(For NFRC Certification and modeling Complex Glazing Systems)

For modeling Cellular Shades, in addition to vacuum glazing, deflected glass, vertical venetian blinds and perforated screens
Download WINDOW 6.3
(for NFRC Certification and complex glazing systems)
Download WINDOW 7.2
Knowledge Base
Check here first if you are experiencing a problem with the software)
Knowledge Base
Check here first if you are experiencing a problem with the software)
New Features  
(includes documentation for
WINDOW 5 and 6)
(includes documentation for
WINDOW 7, 6, and 5)
Window Glass Library Update  
System Requirements  
Tutorials Tutorials

Program Features

WINDOW features include:


a state of the art Microsoft WindowsTM interface


updated algorithms for the calculation of total fenestration product U-values and Solar Heat Gain Coefficient consistent with ASHRAE SPC142, ISO15099, and the National Fenestration Rating Council


a Condensation Resistance Index in accordance with the NFRC 500 Standard


a surface temperature map


an integrated database of properties


links to other LBNL window analysis software:


THERM, for calculating 2-D frame and edge effects


RESFEN, for calculating the energy effects of windows in typical houses throughout the United States


Optics5 for the optical properties of all coated and uncoated glazings, laminates, and applied films.

Program Capabilities

WINDOW 7.2 offers the following features: 

bullet The ability to analyze products made from any combination of glazing layers, gas layers, frames, spacers, and dividers under any environmental conditions and at any tilt;
bullet The ability to model complex glazing systems such as venetian blinds and roller shades.
bullet Directly accessible libraries of window system components, (glazing systems, glazing layers, gas fills, frame and divider elements), and environmental conditions; 
bullet The choice of working in English (IP), or Systeme International (SI) units; 
bullet Help Screens and a manual; 
bullet A print feature which generates detailed results for a window, window component, or library; 
bullet The ability to specify the dimensions and thermal properties of each frame element (header, sills, jamb, mullion) in a window; 
bullet A multi-band (wavelength-by-wavelength) spectral model;
bullet A Glass Library which can access spectral data files for many common glazing materials from the Optics5 database; 
bullet A night-sky radiative model; 
bullet A link with the DOE-2.1E and EnergyPlus building energy analysis program. 

Performance Indices and Other Results

For a user-defined fenestration system and user-defined environmental conditions, WINDOW calculates: 

bullet The U-value, solar heat gain coefficient, shading coefficient, and visible transmittance for the complete window system; 
bullet The U-value, solar heat gain coefficient, shading coefficient, and visible transmittance for the glazing system (center -of-glass values); 
bullet The U-values of the frame and divider elements and corresponding edge-of-glass areas (based on generic correlations); 
bullet The total solar and visible transmittance and reflectances of the glazing system; 
bullet Color properties, i.e. L*, a*, and b* color coordinates, dominant wavelength, and purity for transmitted and reflected (outdoor) solar radiation; 
bullet The damage-weighted transmittance of the glazing system between 0.3 and 0.38 microns; 
bullet The angular dependence of the solar and visible transmittances, solar and visible reflectances, solar absorptance, and solar heat gain coefficient of the glazing system; 
bullet The percent relative humidity of the inside and outside air for which condensation will occur on the interior and exterior glazing surfaces respectively; 
bullet The center-of-glass temperature distribution. 

Updated: 03/11/14