is 2 m/s, whereas the vectorial mean is 0 m/s.   In the vectorial mean, some vector components may cancel. Thus, the scalar mean is greater than (or at least equal to) the vectorial mean.   The IBP weather files also contain information about the distribution of the wind directions (see below). This allows to ignore components that come from 'behind' (and don't contribute to the rain load) and to weight the remaining directions according to the angle they make with the surface.   

* Normal rain / tipping bucket (<TT>real</TT>):
* Normal rain / droplet counter (<TT>real</TT>):   the normal rain (i.e., the rain incident on a horizontal surface in open area) during one hour, measured with a tipping bucket and a droplet counter rain gauge, respectively; in [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The rain load on a wall is determined by the driving rain rather than the normal rain. The driving rain can be estimated from the normal rain and the wind velocity:   The rain coefficients R1 and R2 in the dialog [[1D:Dialog_Orientation | orientation, inclination and height]] serve to estimate the driving rain load on a surface of arbitrary orientation and inclination from data on normal rain, wind velocity and wind direction distributions, using the relation   <CENTER>rain load = rain · (R1 + R2 · wind velocity),</CENTER>
where 'rain' is the normal rain and 'wind velocity' is that component of the mean wind velocity (measured at a height of 10 m, in open area), which is orthogonal to the building surface. This component is determined from the scalar mean of the wind velocity (see above) and the wind direction distribution (see below). R1 and R2 are strongly dependent on the specific location on the building facade. If calculations are to be compared to actual measurements, these coefficients should be experimentally determined for that location. If they cannot be measured, only a very rough estimate is possible. For vertical surfaces, R1 is zero. R2 is about 0.2 s/m for free-standing locations without influence from surrounding buildings etc.; it is markedly less in the center of a facade (e.g. 0.07 s/m); it may even be greater at exposed locations of a building (near edges and corners)[1].  
* Driving rain / tipping bucket (<TT>real</TT>):
* Driving rain / droplet counter (<TT>real</TT>):   the driving rain load on a west-facing wall, measured at a height of 1.50 m with a tipping bucket and a droplet counter rain gauge, respectively. In [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The values in this column can [[2D:Dialog_ClimateFileDetails | optionally be read]] and used for the variable 'rain' in the formula for the rain load (see above: normal rain). Set R1 to 1 and R2 to zero; the resulting rain load will then directly be the measured driving rain.   
* Wind direction distribution (17 * <TT>integer</TT>):   the frequency of wind directions, binned into sectors of 22.5° each.   The wind direction is averaged over 2 minutes and the counter of the corresponding sector then increased by one. A special counter is registering calms. The sum of all counts during one hour should thus be 30 if no interruption of the measurements has occured.   The individual counters are assigned to the following directions:   
<CENTER>NNE-NE-ENE-E-ESE-SE-SSE-S-SSW-SW-WSW-W-WNW-NW-NNW-N-calm</CENTER>
For the calculation of the driving rain load, the contributions of the different directions are determined individually and then summed up. Wind coming 'from behind' does not contribute to the rain load and is ignored. 


A *.WET file supplied by the user must be accompanied by a [[Details:AGD-File | *.AGD file]] which contains geographical information on the climate location.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Künzel, H.M.: Bestimmung der Schlagregenbelastung von Fassadenflächen. IBP-Mitteilung 21 (1994), Nr. 263</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>VDI 3789 Umweltmeteorologie, Blatt 2: Wechselwirkungen zwischen Atmosphäre und Oberflächen; Berechnung der kurz- und der langwelligen Strahlung. Oktober 1994</TD></TR>
</TABLE>

Details:WET-File

2009-03-25T08:09:44Z

Barbara: /* The *.WET Format for Climate Data */

= The *.WET Format for Climate Data =


You can use existing IBP weather files (file format *.WET) to perform WUFI calculations; you can also convert your own weather data to that format and use them.


IBP weather files contain 21 lines of header which explain the meaning of the different data columns and an arbitrary number of lines with hourly weather data. WUFI skips the header.


Example:


[[Bild:WETexample.gif]]


(for formatting reasons, the data lines cannot be reproduced here in their entirety. Please refer to the file IBP1991.WET you received with WUFI for a complete example).


The format of the numbers is free; the only requirement is that a PASCAL program (like WUFI) must be able to read them. 
The file need not conform to a specific column format (as in FORTRAN), the number of decimal places does not matter, floating point numbers need not be in exponential format etc.


The number type <TT>real</TT>/<TT>integer</TT> has to be adhered to, however. The individual numbers must be separated by blanks, not tabulators.


The fact that the floating point numbers in the example all start with a zero is irrelevant (they were created with a FORTRAN program which likes to write numbers this way).


The data in detail:


* Day, month, year, hour (<TT>integer</TT>):   The IBP files contain hourly mean values of the measured data. These time stamps indicate the point in time when each measuring interval of one hour was finished and the measured mean values recorded. I.e., the data line starting with 01 01 91 04 contains the mean values for the hour from 03:00 to 04:00 on January 1, 1991.   Since its data are real-life data, an IBP weather file may contain an intercalary day (February 29). WUFI however knows nothing about intercalary days (at least in the present version). These must be deleted from files you want to use for WUFI calculations.   The time count always refers to winter time (CET). There is no daylight saving time.  

* Exterior air temperature (<TT>real</TT>):   the temperature of the exterior ambient air in [°C]. It is used without change as the exterior air temperature in the WUFI calculation.   

* Temperature of black surface (<TT>real</TT>):
* Temperature of white surface (<TT>real</TT>):   Surface temperatures of west-facing test facade elements painted black ([[Details:ShortWave |as]] ~ 0.9) and white (as ~ 0.4), respectively. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Temperature of Ground Surface (<TT>real</TT>):
* Temperature 50 cm below Ground Surface (<TT>real</TT>):
* Temperature 1 m below Ground Surface (<TT>real</TT>):   Soil temperatures at various depths in [°C]. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Global radiation (<TT>real</TT>):   the sum of the direct and diffuse components of the solar radiation incident on a horizontal surface; in [W/m²].  

* Diffuse radiation (<TT>real</TT>):   the diffuse component of the solar radiation incident on a horizontal surface; in [W/m²].   Subtracting the diffuse radiation from the global radiation results in the direct radiation. From this, the direct normal radiation can be calculated, i.e., the amount of radiation incident on a surface that is orthogonal to the ray direction. This calculation requires knowledge of the time and geographical location of the measurement, since the corresponding position of the sun has to be determined [2].   The direct normal radiation can then be used to calculate the direct radiation incident on a surface with arbitrary orientation and inclination. Addition of the appropriate fraction of diffuse radiation results in the global radiation incident on the building component.   These calculations are automatically done by WUFI during a simulation run.   WUFI uses a [[FAQ:General | simplified radiation model]] which treats the diffuse radiation as isotropic and ignores the albedo of the ground. If you are more demanding or want to allow for local specifics (like shadows etc.), you can perform the conversion yourself and feed the results to WUFI via a [[Details:KLI-File | *.KLI file]].   

* Western radiation (<TT>real</TT>):   the global radiation measured with a west-facing solarimeter; in [W/m²]. [[2D:Dialog_ClimateFileDetails |Optionally]], the radiation component impinging on a (west-facing) facade may directly be read from this column. No conversion is then necessary as would be the case if global and diffuse radiation were used as data source.   

* Relative humidity (<TT>real</TT>):   the relative humidity of the ambient air (0..1). Used by WUFI without change as the exterior relative humidity.  

* Barometric pressure (<TT>real</TT>):   the ambient air pressure reduced to sea level; in [hPA].   

* Wind velocity (<TT>real</TT>):   the scalar mean of the wind velocity; in [m/s]. It is needed to compute the driving rain from the normal rain.   The scalar mean of the wind velocity is the mean value of the readings of an anemometer without the directions taken into account. For example, if for an hour the wind is blowing at 2 m/s but at the same time steadily travelling through all the direcions, then the scalar mean is 2 m/s, whereas the vectorial mean is 0 m/s.   In the vectorial mean, some vector components may cancel. Thus, the scalar mean is greater than (or at least equal to) the vectorial mean.   The IBP weather files also contain information about the distribution of the wind directions (see below). This allows to ignore components that come from 'behind' (and don't contribute to the rain load) and to weight the remaining directions according to the angle they make with the surface.   

* Normal rain / tipping bucket (<TT>real</TT>):
* Normal rain / droplet counter (<TT>real</TT>):   the normal rain (i.e., the rain incident on a horizontal surface in open area) during one hour, measured with a tipping bucket and a droplet counter rain gauge, respectively; in [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The rain load on a wall is determined by the driving rain rather than the normal rain. The driving rain can be estimated from the normal rain and the wind velocity:   The rain coefficients R1 and R2 in the dialog [[1D:Dialog_Orientation | orientation, the inclination and the height]] serve to estimate the driving rain load on a surface of arbitrary orientation and inclination from data on normal rain, wind velocity and wind direction distributions, using the relation   <CENTER>rain load = rain · (R1 + R2 · wind velocity),</CENTER>
where 'rain' is the normal rain and 'wind velocity' is that component of the mean wind velocity (measured at a height of 10 m, in open area), which is orthogonal to the building surface. This component is determined from the scalar mean of the wind velocity (see above) and the wind direction distribution (see below). R1 and R2 are strongly dependent on the specific location on the building facade. If calculations are to be compared to actual measurements, these coefficients should be experimentally determined for that location. If they cannot be measured, only a very rough estimate is possible. For vertical surfaces, R1 is zero. R2 is about 0.2 s/m for free-standing locations without influence from surrounding buildings etc.; it is markedly less in the center of a facade (e.g. 0.07 s/m); it may even be greater at exposed locations of a building (near edges and corners)[1].  
* Driving rain / tipping bucket (<TT>real</TT>):
* Driving rain / droplet counter (<TT>real</TT>):   the driving rain load on a west-facing wall, measured at a height of 1.50 m with a tipping bucket and a droplet counter rain gauge, respectively. In [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The values in this column can [[2D:Dialog_ClimateFileDetails | optionally be read]] and used for the variable 'rain' in the formula for the rain load (see above: normal rain). Set R1 to 1 and R2 to zero; the resulting rain load will then directly be the measured driving rain.   
* Wind direction distribution (17 * <TT>integer</TT>):   the frequency of wind directions, binned into sectors of 22.5° each.   The wind direction is averaged over 2 minutes and the counter of the corresponding sector then increased by one. A special counter is registering calms. The sum of all counts during one hour should thus be 30 if no interruption of the measurements has occured.   The individual counters are assigned to the following directions:   
<CENTER>NNE-NE-ENE-E-ESE-SE-SSE-S-SSW-SW-WSW-W-WNW-NW-NNW-N-calm</CENTER>
For the calculation of the driving rain load, the contributions of the different directions are determined individually and then summed up. Wind coming 'from behind' does not contribute to the rain load and is ignored. 


A *.WET file supplied by the user must be accompanied by a [[Details:AGD-File | *.AGD file]] which contains geographical information on the climate location.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Künzel, H.M.: Bestimmung der Schlagregenbelastung von Fassadenflächen. IBP-Mitteilung 21 (1994), Nr. 263</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>VDI 3789 Umweltmeteorologie, Blatt 2: Wechselwirkungen zwischen Atmosphäre und Oberflächen; Berechnung der kurz- und der langwelligen Strahlung. Oktober 1994</TD></TR>
</TABLE>

1D:Dialog SelectClimateFileFromMap

2009-03-25T07:59:30Z

Barbara: /* Dialog: Select Climate File (from map) */

= Dialog: Select Climate File (from map) =

[[Bild:DialogSelectClimateFileFromMap_04.gif]]


Those locations for which climate files are supplied with WUFI and some predefined
locations for which climate files are available from other
[[Details:SourcesforclimateData | sources]] can be selected from this dialog's
maps with a simple mouse click. 
To select climate files
[[Details:Climate | created by yourself]] or [[Details:SourcesforclimateData | acquired otherwise]], please use the option
[[1D:Dialog_SelectClimateFileFromBrowser | "Select user-defined
file"]].


You may zoom into the maps by dragging open a zoom frame from upper left to
lower right at the desired location. You may pan a zoomed map with the right mouse
button held down. You may zoom out by dragging open a zoom frame from lower right to
upper left. 
  



"Region/Continent":


Select the desired map. Currently Europe, North America and Japan are available. 
  



"Location":


This drop-down list contains all the locations on the map in alphabetic sequence
and offers an alternative way of selecting a location. 
  



"Climate file",


If several files are available for a location (e.g. one warm and one cold year), you
must select here the desired file. 
  



"Remarks":


If comments or remarks are available for the selected file, they can be displayed here. 
  



Currently, the following climate files are supplied with WUFI:

* Holzkirchen (1991),
* Kassel,
* Vienna, Graz, Innsbruck,
* Zürich, Davos, Locarno (one 'warm' and one 'cold' year each),
* Warsaw, Krakow, Kolbrzeg,
* Grenoble,
* Lisbon,
* Espoo (in the Finnish Pro version also Helsinki, Jyväskylä and Sodankylä),
* 12 Norwegian cities
* 55 US-American cities (the 10%-coldest and the 10%-warmest year selected from 30 years),
* 9 Canadian cities (some of them with one warm and one cold year)
* 7 Japanese cities. 
  


Version notice: only WUFI Pro has all these files; WUFI light
has a few of them, depending on the language; WUFI ORNL/IBP has the North-American
cities.


The Holzkirchen weather data are supplied by IBP, other data are courtesy
of Mr. William Seaton, ASHRAE (USA and Canada), Dr. K. Krec, Büro für
Bauphysik (Austria), Dr. Ghazi Wakili, EMPA (Switzerland), Dr. W. Haupt, Uni GH Kassel
(Kassel), CSTB (Grenoble), FEUP, Uni Porto (Lisbon), VTT (Finland), NBI/NTNU (Norway),
TU Lodz (Poland) and the Architectural Institute of Japan (AMeDAS data for Japan).


The colors of the available locations indicate the file format of the respective
weather files. Predefined locations for which weather data can be purchased separately
are initially grey. Please copy such a file into WUFI's
Climate folder; on the next start WUFI will recognize
the file and display the location in color. 
WUFI is prepared to read the Test Reference Years from the German Weather Service DWD,
both the 'old' (Blümel et al., 1986,
[[Details:TRY-File | *.TRY]]; not offered any more by DWD) and
the 'new' files (Christoffer et al., 2004,
[[Details:DAT-File | *.DAT]]). 
There are also 842 predefined locations for Japan (depending on the WUFI version,
data for one or seven locations are included with WUFI). 
See [[Details:SourcesForClimateData | Sources for Climate Data]] for where to
purchase such files.


The Holzkirchen climate file currently supplied with WUFI contains the measured data
from 1991 which is considered typical for Holzkirchen. Future WUFI versions may come
with two Hygrothermal Reference Years representing different stress situations for
building components.

Details:SourcesforclimateData

2009-03-25T07:53:08Z

Barbara: /* METEONORM: */

= Test reference years: =

The German National Meteorological Service DWD offers test reference years for all
climatic regions in Germany, representing typical as well as extreme weather situations:


"New Test Reference Years (TRYs) have been worked
out for Germany. Test Reference Years are datasets of selected meteorological elements
for each hour of the year. They provide climatological boundary conditions for simulating
calculations on an hourly basis, in the first place for the operation of heating and air
conditioning systems. On the basis of a factor and cluster analysis the Federal Republic
has been divided into 15 regions. For each region a representative station has been
determined and a Test Reference Year has been prepared. They replace the previous Test
Reference Years of the old West German states. For those states which acceded to the
Federal Republic after unification such datasets are available for the first time. A
Test Reference Year contains characteristic weather data of a representative year. The
weather sequences have been chosen on the basis of an analysis of the Grosswetterlagen
in such a way that the seasonal mean values of the individual meteorological elements
(especially of temperature and humidity) of the representative stations mainly correspond
with their 30-years mean values. As heating and air conditioning equipment also have to be
designed for extreme situations, additional datasets with the same data structure for a
very cold winter (December 1984 to February 1985) and an extremely hot summer (June to
August 1983) have been compiled."

([http://www.dwd.de/de/wir/Geschaeftsfelder/KlimaUmwelt/Leistungen/Statistiken/TRY/TRY.htm])

Unfortunately, these new test reference years (as opposed to the 'old' test reference
years of 1986) do not contain precipitation data any more. They are thus not suitable
for investigations involving the influence of rain.


The representative stations for the test reference years have already been
[[1D:Dialog_SelectClimateFileFromMap | predefined]] in WUFI's climate selection
map. Just copy the respective files into WUFI's Climate
folder, on the next start WUFI will recognize the files. They can then easily be selected
via the [[1D:Dialog_SelectClimateFileFromMap | climate selection]] map. 
  


=== METEONORM: ===

The Swiss METEOTEST company has developed METEONORM, a program for creating synthetic
hourly weather data, based on measured long-term mean values:


"METEONORM 5.0 (Edition 2003) is based on over
18 years of experience in the development of meteorological databases for energy
applications. It is a comprehensive meteorological reference, incorporating a catalogue
of meteorological data and calculation procedures for solar applications and system design
at any desired location in the world. METEONORM addresses engineers, architects, teachers,
planners and anyone interested in solar energy and climatology. 
... 
Several databases from different parts of the world have been combined and checked for
their reliability. In the present version, most of the data is taken from the GEBA
(Global Energy Balance Archive), from the World Meteorological Organization (WMO/OMM)
Climatological Normals 1961-1990 and from the Swiss database compiled by MeteoSwiss. 
Monthly climatological (long term) means are available for the following parameters: 
* global radiation 
* ambient air temperature 
* humidity 
* precipitation, days with precipitation 
* wind speed and direction 
* sunshine duration 
... 
For many regions of the world, measured data may only be applied within a radius of
50 km from weather stations. This makes it necessary to interpolate parameters between
stations. Interpolation models for solar radiation, temperature and additional parameters,
allowing application at any site in the world, are included in the software. 
... 
From the monthly values (station data, interpolated data or imported data), METEONORM
calculates hourly values of all parameters using a stochastic model. The resulting time
series correspond to "typical years" used for system design. 
  
([http://www.meteotest.ch/en/mn_description?w=ber])

Note: METEONORM can create files in the
[[Details:TRY-File | TRY]] format which can be directly read by
WUFI. 
  


=== Austrian Test Reference Years ===

In addition to the three weather files included with WUFI, weather data for numerous other
Austrian locations are available.


The distributor for these data is

QUADRUPLE-M Elsässer GmbH 
Technisches Büro für Bauphysik 
GF Dr. Manfred Elsässer 
Erzherzog-Eugen-Straße 14/1 
A-6020 Innsbruck 
  
Tel.: +43 512 251401 
Fax: +43 512 378550 
Mobil: +43 664 4324814 
E-mail: office@quad-m.at oder manfred.elsaesser@uibk.ac.at 
  

=== ASHRAE CD-ROM: International Weather for Energy Calculations (IWEC) ===

"Contains "typical" weather data in
ASCII format, suitable for use with building energy simulation programs, for 227
locations outside the USA and Canada. The files are derived from up to 18 years of
DATSAV3 hourly weather data originally archived at the National Climatic Data Center.
The weather data are supplemented by solar radiation estimated on an hourly basis from
earth-sun geometry and hourly weather elements, particularly cloud amount information.
This CD is the result of ASHRAE Research Project 1015. The CD contains the user's manual
and complete research report in PDF, the weather data in printable ASCII format and a
version of Adobe Acrobat Reader. To run Acrobat Reader, a 486 or Pentium-based computer
and either Microsoft Windows 95 or Windows NT 3.5 or later is required. Will also run
on a Macintosh. For Windows 95 and NT, 8MB or RAM (16MB recommended) and 10MB of free
hard-disk space are required."


([http://resourcecenter.ashrae.org/store/ashrae/newstore.cgi?itemid=9448&view=item&page=1&loginid=2167053&words=iwec&method=and&])


Note: the IWEC weather data do not contain quantitative rain data but only a
rain indicator reporting rain intensity categories like "light",
"moderate", "heavy", etc. As long as it has not been worked out
which representative hourly quantities corresponding to these categories should be used
in hygrothermic simulations, WUFI will not use rain data in calculations performed
with *.IWC files.


