The Department of Energy revised its criteria for Energy Star windows, doors and skylights, raising its efficiency standards for 2010. For windows and skylights, the U-factor (which indicates how well a product prevents heat from escaping) and the Solar Heat Gain Coefficient (SHGC) criteria (which indicates how well a product blocks heat from entering) have been tightened. The DOE is expected to require Insulating Glass (IG) certification for Energy Star-qualified doors, windows and skylights by next July.
In addition, the Climate Zone map has changed. To see if your area is affected, go to Energy Star's website.