THERM 7: Knowledge Base 

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Last update:  03/11/15 11:04 AM

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Minimum computer requirements:

bullet Pentium class or better.
bullet At least 64 MB of random access memory (RAM). For optimal operation, 128 MB or more of RAM is preferrable.
bullet Microsoft Windows 98TM, Windows 2000TM, Windows METM,  Windows NTTM.or Windows XPTM
(The program WILL NOT run with Windows 3.1TM,  Windows NT 3.51TM or Windows 95TM). 
bullet Hard disk drive with at least 40 MB of available disk space
bullet Printer supported by Microsoft Windows (serial, parallel, or shared over a network).

Installation Problems 
In order to install the program with the Microsoft NT (4.0), 2000, and XP, you must be Administrator or part of the Administrators Group on your machine. To check if you are Administrator, do the following:

bullet Go to Control Panel, then "Users and Password" in Microsoft 2000, or "User Accounts" in Microsoft XP
bullet Find the current username (yours) and look in the group column. It should say: Administrators
bullet If the current username does NOT say Administrators, contact your IT department to become Administrator, or to have someone with Administrator privileges install the program on the machine.

UNC Paths Not Supported
THERM does not support UNC (Uniform Naming Convention) paths. An example of such a path is:

If you open a file with such a path, the program will crash when you try to import a glazing system.
Look in the INI file for the program in question (such as THERM 7.2.ini). These INI files are found in 
If there is a UNC path in that INI file, change it to the default program path, such as 
You can solve this problem by mapping a normal drive letter to the path that has the UNC path.


Material Library -- General Building Materials
LBNL has made a Material Library that has more general building materials, which can be used when modeling cross-sections other than fenestration systems. Click here to download a zip file which contains this library (Material-Arch), which is called Unzip the Material-Arch.lib file from the zip file, put it in the THERM 'lib" directory (where this is depends on your operating system, see Window7 / Vista Issues), and then in THERM, from the Material Library (accessed from Libraries / Material Library) click the Load Lib button to load it into the program and use it.

For the Microsoft Windows 7 operating system

Boundary Condition Library -- Walls, Floors, Ceilings
LBNL has made a Boundary Condition Library with entries for horizontal and vertical interior and exterior surfaces, such as walls, floors and ceilings, that can be used for modeling cross-sections other than fenestration systems. The Boundary Conditions are based on the ASHRAE 2009 Handbook of Fundamentals, Chapter 26, Table 1. Surface Conductances and Resistances for Air. Download the zip file called, and unzip it into the THERM "lib" directory (where this is depends on your operating system, see  Window7 / Vista Issues), and then in THERM, from the Boundary Condition Library (accessed from Libraries/Boundary Conditions" click on the Load Lib button to load it into the program and use it.

Detailed Radiation Model for Frame Cavities Disabled
The Detailed Radiation Model choice for frame cavities has been disabled because the calculation was being done incorrectly. This feature will be added back to the program at some point in the future.

In addition, a Detailed Radiation Model for frame cavities is not defined in the CEN procedures, so even when we add detailed radiation back to frame cavities, it will only apply to the ISO15099 frame cavity model.


Isotherm Display Control

You can control how the isotherms are displayed, including displaying a single isotherm, as follows:

Go to the Calculation menu/Display Options choice.

Click the Advanced button, and go to the Isotherm Settings. You can adjust the Minimum, Maximum and Interval settings to change the isotherm display.


Array Overflow in Mesher:
When the Quad Tree Mesh Parameter (set in Options/Preferences/Therm File Options) is set too high (usually greater than 9), THERM will display the following message:

To fix this problem, set the Quad Tree Mesh Parameter to a lower number in Options/Preferences/Therm File Options. You may have to simplify your geometry in order for the model to mesh.

Boundary Condition U-factor Tags:
Always check the interior boundary condition U-factor tags to make sure that they are set correctly. THERM will assign them correctly in most cases, but there are some situations where they will not be generated correctly automatically. The two circumstances where this can happen are:

bullet When selecting all the boundary conditions on the interior of the model, and assigning them to the same boundary condition, the program will assign the U-factor tags to "None" for all these boundary conditions.
bullet If there is no "Frame" segment on the glazing system, the program may not assign the U-factor tags correctly. Frame will get assigned to the Edge area, and Edge will get assigned to the None area.

Boundary Conditions Error Message -- Inconsistent boundary condition data:
THERM will give an error message if triangular Frame Cavities are defined:

The solution is to add at least one more point in the frame cavity and move it to make a 4th surface in the frame cavity

Boundary Conditions from older WINDOW5 glazing systems:
If you open a file that has a glazing system in it with "old-style" combined boundary conditions, and you delete the glazing system, and reimport a new WINDOW7 glazing system with the same name (that has the new boundary condition settings in the glazing system import screen), THERM will not use the new ones, but instead will use the old ones. The solution is to delete the glazing system, delete the boundary conditions, save and close the file, reopen the file, then import the glazing system.

