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What is an ENERGY STAR Certified Window? Follow

ENERGY STAR certified windows meet a stringent energy efficiency specification set by the U.S. Environmental protection Agency (EPA) and the U.S. Department of Energy (DOE) and have been tested and certified by the National Fenestration Rating Council (NFRC). The NFRC is an independent, third-party certification agency that assigns specific energy efficiency measures such as U-factor and Solar Heat Gain Coefficient (SHGC) to the complete window system, not simply the glass.

The ENERGY STAR certifications are based on U-factor and SHGC ratings for each of four different climate zones. To meet the U-factor and SHGC levels, ENERGY STAR certified windows, and skylights may use:

  • two or more panes of glass
  • warm-edge spacers between the glass panes
  • inert gases like argon or krypton sealed between the panes of glass
  • improved framing materials
  • Low-E coating(s) which are microscopically thin coatings that helps keep heat inside during the winter and outside during the summer

ENERGY STAR certified windows are not required to have any single feature listed above.  The performance criteria require that the window meet a certain efficiency standard, but it's up to the window manufacturer to determine how to accomplish that.

Learn more about ENERGY STAR certified residential windows, doors and skylights at energystar.gov/windows.

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