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Frequently Asked Questions
Q: Do I have to replace all my windows at the same time?
A: No, but it may cost more per product to replace them one at a time. It may also be difficult to find an installer because companies often prefer doing larger jobs.
Q: I’m choosing between two ENERGY STAR qualified products. How much will my utility bills decrease if I choose the one with the lower U-factor?
A: While energy usage does decrease as U-factor drops, your utility bills depend on regional climate and energy costs. You can calculate the savings yourself by using RESFEN 
, the same computer model that ENERGY STAR and the Lawrence Berkley National Laboratory (LBNL) use to determine the energy savings data for ENERGY STAR qualified products.
Q: What type of spacers, framing material, or glass type should I look for?
A: Just look for the ENERGY STAR label. The ENERGY STAR criteria are based on the performance of the entire window, so spacers, framing material, and glass type are already taken into account. Use the U-factor and Solar Heat Gain Coefficient (SHGC) to further differentiate between ENERGY STAR qualified products. Learn more about U-factor and SHGC.
Q: Does ENERGY STAR for Windows, Doors, and Skylights maintain a list of qualified products?
A: No, but the National Fenestration Rating Council (NFRC) independently tests and certifies ENERGY STAR qualified windows, doors, and skylights, and the NFRC Certified Product Directory includes all ENERGY STAR qualified products. ENERGY STAR for Windows, Doors, and Skylights does maintain lists of retailers and manufacturers of ENERGY STAR qualified products.
Q: I just looked up an ENERGY STAR manufacturer partner in the National Fenestration Rating Council (NFRC) Certified Product Directory (CPD), but the company wasn’t there. Are their products really ENERGY STAR qualified?
A: Probably. Many ENERGY STAR manufacturer partners do not appear in the NFRC CPD because they are private labelers. As a private labeler, a company puts its name on a product manufactured by a second company, typically under a licensing agreement. Privately labeled windows, doors, and skylights are NFRC-certified under the original manufacturer’s name. To find out if the company you are researching is a private labeler, contact ENERGY STAR for Windows, Doors, and Skylights.
Q: How do I qualify for a tax credit for my windows, doors, or skylights?
A: For more information on the tax credit for windows, doors, and skylights, please visit our tax credit page.
