Solar Optical Properties of Windows

To properly calculate dynamic solar gain in buildings, one must know the optical properties of the window in detail. In this paper, we develop a complete set of calculation procedures for determining the solar transmittance, reflectance, and absorptance of a window composed of an arbitrary number of partially transparent layers. Any layer may have a thin-film multilayer coating, such as an anti-reflection coating for increasing solar transmittance, a solar control film for reducing solar heat gain, or a transparent heat-reflecting mirror for improving thermal resistance. The results of sample calculations are given over the range of incidence angles for conventional and advanced energy conserving window designs.