Solar Heat Gain Coefficient (SHGC)
Definition:
The Solar Heat Gain Coefficient (SHGC) measures the fraction of solar radiation admitted through a window, door, or skylight—either transmitted directly or absorbed and subsequently released as heat inside a building. It is expressed as a number between 0 and 1; lower SHGC values indicate less solar heat gain, enhancing a building’s energy efficiency.
Short Description:
SHGC quantifies the amount of solar heat that enters a building through fenestration products; lower values signify better performance in blocking unwanted heat from the sun.
Why It’s Important:
Understanding SHGC is crucial for selecting appropriate windows, doors, and skylights to optimize indoor comfort and energy efficiency. In warmer climates, products with low SHGC values help minimize cooling loads by reducing solar heat gain. Conversely, in colder climates, higher SHGC values can be beneficial by allowing more solar heat to enter, reducing heating demands.
Other Things to Consider:
•Climate Considerations: The ideal SHGC varies based on regional climate. In hot climates, low SHGC values are preferable to keep interiors cool, while in cooler regions, higher SHGC values can aid in passive solar heating.
•Building Orientation: The direction windows face affects solar heat gain. South-facing windows in the Northern Hemisphere receive more direct sunlight, influencing the desired SHGC based on seasonal sun angles.
•Glazing and Coatings: The type of glazing and any applied coatings can alter a window’s SHGC. Low-emissivity (Low-E) coatings, for example, can reduce SHGC while maintaining visible light transmission.
•NFRC Label: The National Fenestration Rating Council (NFRC) label on fenestration products provides certified SHGC ratings, assisting consumers in making informed choices about energy performance.
By considering SHGC alongside other factors like U-Factor and visible transmittance, homeowners and builders can select fenestration products that balance energy efficiency with comfort.