The CD contains files for the following locations:

<TABLE><TR><TD WIDTH="50%">

<TABLE>
<TR><TD VALIGN="TOP">NOR:</TD>
<TD> </TD>
<TD>Bergen, Oslo/Fornebu</TD>
</TR>
<TR><TD VALIGN="TOP">SWE:</TD>
<TD> </TD>
<TD>Kiruna, Ostersund/Froson, Karlstad, Stockholm/Arlanda, Goteborg, Landvetter</TD>
</TR>
<TR><TD VALIGN="TOP">FIN:</TD>
<TD> </TD>
<TD>Tampere, Helsinki</TD>
</TR>
<TR><TD VALIGN="TOP">GBR:</TD>
<TD> </TD>
<TD>Aberdeen/Dyce, Oban, Leuchars, Aughton, Finningley, Hemsby, Birmingham,
London/Gatwick, Jersey/Channel Islands, Belfast</TD>
</TR>
<TR><TD VALIGN="TOP">IRL:</TD>
<TD> </TD>
<TD>Valentia Observatory, Kilkenny, Birr, Dublin, Clones, Belmullet, Malin</TD>
</TR>
<TR><TD VALIGN="TOP">ISL:</TD>
<TD> </TD>
<TD>Reykjavik</TD>
</TR>
<TR><TD VALIGN="TOP">DNK:</TD>
<TD> </TD>
<TD>Copenhagen</TD>
</TR>
<TR><TD VALIGN="TOP">NLD:</TD>
<TD> </TD>
<TD>Amsterdam, Groningen, Beek</TD>
</TR>
<TR><TD VALIGN="TOP">BEL:</TD>
<TD> </TD>
<TD>Oostende, Brussels, Saint Hubert</TD>
</TR>
<TR><TD VALIGN="TOP">CHE:</TD>
<TD> </TD>
<TD>Geneva</TD>
</TR>
<TR><TD VALIGN="TOP">FRA:</TD>
<TD> </TD>
<TD>Brest, Paris/Orly, Nancy, Strasbourg, Nantes, Dijon, Clermont-Ferrand, Lyon,
Bordeaux, Montpellier, Marseille, Nice</TD>
</TR>
<TR><TD VALIGN="TOP">ESP:</TD>
<TD> </TD>
<TD>Santander, Barcelona, Madrid, Valencia, Palma, Sevilla</TD>
</TR>
<TR><TD VALIGN="TOP">PRT:</TD>
<TD> </TD>
<TD>Lajes, Porto, Coimbra, Faro, Evora, Braganca</TD>
</TR>
<TR><TD VALIGN="TOP">DEU:</TD>
<TD> </TD>
<TD>Hamburg, Bremen, Berlin, Dusseldorf, Koln, Frankfurt am Main,
Mannheim, Stuttgart, Munich</TD>
</TR>
<TR><TD VALIGN="TOP">AUT:</TD>
<TD> </TD>
<TD>Linz, Vienna/Schwechat, Innsbruck, Salzburg, Graz</TD>
</TR>
<TR><TD VALIGN="TOP">CZE:</TD>
<TD> </TD>
<TD>Prague, Ostrava</TD>
</TR>
<TR><TD VALIGN="TOP">SVK:</TD>
<TD> </TD>
<TD>Bratislava, Kosice</TD>
</TR>
<TR><TD VALIGN="TOP">POL:</TD>
<TD> </TD>
<TD>Kolobrzeg, Poznan, Warsaw, Krakow</TD>
</TR>
<TR><TD VALIGN="TOP">HUN:</TD>
<TD> </TD>
<TD>Szombathely, Debrecen</TD>
</TR>
<TR><TD VALIGN="TOP">SVN:</TD>
<TD> </TD>
<TD>Ljubljana</TD>
</TR>
<TR><TD VALIGN="TOP">BIH:</TD>
<TD> </TD>
<TD>Banja Luka</TD>
</TR>
<TR><TD VALIGN="TOP">YUG:</TD>
<TD> </TD>
<TD>Belgrade, Podgorica</TD>
</TR>
<TR><TD VALIGN="TOP">ROM:</TD>
<TD> </TD>
<TD>Cluj-Napoca, Timisoara, Galati, Bucharest, Craiova, Constanta</TD>
</TR>
<TR><TD VALIGN="TOP">BGR:</TD>
<TD> </TD>
<TD>Varna, Sofia, Plovdiv</TD>
</TR>
<TR><TD VALIGN="TOP">ITA:</TD>
<TD> </TD>
<TD>Torino, Milan, Venice, Genova, Pisa, Rome, Naples, Brindisi, Palermo, Messina</TD>
</TR>
<TR><TD VALIGN="TOP">GRC:</TD>
<TD> </TD>
<TD>Thessaloniki, Andravida, Athens</TD>
</TR>
<TR><TD VALIGN="TOP">TUR:</TD>
<TD> </TD>
<TD>Istanbul, Ankara, Izmir</TD>
</TR>
<TR><TD VALIGN="TOP">CYP:</TD>
<TD> </TD>
<TD>Larnaca</TD>
</TR>
<TR><TD VALIGN="TOP">RUS:</TD>
<TD> </TD>
<TD>Arkhangel'sk, Yakutsk, Saint-Petersburg, Moscow, Ekaterinburg,
Omsk, Samara, Irkutsk, Chita</TD>
</TR>
<TR><TD VALIGN="TOP">LTU:</TD>
<TD> </TD>
<TD>Kaunas</TD>
</TR>
<TR><TD VALIGN="TOP">BLR:</TD>
<TD> </TD>
<TD>Minsk</TD>
</TR>
<TR><TD VALIGN="TOP">UKR:</TD>
<TD> </TD>
<TD>Kiev, Odessa</TD>
</TR>
<TR><TD VALIGN="TOP">KAZ:</TD>
<TD> </TD>
<TD>Semipalatinsk</TD>
</TR>
<TR><TD VALIGN="TOP">UZB:</TD>
<TD> </TD>
<TD>Tashkent</TD>
</TR>
<TR><TD VALIGN="TOP">SYR:</TD>
<TD> </TD>
<TD>Damascus</TD>
</TR>
<TR><TD VALIGN="TOP">ISR:</TD>
<TD> </TD>
<TD>Jerusalem</TD>
</TR>
<TR><TD VALIGN="TOP">SAU:</TD>
<TD> </TD>
<TD>Riyadh</TD>
</TR>
<TR><TD VALIGN="TOP">ARE:</TD>
<TD> </TD>
<TD>Abu Dhabi</TD>
</TR>
<TR><TD VALIGN="TOP">PAK:</TD>
<TD> </TD>
<TD>Karachi</TD>
</TR>
</TABLE>

</TD><TD>

<TABLE>
<TR><TD VALIGN="TOP">IND:</TD>
<TD> </TD>
<TD>New Delhi, Ahmadabad, Calcutta, Nagpur, Bombay, Goa/Panaji, Madras, Trivandrum</TD>
</TR>
<TR><TD VALIGN="TOP">MNG:</TD>
<TD> </TD>
<TD>Ulaangom, Ulaanbataar</TD>
</TR>
<TR><TD VALIGN="TOP">MAC:</TD>
<TD> </TD>
<TD>Macau</TD>
</TR>
<TR><TD VALIGN="TOP">TWN:</TD>
<TD> </TD>
<TD>Taipei</TD>
</TR>
<TR><TD VALIGN="TOP">PRK:</TD>
<TD> </TD>
<TD>Ch'ongjin, P'yongyang, Haeju</TD>
</TR>
<TR><TD VALIGN="TOP">KOR:</TD>
<TD> </TD>
<TD>Kangnung, Inch'on, Ulsan, Kwangju</TD>
</TR>
<TR><TD VALIGN="TOP">JPN:</TD>
<TD> </TD>
<TD>Sapporo, Matsumoto, Nagoya, Tokyo/Hyakuri, Miho (CIV/JASDF),
Shimonoseki, Osaka, Kagoshima, Tosashimizu</TD>
</TR>
<TR><TD VALIGN="TOP">THA:</TD>
<TD> </TD>
<TD>Bangkok</TD>
</TR>
<TR><TD VALIGN="TOP">MYS:</TD>
<TD> </TD>
<TD>George Town, Kota Baharu, Kuala Lumpur</TD>
</TR>
<TR><TD VALIGN="TOP">SGP:</TD>
<TD> </TD>
<TD>Singapore</TD>
</TR>
<TR><TD VALIGN="TOP">VNM:</TD>
<TD> </TD>
<TD>Hanoi</TD>
</TR>
<TR><TD VALIGN="TOP">CHN:</TD>
<TD> </TD>
<TD>Harbin, Urumqi, Lanzhou, Shenyang, Beijing, Kunming, Shanghai, Guangzhou</TD>
</TR>
<TR><TD VALIGN="TOP">MAR:</TD>
<TD> </TD>
<TD>Casablanca/Nouasser</TD>
</TR>
<TR><TD VALIGN="TOP">DZA:</TD>
<TD> </TD>
<TD>Algiers</TD>
</TR>
<TR><TD VALIGN="TOP">TUN:</TD>
<TD> </TD>
<TD>Tunis</TD>
</TR>
<TR><TD VALIGN="TOP">SEN:</TD>
<TD> </TD>
<TD>Dakar</TD>
</TR>
<TR><TD VALIGN="TOP">LBY:</TD>
<TD> </TD>
<TD>Tripoli</TD>
</TR>
<TR><TD VALIGN="TOP">EGY:</TD>
<TD> </TD>
<TD>Cairo, Aswan</TD>
</TR>
<TR><TD VALIGN="TOP">KEN:</TD>
<TD> </TD>
<TD>Nairobi</TD>
</TR>
<TR><TD VALIGN="TOP">MDG:</TD>
<TD> </TD>
<TD>Antananarivo</TD>
</TR>
<TR><TD VALIGN="TOP">ZWE:</TD>
<TD> </TD>
<TD>Harare</TD>
</TR>
<TR><TD VALIGN="TOP">ZAF:</TD>
<TD> </TD>
<TD>Johannesburg, Cape Town</TD>
</TR>
<TR><TD VALIGN="TOP">MEX:</TD>
<TD> </TD>
<TD>Mexico City, Veracruz, Acapulco</TD>
</TR>
<TR><TD VALIGN="TOP">CUB:</TD>
<TD> </TD>
<TD>Havana</TD>
</TR>
<TR><TD VALIGN="TOP">MTQ:</TD>
<TD> </TD>
<TD>Fort-de-France</TD>
</TR>
<TR><TD VALIGN="TOP">COL:</TD>
<TD> </TD>
<TD>Bogota</TD>
</TR>
<TR><TD VALIGN="TOP">VEN:</TD>
<TD> </TD>
<TD>Caracas</TD>
</TR>
<TR><TD VALIGN="TOP">BRA:</TD>
<TD> </TD>
<TD>Belem, Recife, Brasilia, Sao Paulo</TD>
</TR>
<TR><TD VALIGN="TOP">ECU:</TD>
<TD> </TD>
<TD>Quito</TD>
</TR>
<TR><TD VALIGN="TOP">PER:</TD>
<TD> </TD>
<TD>Lima, Cuzco, Arequipa</TD>
</TR>
<TR><TD VALIGN="TOP">BOL:</TD>
<TD> </TD>
<TD>La Paz</TD>
</TR>
<TR><TD VALIGN="TOP">CHL:</TD>
<TD> </TD>
<TD>Antofagasta, Easter Island, Santiago, Concepcion, Punta Arenas</TD>
</TR>
<TR><TD VALIGN="TOP">PRY:</TD>
<TD> </TD>
<TD>Asuncion</TD>
</TR>
<TR><TD VALIGN="TOP">URY:</TD>
<TD> </TD>
<TD>Montevideo</TD>
</TR>
<TR><TD VALIGN="TOP">ARG:</TD>
<TD> </TD>
<TD>Buenos Aires</TD>
</TR>
<TR><TD VALIGN="TOP">FJI:</TD>
<TD> </TD>
<TD>Nadi</TD>
</TR>
<TR><TD VALIGN="TOP">NZL:</TD>
<TD> </TD>
<TD>Auckland, Wellington, Christchurch</TD>
</TR>
<TR><TD VALIGN="TOP">AUS:</TD>
<TD> </TD>
<TD>Darwin, Learmonth, Port Hedland, Brisbane, Perth, Adelaide, Sydney,
Melbourne, Canberra</TD>
</TR>
<TR><TD VALIGN="TOP">BRN:</TD>
<TD> </TD>
<TD>Bandar Seri Begawan</TD>
</TR>
<TR><TD VALIGN="TOP">MYS:</TD>
<TD> </TD>
<TD>Kuching</TD>
</TR>
<TR><TD VALIGN="TOP">PHL:</TD>
<TD> </TD>
<TD>Manila</TD>
</TR>
</TABLE>

</TD></TR></TABLE>
   

=== Japanese Weather Data ===

Weather data for 842 Japanese locations are available (Expanded AMeDAS Weather Data).


The distributor for these data is


[[Bild:Masazumi_Horiuchi_-_E-Information.gif]]
  
([http://f-ei.jp/archives/wufi_pro])

These locations have already been
[[1D:Dialog_SelectClimateFileFromMap | predefined]] in WUFI's climate selection
map (see there for a list of locations). Just copy the respective files into WUFI's
Climate folder; on the next start WUFI will recognize
the files. They can the easily be selected via the
[[1D:Dialog_SelectClimateFileFromMap | climate selection map]].

Details:SourcesforclimateData

2009-03-25T07:51:16Z

Barbara: /* Test reference years: */

= Test reference years: =

The German National Meteorological Service DWD offers test reference years for all
climatic regions in Germany, representing typical as well as extreme weather situations:


"New Test Reference Years (TRYs) have been worked
out for Germany. Test Reference Years are datasets of selected meteorological elements
for each hour of the year. They provide climatological boundary conditions for simulating
calculations on an hourly basis, in the first place for the operation of heating and air
conditioning systems. On the basis of a factor and cluster analysis the Federal Republic
has been divided into 15 regions. For each region a representative station has been
determined and a Test Reference Year has been prepared. They replace the previous Test
Reference Years of the old West German states. For those states which acceded to the
Federal Republic after unification such datasets are available for the first time. A
Test Reference Year contains characteristic weather data of a representative year. The
weather sequences have been chosen on the basis of an analysis of the Grosswetterlagen
in such a way that the seasonal mean values of the individual meteorological elements
(especially of temperature and humidity) of the representative stations mainly correspond
with their 30-years mean values. As heating and air conditioning equipment also have to be
designed for extreme situations, additional datasets with the same data structure for a
very cold winter (December 1984 to February 1985) and an extremely hot summer (June to
August 1983) have been compiled."

([http://www.dwd.de/de/wir/Geschaeftsfelder/KlimaUmwelt/Leistungen/Statistiken/TRY/TRY.htm])

Unfortunately, these new test reference years (as opposed to the 'old' test reference
years of 1986) do not contain precipitation data any more. They are thus not suitable
for investigations involving the influence of rain.


The representative stations for the test reference years have already been
[[1D:Dialog_SelectClimateFileFromMap | predefined]] in WUFI's climate selection
map. Just copy the respective files into WUFI's Climate
folder, on the next start WUFI will recognize the files. They can then easily be selected
via the [[1D:Dialog_SelectClimateFileFromMap | climate selection]] map. 
  


=== METEONORM: ===

The Swiss METEOTEST company has developed METEONORM, a program for creating synthetic
hourly weather data, based on measured long-term mean values:


"METEONORM 5.0 (Edition 2003) is based on over
18 years of experience in the development of meteorological databases for energy
applications. It is a comprehensive meteorological reference, incorporating a catalogue
of meteorological data and calculation procedures for solar applications and system design
at any desired location in the world. METEONORM addresses engineers, architects, teachers,
planners and anyone interested in solar energy and climatology. 
... 
Several databases from different parts of the world have been combined and checked for
their reliability. In the present version, most of the data is taken from the GEBA
(Global Energy Balance Archive), from the World Meteorological Organization (WMO/OMM)
Climatological Normals 1961-1990 and from the Swiss database compiled by MeteoSwiss. 
Monthly climatological (long term) means are available for the following parameters: 
* global radiation 
* ambient air temperature 
* humidity 
* precipitation, days with precipitation 
* wind speed and direction 
* sunshine duration 
... 
For many regions of the world, measured data may only be applied within a radius of
50 km from weather stations. This makes it necessary to interpolate parameters between
stations. Interpolation models for solar radiation, temperature and additional parameters,
allowing application at any site in the world, are included in the software. 
... 
From the monthly values (station data, interpolated data or imported data), METEONORM
calculates hourly values of all parameters using a stochastic model. The resulting time
series correspond to "typical years" used for system design. 
  
([http://www.meteotest.ch/en/mn_description?w=ber])


Note: METEONORM can create files in the
[[Details:TRY-File | TRY]] format which can be directly read by
WUFI. 
  


=== Austrian Test Reference Years ===

In addition to the three weather files included with WUFI, weather data for numerous other
Austrian locations are available.


The distributor for these data is

QUADRUPLE-M Elsässer GmbH 
Technisches Büro für Bauphysik 
GF Dr. Manfred Elsässer 
Erzherzog-Eugen-Straße 14/1 
A-6020 Innsbruck 
  
Tel.: +43 512 251401 
Fax: +43 512 378550 
Mobil: +43 664 4324814 
E-mail: office@quad-m.at oder manfred.elsaesser@uibk.ac.at 
  

=== ASHRAE CD-ROM: International Weather for Energy Calculations (IWEC) ===

"Contains "typical" weather data in
ASCII format, suitable for use with building energy simulation programs, for 227
locations outside the USA and Canada. The files are derived from up to 18 years of
DATSAV3 hourly weather data originally archived at the National Climatic Data Center.
The weather data are supplemented by solar radiation estimated on an hourly basis from
earth-sun geometry and hourly weather elements, particularly cloud amount information.
This CD is the result of ASHRAE Research Project 1015. The CD contains the user's manual
and complete research report in PDF, the weather data in printable ASCII format and a
version of Adobe Acrobat Reader. To run Acrobat Reader, a 486 or Pentium-based computer
and either Microsoft Windows 95 or Windows NT 3.5 or later is required. Will also run
on a Macintosh. For Windows 95 and NT, 8MB or RAM (16MB recommended) and 10MB of free
hard-disk space are required."


([http://resourcecenter.ashrae.org/store/ashrae/newstore.cgi?itemid=9448&view=item&page=1&loginid=2167053&words=iwec&method=and&])


Note: the IWEC weather data do not contain quantitative rain data but only a
rain indicator reporting rain intensity categories like "light",
"moderate", "heavy", etc. As long as it has not been worked out
which representative hourly quantities corresponding to these categories should be used
in hygrothermic simulations, WUFI will not use rain data in calculations performed
with *.IWC files.


The CD contains files for the following locations:

<TABLE><TR><TD WIDTH="50%">

<TABLE>
<TR><TD VALIGN="TOP">NOR:</TD>
<TD> </TD>
<TD>Bergen, Oslo/Fornebu</TD>
</TR>
<TR><TD VALIGN="TOP">SWE:</TD>
<TD> </TD>
<TD>Kiruna, Ostersund/Froson, Karlstad, Stockholm/Arlanda, Goteborg, Landvetter</TD>
</TR>
<TR><TD VALIGN="TOP">FIN:</TD>
<TD> </TD>
<TD>Tampere, Helsinki</TD>
</TR>
<TR><TD VALIGN="TOP">GBR:</TD>
<TD> </TD>
<TD>Aberdeen/Dyce, Oban, Leuchars, Aughton, Finningley, Hemsby, Birmingham,
London/Gatwick, Jersey/Channel Islands, Belfast</TD>
</TR>
<TR><TD VALIGN="TOP">IRL:</TD>
<TD> </TD>
<TD>Valentia Observatory, Kilkenny, Birr, Dublin, Clones, Belmullet, Malin</TD>
</TR>
<TR><TD VALIGN="TOP">ISL:</TD>
<TD> </TD>
<TD>Reykjavik</TD>
</TR>
<TR><TD VALIGN="TOP">DNK:</TD>
<TD> </TD>
<TD>Copenhagen</TD>
</TR>
<TR><TD VALIGN="TOP">NLD:</TD>
<TD> </TD>
<TD>Amsterdam, Groningen, Beek</TD>
</TR>
<TR><TD VALIGN="TOP">BEL:</TD>
<TD> </TD>
<TD>Oostende, Brussels, Saint Hubert</TD>
</TR>
<TR><TD VALIGN="TOP">CHE:</TD>
<TD> </TD>
<TD>Geneva</TD>
</TR>
<TR><TD VALIGN="TOP">FRA:</TD>
<TD> </TD>
<TD>Brest, Paris/Orly, Nancy, Strasbourg, Nantes, Dijon, Clermont-Ferrand, Lyon,
Bordeaux, Montpellier, Marseille, Nice</TD>
</TR>
<TR><TD VALIGN="TOP">ESP:</TD>
<TD> </TD>
<TD>Santander, Barcelona, Madrid, Valencia, Palma, Sevilla</TD>
</TR>
<TR><TD VALIGN="TOP">PRT:</TD>
<TD> </TD>
<TD>Lajes, Porto, Coimbra, Faro, Evora, Braganca</TD>
</TR>
<TR><TD VALIGN="TOP">DEU:</TD>
<TD> </TD>
<TD>Hamburg, Bremen, Berlin, Dusseldorf, Koln, Frankfurt am Main,
Mannheim, Stuttgart, Munich</TD>
</TR>
<TR><TD VALIGN="TOP">AUT:</TD>
<TD> </TD>
<TD>Linz, Vienna/Schwechat, Innsbruck, Salzburg, Graz</TD>
</TR>
<TR><TD VALIGN="TOP">CZE:</TD>
<TD> </TD>
<TD>Prague, Ostrava</TD>
</TR>
<TR><TD VALIGN="TOP">SVK:</TD>
<TD> </TD>
<TD>Bratislava, Kosice</TD>
</TR>
<TR><TD VALIGN="TOP">POL:</TD>
<TD> </TD>
<TD>Kolobrzeg, Poznan, Warsaw, Krakow</TD>
</TR>
<TR><TD VALIGN="TOP">HUN:</TD>
<TD> </TD>
<TD>Szombathely, Debrecen</TD>
</TR>
<TR><TD VALIGN="TOP">SVN:</TD>
<TD> </TD>
<TD>Ljubljana</TD>
</TR>
<TR><TD VALIGN="TOP">BIH:</TD>
<TD> </TD>
<TD>Banja Luka</TD>
</TR>
<TR><TD VALIGN="TOP">YUG:</TD>
<TD> </TD>
<TD>Belgrade, Podgorica</TD>
</TR>
<TR><TD VALIGN="TOP">ROM:</TD>
<TD> </TD>
<TD>Cluj-Napoca, Timisoara, Galati, Bucharest, Craiova, Constanta</TD>
</TR>
<TR><TD VALIGN="TOP">BGR:</TD>
<TD> </TD>
<TD>Varna, Sofia, Plovdiv</TD>
</TR>
<TR><TD VALIGN="TOP">ITA:</TD>
<TD> </TD>
<TD>Torino, Milan, Venice, Genova, Pisa, Rome, Naples, Brindisi, Palermo, Messina</TD>
</TR>
<TR><TD VALIGN="TOP">GRC:</TD>
<TD> </TD>
<TD>Thessaloniki, Andravida, Athens</TD>
</TR>
<TR><TD VALIGN="TOP">TUR:</TD>
<TD> </TD>
<TD>Istanbul, Ankara, Izmir</TD>
</TR>
<TR><TD VALIGN="TOP">CYP:</TD>
<TD> </TD>
<TD>Larnaca</TD>
</TR>
<TR><TD VALIGN="TOP">RUS:</TD>
<TD> </TD>
<TD>Arkhangel'sk, Yakutsk, Saint-Petersburg, Moscow, Ekaterinburg,
Omsk, Samara, Irkutsk, Chita</TD>
</TR>
<TR><TD VALIGN="TOP">LTU:</TD>
<TD> </TD>
<TD>Kaunas</TD>
</TR>
<TR><TD VALIGN="TOP">BLR:</TD>
<TD> </TD>
<TD>Minsk</TD>
</TR>
<TR><TD VALIGN="TOP">UKR:</TD>
<TD> </TD>
<TD>Kiev, Odessa</TD>
</TR>
<TR><TD VALIGN="TOP">KAZ:</TD>
<TD> </TD>
<TD>Semipalatinsk</TD>
</TR>
<TR><TD VALIGN="TOP">UZB:</TD>
<TD> </TD>
<TD>Tashkent</TD>
</TR>
<TR><TD VALIGN="TOP">SYR:</TD>
<TD> </TD>
<TD>Damascus</TD>
</TR>
<TR><TD VALIGN="TOP">ISR:</TD>
<TD> </TD>
<TD>Jerusalem</TD>
</TR>
<TR><TD VALIGN="TOP">SAU:</TD>
<TD> </TD>
<TD>Riyadh</TD>
</TR>
<TR><TD VALIGN="TOP">ARE:</TD>
<TD> </TD>
<TD>Abu Dhabi</TD>
</TR>
<TR><TD VALIGN="TOP">PAK:</TD>
<TD> </TD>
<TD>Karachi</TD>
</TR>
</TABLE>

