The Solar Heat Gain Coefficient is the fraction of the energy in sunlight that the window transmits. A value closer to 1.0 means that the window is relatively transparent to sunlight, and a value closer to 0.0 means that the window is relatively opaque. Typical windows have SHGC values of 0.5 to 0.75, but may vary from 0.2 (solar-control glazing) to 0.9 (thin, clear glass).

This program uses the whole window SHGC, not the value for the center of glass.

You may encounter the term "shading coefficient" (SC) to describe window energy transmission; to convert SC to SHGC, multiply SC by 0.87.