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Window Performance parameters. Impact of SHGC on heating performance: Should the RTF Specify SHGC in Addition to U-Value for Glazing? May 22, 2007. Window U and SHGC Analysis. Analysis designed to jointly review the performance of windows with U-values below .35
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Window Performance parameters Impact of SHGC on heating performance: Should the RTF Specify SHGC in Addition to U-Value for Glazing? May 22, 2007
Window U and SHGC Analysis • Analysis designed to jointly review the performance of windows with U-values below .35 • EStar prototype used with 2200 sf and 16.7% glazing (equal orientation) • SHGC and U distributions based on about 45,000 tests in the NFRC database. • Only vinyl frame, double glazed window used • All tests have at least one low-e coating
Conclusions • In higher performance windows (U>.34), SHGC should be specified to insure perfromance. • Analysis suggests the fixing the SHGC at a minimum value (.33) provides consistant heating performance improvements. • This may be too restrictive and SHGC • Cooling impacts reduce the advantage of a fixed SHGC • In Boise, reduce the effect by 30% • In Seattle and Missoula, reduce the effect by less than 10%