Building Green Homes

     When searching for products to replace windows, doors, and skylights there are two labels consumers can look out for, they are the National Fenestration Rating Council (NFRC) label and the Energy Star label.  The NFRC is a non-profit organization that provides uniform, independent performance ratings on windows, doors, and skylights.  NFRC does not recommend which products to buy, but simply labels the products with performance ratings.  Their labels include ratings for U-Factor, Solar Heat Gain Coefficient, Visible Transmittance, Condensation Resistance and Air leakage.  U-Factor measures the rate of heat transfer through the product, displaying how well the product insulates.  U-Factor ratings generally range from 0.25-1.25 Btu/h·ft²·°F, and the lower the rating, the better the window insulates.  Solar Heat Gain Coefficient (SHGC) is the fraction of sunlight energy that gets transmitted, displaying how well the product blocks heat.  SHGC is rated on a scale 0-1, and the lower the rating, the less heat the product transmits (the product blocks more heat).  Visible Transmittance (VT) is the amount of light the product allows to pass through.  VT is also measured on a scale of 0-1, the lower the rating, the less light passes through.  Condensation Resistance tells consumers how well the water protects against water build up.  Condensation Resistance is measured on a scale from 0-100.  The lower the rating, the more water build-up the window allows.  Lastly, Air Leakage measures the rate that air passes through the joints of the product.  This is measured by cubic feet of air that passes through one square foot of the product area each minute.  The lower the rating, the less air leakage.[1]

 

     This discusses the NFRC’s rating, but what is the Energy Star Label?  Unlike the NFRC’s rating, the Energy Star rating system allows consumers to easily recognize NFRC-certified products that exhibit “superior energy performance”.  An Energy Star certified product was manufactured by an Energy Star partner, are certified and tested by the NFRC, and have NFRC ratings that meet the strict energy efficiency guidelines provided by the U.S. Department of Energy.[2]

 

     Different climates require different standards for energy ratings.  Some parts of the country need windows that keep the house cool, while others require windows that keep the house warm.  The Energy Star website provides information on which Energy Star Ratings are best for certain parts of the country.  Long Island falls into the North-Central category, suggesting a U-Factor of ≤ 0.32 and a SHGC of ≤ 0.40. 

 

 

 

[1] Energy Star, "Independently Tested and Certified Energy Performance", Accessed 20 Oct 2014

 

[2] Energy Star, “What Makes it Energy Star?”, Accessed 30 Oct. 2014