What Does SHGC Mean When Talking About Glass?
SHGC stands for Solar Heat Gain Coefficient. It measures how much of the sun’s heat will pass through a window.
SHGC can be thought of as a percentage. For example, according to this NFRC Rating below, this window will only let in 32% of the sun’s heat. So a window of a SHGC of 0.50 will let in 50% of the sun’s heat!
The TECHNICAL EXPLANATION
Glass absorbs and redirects heat inward in three different ways: conduction, convection, and radiation. Solar Heat Gain Coefficient (SHGC) is a standard used in the North America to estimate solar radiation that passes through glass relative to the amount of solar radiation hitting the glass. Solar radiation tends to be the primary method of energy transfer through fenestration products. Factors such as reflection, absorption, and transmittance will affect the SHGC. Expressed as a number between 0 and 1 – the lower the SHGC, the less solar heat transmitted and the greater its shading ability. SHGC is tied to visual light transmission (VT) related to how well the glass allows sunlight to pass through it. Therefore the lower the VT, the lower the SHGC tends to be as well.
So, the lower the SHGC rating means less afternoon heat and lower cooling bills for buildings in areas with very hot summers.