</TD><TD>

<TABLE>
<TR><TD VALIGN="TOP">IND:</TD>
<TD> </TD>
<TD>New Delhi, Ahmadabad, Calcutta, Nagpur, Bombay, Goa/Panaji, Madras, Trivandrum</TD>
</TR>
<TR><TD VALIGN="TOP">MNG:</TD>
<TD> </TD>
<TD>Ulaangom, Ulaanbataar</TD>
</TR>
<TR><TD VALIGN="TOP">MAC:</TD>
<TD> </TD>
<TD>Macau</TD>
</TR>
<TR><TD VALIGN="TOP">TWN:</TD>
<TD> </TD>
<TD>Taipei</TD>
</TR>
<TR><TD VALIGN="TOP">PRK:</TD>
<TD> </TD>
<TD>Ch'ongjin, P'yongyang, Haeju</TD>
</TR>
<TR><TD VALIGN="TOP">KOR:</TD>
<TD> </TD>
<TD>Kangnung, Inch'on, Ulsan, Kwangju</TD>
</TR>
<TR><TD VALIGN="TOP">JPN:</TD>
<TD> </TD>
<TD>Sapporo, Matsumoto, Nagoya, Tokyo/Hyakuri, Miho (CIV/JASDF),
Shimonoseki, Osaka, Kagoshima, Tosashimizu</TD>
</TR>
<TR><TD VALIGN="TOP">THA:</TD>
<TD> </TD>
<TD>Bangkok</TD>
</TR>
<TR><TD VALIGN="TOP">MYS:</TD>
<TD> </TD>
<TD>George Town, Kota Baharu, Kuala Lumpur</TD>
</TR>
<TR><TD VALIGN="TOP">SGP:</TD>
<TD> </TD>
<TD>Singapore</TD>
</TR>
<TR><TD VALIGN="TOP">VNM:</TD>
<TD> </TD>
<TD>Hanoi</TD>
</TR>
<TR><TD VALIGN="TOP">CHN:</TD>
<TD> </TD>
<TD>Harbin, Urumqi, Lanzhou, Shenyang, Beijing, Kunming, Shanghai, Guangzhou</TD>
</TR>
<TR><TD VALIGN="TOP">MAR:</TD>
<TD> </TD>
<TD>Casablanca/Nouasser</TD>
</TR>
<TR><TD VALIGN="TOP">DZA:</TD>
<TD> </TD>
<TD>Algiers</TD>
</TR>
<TR><TD VALIGN="TOP">TUN:</TD>
<TD> </TD>
<TD>Tunis</TD>
</TR>
<TR><TD VALIGN="TOP">SEN:</TD>
<TD> </TD>
<TD>Dakar</TD>
</TR>
<TR><TD VALIGN="TOP">LBY:</TD>
<TD> </TD>
<TD>Tripoli</TD>
</TR>
<TR><TD VALIGN="TOP">EGY:</TD>
<TD> </TD>
<TD>Cairo, Aswan</TD>
</TR>
<TR><TD VALIGN="TOP">KEN:</TD>
<TD> </TD>
<TD>Nairobi</TD>
</TR>
<TR><TD VALIGN="TOP">MDG:</TD>
<TD> </TD>
<TD>Antananarivo</TD>
</TR>
<TR><TD VALIGN="TOP">ZWE:</TD>
<TD> </TD>
<TD>Harare</TD>
</TR>
<TR><TD VALIGN="TOP">ZAF:</TD>
<TD> </TD>
<TD>Johannesburg, Cape Town</TD>
</TR>
<TR><TD VALIGN="TOP">MEX:</TD>
<TD> </TD>
<TD>Mexico City, Veracruz, Acapulco</TD>
</TR>
<TR><TD VALIGN="TOP">CUB:</TD>
<TD> </TD>
<TD>Havana</TD>
</TR>
<TR><TD VALIGN="TOP">MTQ:</TD>
<TD> </TD>
<TD>Fort-de-France</TD>
</TR>
<TR><TD VALIGN="TOP">COL:</TD>
<TD> </TD>
<TD>Bogota</TD>
</TR>
<TR><TD VALIGN="TOP">VEN:</TD>
<TD> </TD>
<TD>Caracas</TD>
</TR>
<TR><TD VALIGN="TOP">BRA:</TD>
<TD> </TD>
<TD>Belem, Recife, Brasilia, Sao Paulo</TD>
</TR>
<TR><TD VALIGN="TOP">ECU:</TD>
<TD> </TD>
<TD>Quito</TD>
</TR>
<TR><TD VALIGN="TOP">PER:</TD>
<TD> </TD>
<TD>Lima, Cuzco, Arequipa</TD>
</TR>
<TR><TD VALIGN="TOP">BOL:</TD>
<TD> </TD>
<TD>La Paz</TD>
</TR>
<TR><TD VALIGN="TOP">CHL:</TD>
<TD> </TD>
<TD>Antofagasta, Easter Island, Santiago, Concepcion, Punta Arenas</TD>
</TR>
<TR><TD VALIGN="TOP">PRY:</TD>
<TD> </TD>
<TD>Asuncion</TD>
</TR>
<TR><TD VALIGN="TOP">URY:</TD>
<TD> </TD>
<TD>Montevideo</TD>
</TR>
<TR><TD VALIGN="TOP">ARG:</TD>
<TD> </TD>
<TD>Buenos Aires</TD>
</TR>
<TR><TD VALIGN="TOP">FJI:</TD>
<TD> </TD>
<TD>Nadi</TD>
</TR>
<TR><TD VALIGN="TOP">NZL:</TD>
<TD> </TD>
<TD>Auckland, Wellington, Christchurch</TD>
</TR>
<TR><TD VALIGN="TOP">AUS:</TD>
<TD> </TD>
<TD>Darwin, Learmonth, Port Hedland, Brisbane, Perth, Adelaide, Sydney,
Melbourne, Canberra</TD>
</TR>
<TR><TD VALIGN="TOP">BRN:</TD>
<TD> </TD>
<TD>Bandar Seri Begawan</TD>
</TR>
<TR><TD VALIGN="TOP">MYS:</TD>
<TD> </TD>
<TD>Kuching</TD>
</TR>
<TR><TD VALIGN="TOP">PHL:</TD>
<TD> </TD>
<TD>Manila</TD>
</TR>
</TABLE>

</TD></TR></TABLE>
   

=== Japanese Weather Data ===

Weather data for 842 Japanese locations are available (Expanded AMeDAS Weather Data).


The distributor for these data is


[[Bild:Masazumi_Horiuchi_-_E-Information.gif]]
  
([http://f-ei.jp/archives/wufi_pro])

These locations have already been
[[1D:Dialog_SelectClimateFileFromMap | predefined]] in WUFI's climate selection
map (see there for a list of locations). Just copy the respective files into WUFI's
Climate folder; on the next start WUFI will recognize
the files. They can the easily be selected via the
[[1D:Dialog_SelectClimateFileFromMap | climate selection map]].

Details:Climate

2009-03-25T07:44:35Z

Barbara: /* Climate Data */

= Climate Data =


Starting from specified initial conditions, WUFI computes the temporal evolution of the temperature and moisture distributions in the building component. This evolution is determined not only by the underlying transport equations which govern the processes in the component, but also by the heat and moisture exchange with its surroundings. Thus there are heat and moisture flows through the surfaces, the direction and magnitude of which depend on the conditions in the component as well as on the conditions in the surroundings. The latter are described by the boundary conditions.


Since WUFI has been developed specifically for application in building physics, the surrounding medium is the ambient air (outdoor air, indoor air). Since it is furthermore designed to calculate the behaviour of building components exposed to the weather, it seems natural to describe the condition of the surrounding air in terms of meteorological parameters like temperature, relative humidity, solar radiation etc. In this way, WUFI keeps in close touch with building practice and can use existing measured data.


The choice of expressing the boundary conditions in terms of meteorological parameters does not prevent you from applying WUFI to laboratory investigations like imbibition or drying experiments, since the laboratory conditions can be expressed in meteorological terms as well.


WUFI needs the following climate data for each time step:

* the rain load vertically incident on the exterior surface in [Ltr/m²h]. For the determination of this rain load, the inclination and orientation of the surface must be taken into account.

* the solar radiation vertically incident on the exterior surface in [W/m²]. For the determination of the amount of radiation, the inclination and orientation of the surface must be taken into account.

* the temperature of the exterior air in [°C]

* the relative humidity of the exterior air (0..1)

* the temperature of the interior air in [°C]

* the relative humidity of the interior air (0..1)

* the barometric pressure in [hPa]. Since the barometric pressure has only a minor effect on the calculation, specification of a mean value over the calculation period can be sufficient.

* the long-wave atmospheric counterradiation [W/m²], if radiation cooling is to be accounted for during the night.


The weather file may contain measured weather data (such as IBP weather data), or synthetic but realistic weather data (such as the Test Reference Years), or completely artificial data (which describe, for example, a laboratory experiment).


Since WUFI's main application is the investigation of the hygrothermal behavior of building components exposed to natural weather, it is set up to read files that contain measured weather
data. However, measured data can not always be used directly:


As mentioned above, WUFI needs the rain load and the radiation load incident on the wall or roof surface under investigation. Since rain and radiation are directed quantities, these loads depend on the orientation and the inclination of the individual building component. Unfortunately, in conventional weather measurements they are usually only recorded for horizontal surfaces. 
It is possible, however, to compute them from conventional weather data. The rain load can be determined from the normal rain and the wind velocity and direction. The amount of radiation can be determined from the global (or direct) and diffuse radiation incident on a horizontal surface. WUFI performs these conversions automatically and the user only needs to supply the conventionally measured weather data. In the current WUFI version, this requires a file in [[Details:WET-File | *.WET]] or [[Details:TRY-File | *.TRY]] or [[Details:DAT-File | *.DAT]] or [[Details:IWC-File | *.IWC]] or
[[Details:WAC-File | *.WAC]] or [[Details:WBC-File | *.WBC]] format. Depending on the format, files provided by the user (as opposed to the files supplied with WUFI or files pre-registered in the database) may also require a supporting [[Details:AGD-File | *.AGD file]] which supplies geographical data on the climate location.


On the other hand, WUFI can also read files which directly contain the required rain and radiation loads as determined for the specific surface in question, so that no further conversion is necessary.
This may be convenient if

* you want to convert the weather data with more sophisticated algorithms than WUFI does, or if

* you want to employ data that have been directly measured at the surface in question and thus need not be converted, or if

* you want to use data synthesized by your own climate simulator, or if

* you want to use data which describe the conditions of a laboratory experiment,

* etc.


These files must be in [[Details:KLI-File | *.KLI]] format.


The following sections explain these file formats in detail:


[[Details:WET-File | The *.WET Format for Climate Data]] 
  
[[Details:TRY-File | The *.TRY Format for Climate Data]] 
  
[[Details:DAT-File | The *.DAT Format for Climate Data]] 
  
[[Details:IWC-File | The *.IWC Format for Climate Data]] 
  
[[Details:WAC-File | The *.WAC Format for Climate Data]] 
  
[[Details:WBC-File | The *.WBC Format for Climate Data]] 
  
[[Details:KLI-File | The *.KLI Format for Climate Data]] 
  
[[Details:AGD-File | The *.AGD File]] 

 

The method used by WUFI to convert radiation data is described in the [[FAQ:MainQandA | Frequently Asked Questions]] section.

  

=== Sources for Climate Data ===

Several climate files are [[1D:Dialog_SelectClimateFileFromMap | supplied with
WUFI]]. The following are some sources offering weather data for additional locations.
WUFI can read the respective file formats; the user must judge to which degree these
data are useful and appropriate for his specific application.

Additional information of different sources for climate date are discribed [[Details:SourcesforclimateData | here]].

Details:Climate

2009-03-25T07:43:46Z

Barbara: /* Climate Data */

= Climate Data =


Starting from specified initial conditions, WUFI computes the temporal evolution of the temperature and moisture distributions in the building component. This evolution is determined not only by the underlying transport equations which govern the processes in the component, but also by the heat and moisture exchange with its surroundings. Thus there are heat and moisture flows through the surfaces, the direction and magnitude of which depend on the conditions in the component as well as on the conditions in the surroundings. The latter are described by the boundary conditions.


Since WUFI has been developed specifically for application in building physics, the surrounding medium is the ambient air (outdoor air, indoor air). Since it is furthermore designed to calculate the behaviour of building components exposed to the weather, it seems natural to describe the condition of the surrounding air in terms of meteorological parameters like temperature, relative humidity, solar radiation etc. In this way, WUFI keeps in close touch with building practice and can use existing measured data.


The choice of expressing the boundary conditions in terms of meteorological parameters does not prevent you from applying WUFI to laboratory investigations like imbibition or drying experiments, since the laboratory conditions can be expressed in meteorological terms as well.


WUFI needs the following climate data for each time step:

* the rain load vertically incident on the exterior surface in [Ltr/m²h]. For the determination of this rain load, the inclination and orientation of the surface must be taken into account.

* the solar radiation vertically incident on the exterior surface in [W/m²]. For the determination of the amount of radiation, the inclination and orientation of the surface must be taken into account.

* the temperature of the exterior air in [°C]

* the relative humidity of the exterior air (0..1)

* the temperature of the interior air in [°C]

* the relative humidity of the interior air (0..1)

* the barometric pressure in [hPa]. Since the barometric pressure has only a minor effect on the calculation, specification of a mean value over the calculation period can be sufficient.

* the long-wave atmospheric counterradiation [W/m²], if radiation cooling is to be accounted for during the night. Counterradiation data are only rarely available, however


The weather file may contain measured weather data (such as IBP weather data), or synthetic but realistic weather data (such as the Test Reference Years), or completely artificial data (which describe, for example, a laboratory experiment).


Since WUFI's main application is the investigation of the hygrothermal behavior of building components exposed to natural weather, it is set up to read files that contain measured weather
data. However, measured data can not always be used directly:


As mentioned above, WUFI needs the rain load and the radiation load incident on the wall or roof surface under investigation. Since rain and radiation are directed quantities, these loads depend on the orientation and the inclination of the individual building component. Unfortunately, in conventional weather measurements they are usually only recorded for horizontal surfaces. 
It is possible, however, to compute them from conventional weather data. The rain load can be determined from the normal rain and the wind velocity and direction. The amount of radiation can be determined from the global (or direct) and diffuse radiation incident on a horizontal surface. WUFI performs these conversions automatically and the user only needs to supply the conventionally measured weather data. In the current WUFI version, this requires a file in [[Details:WET-File | *.WET]] or [[Details:TRY-File | *.TRY]] or [[Details:DAT-File | *.DAT]] or [[Details:IWC-File | *.IWC]] or
[[Details:WAC-File | *.WAC]] or [[Details:WBC-File | *.WBC]] format. Depending on the format, files provided by the user (as opposed to the files supplied with WUFI or files pre-registered in the database) may also require a supporting [[Details:AGD-File | *.AGD file]] which supplies geographical data on the climate location.


On the other hand, WUFI can also read files which directly contain the required rain and radiation loads as determined for the specific surface in question, so that no further conversion is necessary.
This may be convenient if

* you want to convert the weather data with more sophisticated algorithms than WUFI does, or if

* you want to employ data that have been directly measured at the surface in question and thus need not be converted, or if

* you want to use data synthesized by your own climate simulator, or if

* you want to use data which describe the conditions of a laboratory experiment,

* etc.


These files must be in [[Details:KLI-File | *.KLI]] format.


The following sections explain these file formats in detail:


[[Details:WET-File | The *.WET Format for Climate Data]] 
  
[[Details:TRY-File | The *.TRY Format for Climate Data]] 
  
[[Details:DAT-File | The *.DAT Format for Climate Data]] 
  
[[Details:IWC-File | The *.IWC Format for Climate Data]] 
  
[[Details:WAC-File | The *.WAC Format for Climate Data]] 
  
[[Details:WBC-File | The *.WBC Format for Climate Data]] 
  
[[Details:KLI-File | The *.KLI Format for Climate Data]] 
  
[[Details:AGD-File | The *.AGD File]] 

 

The method used by WUFI to convert radiation data is described in the [[FAQ:MainQandA | Frequently Asked Questions]] section.

  

=== Sources for Climate Data ===

Several climate files are [[1D:Dialog_SelectClimateFileFromMap | supplied with
WUFI]]. The following are some sources offering weather data for additional locations.
WUFI can read the respective file formats; the user must judge to which degree these
data are useful and appropriate for his specific application.

Additional information of different sources for climate date are discribed [[Details:SourcesforclimateData | here]].

Details:WaterVaporDiffusion

2009-03-25T07:31:21Z

Barbara: /* Vapor diffusion thickness, sd-value */

= Water Vapor Diffusion =


This help topic discusses several physical quantities used to describe water
vapor diffusion, since these quantities and their interrelationships may not be
familiar to all WUFI users.


=== Water vapor diffusion resistance factor, µ-value ===

Diffusion of water vapor in air can be described by the equation

<TABLE>
<TR><TD COLSPAN="3"><TT>gv = -δ * dp/dx </TT>(in air),</TD></TR>

<TR><TD><TT>gv</TT></TD><TD ALIGN="RIGHT">[kg/m²s]:</TD><TD>water vapor flux density</TD></TR>
<TR><TD><TT>p</TT></TD><TD ALIGN="RIGHT">[Pa]:</TD><TD>water vapor partial pressure</TD></TR>
<TR><TD>δ </TD><TD ALIGN="RIGHT">[kg/(msPa)]:</TD><TD>water vapor diffusion coefficient in air,</TD></TR>

<TR><TD COLSPAN="3">where</TD></TR>
<TR><TD COLSPAN="3"><TT>δ = 2.0·10-7 T0.81 / PL </TT> [1]</TD></TR>

<TR><TD><TT>T</TT></TD><TD ALIGN="RIGHT">[K]:</TD><TD>absolute ambient temperature</TD></TR>
<TR><TD><TT>PL</TT></TD><TD ALIGN="RIGHT">[Pa]:</TD><TD>ambient atmospheric pressure.</TD></TR>
</TABLE>


In porous building materials, diffusion likewise takes place in air (in the pore spaces),
but it is impeded by the reduction of the accessible cross-section, adsorption effects
at the pore walls and the tortuosity of the pore paths. In the context of building
physics, it is admissible to allow for this by simply introducing a diffusion
resistance factor µ:


<TABLE>
<TR><TD COLSPAN="3"><TT>gv = -(d/µ) * dp/dx </TT>(in porous material),</TD></TR>
<TR><TD>µ</TD><TD>[-]:</TD><TD>water vapor diffusion resistance factor.</TD></TR>
</TABLE>


Retaining δ as a separate coefficient in the above
equation has the advantage that it already describes the temperature and pressure
dependence of water vapor diffusion and µ is therefore practically independent
of temperature and pressure, i.e. it is a constant which only depends on the material
in question.


