LOOK FOR THE NFRC LABEL ON EVERY WINDOW YOU BUY.
How can you tell one replacement window from another? How do you know which window will provide the best performance when it comes to comfort, safety and energy efficiency?
Look for the label!
The National Fenestration Rating Council (NFRC), an independent, non-profit organization, administers t he only nationally accepted rating system for energy performance of windows.The NFRC provides fair, accurate and reliable energy performance ratings so that architects, engineers, builders, code officials, contractors and homeowners can compare different products and make informed choices.
The most important measure of a window’s performance is its U-Factor. The U-Factor indicates the rate of heat flow through a window. The lower the U-Factor, the more energy efficient the window will be. U-Factor measures the entire window unit — glass, frame, sash, spacers — and is the only measurement accepted by the U.S. Department of Energy’s EnergyStar program. U-Factor ratings generally fall between 0.20 and 1.20. The lower the U-value, the greater a window’s resistance to heat flow and the better its insulating value.
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.
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 (AL) 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.
Condensation Resistance (CR) measures the ability of a product to resist the formation of condensation on the interior surface of that product. The higher the CR rating, the better that product is at resisting condensation formation. While this rating cannot predict condensation, it can provide a credible method of comparing the potential of various products for condensation formation. CR is expressed as a number between 0 and 100.