Among the most notable changes made in the final document are changes concerning the window criteria for the Northern zone. DOE tightened the U-factor criteria to the 0.27 level. To maximize the number of products qualifying in the zone, DOE chose not to set an SHGC maximum. DOE determines it was worthwhile to recognize the benefits of higher solar gain in some applications.
In the Southern zone SHGC is allowed up to 0.25. DOE officials note that stakeholders had expressed concern that the very low SHGC previously proposed would have reduced visible light transmission and DOE decided it did not want to encourage production of windows providing less visible light.
The new Energy Star criteria goes into effect January 1, 2015.