However, measurements of µ which are performed at different levels of relative
humidity (dry-cup and wet-cup) may result in different values for one and the same
material. This is due to surface diffusion which becomes noticeable at higher
humidities but would be more properly treated as
[[Details:LiquidTransportCoefficients|liquid transport]] [2]. This additional
moisture transport is usually not separated out in the analysis of the measurements
and, lumped together with vapor diffusion, reduces the apparent diffusion resistance,
resulting in a lower µ-value. In these cases, it is more appropriate to use
a [[Details:BasicMaterialData|constant]] µ-value and to adjust the
[[Details:LiquidTransportCoefficients|liquid transport coefficients]] to include
surface diffusion. However, WUFI also allows to use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value to simplify the treatment of cases where this distinction can be
neglected.


The µ-value represents the ratio of the diffusion coefficients of water
vapor in air and in the building material and has therefore a simple interpretation:
it is the factor by which the vapor diffusion in the material is impeded, as
compared to diffusion in stagnant air. For very permeable materials, such as mineral
wool, the µ-value is thus close to 1, whereas it increases for materials with
greater diffusion resistance.



The following table lists µ-values for some common materials:

<TABLE>
<TR><TD> </TD><TD COLSPAN="2" ALIGN="CENTER">µ-value</TD></TR>
<TR><TD> </TD><TD ALIGN="CENTER">dry-cup (3% - 50% RH)</TD><TD ALIGN="CENTER">wet-cup (50%-93% RH)</TD></TR>

<TR><TD>cellular concrete</TD> <TD ALIGN="CENTER">7.7</TD><TD ALIGN="CENTER">7.1</TD></TR>
<TR><TD>lime silica brick</TD> <TD ALIGN="CENTER">27</TD> <TD ALIGN="CENTER">18</TD></TR>
<TR><TD>solid brick</TD> <TD ALIGN="CENTER">9.5</TD><TD ALIGN="CENTER">8.0</TD></TR>
<TR><TD>gypsum board</TD> <TD ALIGN="CENTER">8.3</TD><TD ALIGN="CENTER">7.3</TD></TR>
<TR><TD>concrete (B25)</TD> <TD ALIGN="CENTER">110</TD><TD ALIGN="CENTER">150 (*)</TD></TR>
<TR><TD>cement-lime plaster</TD> <TD ALIGN="CENTER">19</TD> <TD ALIGN="CENTER">18</TD></TR>
<TR><TD>lime plaster</TD> <TD ALIGN="CENTER">7.3</TD><TD ALIGN="CENTER">6.4</TD></TR>
<TR><TD>Saaler sandstone</TD> <TD ALIGN="CENTER">60</TD> <TD ALIGN="CENTER">28</TD></TR>
<TR><TD>Baumberger sandstone</TD> <TD ALIGN="CENTER">20</TD> <TD ALIGN="CENTER">17</TD></TR>
<TR><TD>Worzeldorfer sandstone</TD><TD ALIGN="CENTER">38</TD> <TD ALIGN="CENTER">22</TD></TR>
</TABLE>
(*) the increase of the µ-value
in the wet-cup measurement of concrete is probably due to
swelling effects [3].


In WUFI, the µ-value is one of the [[Details:BasicMaterialData|basic material
properties]] which needs to be [[2D:DialogEditMaterial|specified for
each material]].

  

=== Vapor diffusion thickness, sd-value ===


Assuming constant temperature and µ-value, the diffusion flow through a
material layer with thickness Dx=s is


<TT>gv_mat = -δ/µ * Δp/Δx = -δ/(µ*s) * Δp</TT>,


whereas the diffusion flow through a stagnant air layer (µ=1) with thickness
sd is


<TT>gv_air = -δ/µ * Δp/Δx = -δ/(1*sd) * Δp = -δ / sd * Δp</TT>.


Dividing the former equation by the latter yields


<TT>gv_mat / gv_air = sd / (µ*s)</TT>.


If the air layer is chosen so that its vapor diffusion resistance is the same
as that of the material layer of thickness <TT>s</TT> (and therefore
gv_mat = gv_air), then its thickness
<TT>sd</TT> must be


<TT>sd = µ*s</TT>.


For a material layer with diffusion resistance factor µ and thickness
<TT>s</TT>, the product <TT>µ*s</TT> thus gives the thickness which
a stagnant air layer would need in order to have the same diffusion resistance.
This "sd-value" or "vapor diffusion thickness" expresses the
diffusion resistance of a layer in a form which is easily understood and applied.


Since the definition of the sd-value contains the the thickness
<TT>Δx</TT> of the layer, the sd-value
is a property of the given layer, not of the material itself. Two layers
made from the same material but with different thicknesses will have different
sd-values, but in both cases the material will have the same
µ-value.


For some building components, only their total diffusion resistance is of importance
but not their µ-value and their thickness separately. They may then simply
be specified in terms of their sd-value. Also, measuring the
sd-value does not require to determine the thickness of the sample. 
In particular, the sd-value is used to characterise vapor retarders
(sd >= 10 m), vapor barriers (sd >= 1000 m) and
surface coatings (mineral paints: sd ~ 0.04 m, oil paints:
sd = 1.0 .. 2.6 m), where it can be difficult to determine
their thickness properly.


In WUFI, [[Details:SurfaceCoatings|surface coatings]] on the component need
not be explicitly modelled in the
[[2D:Dialog_Geometry|component assembly]]; their diffusion resistance
may instead be taken into account by simply specifying their sd-value
in the dialog
[[2D:Dialog_EditSurfaceCoefficients|Edit Surface Coefficients]].

  

<H3>Permeance, Permeability</H3>


In the formula for water vapor diffusion in a porous material


<TT>gv = -δ/µ * Δp/Δx = - δ/sd * Δp =: - Δ * Δp</TT>


the so-called permeance Δ may be introduced by defining


<TT>Δ := δ/sd </TT>[kg/(m²sPa)].


Since the definition of the permeance contains the thickness
<TT>Δx</TT> of the layer, the permeance is a property of the
given layer, not of the material itself. Two layers made from the same material
but with different thicknesses will have different permeances.


In Inch-Pound units the permeance is measured in perm. One perm is one
grain (avoirdupois) of water vapor per hour flowing through one square foot of a layer,
induced by a vapor pressure difference of one inch of mercury across the two surfaces.
In SI units, this corresponds to 57.45e-12 kg/(m²sPa) [4]. Therefore, with
Δ expressed in perm:


<TT>57.45e-12*Δ = δ/sd </TT> [kg/(m²sPa)], or 
<TT>sd = δ/(57.45e-12*Δ) </TT> [m].


For a reference temperature of 5°C and a barometric pressure of 1013.25 hPa,
δ has the value 1.884e-10 kg/(msPa) (see above),
and we obtain

<TT>sd = 3.28/Δ</TT>,

where Δ is expressed in perm and sd in m.



The permeance describes a property of a specific construction layer with a given
thickness. Multiplying the permeance by the layer thickness
Δx yields the
permeability Π [perm inch]
of the layer material:



<TT>Δ * Δx = δ/sd * Δx = δ/µ =: Π </TT>, so that 
<TT>gv = Π Δp/Δx</TT>.



The conversion factor for Δ*Δx is
57.45e-12 [kg/(m²sPa)]/[perm] * 0.0254 [m]/[in] = 1.459e-12 [kg/(msPa)]/[perm in]:


<TT>1.459e-12*Π = δ/µ </TT> [kg/(msPa)],


and with the same reference value for δ as above:


<TT>7.744e-3*Π = 1/µ </TT> [-], or


<TT>µ = 129 / Π </TT> [-],


where Π is expressed in perm inch and µ is
dimensionless.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Schirmer, R.: Die Diffusionszahl von Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, 
Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177.</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>Krus, M.: Moisture Transport and Storage Coefficients of Porous Mineral Building Materials. Theoretical Principles and New Test Methods 
Fraunhofer IRB Verlag, 1996</TD></TR>

<TR><TD VALIGN="TOP">[3]</TD><TD>Holm, A., Krus, M., Künzel, H.M.: Concrete from the viewpoint of moisture technology: Parameters and mathematical approaches to the evaluation of climatic effects in external structural elements made of concrete. 
To be published in Concrete Science and Engineering</TD></TR>

<TR><TD VALIGN="TOP">[4]</TD><TD>ASHRAE Terminology of Heating, Ventilation, Air Conditioning, & Refrigeration, 2nd ed. 1991</TD></TR>
</TABLE>

Details:WaterVaporDiffusion

2009-03-25T07:30:23Z

Barbara: /* Vapor diffusion thickness, sd-value */

= Water Vapor Diffusion =


This help topic discusses several physical quantities used to describe water
vapor diffusion, since these quantities and their interrelationships may not be
familiar to all WUFI users.


=== Water vapor diffusion resistance factor, µ-value ===

Diffusion of water vapor in air can be described by the equation

<TABLE>
<TR><TD COLSPAN="3"><TT>gv = -δ * dp/dx </TT>(in air),</TD></TR>

<TR><TD><TT>gv</TT></TD><TD ALIGN="RIGHT">[kg/m²s]:</TD><TD>water vapor flux density</TD></TR>
<TR><TD><TT>p</TT></TD><TD ALIGN="RIGHT">[Pa]:</TD><TD>water vapor partial pressure</TD></TR>
<TR><TD>δ </TD><TD ALIGN="RIGHT">[kg/(msPa)]:</TD><TD>water vapor diffusion coefficient in air,</TD></TR>

<TR><TD COLSPAN="3">where</TD></TR>
<TR><TD COLSPAN="3"><TT>δ = 2.0·10-7 T0.81 / PL </TT> [1]</TD></TR>

<TR><TD><TT>T</TT></TD><TD ALIGN="RIGHT">[K]:</TD><TD>absolute ambient temperature</TD></TR>
<TR><TD><TT>PL</TT></TD><TD ALIGN="RIGHT">[Pa]:</TD><TD>ambient atmospheric pressure.</TD></TR>
</TABLE>


In porous building materials, diffusion likewise takes place in air (in the pore spaces),
but it is impeded by the reduction of the accessible cross-section, adsorption effects
at the pore walls and the tortuosity of the pore paths. In the context of building
physics, it is admissible to allow for this by simply introducing a diffusion
resistance factor µ:


<TABLE>
<TR><TD COLSPAN="3"><TT>gv = -(d/µ) * dp/dx </TT>(in porous material),</TD></TR>
<TR><TD>µ</TD><TD>[-]:</TD><TD>water vapor diffusion resistance factor.</TD></TR>
</TABLE>


Retaining δ as a separate coefficient in the above
equation has the advantage that it already describes the temperature and pressure
dependence of water vapor diffusion and µ is therefore practically independent
of temperature and pressure, i.e. it is a constant which only depends on the material
in question.


However, measurements of µ which are performed at different levels of relative
humidity (dry-cup and wet-cup) may result in different values for one and the same
material. This is due to surface diffusion which becomes noticeable at higher
humidities but would be more properly treated as
[[Details:LiquidTransportCoefficients|liquid transport]] [2]. This additional
moisture transport is usually not separated out in the analysis of the measurements
and, lumped together with vapor diffusion, reduces the apparent diffusion resistance,
resulting in a lower µ-value. In these cases, it is more appropriate to use
a [[Details:BasicMaterialData|constant]] µ-value and to adjust the
[[Details:LiquidTransportCoefficients|liquid transport coefficients]] to include
surface diffusion. However, WUFI also allows to use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value to simplify the treatment of cases where this distinction can be
neglected.


The µ-value represents the ratio of the diffusion coefficients of water
vapor in air and in the building material and has therefore a simple interpretation:
it is the factor by which the vapor diffusion in the material is impeded, as
compared to diffusion in stagnant air. For very permeable materials, such as mineral
wool, the µ-value is thus close to 1, whereas it increases for materials with
greater diffusion resistance.



The following table lists µ-values for some common materials:

<TABLE>
<TR><TD> </TD><TD COLSPAN="2" ALIGN="CENTER">µ-value</TD></TR>
<TR><TD> </TD><TD ALIGN="CENTER">dry-cup (3% - 50% RH)</TD><TD ALIGN="CENTER">wet-cup (50%-93% RH)</TD></TR>

<TR><TD>cellular concrete</TD> <TD ALIGN="CENTER">7.7</TD><TD ALIGN="CENTER">7.1</TD></TR>
<TR><TD>lime silica brick</TD> <TD ALIGN="CENTER">27</TD> <TD ALIGN="CENTER">18</TD></TR>
<TR><TD>solid brick</TD> <TD ALIGN="CENTER">9.5</TD><TD ALIGN="CENTER">8.0</TD></TR>
<TR><TD>gypsum board</TD> <TD ALIGN="CENTER">8.3</TD><TD ALIGN="CENTER">7.3</TD></TR>
<TR><TD>concrete (B25)</TD> <TD ALIGN="CENTER">110</TD><TD ALIGN="CENTER">150 (*)</TD></TR>
<TR><TD>cement-lime plaster</TD> <TD ALIGN="CENTER">19</TD> <TD ALIGN="CENTER">18</TD></TR>
<TR><TD>lime plaster</TD> <TD ALIGN="CENTER">7.3</TD><TD ALIGN="CENTER">6.4</TD></TR>
<TR><TD>Saaler sandstone</TD> <TD ALIGN="CENTER">60</TD> <TD ALIGN="CENTER">28</TD></TR>
<TR><TD>Baumberger sandstone</TD> <TD ALIGN="CENTER">20</TD> <TD ALIGN="CENTER">17</TD></TR>
<TR><TD>Worzeldorfer sandstone</TD><TD ALIGN="CENTER">38</TD> <TD ALIGN="CENTER">22</TD></TR>
</TABLE>
(*) the increase of the µ-value
in the wet-cup measurement of concrete is probably due to
swelling effects [3].


In WUFI, the µ-value is one of the [[Details:BasicMaterialData|basic material
properties]] which needs to be [[2D:DialogEditMaterial|specified for
each material]].

  

=== Vapor diffusion thickness, sd-value ===


Assuming constant temperature and µ-value, the diffusion flow through a
material layer with thickness Dx=s is


<TT>gv_mat = -δ/µ * Δp/Δx = -δ/(µ*s) * Δp</TT>,


whereas the diffusion flow through a stagnant air layer (µ=1) with thickness
sd is


<TT>gv_air = -δ/µ * Δp/Δx = -δ/(1*sd) * Δp = -δ / sd * Δp</TT>.


Dividing the former equation by the latter yields


<TT>gv_mat / gv_air = sd / (µ*s)</TT>.


If the air layer is chosen so that its vapor diffusion resistance is the same
as that of the material layer of thickness <TT>s</TT> (and therefore
gv_mat = gv_air), then its thickness
<TT>sd</TT> must be


<TT>sd = µ*s</TT>.


For a material layer with diffusion resistance factor µ and thickness
<TT>s</TT>, the product <TT>µ*s</TT> thus gives the thickness which
a stagnant air layer would need in order to have the same diffusion resistance.
This "sd-value" or "vapor diffusion thickness" expresses the
diffusion resistance of a layer in a form which is easily understood and applied.


Since the definition of the sd-value contains the the thickness
<TT>Δx</TT> of the layer, the sd-value
is a property of the given layer, not of the material itself. Two layers
made from the same material but with different thicknesses will have different
sd-values, but in both cases the material will have the same
µ-value.


For some building components, only their total diffusion resistance is of importance
but not their µ-value and their thickness separately. They may then simply
be specified in terms of their sd-value. Also, measuring the
sd-value does not require to determine the thickness of the sample. 
In particular, the sd-value is used to characterise vapor retarders
(sd >= 10 m), vapor barriers (sd >= 1000 m) and
surface coatings (mineral paints: sd ~ 0.04 m, oil paints:
sd = 1.0 .. 2.6 m), where it can be difficult to determine
their thickness properly.


In WUFI, [[Details:SurfaceCoatings|surface coatings]] on the component need
not be explicitly modelled in the
[[2D:Dialog_Geometry|component assembly]]; their diffusion resistance
may instead be taken into account by simply specifying their sd-value
in the dialog
[[2D:Dialog_EditSurfaceCoefficients|Edit Surface Coefficients]].

  

<H3>Permeance, Permeability</H3>


In the formula for water vapor diffusion in a porous material


<TT>gv = -δ/µ * Δp/Δx = - δ/sd * Δp =: - Δ * Δp</TT>


the so-called permeance Δ may be introduced by defining


<TT>Δ := δ/sd </TT>[kg/(m²sPa)].


Since the definition of the permeance contains the thickness
<TT>Δx</TT> of the layer, the permeance is a property of the
given layer, not of the material itself. Two layers made from the same material
but with different thicknesses will have different permeances.


In Inch-Pound units the permeance is measured in perm. One perm is one
grain (avoirdupois) of water vapor per hour flowing through one square foot of a layer,
induced by a vapor pressure difference of one inch of mercury across the two surfaces.
In SI units, this corresponds to 57.45e-12 kg/(m²sPa) [4]. Therefore, with
Δ expressed in perm:


<TT>57.45e-12*Δ = δ/sd </TT> [kg/(m²sPa)], or 
<TT>sd = δ/(57.45e-12*Δ) </TT> [m].


For a reference temperature of 5°C and a barometric pressure of 1013.25 hPa,
δ has the value 1.884e-10 kg/(msPa) (see above),
and we obtain

<TT>sd = 3.28/Δ</TT>,

where Δ is expressed in perm and sd in m.



The permeance describes a property of a specific construction layer with a given
thickness. Multiplying the permeance by the layer thickness
Δx yields the
permeability Π [perm inch]
of the layer material:



<TT>Δ * Δx = δ/sd * Δx = δ/µ =: Π </TT>, so that 
<TT>gv = Π Δp/Δx</TT>.



The conversion factor for Δ*Δx is
57.45e-12 [kg/(m²sPa)]/[perm] * 0.0254 [m]/[in] = 1.459e-12 [kg/(msPa)]/[perm in]:


<TT>1.459e-12*Π = δ/µ </TT> [kg/(msPa)],


and with the same reference value for δ as above:


<TT>7.744e-3*Π = 1/µ </TT> [-], or


<TT>µ = 129 / Π </TT> [-],


where Π is expressed in perm inch and µ is
dimensionless.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Schirmer, R.: Die Diffusionszahl von
Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, 
Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177.</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>Krus, M.: Moisture Transport and Storage
Coefficients of Porous Mineral Building Materials. Theoretical Principles
and New Test Methods 
Fraunhofer IRB Verlag, 1996</TD></TR>

<TR><TD VALIGN="TOP">[3]</TD><TD>Holm, A., Krus, M., Künzel, H.M.: Concrete from
the viewpoint of moisture technology: Parameters and mathematical approaches
to the evaluation of climatic effects in external structural elements made
of concrete. 
To be published in Concrete Science and Engineering</TD></TR>

<TR><TD VALIGN="TOP">[4]</TD><TD>ASHRAE Terminology of Heating, Ventilation, Air
Conditioning, & Refrigeration, 2nd ed. 1991</TD></TR>
</TABLE>

Details:WaterVaporDiffusion

2009-03-25T07:27:35Z

Barbara: /* Vapor diffusion thickness, sd-value */

= Water Vapor Diffusion =


This help topic discusses several physical quantities used to describe water
vapor diffusion, since these quantities and their interrelationships may not be
familiar to all WUFI users.


=== Water vapor diffusion resistance factor, µ-value ===

Diffusion of water vapor in air can be described by the equation

<TABLE>
<TR><TD COLSPAN="3"><TT>gv = -δ * dp/dx </TT>(in air),</TD></TR>

<TR><TD><TT>gv</TT></TD><TD ALIGN="RIGHT">[kg/m²s]:</TD><TD>water vapor flux density</TD></TR>
<TR><TD><TT>p</TT></TD><TD ALIGN="RIGHT">[Pa]:</TD><TD>water vapor partial pressure</TD></TR>
<TR><TD>δ </TD><TD ALIGN="RIGHT">[kg/(msPa)]:</TD><TD>water vapor diffusion coefficient in air,</TD></TR>

<TR><TD COLSPAN="3">where</TD></TR>
<TR><TD COLSPAN="3"><TT>δ = 2.0·10-7 T0.81 / PL </TT> [1]</TD></TR>

<TR><TD><TT>T</TT></TD><TD ALIGN="RIGHT">[K]:</TD><TD>absolute ambient temperature</TD></TR>
<TR><TD><TT>PL</TT></TD><TD ALIGN="RIGHT">[Pa]:</TD><TD>ambient atmospheric pressure.</TD></TR>
</TABLE>


In porous building materials, diffusion likewise takes place in air (in the pore spaces),
but it is impeded by the reduction of the accessible cross-section, adsorption effects
at the pore walls and the tortuosity of the pore paths. In the context of building
physics, it is admissible to allow for this by simply introducing a diffusion
resistance factor µ:


<TABLE>
<TR><TD COLSPAN="3"><TT>gv = -(d/µ) * dp/dx </TT>(in porous material),</TD></TR>
<TR><TD>µ</TD><TD>[-]:</TD><TD>water vapor diffusion resistance factor.</TD></TR>
</TABLE>


Retaining δ as a separate coefficient in the above
equation has the advantage that it already describes the temperature and pressure
dependence of water vapor diffusion and µ is therefore practically independent
of temperature and pressure, i.e. it is a constant which only depends on the material
in question.


