Rating Labels for Vinyl Replacement Windows

December 11, 2009

Understanding replacement window rating labels can help you select vinyl windows that suit your climate, budget, and home. Window labels generally divide ratings into two categories including residential and non-residential. Make sure you're looking at the residential ratings if you're checking out replacement window options.

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  • National Fenestration Rating Council (NFRC) ratings: Windows carrying ratings from the NFRC have been independently tested for multiple performance factors.
  • Energy Star ratings: Windows carrying the Energy Star label have been rated by tehe Us Department of Energy according to energy efficiency.

Here are some common replacement window rating categories:

  • U-Factor: This rating measures how efficiently heat can pass in or out of a closed window. The lower the U-factor, the less heat passes through. Less is better if you want to keep heat indoors during winter, or keep it out in hot climates.
  • Solar Heat Gain Coefficient (SHGC): This rating measures how much sunlight passes through a window as radiant energy. Radiant heat passing through glass can be influenced by the size of solid window frame materials; vinyl window frames are typically thicker and do not conduct as much heat as metal frames. The lower its SHGC rating, the less radiant heat passes through a window.
  • Visible Light Transmission: This rating measures how much visible light is transmitted through window glass. Thicker frames and multiple layers of glass can reduce VLT. In this case, a higher rating indicates that more visible light is transmitted through the window. If having a lot of natural light indoors is important to you, pay close attention to VLT ratings. A VLT rating of .50 indicates that only 50 percent of light is penetrating through the glass.

Ask window dealers for help with window replacement rating scales and selecting windows appropriate for your needs.

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