Determining energy efficiency
Look for the NFRC label
The National Fenestration Rating Council (NFRC) is a nonprofit organization that developed an energy rating program based on "whole product" performance — not just the glass.
The NFRC label is found on every window. It’s the most reliable way to determine a window’s "whole unit" energy performance.
NFRC-certified products
All reputable window manufacturers rate and certify their products according to National Fenestration Rating Council requirements.
U-Factor
This number tells you how well the window insulates.
The lower the U-Factor, the better. To qualify for the Federal Energy Tax Credit available through December 31, 2010, this number must be 0.30 or lower.
Solar Heat Gain Coefficient (SHGC)
This number tells how effective the window is at blocking the sun’s radiant heat. The lower the SHGC, the less solar heat the window allows into your home. To qualify for the Federal Energy Tax Credit available through December 31, 2010, this number must be 0.30 or lower.
Check that the manufacturer reports "whole product energy performance"
This is the best way to know how your window will perform — versus only reporting the “center of glass” performance.
The ENERGY STAR® logo
When you see this logo on the NFRC label, you can be assured you've purchased a high-efficiency window or door that meets ENERGY STAR® guidelines.
Look for the ENERGY STAR® label
To ensure your product will deliver ENERGY STAR performance, refer to the chart and map below to help determine the guidelines for your area of the country. Then compare these numbers with the “whole unit” U-Factors and SHGC ratings printed on your windows’ NFRC label.
