Window Efficiency

With the new ENERGY STAR criteria in effect as of January 2010, the Efficient Windows Collaborative updated its state fact sheets. In addition to the new ENERGY STAR specs these new fact sheets show updated energy cost estimates for various window options in a typical home using new modeling assumptions from Lawrence Berkeley National Laboratory’s 2008 ENERGY STAR analysis and replacing earlier estimates derived with RESFEN 5.0. Changes in typical residential building energy properties due to new codes and equipment standards are taken into account by these revised assumptions. To reflect new trends in window design, EWC has also revised some of the generic window options shown on the fact sheets. For instance, low-E glazing with very low SHGC properties has become more widely available, as have dual-pane windows with U-factors of 0.30 or lower. These changes will also be reflected in the EWC Window Selection Tool, which is currently being revised.