Windows must meet minimum performance criteria during testing to qualify for the ENERGY STAR label. Whole-window U-values are one of the criteria used to label window and door products in the ENERGY STAR program. Windows with clear single-pane glass can’t achieve the ratings necessary to qualify for ENERGY STAR labeling. High-performance glass systems, which consist of double- or tripleinsulating glass, low-emissivity (Low-E) coatings and usually an inert gas between the glass panes, are often used to help windows to comply with ENERGY STAR requirements.
How to Compare Whole-Window U-Values
When comparing whole-window U-values, we suggest that you evaluate windows based on the sizes dictated by the National Fenestration Rating Council (NFRC). This ensures an accurate comparison of performance among windows. This data is available on www.nfrc.org, which provides links to NFRC data for all participating window manufacturers. If the window manufacturer you are considering is not represented on www.nfrc.org, then it is likely that the company does not participate in the ENERGY STAR® program, and that could tell you something about how energy efficient that company’s windows really are.
“R-values,” “whole-window U-values,” “center-of- glass U-values” and other window terms can boggle the mind. Confused by all the different window performance terminology you’re hearing and seeing? You don’t need to be. The information presented in this leaflet will help so that you can make educated purchasing decisions. If there’s ONE thing you should know, it’s this: When considering windows and determining the type of glass that will be used in them, the performance criterion you need to focus on is the whole-window U-value.
A window’s “U-value” indicates the rate of heat flow through a window. The lower the number, the more energy efficient the window is. Whole-window U-values are an indication of the performance of the window’s glass and its other components and characteristics. The thermal properties of its frame, spacer system, weather stripping and even grids, if the window has them, all have a bearing on the window’s wholewindow U-value. The whole-window U-value is the only form of measurement accepted by the ENERGY STAR® program for determining whether windows qualify for the ENERGY STAR label. For more information on ENERGY STAR qualified windows, visit www.energystar.gov.
Don’t Be Fooled
For an accurate comparison of windows and doors, ask to see the products’ WHOLEWINDOW U-VALUES with the particular type of glass system you are considering. Ensure that the data you are being shown is NOT center-of-glass U-values or R-values. This is important, because the more thermally efficient your windows and doors are, the more comfortable you will be in your home—and the more money you will save with lower energy bills.
For More information on Energy Efficient Windows for Pennsylvania and the Northeast Region. Check General Manager
A&B Sunroom &Remodeling
570.574.0457
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