To do this, the NFRC window label gets into the nitty-gritty of how a window performs, including how well it insulates, how much of the sun’s heat and light it allows in, and how well it limits air leakage when closed, information that can be useful when comparison shopping.
NFRC ratings are based on data from third-party labs, and past tests by CR found them to be accurate and reliable. As a result, we devised our replacement window test procedure to be complementary.
Here, we break down the meaning of each figure on the NFRC sticker. Hover over each rating for a description, or see below.