However, measurements of µ which are performed at different levels of relative
humidity (dry-cup and wet-cup) may result in different values for one and the same
material. This is due to surface diffusion which becomes noticeable at higher
humidities but would be more properly treated as
[[Details:LiquidTransportCoefficients|liquid transport]] [2]. This additional
moisture transport is usually not separated out in the analysis of the measurements
and, lumped together with vapor diffusion, reduces the apparent diffusion resistance,
resulting in a lower µ-value. In these cases, it is more appropriate to use
a [[Details:BasicMaterialData|constant]] µ-value and to adjust the
[[Details:LiquidTransportCoefficients|liquid transport coefficients]] to include
surface diffusion. However, WUFI also allows to use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value to simplify the treatment of cases where this distinction can be
neglected.


The µ-value represents the ratio of the diffusion coefficients of water
vapor in air and in the building material and has therefore a simple interpretation:
it is the factor by which the vapor diffusion in the material is impeded, as
compared to diffusion in stagnant air. For very permeable materials, such as mineral
wool, the µ-value is thus close to 1, whereas it increases for materials with
greater diffusion resistance.



The following table lists µ-values for some common materials:

<TABLE>
<TR><TD> </TD><TD COLSPAN="2" ALIGN="CENTER">µ-value</TD></TR>
<TR><TD> </TD><TD ALIGN="CENTER">dry-cup (3% - 50% RH)</TD><TD ALIGN="CENTER">wet-cup (50%-93% RH)</TD></TR>

<TR><TD>cellular concrete</TD> <TD ALIGN="CENTER">7.7</TD><TD ALIGN="CENTER">7.1</TD></TR>
<TR><TD>lime silica brick</TD> <TD ALIGN="CENTER">27</TD> <TD ALIGN="CENTER">18</TD></TR>
<TR><TD>solid brick</TD> <TD ALIGN="CENTER">9.5</TD><TD ALIGN="CENTER">8.0</TD></TR>
<TR><TD>gypsum board</TD> <TD ALIGN="CENTER">8.3</TD><TD ALIGN="CENTER">7.3</TD></TR>
<TR><TD>concrete (B25)</TD> <TD ALIGN="CENTER">110</TD><TD ALIGN="CENTER">150 (*)</TD></TR>
<TR><TD>cement-lime plaster</TD> <TD ALIGN="CENTER">19</TD> <TD ALIGN="CENTER">18</TD></TR>
<TR><TD>lime plaster</TD> <TD ALIGN="CENTER">7.3</TD><TD ALIGN="CENTER">6.4</TD></TR>
<TR><TD>Saaler sandstone</TD> <TD ALIGN="CENTER">60</TD> <TD ALIGN="CENTER">28</TD></TR>
<TR><TD>Baumberger sandstone</TD> <TD ALIGN="CENTER">20</TD> <TD ALIGN="CENTER">17</TD></TR>
<TR><TD>Worzeldorfer sandstone</TD><TD ALIGN="CENTER">38</TD> <TD ALIGN="CENTER">22</TD></TR>
</TABLE>
(*) the increase of the µ-value
in the wet-cup measurement of concrete is probably due to
swelling effects [3].


In WUFI, the µ-value is one of the [[Details:BasicMaterialData|basic material
properties]] which needs to be [[2D:DialogEditMaterial|specified for
each material]].

  

=== Vapor diffusion thickness, sd-value ===


Assuming constant temperature and µ-value, the diffusion flow through a
material layer with thickness Dx=s is


<TT>gv_mat = -δ/µ * Δp/Δx = -δ/(µ*s) * Δp</TT>,


whereas the diffusion flow through a stagnant air layer (µ=1) with thickness
sd is


<TT>gv_air = -δ/µ * Δp/Δx = -δ/(1*sd) * Δp = -δ / sd * Δp</TT>.


Dividing the former equation by the latter yields


<TT>gv_mat / gv_air = sd / (µ*s)</TT>.


If the air layer is chosen so that its vapor diffusion resistance is the same
as that of the material layer of thickness <TT>s</TT> (and therefore
gv_mat = gv_air), then its thickness
<TT>sd</TT> must be


<TT>sd = µ*s</TT>.


For a material layer with diffusion resistance factor µ and thickness
<TT>s</TT>, the product <TT>µ*s</TT> thus gives the thickness which
a stagnant air layer would need in order to have the same diffusion resistance.
This "sd-value" or "vapor diffusion thickness" expresses the
diffusion resistance of a layer in a form which is easily understood and applied.


Since the definition of the sd-value contains the the thickness
<TT>Δx</TT> of the layer, the sd-value
is a property of the given layer, not of the material itself. Two layers
made from the same material but with different thicknesses will have different
sd-values, but in both cases the material will have the same
µ-value.


For some building components, only their total diffusion resistance is of importance
but not their µ-value and their thickness separately. They may then simply
be specified in terms of their sd-value. Also, measuring the
sd-value does not require to determine the thickness of the sample. 
In particular, the sd-value is used to characterise vapor retarders
(sd >= 10 m), vapor barriers (sd >= 1000 m) and
surface coatings (mineral paints: sd ~ 0.04 m, oil paints:
sd = 1.0 .. 2.6 m), where it can be difficult to determine
their thickness properly.


In WUFI, [[Details:SurfaceCoatings|surface coatings]] on the component need
not be explicitly modelled in the
[[2D:Dialog_Geometry|component assembly]]; their diffusion resistance
may instead be taken into account by simply specifying their sd-value
in the dialog
[[2D:Dialog_EditSurfaceCoefficients|Edit Surface Coefficients]].

  

<H3>Permeance, Permeability</H3>


In the formula for water vapor diffusion in a porous material


<TT>gv = -δ/µ * Δp/Δx = - δ/sd * Δp =: - Δ * Δp</TT>


the so-called permeance Δ may be introduced by defining


<TT>Δ := δ/sd </TT>[kg/(m²sPa)].


Since the definition of the permeance contains the thickness
<TT>Δx</TT> of the layer, the permeance is a property of the
given layer, not of the material itself. Two layers made from the same material
but with different thicknesses will have different permeances.


In Inch-Pound units the permeance is measured in perm. One perm is one
grain (avoirdupois) of water vapor per hour flowing through one square foot of a layer,
induced by a vapor pressure difference of one inch of mercury across the two surfaces.
In SI units, this corresponds to 57.45e-12 kg/(m²sPa) [4]. Therefore, with
Δ expressed in perm:


<TT>57.45e-12*Δ = δ/sd </TT> [kg/(m²sPa)], or 
<TT>sd = δ/(57.45e-12*Δ) </TT> [m].


For a reference temperature of 5°C and a barometric pressure of 1013.25 hPa,
δ has the value 1.884e-10 kg/(msPa) (see above),
and we obtain

<TT>sd = 3.28/Δ</TT>,

where Δ is expressed in perm and sd in m.



The permeance describes a property of a specific construction layer with a given
thickness. Multiplying the permeance by the layer thickness
Δx yields the
permeability Π [perm inch]
of the layer material:



<TT>Δ * Δx = δ/sd * Δx = δ/µ =: Π </TT>, so that 
<TT>gv = Π Δp/Δx</TT>.



The conversion factor for D*Dx is
57.45e-12 [kg/(m²sPa)]/[perm] * 0.0254 [m]/[in] = 1.459e-12 [kg/(msPa)]/[perm in]:


<TT>1.459e-12*P = d/µ </TT> [kg/(msPa)],


and with the same reference value for d as above:


<TT>7.744e-3*P = 1/µ </TT> [-], or


<TT>µ = 129 / P </TT> [-],


where P is expressed in perm inch and µ is
dimensionless.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Schirmer, R.: Die Diffusionszahl von
Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, 
Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177.</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>Krus, M.: Moisture Transport and Storage
Coefficients of Porous Mineral Building Materials. Theoretical Principles
and New Test Methods 
Fraunhofer IRB Verlag, 1996</TD></TR>

<TR><TD VALIGN="TOP">[3]</TD><TD>Holm, A., Krus, M., Künzel, H.M.: Concrete from
the viewpoint of moisture technology: Parameters and mathematical approaches
to the evaluation of climatic effects in external structural elements made
of concrete. 
To be published in Concrete Science and Engineering</TD></TR>

<TR><TD VALIGN="TOP">[4]</TD><TD>ASHRAE Terminology of Heating, Ventilation, Air
Conditioning, & Refrigeration, 2nd ed. 1991</TD></TR>
</TABLE>

Details:WaterVaporDiffusion

2009-03-25T07:22:01Z

Barbara: /* Vapor diffusion thickness, sd-value */

= Water Vapor Diffusion =


This help topic discusses several physical quantities used to describe water
vapor diffusion, since these quantities and their interrelationships may not be
familiar to all WUFI users.


=== Water vapor diffusion resistance factor, µ-value ===

Diffusion of water vapor in air can be described by the equation

<TABLE>
<TR><TD COLSPAN="3"><TT>gv = -δ * dp/dx </TT>(in air),</TD></TR>

<TR><TD><TT>gv</TT></TD><TD ALIGN="RIGHT">[kg/m²s]:</TD><TD>water vapor flux density</TD></TR>
<TR><TD><TT>p</TT></TD><TD ALIGN="RIGHT">[Pa]:</TD><TD>water vapor partial pressure</TD></TR>
<TR><TD>δ </TD><TD ALIGN="RIGHT">[kg/(msPa)]:</TD><TD>water vapor diffusion coefficient in air,</TD></TR>

<TR><TD COLSPAN="3">where</TD></TR>
<TR><TD COLSPAN="3"><TT>δ = 2.0·10-7 T0.81 / PL </TT> [1]</TD></TR>

<TR><TD><TT>T</TT></TD><TD ALIGN="RIGHT">[K]:</TD><TD>absolute ambient temperature</TD></TR>
<TR><TD><TT>PL</TT></TD><TD ALIGN="RIGHT">[Pa]:</TD><TD>ambient atmospheric pressure.</TD></TR>
</TABLE>


In porous building materials, diffusion likewise takes place in air (in the pore spaces),
but it is impeded by the reduction of the accessible cross-section, adsorption effects
at the pore walls and the tortuosity of the pore paths. In the context of building
physics, it is admissible to allow for this by simply introducing a diffusion
resistance factor µ:


<TABLE>
<TR><TD COLSPAN="3"><TT>gv = -(d/µ) * dp/dx </TT>(in porous material),</TD></TR>
<TR><TD>µ</TD><TD>[-]:</TD><TD>water vapor diffusion resistance factor.</TD></TR>
</TABLE>


Retaining δ as a separate coefficient in the above
equation has the advantage that it already describes the temperature and pressure
dependence of water vapor diffusion and µ is therefore practically independent
of temperature and pressure, i.e. it is a constant which only depends on the material
in question.


However, measurements of µ which are performed at different levels of relative
humidity (dry-cup and wet-cup) may result in different values for one and the same
material. This is due to surface diffusion which becomes noticeable at higher
humidities but would be more properly treated as
[[Details:LiquidTransportCoefficients|liquid transport]] [2]. This additional
moisture transport is usually not separated out in the analysis of the measurements
and, lumped together with vapor diffusion, reduces the apparent diffusion resistance,
resulting in a lower µ-value. In these cases, it is more appropriate to use
a [[Details:BasicMaterialData|constant]] µ-value and to adjust the
[[Details:LiquidTransportCoefficients|liquid transport coefficients]] to include
surface diffusion. However, WUFI also allows to use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value to simplify the treatment of cases where this distinction can be
neglected.


The µ-value represents the ratio of the diffusion coefficients of water
vapor in air and in the building material and has therefore a simple interpretation:
it is the factor by which the vapor diffusion in the material is impeded, as
compared to diffusion in stagnant air. For very permeable materials, such as mineral
wool, the µ-value is thus close to 1, whereas it increases for materials with
greater diffusion resistance.



The following table lists µ-values for some common materials:

<TABLE>
<TR><TD> </TD><TD COLSPAN="2" ALIGN="CENTER">µ-value</TD></TR>
<TR><TD> </TD><TD ALIGN="CENTER">dry-cup (3% - 50% RH)</TD><TD ALIGN="CENTER">wet-cup (50%-93% RH)</TD></TR>

<TR><TD>cellular concrete</TD> <TD ALIGN="CENTER">7.7</TD><TD ALIGN="CENTER">7.1</TD></TR>
<TR><TD>lime silica brick</TD> <TD ALIGN="CENTER">27</TD> <TD ALIGN="CENTER">18</TD></TR>
<TR><TD>solid brick</TD> <TD ALIGN="CENTER">9.5</TD><TD ALIGN="CENTER">8.0</TD></TR>
<TR><TD>gypsum board</TD> <TD ALIGN="CENTER">8.3</TD><TD ALIGN="CENTER">7.3</TD></TR>
<TR><TD>concrete (B25)</TD> <TD ALIGN="CENTER">110</TD><TD ALIGN="CENTER">150 (*)</TD></TR>
<TR><TD>cement-lime plaster</TD> <TD ALIGN="CENTER">19</TD> <TD ALIGN="CENTER">18</TD></TR>
<TR><TD>lime plaster</TD> <TD ALIGN="CENTER">7.3</TD><TD ALIGN="CENTER">6.4</TD></TR>
<TR><TD>Saaler sandstone</TD> <TD ALIGN="CENTER">60</TD> <TD ALIGN="CENTER">28</TD></TR>
<TR><TD>Baumberger sandstone</TD> <TD ALIGN="CENTER">20</TD> <TD ALIGN="CENTER">17</TD></TR>
<TR><TD>Worzeldorfer sandstone</TD><TD ALIGN="CENTER">38</TD> <TD ALIGN="CENTER">22</TD></TR>
</TABLE>
(*) the increase of the µ-value
in the wet-cup measurement of concrete is probably due to
swelling effects [3].


In WUFI, the µ-value is one of the [[Details:BasicMaterialData|basic material
properties]] which needs to be [[2D:DialogEditMaterial|specified for
each material]].

  

=== Vapor diffusion thickness, sd-value ===


Assuming constant temperature and µ-value, the diffusion flow through a
material layer with thickness Dx=s is


<TT>gv_mat = -δ/µ * Δp/Δx = -δ/(µ*s) * Δp</TT>,


whereas the diffusion flow through a stagnant air layer (µ=1) with thickness
sd is


<TT>gv_air = -δ/µ * Δp/Δx = -δ/(1*sd) * Δp = -δ / sd * Δp</TT>.


Dividing the former equation by the latter yields


<TT>gv_mat / gv_air = sd / (µ*s)</TT>.


If the air layer is chosen so that its vapor diffusion resistance is the same
as that of the material layer of thickness <TT>s</TT> (and therefore
gv_mat = gv_air), then its thickness
<TT>sd</TT> must be


<TT>sd = µ*s</TT>.


For a material layer with diffusion resistance factor µ and thickness
<TT>s</TT>, the product <TT>µ*s</TT> thus gives the thickness which
a stagnant air layer would need in order to have the same diffusion resistance.
This "sd-value" or "vapor diffusion thickness" expresses the
diffusion resistance of a layer in a form which is easily understood and applied.


Since the definition of the sd-value contains the the thickness
<TT>Δx</TT> of the layer, the sd-value
is a property of the given layer, not of the material itself. Two layers
made from the same material but with different thicknesses will have different
sd-values, but in both cases the material will have the same
µ-value.


For some building components, only their total diffusion resistance is of importance
but not their µ-value and their thickness separately. They may then simply
be specified in terms of their sd-value. Also, measuring the
sd-value does not require to determine the thickness of the sample. 
In particular, the sd-value is used to characterise vapor retarders
(sd >= 10 m), vapor barriers (sd >= 1000 m) and
surface coatings (mineral paints: sd ~ 0.04 m, oil paints:
sd = 1.0 .. 2.6 m), where it can be difficult to determine
their thickness properly.


In WUFI, [[Details:SurfaceCoatings|surface coatings]] on the component need
not be explicitly modelled in the
[[2D:Dialog_Geometry|component assembly]]; their diffusion resistance
may instead be taken into account by simply specifying their sd-value
in the dialog
[[2D:Dialog_EditSurfaceCoefficients|Edit Surface Coefficients]].

  

<H3>Permeance, Permeability</H3>


In the formula for water vapor diffusion in a porous material


<TT>gv = -δ/µ * Δp/Δx = - δ/sd * Δp =: - Δ * Δp</TT>


the so-called permeance Δ may be introduced by defining


<TT>Δ := δ/sd </TT>[kg/(m²sPa)].


Since the definition of the permeance contains the thickness
<TT>Δx</TT> of the layer, the permeance is a property of the
given layer, not of the material itself. Two layers made from the same material
but with different thicknesses will have different permeances.


In Inch-Pound units the permeance is measured in perm. One perm is one
grain (avoirdupois) of water vapor per hour flowing through one square foot of a layer,
induced by a vapor pressure difference of one inch of mercury across the two surfaces.
In SI units, this corresponds to 57.45e-12 kg/(m²sPa) [4]. Therefore, with
Δ expressed in perm:


<TT>57.45e-12*Δ = δ/sd </TT> [kg/(m²sPa)], or 
<TT>sd = δ/(57.45e-12*Δ) </TT> [m].


For a reference temperature of 5°C and a barometric pressure of 1013.25 hPa,
δ has the value 1.884e-10 kg/(msPa) (see above),
and we obtain

<TT>sd = 3.28/Δ</TT>,

where Δ is expressed in perm and sd in m.



The permeance describes a property of a specific construction layer with a given
thickness. Multiplying the permeance by the layer thickness
Dx yields the
permeability P [perm inch]
of the layer material:



<TT>D * Dx = d/sd * Dx = d/µ =: P </TT>, so that 
<TT>gv = P Dp/Dx</TT>.



The conversion factor for D*Dx is
57.45e-12 [kg/(m²sPa)]/[perm] * 0.0254 [m]/[in] = 1.459e-12 [kg/(msPa)]/[perm in]:


<TT>1.459e-12*P = d/µ </TT> [kg/(msPa)],


and with the same reference value for d as above:


<TT>7.744e-3*P = 1/µ </TT> [-], or


<TT>µ = 129 / P </TT> [-],


where P is expressed in perm inch and µ is
dimensionless.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Schirmer, R.: Die Diffusionszahl von
Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, 
Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177.</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>Krus, M.: Moisture Transport and Storage
Coefficients of Porous Mineral Building Materials. Theoretical Principles
and New Test Methods 
Fraunhofer IRB Verlag, 1996</TD></TR>

<TR><TD VALIGN="TOP">[3]</TD><TD>Holm, A., Krus, M., Künzel, H.M.: Concrete from
the viewpoint of moisture technology: Parameters and mathematical approaches
to the evaluation of climatic effects in external structural elements made
of concrete. 
To be published in Concrete Science and Engineering</TD></TR>

<TR><TD VALIGN="TOP">[4]</TD><TD>ASHRAE Terminology of Heating, Ventilation, Air
Conditioning, & Refrigeration, 2nd ed. 1991</TD></TR>
</TABLE>

Details:WaterVaporDiffusion

2009-03-25T07:17:56Z

Barbara: /* Vapor diffusion thickness, sd-value */

= Water Vapor Diffusion =


This help topic discusses several physical quantities used to describe water
vapor diffusion, since these quantities and their interrelationships may not be
familiar to all WUFI users.


=== Water vapor diffusion resistance factor, µ-value ===

Diffusion of water vapor in air can be described by the equation

<TABLE>
<TR><TD COLSPAN="3"><TT>gv = -δ * dp/dx </TT>(in air),</TD></TR>

<TR><TD><TT>gv</TT></TD><TD ALIGN="RIGHT">[kg/m²s]:</TD><TD>water vapor flux density</TD></TR>
<TR><TD><TT>p</TT></TD><TD ALIGN="RIGHT">[Pa]:</TD><TD>water vapor partial pressure</TD></TR>
<TR><TD>δ </TD><TD ALIGN="RIGHT">[kg/(msPa)]:</TD><TD>water vapor diffusion coefficient in air,</TD></TR>

<TR><TD COLSPAN="3">where</TD></TR>
<TR><TD COLSPAN="3"><TT>δ = 2.0·10-7 T0.81 / PL </TT> [1]</TD></TR>

<TR><TD><TT>T</TT></TD><TD ALIGN="RIGHT">[K]:</TD><TD>absolute ambient temperature</TD></TR>
<TR><TD><TT>PL</TT></TD><TD ALIGN="RIGHT">[Pa]:</TD><TD>ambient atmospheric pressure.</TD></TR>
</TABLE>


In porous building materials, diffusion likewise takes place in air (in the pore spaces),
but it is impeded by the reduction of the accessible cross-section, adsorption effects
at the pore walls and the tortuosity of the pore paths. In the context of building
physics, it is admissible to allow for this by simply introducing a diffusion
resistance factor µ:


<TABLE>
<TR><TD COLSPAN="3"><TT>gv = -(d/µ) * dp/dx </TT>(in porous material),</TD></TR>
<TR><TD>µ</TD><TD>[-]:</TD><TD>water vapor diffusion resistance factor.</TD></TR>
</TABLE>


Retaining δ as a separate coefficient in the above
equation has the advantage that it already describes the temperature and pressure
dependence of water vapor diffusion and µ is therefore practically independent
of temperature and pressure, i.e. it is a constant which only depends on the material
in question.