Check Gravity Vector on Condensation Resistance Files Before Simulating:  
Use the View/Gravity Arrow feature to make sure that the gravity vector is pointing in the correct direction in files that are to be used to calculate the Condensation Resistance values. The gravity vectors should be the following:

Cross Section Type
File/Preferences Setting
File orientation Gravity Vector Orientation
Sill glazing system pointing up pointing down
Head glazing system pointing down pointing down
Head glazing system pointing up pointing up
Jamb glazing system pointing up pointing into the screen, ie, you will see what looks like an X
Meeting Rail (vertical)
such as for a horizontal slider
glazing systems pointing up and down pointing into the screen, ie, you will see what looks like an X
Meeting Rail (horizontal)
such as for a vertical slider
glazing systems pointing up and down pointing down
Divider (vertical) glazing systems pointing up and down pointing into the screen, ie, you will see what looks like an X
Divider (horizontal) glazing systems pointing up and down pointing down

An indication that something may be wrong in the Condensation Resistance (CR) calculation is if the gravity vector is not set according to the table above. Also check the temperatures and "sides" of the CR boundary conditions inside the glazing system cavity (by double clicking on them) to make sure that "Left" is really the left side of the cavity and "Right" is the right side of the cavity, and that the temperature settings make sense. If either or both the sides or the temperatures are wrong, delete the glazing system, check to make sure the File/Properties Cross Section Type is set correctly, realign the gravity vector, and reimport the glazing system.

Combined  Condensation Resistance and U-factor Calculations: 
Before simulating a file that has the Condensation Model activated (ie, there are red boundary conditions inside the glazing system), go to the Options menu, Preferences menu choice, THERM File Options tab and make sure the checkbox labeled "Use CI Model for Glazing Systems" is checked. In some instances, even though the glazing system was imported with the Condensation Resistance model turned on, and there are red boundary conditions in the glazing system cavity, the "Use CI Model for Glazing Systems" box will NOT be checked in the Options/Preferences/THERM File Options tab. This will be fixed in future versions so that this step is not necessary.

Condensation Resistance Calculation Error Message in WINDOW
If you get the following message in the WINDOW Window Library when doing a calculation, you need to recalculate the file in THERM, setting the Preferences as listed below:

In order for WINDOW to calculate the Condensation Resistance in the Window Library, you must have the following Preference set in THERM:

Crash due to "." in filename: 
We advise not using the period "." in filenames, as it can cause the program to crash in some circumstances (it can cause glazing system boundary conditions to be undefined, which will lead to the program crashing upon simulation).

Importing THERM file into WINDOW generates "unnamed file has a bad format" error message: 
If importing a file into WINDOW generates the error message:

"Unnamed file has a bad format"

this means that there is a problem with the THERM file, in that the file results are spanning a buffer when being read. One work around to try is to add comments to one of the input fields in the File/Properties menu -- it shouldn't take more than 15 characters.

Mesh Error -- Mesh appears to have gaps: 

After a simulation, if the program displays the Warning message below that "the mesh appears to have gaps", it means that one or more polygons have not been meshed properly. It is necessary to find the polygon that has not meshed (turn on the mesh display from the Calculation/Display Options menu, and select "Finite Element Mesh"). You should see one or more polygons that do not have a mesh drawn in them.


Delete the unmeshed polygons and redraw them, changing the position (even very slightly) of one point. Regenerate the boundary conditions and resimulate the problem. Changing the position of a point should solve the problem.

Migrating Files from THERM 5 or 6 to 7

Reassign Exterior BCs before simulating
THERM will automatically regenerate the BCs (based on option 2, the way that they are defined) the first time a THERM 5/6 file is simulated in THERM 7.
Re-simulate all files migrated from THERM 5/6 to THERM 7

Print and Print Preview Does Not Show A Model

There are some circumstances where the Print or Print Preview options do not produce a picture of the THERM model. Instead you just get a blank page with a header on it.

The most likely cause for this problem is that the model is very small relative to the size of the drawing, and so it is just an invisible speck on the paper.

One way to fix this problem is to select the entire model (Edit/Select All), then copy (Edit/Copy) this model and paste it into a new model (File/New, then Edit/Paste). Then do a Print Preview (File/Print Preview) and see if the model appears.

You can see that the "drawing size" is most likely the problem -- in one example, where the model did not appear in Print Preview, the drawing size (Options/Preferences/Drawing Options) was 14884 mm hight x 18678 mm wide, while the actual model was 247 mm high and 67 mm wide. After copying the model into a new document, the drawing size was 500 mm x 500 mm, and the model image appeared in the Print Preview.


Changing the drawing size in the original drawing to a more reasonable size does not "stick" -- the program reverts back to the large size, or close to it.

One possible cause of the large drawing size is to use a DXF as an underlay that is very large. So one prevention measure would be to use an appropriately sized DXF file.

Program Crashes when Zooming with Windows 95 or Windows 98 Operating Systems:
If the program is crashing when you use the Zoom feature, go to Options/Preferences and "check" the "Windows 95" box. This should solve the problem. 

