The short answer
An ENERGY STAR certified window has been independently certified to meet applicable program performance criteria for an identified climate zone. Use the ENERGY STAR information together with the NFRC label for the exact product. Certification does not guarantee a specific bill reduction, comfort result, installation quality, or fit for every opening.
Read both labels
Confirm the exact product
Match manufacturer, product line, operation, size, and glazing configuration to the quote.
Check the applicable climate zone
Verify that certification applies where the project is located.
Read the NFRC metrics
Compare U-factor, solar heat gain coefficient, visible transmittance, and other reported values separately.
Define installation
Put removal, flashing, sealing, insulation, trim, and finish responsibilities in writing.
Common questions
Common questions
Does an ENERGY STAR window automatically have the lowest U-factor?
Not necessarily. Certification uses applicable program criteria, while individual certified products can have different ratings. Compare the exact NFRC label.
Sources
Sources
- Residential Windows, Doors, and Skylights — ENERGY STAR
- What Makes a Product ENERGY STAR — ENERGY STAR
- Window Energy Performance Ratings — National Fenestration Rating Council
- Window Installation — U.S. Department of Energy