However, measurements of µ which are performed at different levels of relative
humidity (dry-cup and wet-cup) may result in different values for one and the same
material. This is due to surface diffusion which becomes noticeable at higher
humidities but would be more properly treated as
[[Details:LiquidTransportCoefficients|liquid transport]] [2]. This additional
moisture transport is usually not separated out in the analysis of the measurements
and, lumped together with vapor diffusion, reduces the apparent diffusion resistance,
resulting in a lower µ-value. In these cases, it is more appropriate to use
a [[Details:BasicMaterialData|constant]] µ-value and to adjust the
[[Details:LiquidTransportCoefficients|liquid transport coefficients]] to include
surface diffusion. However, WUFI also allows to use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value to simplify the treatment of cases where this distinction can be
neglected.


The µ-value represents the ratio of the diffusion coefficients of water
vapor in air and in the building material and has therefore a simple interpretation:
it is the factor by which the vapor diffusion in the material is impeded, as
compared to diffusion in stagnant air. For very permeable materials, such as mineral
wool, the µ-value is thus close to 1, whereas it increases for materials with
greater diffusion resistance.



The following table lists µ-values for some common materials:

<TABLE>
<TR><TD> </TD><TD COLSPAN="2" ALIGN="CENTER">µ-value</TD></TR>
<TR><TD> </TD><TD ALIGN="CENTER">dry-cup (3% - 50% RH)</TD><TD ALIGN="CENTER">wet-cup (50%-93% RH)</TD></TR>

<TR><TD>cellular concrete</TD> <TD ALIGN="CENTER">7.7</TD><TD ALIGN="CENTER">7.1</TD></TR>
<TR><TD>lime silica brick</TD> <TD ALIGN="CENTER">27</TD> <TD ALIGN="CENTER">18</TD></TR>
<TR><TD>solid brick</TD> <TD ALIGN="CENTER">9.5</TD><TD ALIGN="CENTER">8.0</TD></TR>
<TR><TD>gypsum board</TD> <TD ALIGN="CENTER">8.3</TD><TD ALIGN="CENTER">7.3</TD></TR>
<TR><TD>concrete (B25)</TD> <TD ALIGN="CENTER">110</TD><TD ALIGN="CENTER">150 (*)</TD></TR>
<TR><TD>cement-lime plaster</TD> <TD ALIGN="CENTER">19</TD> <TD ALIGN="CENTER">18</TD></TR>
<TR><TD>lime plaster</TD> <TD ALIGN="CENTER">7.3</TD><TD ALIGN="CENTER">6.4</TD></TR>
<TR><TD>Saaler sandstone</TD> <TD ALIGN="CENTER">60</TD> <TD ALIGN="CENTER">28</TD></TR>
<TR><TD>Baumberger sandstone</TD> <TD ALIGN="CENTER">20</TD> <TD ALIGN="CENTER">17</TD></TR>
<TR><TD>Worzeldorfer sandstone</TD><TD ALIGN="CENTER">38</TD> <TD ALIGN="CENTER">22</TD></TR>
</TABLE>
(*) the increase of the µ-value
in the wet-cup measurement of concrete is probably due to
swelling effects [3].


In WUFI, the µ-value is one of the [[Details:BasicMaterialData|basic material
properties]] which needs to be [[2D:DialogEditMaterial|specified for
each material]].

  

=== Vapor diffusion thickness, sd-value ===


Assuming constant temperature and µ-value, the diffusion flow through a
material layer with thickness Dx=s is


<TT>gv_mat = -δ/µ * Δp/Δx = -δ/(µ*s) * Δp</TT>,


whereas the diffusion flow through a stagnant air layer (µ=1) with thickness
sd is


<TT>gv_air = -δ/µ * Δp/Δx = -δ/(1*sd) * Δp = -δ / sd * Δp</TT>.


Dividing the former equation by the latter yields


<TT>gv_mat / gv_air = sd / (µ*s)</TT>.


If the air layer is chosen so that its vapor diffusion resistance is the same
as that of the material layer of thickness <TT>s</TT> (and therefore
gv_mat = gv_air), then its thickness
<TT>sd</TT> must be


<TT>sd = µ*s</TT>.


For a material layer with diffusion resistance factor µ and thickness
<TT>s</TT>, the product <TT>µ*s</TT> thus gives the thickness which
a stagnant air layer would need in order to have the same diffusion resistance.
This "sd-value" or "vapor diffusion thickness" expresses the
diffusion resistance of a layer in a form which is easily understood and applied.


Since the definition of the sd-value contains the the thickness
<TT>Δx</TT> of the layer, the sd-value
is a property of the given layer, not of the material itself. Two layers
made from the same material but with different thicknesses will have different
sd-values, but in both cases the material will have the same
µ-value.


For some building components, only their total diffusion resistance is of importance
but not their µ-value and their thickness separately. They may then simply
be specified in terms of their sd-value. Also, measuring the
sd-value does not require to determine the thickness of the sample. 
In particular, the sd-value is used to characterise vapor retarders
(sd >= 10 m), vapor barriers (sd >= 1000 m) and
surface coatings (mineral paints: sd ~ 0.04 m, oil paints:
sd = 1.0 .. 2.6 m), where it can be difficult to determine
their thickness properly.


In WUFI, [[Details:SurfaceCoatings|surface coatings]] on the component need
not be explicitly modelled in the
[[2D:Dialog_Geometry|component assembly]]; their diffusion resistance
may instead be taken into account by simply specifying their sd-value
in the dialog
[[2D:Dialog_EditSurfaceCoefficients|Edit Surface Coefficients]].

  

<H3>Permeance, Permeability</H3>


In the formula for water vapor diffusion in a porous material


<TT>gv = -δ/µ * Δp/Δx = - δ/sd * Δp =: - Δ * Δp</TT>


the so-called permeance Δ may be introduced by defining


<TT>Δ := δ/sd </TT>[kg/(m²sPa)].


Since the definition of the permeance contains the thickness
<TT>Δx</TT> of the layer, the permeance is a property of the
given layer, not of the material itself. Two layers made from the same material
but with different thicknesses will have different permeances.


In Inch-Pound units the permeance is measured in perm. One perm is one
grain (avoirdupois) of water vapor per hour flowing through one square foot of a layer,
induced by a vapor pressure difference of one inch of mercury across the two surfaces.
In SI units, this corresponds to 57.45e-12 kg/(m²sPa) [4]. Therefore, with
Δ expressed in perm:


<TT>57.45e-12*Δ = δ/sd </TT> [kg/(m²sPa)], or 
<TT>sd = δ/(57.45e-12*Δ) </TT> [m].


For a reference temperature of 5°C and a barometric pressure of 1013.25 hPa,
d has the value 1.884e-10 kg/(msPa) (see above),
and we obtain

<TT>sd = 3.28/D</TT>,

where D is expressed in perm and sd in m.



The permeance describes a property of a specific construction layer with a given
thickness. Multiplying the permeance by the layer thickness
Dx yields the
permeability P [perm inch]
of the layer material:



<TT>D * Dx = d/sd * Dx = d/µ =: P </TT>, so that 
<TT>gv = P Dp/Dx</TT>.



The conversion factor for D*Dx is
57.45e-12 [kg/(m²sPa)]/[perm] * 0.0254 [m]/[in] = 1.459e-12 [kg/(msPa)]/[perm in]:


<TT>1.459e-12*P = d/µ </TT> [kg/(msPa)],


and with the same reference value for d as above:


<TT>7.744e-3*P = 1/µ </TT> [-], or


<TT>µ = 129 / P </TT> [-],


where P is expressed in perm inch and µ is
dimensionless.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Schirmer, R.: Die Diffusionszahl von
Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, 
Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177.</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>Krus, M.: Moisture Transport and Storage
Coefficients of Porous Mineral Building Materials. Theoretical Principles
and New Test Methods 
Fraunhofer IRB Verlag, 1996</TD></TR>

<TR><TD VALIGN="TOP">[3]</TD><TD>Holm, A., Krus, M., Künzel, H.M.: Concrete from
the viewpoint of moisture technology: Parameters and mathematical approaches
to the evaluation of climatic effects in external structural elements made
of concrete. 
To be published in Concrete Science and Engineering</TD></TR>

<TR><TD VALIGN="TOP">[4]</TD><TD>ASHRAE Terminology of Heating, Ventilation, Air
Conditioning, & Refrigeration, 2nd ed. 1991</TD></TR>
</TABLE>

Details:WaterVaporDiffusion

2009-03-25T07:14:08Z

Barbara: /* Vapor diffusion thickness, sd-value */

= Water Vapor Diffusion =


This help topic discusses several physical quantities used to describe water
vapor diffusion, since these quantities and their interrelationships may not be
familiar to all WUFI users.


=== Water vapor diffusion resistance factor, µ-value ===

Diffusion of water vapor in air can be described by the equation

<TABLE>
<TR><TD COLSPAN="3"><TT>gv = -δ * dp/dx </TT>(in air),</TD></TR>

<TR><TD><TT>gv</TT></TD><TD ALIGN="RIGHT">[kg/m²s]:</TD><TD>water vapor flux density</TD></TR>
<TR><TD><TT>p</TT></TD><TD ALIGN="RIGHT">[Pa]:</TD><TD>water vapor partial pressure</TD></TR>
<TR><TD>δ </TD><TD ALIGN="RIGHT">[kg/(msPa)]:</TD><TD>water vapor diffusion coefficient in air,</TD></TR>

<TR><TD COLSPAN="3">where</TD></TR>
<TR><TD COLSPAN="3"><TT>δ = 2.0·10-7 T0.81 / PL </TT> [1]</TD></TR>

<TR><TD><TT>T</TT></TD><TD ALIGN="RIGHT">[K]:</TD><TD>absolute ambient temperature</TD></TR>
<TR><TD><TT>PL</TT></TD><TD ALIGN="RIGHT">[Pa]:</TD><TD>ambient atmospheric pressure.</TD></TR>
</TABLE>


In porous building materials, diffusion likewise takes place in air (in the pore spaces),
but it is impeded by the reduction of the accessible cross-section, adsorption effects
at the pore walls and the tortuosity of the pore paths. In the context of building
physics, it is admissible to allow for this by simply introducing a diffusion
resistance factor µ:


<TABLE>
<TR><TD COLSPAN="3"><TT>gv = -(d/µ) * dp/dx </TT>(in porous material),</TD></TR>
<TR><TD>µ</TD><TD>[-]:</TD><TD>water vapor diffusion resistance factor.</TD></TR>
</TABLE>


Retaining δ as a separate coefficient in the above
equation has the advantage that it already describes the temperature and pressure
dependence of water vapor diffusion and µ is therefore practically independent
of temperature and pressure, i.e. it is a constant which only depends on the material
in question.


However, measurements of µ which are performed at different levels of relative
humidity (dry-cup and wet-cup) may result in different values for one and the same
material. This is due to surface diffusion which becomes noticeable at higher
humidities but would be more properly treated as
[[Details:LiquidTransportCoefficients|liquid transport]] [2]. This additional
moisture transport is usually not separated out in the analysis of the measurements
and, lumped together with vapor diffusion, reduces the apparent diffusion resistance,
resulting in a lower µ-value. In these cases, it is more appropriate to use
a [[Details:BasicMaterialData|constant]] µ-value and to adjust the
[[Details:LiquidTransportCoefficients|liquid transport coefficients]] to include
surface diffusion. However, WUFI also allows to use a
[[Details:DiffusionResistanceFactorMoistureDependent|moisture-dependent]]
µ-value to simplify the treatment of cases where this distinction can be
neglected.


The µ-value represents the ratio of the diffusion coefficients of water
vapor in air and in the building material and has therefore a simple interpretation:
it is the factor by which the vapor diffusion in the material is impeded, as
compared to diffusion in stagnant air. For very permeable materials, such as mineral
wool, the µ-value is thus close to 1, whereas it increases for materials with
greater diffusion resistance.



The following table lists µ-values for some common materials:

<TABLE>
<TR><TD> </TD><TD COLSPAN="2" ALIGN="CENTER">µ-value</TD></TR>
<TR><TD> </TD><TD ALIGN="CENTER">dry-cup (3% - 50% RH)</TD><TD ALIGN="CENTER">wet-cup (50%-93% RH)</TD></TR>

<TR><TD>cellular concrete</TD> <TD ALIGN="CENTER">7.7</TD><TD ALIGN="CENTER">7.1</TD></TR>
<TR><TD>lime silica brick</TD> <TD ALIGN="CENTER">27</TD> <TD ALIGN="CENTER">18</TD></TR>
<TR><TD>solid brick</TD> <TD ALIGN="CENTER">9.5</TD><TD ALIGN="CENTER">8.0</TD></TR>
<TR><TD>gypsum board</TD> <TD ALIGN="CENTER">8.3</TD><TD ALIGN="CENTER">7.3</TD></TR>
<TR><TD>concrete (B25)</TD> <TD ALIGN="CENTER">110</TD><TD ALIGN="CENTER">150 (*)</TD></TR>
<TR><TD>cement-lime plaster</TD> <TD ALIGN="CENTER">19</TD> <TD ALIGN="CENTER">18</TD></TR>
<TR><TD>lime plaster</TD> <TD ALIGN="CENTER">7.3</TD><TD ALIGN="CENTER">6.4</TD></TR>
<TR><TD>Saaler sandstone</TD> <TD ALIGN="CENTER">60</TD> <TD ALIGN="CENTER">28</TD></TR>
<TR><TD>Baumberger sandstone</TD> <TD ALIGN="CENTER">20</TD> <TD ALIGN="CENTER">17</TD></TR>
<TR><TD>Worzeldorfer sandstone</TD><TD ALIGN="CENTER">38</TD> <TD ALIGN="CENTER">22</TD></TR>
</TABLE>
(*) the increase of the µ-value
in the wet-cup measurement of concrete is probably due to
swelling effects [3].


In WUFI, the µ-value is one of the [[Details:BasicMaterialData|basic material
properties]] which needs to be [[2D:DialogEditMaterial|specified for
each material]].

  

=== Vapor diffusion thickness, sd-value ===


Assuming constant temperature and µ-value, the diffusion flow through a
material layer with thickness Dx=s is


<TT>gv_mat = -δ/µ * Δp/Δx = -δ/(µ*s) * Δp</TT>,


whereas the diffusion flow through a stagnant air layer (µ=1) with thickness
sd is


<TT>gv_air = -δ/µ * Δp/Δx = -δ/(1*sd) * Δp = -δ / sd * Δp</TT>.


Dividing the former equation by the latter yields


<TT>gv_mat / gv_air = sd / (µ*s)</TT>.


If the air layer is chosen so that its vapor diffusion resistance is the same
as that of the material layer of thickness <TT>s</TT> (and therefore
gv_mat = gv_air), then its thickness
<TT>sd</TT> must be


<TT>sd = µ*s</TT>.


For a material layer with diffusion resistance factor µ and thickness
<TT>s</TT>, the product <TT>µ*s</TT> thus gives the thickness which
a stagnant air layer would need in order to have the same diffusion resistance.
This "sd-value" or "vapor diffusion thickness" expresses the
diffusion resistance of a layer in a form which is easily understood and applied.


Since the definition of the sd-value contains the the thickness
<TT>Δx</TT> of the layer, the sd-value
is a property of the given layer, not of the material itself. Two layers
made from the same material but with different thicknesses will have different
sd-values, but in both cases the material will have the same
µ-value.


For some building components, only their total diffusion resistance is of importance
but not their µ-value and their thickness separately. They may then simply
be specified in terms of their sd-value. Also, measuring the
sd-value does not require to determine the thickness of the sample. 
In particular, the sd-value is used to characterise vapor retarders
(sd >= 10 m), vapor barriers (sd >= 1000 m) and
surface coatings (mineral paints: sd ~ 0.04 m, oil paints:
sd = 1.0 .. 2.6 m), where it can be difficult to determine
their thickness properly.


In WUFI, [[Details:SurfaceCoatings|surface coatings]] on the component need
not be explicitly modelled in the
[[2D:Dialog_Geometry|component assembly]]; their diffusion resistance
may instead be taken into account by simply specifying their sd-value
in the dialog
[[2D:Dialog_EditSurfaceCoefficients|Edit Surface Coefficients]].

  

<H3>Permeance, Permeability</H3>


In the formula for water vapor diffusion in a porous material


<TT>gv = -δ/µ * Δp/Δx = - δ/sd * Δp =: - Δ * Δp</TT>


the so-called permeance Δ may be introduced by defining


<TT>Δ := δ/sd </TT>[kg/(m²sPa)].


Since the definition of the permeance contains the thickness
<TT>Δx</TT> of the layer, the permeance is a property of the
given layer, not of the material itself. Two layers made from the same material
but with different thicknesses will have different permeances.


In Inch-Pound units the permeance is measured in perm. One perm is one
grain (avoirdupois) of water vapor per hour flowing through one square foot of a layer,
induced by a vapor pressure difference of one inch of mercury across the two surfaces.
In SI units, this corresponds to 57.45e-12 kg/(m²sPa) [4]. Therefore, with
D expressed in perm:


<TT>57.45e-12*D = d/sd </TT> [kg/(m²sPa)], or 
<TT>sd = d/(57.45e-12*D) </TT> [m].


For a reference temperature of 5°C and a barometric pressure of 1013.25 hPa,
d has the value 1.884e-10 kg/(msPa) (see above),
and we obtain

<TT>sd = 3.28/D</TT>,

where D is expressed in perm and sd in m.



The permeance describes a property of a specific construction layer with a given
thickness. Multiplying the permeance by the layer thickness
Dx yields the
permeability P [perm inch]
of the layer material:



<TT>D * Dx = d/sd * Dx = d/µ =: P </TT>, so that 
<TT>gv = P Dp/Dx</TT>.



The conversion factor for D*Dx is
57.45e-12 [kg/(m²sPa)]/[perm] * 0.0254 [m]/[in] = 1.459e-12 [kg/(msPa)]/[perm in]:


<TT>1.459e-12*P = d/µ </TT> [kg/(msPa)],


and with the same reference value for d as above:


<TT>7.744e-3*P = 1/µ </TT> [-], or


<TT>µ = 129 / P </TT> [-],


where P is expressed in perm inch and µ is
dimensionless.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Schirmer, R.: Die Diffusionszahl von
Wasserdampf-Luft-Gemischen und die Verdampfungsgeschwindigkeit, 
Beiheft VDI-Zeitschrift, Verfahrenstechnik (1938), H. 6, p. 170-177.</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>Krus, M.: Moisture Transport and Storage
Coefficients of Porous Mineral Building Materials. Theoretical Principles
and New Test Methods 
Fraunhofer IRB Verlag, 1996</TD></TR>

<TR><TD VALIGN="TOP">[3]</TD><TD>Holm, A., Krus, M., Künzel, H.M.: Concrete from
the viewpoint of moisture technology: Parameters and mathematical approaches
to the evaluation of climatic effects in external structural elements made
of concrete. 
To be published in Concrete Science and Engineering</TD></TR>

<TR><TD VALIGN="TOP">[4]</TD><TD>ASHRAE Terminology of Heating, Ventilation, Air
Conditioning, & Refrigeration, 2nd ed. 1991</TD></TR>
</TABLE>

Details:WET-File

2009-03-24T09:36:37Z

Barbara: /* The *.WET Format for Climate Data */

= The *.WET Format for Climate Data =


You can use existing IBP weather files (file format *.WET) to perform WUFI calculations; you can also convert your own weather data to that format and use them.


IBP weather files contain 21 lines of header which explain the meaning of the different data columns and an arbitrary number of lines with hourly weather data. WUFI skips the header.


Example:


[[Bild:WETexample.gif]]


(for formatting reasons, the data lines cannot be reproduced here in their entirety. Please refer to the file IBP1991.WET you received with WUFI for a complete example).


The format of the numbers is free; the only requirement is that a PASCAL program (like WUFI) must be able to read them. 
The file need not conform to a specific column format (as in FORTRAN), the number of decimal places does not matter, floating point numbers need not be in exponential format etc.


The number type <TT>real</TT>/<TT>integer</TT> has to be adhered to, however. The individual numbers must be separated by blanks, not tabulators.


The fact that the floating point numbers in the example all start with a zero is irrelevant (they were created with a FORTRAN program which likes to write numbers this way).


The data in detail:


* Day, month, year, hour (<TT>integer</TT>):   The IBP files contain hourly mean values of the measured data. These time stamps indicate the point in time when each measuring interval of one hour was finished and the measured mean values recorded. I.e., the data line starting with 01 01 91 04 contains the mean values for the hour from 03:00 to 04:00 on January 1, 1991.   Since its data are real-life data, an IBP weather file may contain an intercalary day (February 29). WUFI however knows nothing about intercalary days (at least in the present version). These must be deleted from files you want to use for WUFI calculations.   The time count always refers to winter time (CET). There is no daylight saving time.  

* Exterior air temperature (<TT>real</TT>):   the temperature of the exterior ambient air in [°C]. It is used without change as the exterior air temperature in the WUFI calculation.   

