Understanding Vinyl Replacement Window Rating Information

July 11, 2010

Vinyl windows are a popular choice for replacing outdated windows. When shopping for vinyl replacement windows, you'll notice numerical ratings on window labeling; these ratings measure specific aspects of window performance and are useful for selecting specific qualities you want in replacement windows.

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Vinyl Replacement Window Ratings De-mystified

The National Fenestration Ratings Council (NFRC) is an industry advocacy organization that has standardized performance ratings for windows and doors. NFRC ratings include the entire products structure as opposed to rating glass only.Here are examples of their ratings and what they mean:

  • U Factor: This rating measures how fast heat can escape through a closed window. A lower U factor rating indicates less heat flow. Ratings range from .20 to 1.20.
  • Air flow (AL): This rating measures the amount of air flow that can enter or escape your home through cracks or other imperfections of a window's structure. A lower AL indicates that less air can flow through.
  • Solar Heat Cain Co-efficient (SHGC): The SHGC measures how a window transmits solar heat. Rated between 0 and 1, the lower a window's SHGC, the less solar heat it transmits,
  • Visible Transmittance (VT): This rating measures how much light is transmitted through a window. Vinyl windows typically transmit less light due to their thicker frames. VT is rated on a scale of 0 to 1, with higher ratings indicating more light transmission.
  • Condensation Resistance (CR): The higher a window's CR rating the less likely the nuisance of condensation forming between glass layers. This rating is measured from 0 to 100. Although this rating does not guarantee against windows forming condensation, it's a useful indicator if you expect condensation to occur.

There are additional window ratings, including Energy Star, that can help you find windows matching your priorities. Shopping online and visiting window dealers is helpful for comparing products, window ratings, and finding solutions.

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