If this is happening even when you reduce the Mesh Parameter, go to Options/Preferences/Simulation, and make sure that the "Automatically increment mesh parameter" is turned OFF, ie, "unchecked". If this option is checked, the program will keep increasing the mesh parameter automatically until it can either simulate the problem or the array overflow occurs, even if you reset the mesh parameter to a smaller number. 

Report Does Not Print

THERM needs the file RICHTX32.OCX in order for the Report feature to work. This file is used by many programs so it may already be installed on your computer, and THERM will display the Report properly. However, if the Report button doesn't display anything, you need to the following:

Download the RICHTX32.ocx file by clicking here.

and save or copy it into your system directory. The standard system directories for the various versions of MS Windows are listed below:

For MS Windows 7, 32 bit computers:

copy file into c:\windows\system32

For MS Windows Windows 7, 64 bit computers:

copy file into c:\windows\syswow64

You also need to "register" the file. Click here for complete instructions about how to register the OCX file.

Steady solution is diverging in ConRad:  
If this message appears at the end of a simulation, the program will not have been able to calculate a solution to the model. Go to the Options menu, select Preferences, and go to the Simulation tab. Changing the Relaxation Parameter will probably allow the file to simulate. The default setting for Relaxation Parameter should be 1.0 and that is the setting to try first. If that does not allow the program to simulate, increment that value down in 0.01 increments until the problem simulates, without going below a value of 0.90. For example, if the problem didn't converge at 1.0, the next Relaxation Parameter to try is 0.99, then 0.98, until you reach 0.90.

Underlays with AutoCAD versions 2000 and newer:  
THERM cannot read DXF files from AutoCAD versions 2000 and newer, so in the File/Save As dialog box in either of those AutoCADversions, set the Type to either AutoCAD12 or AutoCAD13 DXF format files.

Exporting sections or parts of a file (Autocad 2000):

To prepare an AutoCAD dxf section for use in Therm, follow the steps below. Note that you may want to use only part of the drawing. You can save each section in a separate file or save the entire vertical or horizontal section in a single file.

Note that parts in a drawing may not be able to be completely exploded and may not appear in Therm. You may have to go back to the originator of the file and ask them to make sure that the parts are able to be exploded.

Whole product SHGC calculations:  
The ISO 15099 formula for the frame Solar Heat Gain Coefficient (SHGC) specifies that the surface area (Asurf) should be the outdoor wetted surface, while the frame area (Af) should be the indoor projected surface area. By default, if there are no exterior U-factor tags, THERM passes the inside wetted length to WINDOW5 for the SHGC calculation. In order for THERM to pass the exterior wetted surface length, tag the exterior frame boundary conditions with the U-factor tag of "SHGC Exterior". In the latest installation of THERM, this tag is in the default U-factor tag library, but if it is not there, you can be added to the library.


Frame Cavity Emissivities
There are some circumstances where the program will assign frame cavity surface emissivities based on the emissivities of the glazing system layers, rather than the emissivities of the surrounding surfaces. This problem occurs only with frame cavities using the advanced radiation model or the iso model, and is partly based on the geometry of the frame cavity as it relates to the glazing system. It is hard to predict when it will happen, and so the best way to make sure this is not happening in a particular file is to print out the Report for the file (File/Report), and examine the emissivities of all the frame cavities to see if there are any that do not seem to make sense.


If some questionable values are found, it is possible to then example the frame cavity in question (the Polygon ID is listed in the report in the first column, and that polygon can be selected in the THERM file by using the Edit/Select Special menu and then typing the Polygon ID number in the ID field). Once the problem polygon is selected, double click on each frame cavity surface and the emissivity of that surface will be displayed. In general, unless overridden by the user, these emissivities should be the emissivities of the materials the surface is touching. If these emissivities are found to be incorrect (if the problem is from this bug, the emissivities will be set to one of the glass layer emissivities, so it should be obvious if that is the problem), then the emissivity can be changed by inputting the correct value into this dialog box, and rerunning the file.


Boundary Conditions Changed from Comprehensive to Simplified
If a Boundary Condition is initially defined with the Model = Comprehensive in the Boundary Condition Library and applied to a cross section surface, an then is later changed to Model = Simplified in the Boundary Condition Library, if the applied boundary condition is "clicked on", the Radiation model will still be set to "AutoEnclosure" even though it shouldn't be. The solution is to make a completely new Boundary Condition with the Model = Simplified, rather than taking one that was originally defined with the Model = Comprehensive.


Boundary Condition is originally defined as Model = Comprehensive


Boundary Condition is changed to Model = Simplified


When a boundary condition segment is clicked on, the Radiation Model is still set to AutoEnclosure, even though it shouldn't be.

Two Automatic Radiation Enclosures in the Same Model
If there are two Automatic Radiation Enclosures in the same THERM cross section, the program will not necessarily calculate the results correctly. The solution until this bug is fixed is to set one set of boundary conditions to "Blackbody" and the other to "Automatic Radiation Enclosure". If you have a model where you want to do this and have questions about to set up the model, send email to