* Temperature of black surface (<TT>real</TT>):
* Temperature of white surface (<TT>real</TT>):   Surface temperatures of west-facing test facade elements painted black ([[Details:ShortWave |as]] ~ 0.9) and white (as ~ 0.4), respectively. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Temperature of Ground Surface (<TT>real</TT>):
* Temperature 50 cm below Ground Surface (<TT>real</TT>):
* Temperature 1 m below Ground Surface (<TT>real</TT>):   Soil temperatures at various depths in [°C]. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Global radiation (<TT>real</TT>):   the sum of the direct and diffuse components of the solar radiation incident on a horizontal surface; in [W/m²].  

* Diffuse radiation (<TT>real</TT>):   the diffuse component of the solar radiation incident on a horizontal surface; in [W/m²].   Subtracting the diffuse radiation from the global radiation results in the direct radiation. From this, the direct normal radiation can be calculated, i.e., the amount of radiation incident on a surface that is orthogonal to the ray direction. This calculation requires knowledge of the time and geographical location of the measurement, since the corresponding position of the sun has to be determined [2].   The direct normal radiation can then be used to calculate the direct radiation incident on a surface with arbitrary orientation and inclination. Addition of the appropriate fraction of diffuse radiation results in the global radiation incident on the building component.   These calculations are automatically done by WUFI during a simulation run.   WUFI uses a [[FAQ:General | simplified radiation model]] which treats the diffuse radiation as isotropic and ignores the albedo of the ground. If you are more demanding or want to allow for local specifics (like shadows etc.), you can perform the conversion yourself and feed the results to WUFI via a [[Details:KLI-File | *.KLI file]].   

* Western radiation (<TT>real</TT>):   the global radiation measured with a west-facing solarimeter; in [W/m²]. [[2D:Dialog_ClimateFileDetails |Optionally]], the radiation component impinging on a (west-facing) facade may directly be read from this column. No conversion is then necessary as would be the case if global and diffuse radiation were used as data source.   

* Relative humidity (<TT>real</TT>):   the relative humidity of the ambient air (0..1). Used by WUFI without change as the exterior relative humidity.  

* Barometric pressure (<TT>real</TT>):   the ambient air pressure reduced to sea level; in [hPA].   

* Wind velocity (<TT>real</TT>):   the scalar mean of the wind velocity; in [m/s]. It is needed to compute the driving rain from the normal rain.   The scalar mean of the wind velocity is the mean value of the readings of an anemometer without the directions taken into account. For example, if for an hour the wind is blowing at 2 m/s but at the same time steadily travelling through all the direcions, then the scalar mean is 2 m/s, whereas the vectorial mean is 0 m/s.   In the vectorial mean, some vector components may cancel. Thus, the scalar mean is greater than (or at least equal to) the vectorial mean.   The IBP weather files also contain information about the distribution of the wind directions (see below). This allows to ignore components that come from 'behind' (and don't contribute to the rain load) and to weight the remaining directions according to the angle they make with the surface.   

* Normal rain / tipping bucket (<TT>real</TT>):
* Normal rain / droplet counter (<TT>real</TT>):   the normal rain (i.e., the rain incident on a horizontal surface in open area) during one hour, measured with a tipping bucket and a droplet counter rain gauge, respectively; in [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The rain load on a wall is determined by the driving rain rather than the normal rain. The driving rain can be estimated from the normal rain and the wind velocity:   The rain coefficients R1 and R2 in the [[2D:Dialog_EditSurfaceCoefficients | dialog "Edit Surface Coefficients.htm"]] serve to estimate the driving rain load on a surface of arbitrary orientation and inclination from data on normal rain, wind velocity and wind direction distributions, using the relation   <CENTER>rain load = rain · (R1 + R2 · wind velocity),</CENTER>
where 'rain' is the normal rain and 'wind velocity' is that component of the mean wind velocity (measured at a height of 10 m, in open area), which is orthogonal to the building surface. This component is determined from the scalar mean of the wind velocity (see above) and the wind direction distribution (see below). R1 and R2 are strongly dependent on the specific location on the building facade. If calculations are to be compared to actual measurements, these coefficients should be experimentally determined for that location. If they cannot be measured, only a very rough estimate is possible. For vertical surfaces, R1 is zero. R2 is about 0.2 s/m for free-standing locations without influence from surrounding buildings etc.; it is markedly less in the center of a facade (e.g. 0.07 s/m); it may even be greater at exposed locations of a building (near edges and corners)[1].  
* Driving rain / tipping bucket (<TT>real</TT>):
* Driving rain / droplet counter (<TT>real</TT>):   the driving rain load on a west-facing wall, measured at a height of 1.50 m with a tipping bucket and a droplet counter rain gauge, respectively. In [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The values in this column can [[2D:Dialog_ClimateFileDetails | optionally be read]] and used for the variable 'rain' in the formula for the rain load (see above: normal rain). Set R1 to 1 and R2 to zero; the resulting rain load will then directly be the measured driving rain.   
* Wind direction distribution (17 * <TT>integer</TT>):   the frequency of wind directions, binned into sectors of 22.5° each.   The wind direction is averaged over 2 minutes and the counter of the corresponding sector then increased by one. A special counter is registering calms. The sum of all counts during one hour should thus be 30 if no interruption of the measurements has occured.   The individual counters are assigned to the following directions:   
<CENTER>NNE-NE-ENE-E-ESE-SE-SSE-S-SSW-SW-WSW-W-WNW-NW-NNW-N-calm</CENTER>
For the calculation of the driving rain load, the contributions of the different directions are determined individually and then summed up. Wind coming 'from behind' does not contribute to the rain load and is ignored. 


A *.WET file supplied by the user must be accompanied by a [[Details:AGD-File | *.AGD file]] which contains geographical information on the climate location.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Künzel, H.M.: Bestimmung der Schlagregenbelastung von Fassadenflächen. IBP-Mitteilung 21 (1994), Nr. 263</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>VDI 3789 Umweltmeteorologie, Blatt 2: Wechselwirkungen zwischen Atmosphäre und Oberflächen; Berechnung der kurz- und der langwelligen Strahlung. Oktober 1994</TD></TR>
</TABLE>

Details:WET-File

2009-03-24T09:34:08Z

Barbara: /* The *.WET Format for Climate Data */

= The *.WET Format for Climate Data =


You can use existing IBP weather files (file format *.WET) to perform WUFI calculations; you can also convert your own weather data to that format and use them.


IBP weather files contain 21 lines of header which explain the meaning of the different data columns and an arbitrary number of lines with hourly weather data. WUFI skips the header.


Example:


[[Bild:WETexample.gif]]


(for formatting reasons, the data lines cannot be reproduced here in their entirety. Please refer to the file IBP1991.WET you received with WUFI for a complete example).


The format of the numbers is free; the only requirement is that a PASCAL program (like WUFI) must be able to read them. 
The file need not conform to a specific column format (as in FORTRAN), the number of decimal places does not matter, floating point numbers need not be in exponential format etc.


The number type <TT>real</TT>/<TT>integer</TT> has to be adhered to, however. The individual numbers must be separated by blanks, not tabulators.


The fact that the floating point numbers in the example all start with a zero is irrelevant (they were created with a FORTRAN program which likes to write numbers this way).


The data in detail:


* Day, month, year, hour (<TT>integer</TT>):   The IBP files contain hourly mean values of the measured data. These time stamps indicate the point in time when each measuring interval of one hour was finished and the measured mean values recorded. I.e., the data line starting with 01 01 91 04 contains the mean values for the hour from 03:00 to 04:00 on January 1, 1991.   Since its data are real-life data, an IBP weather file may contain an intercalary day (February 29). WUFI however knows nothing about intercalary days (at least in the present version). These must be deleted from files you want to use for WUFI calculations.   The time count always refers to winter time (CET). There is no daylight saving time.  

* Exterior air temperature (<TT>real</TT>):   the temperature of the exterior ambient air in [°C]. It is used without change as the exterior air temperature in the WUFI calculation.   

* Temperature of black surface (<TT>real</TT>):
* Temperature of white surface (<TT>real</TT>):   Surface temperatures of west-facing test facade elements painted black ([[Details:ShortWave |as]] ~ 0.9) and white (as ~ 0.4), respectively. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Temperature of Ground Surface (<TT>real</TT>):
* Temperature 50 cm below Ground Surface (<TT>real</TT>):
* Temperature 1 m below Ground Surface (<TT>real</TT>):   Soil temperatures at various depths in [°C]. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Global radiation (<TT>real</TT>):   the sum of the direct and diffuse components of the solar radiation incident on a horizontal surface; in [W/m²].  

* Diffuse radiation (<TT>real</TT>):   the diffuse component of the solar radiation incident on a horizontal surface; in [W/m²].   Subtracting the diffuse radiation from the global radiation results in the direct radiation. From this, the direct normal radiation can be calculated, i.e., the amount of radiation incident on a surface that is orthogonal to the ray direction. This calculation requires knowledge of the time and geographical location of the measurement, since the corresponding position of the sun has to be determined [2].   The direct normal radiation can then be used to calculate the direct radiation incident on a surface with arbitrary orientation and inclination. Addition of the appropriate fraction of diffuse radiation results in the global radiation incident on the building component.   These calculations are automatically done by WUFI during a simulation run.   WUFI uses a [[FAQ:General | simplified radiation model]] which treats the diffuse radiation as isotropic and ignores the albedo of the ground. If you are more demanding or want to allow for local specifics (like shadows etc.), you can perform the conversion yourself and feed the results to WUFI via a [[Details:KLI-File | *.KLI file]].   

* Western radiation (<TT>real</TT>):   the global radiation measured with a west-facing solarimeter; in [W/m²]. [[2D:Dialog_ClimateFileDetails |Optionally]], the radiation component impinging on a (west-facing) facade may directly be read from this column. No conversion is then necessary as would be the case if global and diffuse radiation were used as data source.   
* Relative humidity (<TT>real</TT>):   the relative humidity of the ambient air (0..1). Used by WUFI without change as the exterior relative humidity.  
* Barometric pressure (<TT>real</TT>):   the ambient air pressure reduced to sea level; in [hPA].   
* Wind velocity (<TT>real</TT>):   the scalar mean of the wind velocity; in [m/s]. It is needed to compute the driving rain from the normal rain.   The scalar mean of the wind velocity is the mean value of the readings of an anemometer without the directions taken into account. For example, if for an hour the wind is blowing at 2 m/s but at the same time steadily travelling through all the direcions, then the scalar mean is 2 m/s, whereas the vectorial mean is 0 m/s.   In the vectorial mean, some vector components may cancel. Thus, the scalar mean is greater than (or at least equal to) the vectorial mean.   The IBP weather files also contain information about the distribution of the wind directions (see below). This allows to ignore components that come from 'behind' (and don't contribute to the rain load) and to weight the remaining directions according to the angle they make with the surface.   
* Normal rain / tipping bucket (<TT>real</TT>):
* Normal rain / droplet counter (<TT>real</TT>):   the normal rain (i.e., the rain incident on a horizontal surface in open area) during one hour, measured with a tipping bucket and a droplet counter rain gauge, respectively; in [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The rain load on a wall is determined by the driving rain rather than the normal rain. The driving rain can be estimated from the normal rain and the wind velocity:   The rain coefficients R1 and R2 in the [[2D:Dialog_EditSurfaceCoefficients | dialog "Edit Surface Coefficients.htm"]] serve to estimate the driving rain load on a surface of arbitrary orientation and inclination from data on normal rain, wind velocity and wind direction distributions, using the relation   <CENTER>rain load = rain · (R1 + R2 · wind velocity),</CENTER>
where 'rain' is the normal rain and 'wind velocity' is that component of the mean wind velocity (measured at a height of 10 m, in open area), which is orthogonal to the building surface. This component is determined from the scalar mean of the wind velocity (see above) and the wind direction distribution (see below). R1 and R2 are strongly dependent on the specific location on the building facade. If calculations are to be compared to actual measurements, these coefficients should be experimentally determined for that location. If they cannot be measured, only a very rough estimate is possible. For vertical surfaces, R1 is zero. R2 is about 0.2 s/m for free-standing locations without influence from surrounding buildings etc.; it is markedly less in the center of a facade (e.g. 0.07 s/m); it may even be greater at exposed locations of a building (near edges and corners)[1].  
* Driving rain / tipping bucket (<TT>real</TT>):
* Driving rain / droplet counter (<TT>real</TT>):   the driving rain load on a west-facing wall, measured at a height of 1.50 m with a tipping bucket and a droplet counter rain gauge, respectively. In [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The values in this column can [[2D:Dialog_ClimateFileDetails | optionally be read]] and used for the variable 'rain' in the formula for the rain load (see above: normal rain). Set R1 to 1 and R2 to zero; the resulting rain load will then directly be the measured driving rain.   
* Wind direction distribution (17 * <TT>integer</TT>):   the frequency of wind directions, binned into sectors of 22.5° each.   The wind direction is averaged over 2 minutes and the counter of the corresponding sector then increased by one. A special counter is registering calms. The sum of all counts during one hour should thus be 30 if no interruption of the measurements has occured.   The individual counters are assigned to the following directions:   
<CENTER>NNE-NE-ENE-E-ESE-SE-SSE-S-SSW-SW-WSW-W-WNW-NW-NNW-N-calm</CENTER>
For the calculation of the driving rain load, the contributions of the different directions are determined individually and then summed up. Wind coming 'from behind' does not contribute to the rain load and is ignored. 


A *.WET file supplied by the user must be accompanied by a [[Details:AGD-File | *.AGD file]] which contains geographical information on the climate location.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Künzel, H.M.: Bestimmung der Schlagregenbelastung von Fassadenflächen. IBP-Mitteilung 21 (1994), Nr. 263</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>VDI 3789 Umweltmeteorologie, Blatt 2: Wechselwirkungen zwischen Atmosphäre und Oberflächen; Berechnung der kurz- und der langwelligen Strahlung. Oktober 1994</TD></TR>
</TABLE>

Details:WET-File

2009-03-24T09:31:33Z

Barbara: /* The *.WET Format for Climate Data */

= The *.WET Format for Climate Data =


You can use existing IBP weather files (file format *.WET) to perform WUFI calculations; you can also convert your own weather data to that format and use them.


IBP weather files contain 21 lines of header which explain the meaning of the different data columns and an arbitrary number of lines with hourly weather data. WUFI skips the header.


Example:


[[Bild:WETexample.gif]]


(for formatting reasons, the data lines cannot be reproduced here in their entirety. Please refer to the file IBP1991.WET you received with WUFI for a complete example).


The format of the numbers is free; the only requirement is that a PASCAL program (like WUFI) must be able to read them. 
The file need not conform to a specific column format (as in FORTRAN), the number of decimal places does not matter, floating point numbers need not be in exponential format etc.


The number type <TT>real</TT>/<TT>integer</TT> has to be adhered to, however. The individual numbers must be separated by blanks, not tabulators.


The fact that the floating point numbers in the example all start with a zero is irrelevant (they were created with a FORTRAN program which likes to write numbers this way).


The data in detail:


* Day, month, year, hour (<TT>integer</TT>):   The IBP files contain hourly mean values of the measured data. These time stamps indicate the point in time when each measuring interval of one hour was finished and the measured mean values recorded. I.e., the data line starting with 01 01 91 04 contains the mean values for the hour from 03:00 to 04:00 on January 1, 1991.   Since its data are real-life data, an IBP weather file may contain an intercalary day (February 29). WUFI however knows nothing about intercalary days (at least in the present version). These must be deleted from files you want to use for WUFI calculations.   The time count always refers to winter time (CET). There is no daylight saving time.  

* Exterior air temperature (<TT>real</TT>):   the temperature of the exterior ambient air in [°C]. It is used without change as the exterior air temperature in the WUFI calculation.   

* Temperature of black surface (<TT>real</TT>):
* Temperature of white surface (<TT>real</TT>):   Surface temperatures of west-facing test facade elements painted black ([[Details:ShortWave |as]] ~ 0.9) and white (as ~ 0.4), respectively. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Temperature of Ground Surface (<TT>real</TT>):
* Temperature 50 cm below Ground Surface (<TT>real</TT>):
* Temperature 1 m below Ground Surface (<TT>real</TT>):   Soil temperatures at various depths in [°C]. These may [[2D:Dialog_ClimateFileDetails |optionally]] be read instead of the exterior air temperature.  

* Global radiation (<TT>real</TT>):   the sum of the direct and diffuse components of the solar radiation incident on a horizontal surface; in [W/m²].  
* Diffuse radiation (<TT>real</TT>):   the diffuse component of the solar radiation incident on a horizontal surface; in [W/m²].   Subtracting the diffuse radiation from the global radiation results in the direct radiation. From this, the direct normal radiation can be calculated, i.e., the amount of radiation incident on a surface that is orthogonal to the ray direction. This calculation requires knowledge of the time and geographical location of the measurement, since the corresponding position of the sun has to be determined [2].   The direct normal radiation can then be used to calculate the direct radiation incident on a surface with arbitrary orientation and inclination. Addition of the appropriate fraction of diffuse radiation results in the global radiation incident on the building component.   These calculations are automatically done by WUFI during a simulation run.   WUFI uses a [[FAQ:General | simplified radiation model]] which treats the diffuse radiation as isotropic and ignores the albedo of the ground. If you are more demanding or want to allow for local specifics (like shadows etc.), you can perform the conversion yourself and feed the results to WUFI via a [[Details:KLI-File | *.KLI file]].   
* Western radiation (<TT>real</TT>):   the global radiation measured with a west-facing solarimeter; in [W/m²]. Optionally, the radiation component impinging on a (west-facing) facade may [[2D:Dialog_ClimateFileDetails | directly be read from this column]]. No conversion is then necessary as would be the case if global and diffuse radiation were used as data source.   
* Relative humidity (<TT>real</TT>):   the relative humidity of the ambient air (0..1). Used by WUFI without change as the exterior relative humidity.  
* Barometric pressure (<TT>real</TT>):   the ambient air pressure reduced to sea level; in [hPA].   
* Wind velocity (<TT>real</TT>):   the scalar mean of the wind velocity; in [m/s]. It is needed to compute the driving rain from the normal rain.   The scalar mean of the wind velocity is the mean value of the readings of an anemometer without the directions taken into account. For example, if for an hour the wind is blowing at 2 m/s but at the same time steadily travelling through all the direcions, then the scalar mean is 2 m/s, whereas the vectorial mean is 0 m/s.   In the vectorial mean, some vector components may cancel. Thus, the scalar mean is greater than (or at least equal to) the vectorial mean.   The IBP weather files also contain information about the distribution of the wind directions (see below). This allows to ignore components that come from 'behind' (and don't contribute to the rain load) and to weight the remaining directions according to the angle they make with the surface.   
* Normal rain / tipping bucket (<TT>real</TT>):
* Normal rain / droplet counter (<TT>real</TT>):   the normal rain (i.e., the rain incident on a horizontal surface in open area) during one hour, measured with a tipping bucket and a droplet counter rain gauge, respectively; in [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The rain load on a wall is determined by the driving rain rather than the normal rain. The driving rain can be estimated from the normal rain and the wind velocity:   The rain coefficients R1 and R2 in the [[2D:Dialog_EditSurfaceCoefficients | dialog "Edit Surface Coefficients.htm"]] serve to estimate the driving rain load on a surface of arbitrary orientation and inclination from data on normal rain, wind velocity and wind direction distributions, using the relation   <CENTER>rain load = rain · (R1 + R2 · wind velocity),</CENTER>
where 'rain' is the normal rain and 'wind velocity' is that component of the mean wind velocity (measured at a height of 10 m, in open area), which is orthogonal to the building surface. This component is determined from the scalar mean of the wind velocity (see above) and the wind direction distribution (see below). R1 and R2 are strongly dependent on the specific location on the building facade. If calculations are to be compared to actual measurements, these coefficients should be experimentally determined for that location. If they cannot be measured, only a very rough estimate is possible. For vertical surfaces, R1 is zero. R2 is about 0.2 s/m for free-standing locations without influence from surrounding buildings etc.; it is markedly less in the center of a facade (e.g. 0.07 s/m); it may even be greater at exposed locations of a building (near edges and corners)[1].  
* Driving rain / tipping bucket (<TT>real</TT>):
* Driving rain / droplet counter (<TT>real</TT>):   the driving rain load on a west-facing wall, measured at a height of 1.50 m with a tipping bucket and a droplet counter rain gauge, respectively. In [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The values in this column can [[2D:Dialog_ClimateFileDetails | optionally be read]] and used for the variable 'rain' in the formula for the rain load (see above: normal rain). Set R1 to 1 and R2 to zero; the resulting rain load will then directly be the measured driving rain.   
* Wind direction distribution (17 * <TT>integer</TT>):   the frequency of wind directions, binned into sectors of 22.5° each.   The wind direction is averaged over 2 minutes and the counter of the corresponding sector then increased by one. A special counter is registering calms. The sum of all counts during one hour should thus be 30 if no interruption of the measurements has occured.   The individual counters are assigned to the following directions:   
<CENTER>NNE-NE-ENE-E-ESE-SE-SSE-S-SSW-SW-WSW-W-WNW-NW-NNW-N-calm</CENTER>
For the calculation of the driving rain load, the contributions of the different directions are determined individually and then summed up. Wind coming 'from behind' does not contribute to the rain load and is ignored. 


