What is U-factor? Can it help me choose a better window?
The U-factor is a standard measure of heat transfer through an entire window unit. The methods for measuring U-factor ratings were developed by the national Fenestration Rating Council (NFRC) at the request of the U.S. Department of Energy and the Federal Trade Commission. The lower the U-factor the better the window’s insulating ability. A window’s U-factor is the reciprocal of its R-factor, they both measure its insulating ability. Look for windows with low U-factors and high R-values.
