Solar Heat Gain Coefficient (SHGC) measures the fraction of solar radiation that passes through a window and enters a building, expressed as a decimal from 0.0 to 1.0. An SHGC of 0.40 means 40 percent of incident solar energy is transmitted through the window as heat. SHGC values guide window selection based on climate and building orientation to optimize heating and cooling efficiency.
Climate-Based Selection
Cold climates benefit from higher SHGC values (0.60 to 0.78) to maximize solar heat gain and reduce heating loads. Hot climates require lower SHGC values (0.23 to 0.40) to minimize cooling loads. Low-emissivity coatings, tints, and reflective films reduce SHGC from typical clear glass values of 0.78 to as low as 0.20 in high-performance products.
Energy and Comfort Benefits
Proper SHGC selection reduces cooling costs by 15-25 percent in hot climates and increases passive solar heating efficiency in cold climates. NFRC labels include SHGC alongside U Factor and Visible Transmittance for comprehensive window performance evaluation. Strategic window placement combined with appropriate SHGC ratings significantly improves building energy performance and occupant comfort.