Frequently Asked Questions

There is only one reliable way to compare windows and that is by asking for the NFRC* rating for each window that you are considering. NFRC labels are independently certified and rate the whole window performance by U-Factor and Solar Heat Gain Coefficient (SHGC). The lower these ratings are the better the window will perform. The priority of U-Factor versus SHGC depends on your climate. You should ignore all the sales hype and choose the best NFRC ratings for your climate at the best cost.

Energy Star is a window certification program administered by the Federal Government to help you select energy efficient windows optimized for your climate. A window must meet minimum performance criteria to qualify. These criteria are based on NFRC whole window performance ratings and are different for each of four climate zones as follows:

Northern Zone (blue): U-Factor of .30 or less, SHGC any
North Central Zone (yellow): U-Factor of .32 or less, SHGC of .40 or less
South Central Zone (orange): U-Factor of .35 or less, SHGC of .30 or less
Southern Zone (red): U-Factor of .60 or less, SHGC of .27 or less