For a highly efficient window that will meet the 2015 IECC in all Texas climate zones, we recommend selecting a window with no more than 0.35 U-Factor and no more than 0.25 Solar Heat Gain Coefficient. For additional details on Selecting Energy Efficient Windows in Texas, consult the Efficient Window Collaborative's Texas Factsheet.
The National Fenestration Rating Council (NFRC) is an international coalition that administers testing, certification and labeling of windows, skylights and doors. NFRC sets energy test standards and administers ratings by independent labs. The NFRC energy performance label helps builders, retailers and consumers reliably compare one product to another.
The NFRC label contains the following performance data:
The 2 most important values to look for are: U-factor and Solar Heat Gain Coefficient (SHGC).
As a good rule of thumb, use the NFRC label to look for products with an SHGC below 0.25 and ideally lower. The lower the SHGC, the more cooling savings one can expect in Texas. The U-factor is more important in determining heating savings, so look for a U-factor below 0.35 in all Texas climate zones.