In the Northern Region (>6000 Heating Degree Days), windows and doors must meet a U-factor of 0.35; in the Central Region (2000-5999 HDD), a U-factor of 0.40 and a Solar Heat Gain Coefficient of 0.40 are required, and in the Southern Region (0-1999 HDD), a U-factor 0f 0.75 and a Solar Heat Gain Coefficient of 0.40 are required.
The new requirement for skylights in the Northern Region is a U-factor of 0.45, in the Central Region a U-factor of 0.45 and Solar Heat Gain Coefficient of 0.40 are required, and in the Southern Region a U-factor of 0.75 and Solar Heat Gain Coefficient of 0.40 are required.
In August, 2001, DOE issued a draft proposal and sought industry comments. The draft proposed criteria changes in year 2002 and elimination in year 2003 of the three climate zones in favor of a single national specification. Based on a broad range of industry views, DOE has concluded that a single national specification should not be adopted at this time and that a multi-climate approach allows for regional marketing of glass and window technologies best suited to particular areas of the country. The revisions will go into effect January 1, 2002.