One of the major performance rating categories listed on an NFRC label is the Solar Heat Gain Coefficient (SHGC). This measurement is also sometimes called Passive Solar Gain (PSG). The SHGC measures the amount of solar radiation (heat from the sun) that a window allows through the glass. While a U-Factor measures the amount of heat that passes from inside a home to the outside, the SHGC measures the opposite—how effective a window is at preventing outside heat from getting into the home.
The SHGC of a window takes into consideration the amount of heat that is transmitted directly through the glass, as well as the amount of heat that is absorbed by the glass and then slowly released into the home over time. The SHGC is expressed as a value between zero and one, and most replacement windows made nowadays have an SHGC of between 0.25 and 0.35.
The lower SHGC a window has, the less solar radiation is able to pass through the glass, so generally speaking, the closer an SHGC is to zero, the better. However, in regions with colder climates, the solar heat that passes through a window can actually help a home stay warmer in the winter. For this reason, higher SHGC values are sometimes sought after by homeowners in such regions.
For more information about how a replacement window’s Solar Heat Gain Coefficient rating can affect your home’s energy performance, click here to locate a Sunrise Windows dealer in your area.