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What is a U-Factor and how does it relate to ENERGY STAR? The higher its R-value, the greater its insulating ability. The R-factor of a window is the measure of its resistance to the transfer of heat flow.
#WINDOWS R RATING WINDOWS#
What is an R-value and how important is it in selecting windows?Īlthough the U-value is actually the important number in evaluating windows and doors, most people are more familiar with the related concept of R-value (or R-factor). By selecting ENERGY STAR products, you can reduce your energy costs and help make the environment cleaner. Windows and doors can only carry the ENERGY STAR label if they are tested by an independent laboratory through the NFRC program and meet specific, predetermined U-value ratings. government program administered by the Department of Energy and the Environmental Protection Agency with the cooperation of manufacturers that is designed to reduce the consumption of fossil fuels through the education of consumers. What is ENERGY STAR® and what does it have to do with windows and doors?ĮNERGY STAR is a U.S. Numerous factors, including how the frame and sash are engineered and built, the type of glass used (single-, double- or triple-pane), the weatherstripping, the type of low-emissivity coating on the glass and the presence of argon or krypton gas. What makes a window or door energy efficient?