Experimental Verification of a Model of Heat Transfer Through Windows

A procedure has been developed for calculating the one-dimensional heat flux through complex window systems. A computer program embodying this procedure (WINDOW 2.0) is available to the public. The window may consist of multiple glass or plastic layers, separated by gas-filled spaces. Gases other than air may fill the space between solid layers, and the layers may have low-emissivity coatings. Measurements from five different manufacturers and researchers of the overall thermal conductance of various window systems confirm the validity of this model for a range of temperatures and layer spacings less than 3 cm (1.2 in). A list of U-values and shading coefficients is given for a representative group of windows.