What is meant by “Solar Heat Gain Coefficient” (or, sometimes expressed as “SHGC”)?
The number to know when selecting windows and patio doors – it measures how much of the sun’s heat is transmitted through these fixtures, expressed in a number from zero to one. A window that has a SHGC of .30 will allow 30 percent of the sun’s heat to pass through. Whether you want a higher or lower number will depend on your goal. Especially in the South, you will be primarily interested in a window or patio door with a low SHGC that will help to block solar heat gain inside your home, thus reducing cooling loads in hot weather. Northern climates often look for higher SHGC performance to harness passive solar warmth on cold, sunny winter days.