A *.WET file supplied by the user must be accompanied by a [[Details:AGD-File | *.AGD file]] which contains geographical information on the climate location.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Künzel, H.M.: Bestimmung der Schlagregenbelastung von Fassadenflächen. IBP-Mitteilung 21 (1994), Nr. 263</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>VDI 3789 Umweltmeteorologie, Blatt 2: Wechselwirkungen zwischen Atmosphäre und Oberflächen; Berechnung der kurz- und der langwelligen Strahlung. Oktober 1994</TD></TR>
</TABLE>

Details:WET-File

2009-03-24T09:27:12Z

Barbara: /* The *.WET Format for Climate Data */

= The *.WET Format for Climate Data =


You can use existing IBP weather files (file format *.WET) to perform WUFI calculations; you can also convert your own weather data to that format and use them.


IBP weather files contain 21 lines of header which explain the meaning of the different data columns and an arbitrary number of lines with hourly weather data. WUFI skips the header.


Example:


[[Bild:WETexample.gif]]


(for formatting reasons, the data lines cannot be reproduced here in their entirety. Please refer to the file IBP1991.WET you received with WUFI for a complete example).


The format of the numbers is free; the only requirement is that a PASCAL program (like WUFI) must be able to read them. 
The file need not conform to a specific column format (as in FORTRAN), the number of decimal places does not matter, floating point numbers need not be in exponential format etc.


The number type <TT>real</TT>/<TT>integer</TT> has to be adhered to, however. The individual numbers must be separated by blanks, not tabulators.


The fact that the floating point numbers in the example all start with a zero is irrelevant (they were created with a FORTRAN program which likes to write numbers this way).


The data in detail:


* Day, month, year, hour (<TT>integer</TT>):   The IBP files contain hourly mean values of the measured data. These time stamps indicate the point in time when each measuring interval of one hour was finished and the measured mean values recorded. I.e., the data line starting with 01 01 91 04 contains the mean values for the hour from 03:00 to 04:00 on January 1, 1991.   Since its data are real-life data, an IBP weather file may contain an intercalary day (February 29). WUFI however knows nothing about intercalary days (at least in the present version). These must be deleted from files you want to use for WUFI calculations.   The time count always refers to winter time (CET). There is no daylight saving time.  

* Exterior air temperature (<TT>real</TT>):   the temperature of the exterior ambient air in [°C]. It is used without change as the exterior air temperature in the WUFI calculation.   

* Temperature of black surface (<TT>real</TT>):
* Temperature of white surface (<TT>real</TT>):   Surface temperatures of west-facing test facade elements painted black ([[Details:ShortWave |as]] ~ 0.9) and white (as ~ 0.4), respectively. These may optionally be read [[2D:Dialog_ClimateFileDetails | instead of the exterior air temperature]].  

* Temperature of Ground Surface (<TT>real</TT>):
* Temperature 50 cm below Ground Surface (<TT>real</TT>):
* Temperature 1 m below Ground Surface (<TT>real</TT>):   Soil temperatures at various depths in [°C]. These may optionally be read [[2D:Dialog_ClimateFileDetails | instead of the exterior air temperature]].  
* Global radiation (<TT>real</TT>):   the sum of the direct and diffuse components of the solar radiation incident on a horizontal surface; in [W/m²].  
* Diffuse radiation (<TT>real</TT>):   the diffuse component of the solar radiation incident on a horizontal surface; in [W/m²].   Subtracting the diffuse radiation from the global radiation results in the direct radiation. From this, the direct normal radiation can be calculated, i.e., the amount of radiation incident on a surface that is orthogonal to the ray direction. This calculation requires knowledge of the time and geographical location of the measurement, since the corresponding position of the sun has to be determined [2].   The direct normal radiation can then be used to calculate the direct radiation incident on a surface with arbitrary orientation and inclination. Addition of the appropriate fraction of diffuse radiation results in the global radiation incident on the building component.   These calculations are automatically done by WUFI during a simulation run.   WUFI uses a [[FAQ:General | simplified radiation model]] which treats the diffuse radiation as isotropic and ignores the albedo of the ground. If you are more demanding or want to allow for local specifics (like shadows etc.), you can perform the conversion yourself and feed the results to WUFI via a [[Details:KLI-File | *.KLI file]].   
* Western radiation (<TT>real</TT>):   the global radiation measured with a west-facing solarimeter; in [W/m²]. Optionally, the radiation component impinging on a (west-facing) facade may [[2D:Dialog_ClimateFileDetails | directly be read from this column]]. No conversion is then necessary as would be the case if global and diffuse radiation were used as data source.   
* Relative humidity (<TT>real</TT>):   the relative humidity of the ambient air (0..1). Used by WUFI without change as the exterior relative humidity.  
* Barometric pressure (<TT>real</TT>):   the ambient air pressure reduced to sea level; in [hPA].   
* Wind velocity (<TT>real</TT>):   the scalar mean of the wind velocity; in [m/s]. It is needed to compute the driving rain from the normal rain.   The scalar mean of the wind velocity is the mean value of the readings of an anemometer without the directions taken into account. For example, if for an hour the wind is blowing at 2 m/s but at the same time steadily travelling through all the direcions, then the scalar mean is 2 m/s, whereas the vectorial mean is 0 m/s.   In the vectorial mean, some vector components may cancel. Thus, the scalar mean is greater than (or at least equal to) the vectorial mean.   The IBP weather files also contain information about the distribution of the wind directions (see below). This allows to ignore components that come from 'behind' (and don't contribute to the rain load) and to weight the remaining directions according to the angle they make with the surface.   
* Normal rain / tipping bucket (<TT>real</TT>):
* Normal rain / droplet counter (<TT>real</TT>):   the normal rain (i.e., the rain incident on a horizontal surface in open area) during one hour, measured with a tipping bucket and a droplet counter rain gauge, respectively; in [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The rain load on a wall is determined by the driving rain rather than the normal rain. The driving rain can be estimated from the normal rain and the wind velocity:   The rain coefficients R1 and R2 in the [[2D:Dialog_EditSurfaceCoefficients | dialog "Edit Surface Coefficients.htm"]] serve to estimate the driving rain load on a surface of arbitrary orientation and inclination from data on normal rain, wind velocity and wind direction distributions, using the relation   <CENTER>rain load = rain · (R1 + R2 · wind velocity),</CENTER>
where 'rain' is the normal rain and 'wind velocity' is that component of the mean wind velocity (measured at a height of 10 m, in open area), which is orthogonal to the building surface. This component is determined from the scalar mean of the wind velocity (see above) and the wind direction distribution (see below). R1 and R2 are strongly dependent on the specific location on the building facade. If calculations are to be compared to actual measurements, these coefficients should be experimentally determined for that location. If they cannot be measured, only a very rough estimate is possible. For vertical surfaces, R1 is zero. R2 is about 0.2 s/m for free-standing locations without influence from surrounding buildings etc.; it is markedly less in the center of a facade (e.g. 0.07 s/m); it may even be greater at exposed locations of a building (near edges and corners)[1].  
* Driving rain / tipping bucket (<TT>real</TT>):
* Driving rain / droplet counter (<TT>real</TT>):   the driving rain load on a west-facing wall, measured at a height of 1.50 m with a tipping bucket and a droplet counter rain gauge, respectively. In [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The values in this column can [[2D:Dialog_ClimateFileDetails | optionally be read]] and used for the variable 'rain' in the formula for the rain load (see above: normal rain). Set R1 to 1 and R2 to zero; the resulting rain load will then directly be the measured driving rain.   
* Wind direction distribution (17 * <TT>integer</TT>):   the frequency of wind directions, binned into sectors of 22.5° each.   The wind direction is averaged over 2 minutes and the counter of the corresponding sector then increased by one. A special counter is registering calms. The sum of all counts during one hour should thus be 30 if no interruption of the measurements has occured.   The individual counters are assigned to the following directions:   
<CENTER>NNE-NE-ENE-E-ESE-SE-SSE-S-SSW-SW-WSW-W-WNW-NW-NNW-N-calm</CENTER>
For the calculation of the driving rain load, the contributions of the different directions are determined individually and then summed up. Wind coming 'from behind' does not contribute to the rain load and is ignored. 


A *.WET file supplied by the user must be accompanied by a [[Details:AGD-File | *.AGD file]] which contains geographical information on the climate location.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Künzel, H.M.: Bestimmung der Schlagregenbelastung von Fassadenflächen. IBP-Mitteilung 21 (1994), Nr. 263</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>VDI 3789 Umweltmeteorologie, Blatt 2: Wechselwirkungen zwischen Atmosphäre und Oberflächen; Berechnung der kurz- und der langwelligen Strahlung. Oktober 1994</TD></TR>
</TABLE>

Details:WET-File

2009-03-24T09:25:36Z

Barbara: /* The *.WET Format for Climate Data */

= The *.WET Format for Climate Data =


You can use existing IBP weather files (file format *.WET) to perform WUFI calculations; you can also convert your own weather data to that format and use them.


IBP weather files contain 21 lines of header which explain the meaning of the different data columns and an arbitrary number of lines with hourly weather data. WUFI skips the header.


Example:


[[Bild:WETexample.gif]]


(for formatting reasons, the data lines cannot be reproduced here in their entirety. Please refer to the file IBP1991.WET you received with WUFI for a complete example).


The format of the numbers is free; the only requirement is that a PASCAL program (like WUFI) must be able to read them. 
The file need not conform to a specific column format (as in FORTRAN), the number of decimal places does not matter, floating point numbers need not be in exponential format etc.


The number type <TT>real</TT>/<TT>integer</TT> has to be adhered to, however. The individual numbers must be separated by blanks, not tabulators.


The fact that the floating point numbers in the example all start with a zero is irrelevant (they were created with a FORTRAN program which likes to write numbers this way).


The data in detail:


* Day, month, year, hour (<TT>integer</TT>):   The IBP files contain hourly mean values of the measured data. These time stamps indicate the point in time when each measuring interval of one hour was finished and the measured mean values recorded. I.e., the data line starting with 01 01 91 04 contains the mean values for the hour from 03:00 to 04:00 on January 1, 1991.   Since its data are real-life data, an IBP weather file may contain an intercalary day (February 29). WUFI however knows nothing about intercalary days (at least in the present version). These must be deleted from files you want to use for WUFI calculations.   The time count always refers to winter time (CET). There is no daylight saving time.  

* Exterior air temperature (<TT>real</TT>):   the temperature of the exterior ambient air in [°C]. It is used without change as the exterior air temperature in the WUFI calculation.   

* Temperature of black surface (<TT>real</TT>):
* Temperature of white surface (<TT>real</TT>):   Surface temperatures of west-facing test facade elements painted black ([[Details:ShortWave | >as]] ~ 0.9) and white (as ~ 0.4), respectively. These may optionally be read [[2D:Dialog_ClimateFileDetails | instead of the exterior air temperature]].  

* Temperature of Ground Surface (<TT>real</TT>):
* Temperature 50 cm below Ground Surface (<TT>real</TT>):
* Temperature 1 m below Ground Surface (<TT>real</TT>):   Soil temperatures at various depths in [°C]. These may optionally be read [[2D:Dialog_ClimateFileDetails | instead of the exterior air temperature]].  
* Global radiation (<TT>real</TT>):   the sum of the direct and diffuse components of the solar radiation incident on a horizontal surface; in [W/m²].  
* Diffuse radiation (<TT>real</TT>):   the diffuse component of the solar radiation incident on a horizontal surface; in [W/m²].   Subtracting the diffuse radiation from the global radiation results in the direct radiation. From this, the direct normal radiation can be calculated, i.e., the amount of radiation incident on a surface that is orthogonal to the ray direction. This calculation requires knowledge of the time and geographical location of the measurement, since the corresponding position of the sun has to be determined [2].   The direct normal radiation can then be used to calculate the direct radiation incident on a surface with arbitrary orientation and inclination. Addition of the appropriate fraction of diffuse radiation results in the global radiation incident on the building component.   These calculations are automatically done by WUFI during a simulation run.   WUFI uses a [[FAQ:General | simplified radiation model]] which treats the diffuse radiation as isotropic and ignores the albedo of the ground. If you are more demanding or want to allow for local specifics (like shadows etc.), you can perform the conversion yourself and feed the results to WUFI via a [[Details:KLI-File | *.KLI file]].   
* Western radiation (<TT>real</TT>):   the global radiation measured with a west-facing solarimeter; in [W/m²]. Optionally, the radiation component impinging on a (west-facing) facade may [[2D:Dialog_ClimateFileDetails | directly be read from this column]]. No conversion is then necessary as would be the case if global and diffuse radiation were used as data source.   
* Relative humidity (<TT>real</TT>):   the relative humidity of the ambient air (0..1). Used by WUFI without change as the exterior relative humidity.  
* Barometric pressure (<TT>real</TT>):   the ambient air pressure reduced to sea level; in [hPA].   
* Wind velocity (<TT>real</TT>):   the scalar mean of the wind velocity; in [m/s]. It is needed to compute the driving rain from the normal rain.   The scalar mean of the wind velocity is the mean value of the readings of an anemometer without the directions taken into account. For example, if for an hour the wind is blowing at 2 m/s but at the same time steadily travelling through all the direcions, then the scalar mean is 2 m/s, whereas the vectorial mean is 0 m/s.   In the vectorial mean, some vector components may cancel. Thus, the scalar mean is greater than (or at least equal to) the vectorial mean.   The IBP weather files also contain information about the distribution of the wind directions (see below). This allows to ignore components that come from 'behind' (and don't contribute to the rain load) and to weight the remaining directions according to the angle they make with the surface.   
* Normal rain / tipping bucket (<TT>real</TT>):
* Normal rain / droplet counter (<TT>real</TT>):   the normal rain (i.e., the rain incident on a horizontal surface in open area) during one hour, measured with a tipping bucket and a droplet counter rain gauge, respectively; in [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The rain load on a wall is determined by the driving rain rather than the normal rain. The driving rain can be estimated from the normal rain and the wind velocity:   The rain coefficients R1 and R2 in the [[2D:Dialog_EditSurfaceCoefficients | dialog "Edit Surface Coefficients.htm"]] serve to estimate the driving rain load on a surface of arbitrary orientation and inclination from data on normal rain, wind velocity and wind direction distributions, using the relation   <CENTER>rain load = rain · (R1 + R2 · wind velocity),</CENTER>
where 'rain' is the normal rain and 'wind velocity' is that component of the mean wind velocity (measured at a height of 10 m, in open area), which is orthogonal to the building surface. This component is determined from the scalar mean of the wind velocity (see above) and the wind direction distribution (see below). R1 and R2 are strongly dependent on the specific location on the building facade. If calculations are to be compared to actual measurements, these coefficients should be experimentally determined for that location. If they cannot be measured, only a very rough estimate is possible. For vertical surfaces, R1 is zero. R2 is about 0.2 s/m for free-standing locations without influence from surrounding buildings etc.; it is markedly less in the center of a facade (e.g. 0.07 s/m); it may even be greater at exposed locations of a building (near edges and corners)[1].  
* Driving rain / tipping bucket (<TT>real</TT>):
* Driving rain / droplet counter (<TT>real</TT>):   the driving rain load on a west-facing wall, measured at a height of 1.50 m with a tipping bucket and a droplet counter rain gauge, respectively. In [Ltr/m²h] or, equivalently, [mm/h].   WUFI uses the readings of the droplet counter, since it is in general more reliable.   The values in this column can [[2D:Dialog_ClimateFileDetails | optionally be read]] and used for the variable 'rain' in the formula for the rain load (see above: normal rain). Set R1 to 1 and R2 to zero; the resulting rain load will then directly be the measured driving rain.   
* Wind direction distribution (17 * <TT>integer</TT>):   the frequency of wind directions, binned into sectors of 22.5° each.   The wind direction is averaged over 2 minutes and the counter of the corresponding sector then increased by one. A special counter is registering calms. The sum of all counts during one hour should thus be 30 if no interruption of the measurements has occured.   The individual counters are assigned to the following directions:   
<CENTER>NNE-NE-ENE-E-ESE-SE-SSE-S-SSW-SW-WSW-W-WNW-NW-NNW-N-calm</CENTER>
For the calculation of the driving rain load, the contributions of the different directions are determined individually and then summed up. Wind coming 'from behind' does not contribute to the rain load and is ignored. 


A *.WET file supplied by the user must be accompanied by a [[Details:AGD-File | *.AGD file]] which contains geographical information on the climate location.



Literature:

<TABLE>
<TR><TD VALIGN="TOP">[1]</TD><TD>Künzel, H.M.: Bestimmung der Schlagregenbelastung von Fassadenflächen. IBP-Mitteilung 21 (1994), Nr. 263</TD></TR>

<TR><TD VALIGN="TOP">[2]</TD><TD>VDI 3789 Umweltmeteorologie, Blatt 2: Wechselwirkungen zwischen Atmosphäre und Oberflächen; Berechnung der kurz- und der langwelligen Strahlung. Oktober 1994</TD></TR>
</TABLE>

Details:Climate

2009-03-24T09:20:23Z

Barbara: /* Climate Data */

= Climate Data =


Starting from specified initial conditions, WUFI computes the temporal evolution of the temperature and moisture distributions in the building component. This evolution is determined not only by the underlying transport equations which govern the processes in the component, but also by the heat and moisture exchange with its surroundings. Thus there are heat and moisture flows through the surfaces, the direction and magnitude of which depend on the conditions in the component as well as on the conditions in the surroundings. The latter are described by the boundary conditions.


Since WUFI has been developed specifically for application in building physics, the surrounding medium is the ambient air (outdoor air, indoor air). Since it is furthermore designed to calculate the behaviour of building components exposed to the weather, it seems natural to describe the condition of the surrounding air in terms of meteorological parameters like temperature, relative humidity, solar radiation etc. In this way, WUFI keeps in close touch with building practice and can use existing measured data.


The choice of expressing the boundary conditions in terms of meteorological parameters does not prevent you from applying WUFI to laboratory investigations like imbibition or drying experiments, since the laboratory conditions can be expressed in meteorological terms as well.


WUFI needs the following climate data for each time step:

* the rain load vertically incident on the exterior surface in [Ltr/m²h]. For the determination of this rain load, the inclination and orientation of the surface must be taken into account.

* the solar radiation vertically incident on the exterior surface in [W/m²]. For the determination of the amount of radiation, the inclination and orientation of the surface must be taken into account.

* the temperature of the ambient air in [°C]

* the relative humidity of the ambient air (0..1)

* the barometric pressure in [hPa]. Since the barometric pressure has only a minor effect on the calculation, specification of a mean value over the calculation period can be sufficient.

* the long-wave atmospheric counterradiation [W/m²], if radiation cooling is to be accounted for during the night. Counterradiation data are only rarely available, however


The weather file may contain measured weather data (such as IBP weather data), or synthetic but realistic weather data (such as the Test Reference Years), or completely artificial data (which describe, for example, a laboratory experiment).


Since WUFI's main application is the investigation of the hygrothermal behavior of building components exposed to natural weather, it is set up to read files that contain measured weather
data. However, measured data can not always be used directly:


As mentioned above, WUFI needs the rain load and the radiation load incident on the wall or roof surface under investigation. Since rain and radiation are directed quantities, these loads depend on the orientation and the inclination of the individual building component. Unfortunately, in conventional weather measurements they are usually only recorded for horizontal surfaces. 
It is possible, however, to compute them from conventional weather data. The rain load can be determined from the normal rain and the wind velocity and direction. The amount of radiation can be determined from the global (or direct) and diffuse radiation incident on a horizontal surface. WUFI performs these conversions automatically and the user only needs to supply the conventionally measured weather data. In the current WUFI version, this requires a file in [[Details:WET-File | *.WET]] or [[Details:TRY-File | *.TRY]] or [[Details:DAT-File | *.DAT]] or [[Details:IWC-File | *.IWC]] or
[[Details:WAC-File | *.WAC]] or [[Details:WBC-File | *.WBC]] format. Depending on the format, files provided by the user (as opposed to the files supplied with WUFI or files pre-registered in the database) may also require a supporting [[Details:AGD-File | *.AGD file]] which supplies geographical data on the climate location.


On the other hand, WUFI can also read files which directly contain the required rain and radiation loads as determined for the specific surface in question, so that no further conversion is necessary.
This may be convenient if

* you want to convert the weather data with more sophisticated algorithms than WUFI does, or if

* you want to employ data that have been directly measured at the surface in question and thus need not be converted, or if

* you want to use data synthesized by your own climate simulator, or if

* you want to use data which describe the conditions of a laboratory experiment,

* etc.


These files must be in [[Details:KLI-File | *.KLI]] format.


The following sections explain these file formats in detail:


[[Details:WET-File | The *.WET Format for Climate Data]] 
  
[[Details:TRY-File | The *.TRY Format for Climate Data]] 
  
[[Details:DAT-File | The *.DAT Format for Climate Data]] 
  
[[Details:IWC-File | The *.IWC Format for Climate Data]] 
  
[[Details:WAC-File | The *.WAC Format for Climate Data]] 
  
[[Details:WBC-File | The *.WBC Format for Climate Data]] 
  
[[Details:KLI-File | The *.KLI Format for Climate Data]] 
  
[[Details:AGD-File | The *.AGD File]] 

 

The method used by WUFI to convert radiation data is described in the [[FAQ:MainQandA | Frequently Asked Questions]] section.

  

=== Sources for Climate Data ===

Several climate files are [[1D:Dialog_SelectClimateFileFromMap | supplied with
WUFI]]. The following are some sources offering weather data for additional locations.
WUFI can read the respective file formats; the user must judge to which degree these
data are useful and appropriate for his specific application.

Additional information of different sources for climate date are discribed [[Details:SourcesforclimateData | here]].