It is comprised of manufacturers, suppliers, builders, architects and designers, code officials, utilities and government agencies. NFRC provides consistent ratings on window, door and skylight products. The National Fenestration Rating Council (NFRC) energy performance label can help you determine how well a product will keep your home cool in the summer and warm in the winter. By using the information contained on the label, you can reliably compare one product with another and make informed decisions about the windows you buy.

U-Factor

measures how well a product prevents heat from escaping. The rate of heat loss is indicated in terms of the U-factor (U-value) of a window assembly. t. The lower the U-value, the greater a window's resistance to heat flow and the better its insulating value. A window must have a U-Factor of .30 or lower to qualify as an Energystar product.

Solar Heat Gain Coefficient (SHGC)

measures how well a product blocks heat caused by sunlight. The SHGC is the fraction of incident solar radiation admitted through a window (both directly transmitted and absorbed) and subsequently released inward. SHGC is expressed as a number between 0 and 1. The lower a window's solar heat gain coefficient, the less solar heat it transmits in the house. A window must have a SHGC of .40 or lower to qualify as an Energystar product.

Visible Transmittance (VT)

measures how much light comes through a product. The visible transmittance is an optical property that indicates the amount of visible light transmitted. VT is expressed as a number between 0 and 1. The higher the VT, the more light is transmitted.

Air Leakage

is indicated by an air leakage rating expressed as the equivalent cubic feet of air passing through a square foot of window area (cfm/sq ft). Heat loss and gain occur by infiltration through cracks in the window assembly. The lower the AL, the less air will pass through cracks in the window assembly. NFRC does not display the actual air infiltration test result. It displays less than or equal to .30 if the window meets this standard.

Ask for the actual air infiltration test results as the differences can be significant. See our comparison chart for the air infiltration results on the brands we carry