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Understanding Window Energy Ratings

For energy-conscious consumers, window manufacturers are continuously releasing a wide range of frame, window glass and vinyl products designed to cut utility bills and protect your home from energy leaks. The manufacturers attach rating labels showing levels established by the National Fenestration Rating Council (NFRC) on the windows themselves. You'll see the labels in the showroom or on sample windows that contractors bring over for your review.

The Importance of Labels

The window label makes comparing products easy, once you know how windows are rated. Vinyl replacement window ratings are recorded on window labesl in separate panels that show:

  • U-Factors
  • Solar Heat Gain Coefficient (SHGC)
  • Visible Transmittance
  • Condensation Resistance

Each of these ratings is explained below in layman's terms. After familiarizing yourself with the basics, ask your window dealer or contractor any questions that you have about the ratings and how they may translate into a window's performance in your home.

Behind the NFRC Window Ratings

Vinyl replacement window ratings often include a national map, with a colored section that indicates the product is well-suited to your climate. U-factor ratings show how well the window blocks heat transfer. The lower the rating, the greater the insulating quality. So, if your climate includes severe weather, a low U-factor may be highly desirable.

SHGC measures heat flow. The lower the SHGHC numbers, the better the vinyl replacement window ratings on your replacement product. Visible Transmittance ratings indicate how much light penetrates the window into your home. In this case, a higher rating number is a better value. Condensation Resistance ratings are important for anyone who has experienced a clouded or moldy window. The higher the number, the better the product is in fighting off moisture.

Now you are armed with the essential knowledge on window ratings. Compare the advantages of various products within your price range and choose the window likely to perform best in your home.