Impact 4000 Data Sheet with options – http://www.krestmark.com/wp-content/uploads/2014/08/Impact-SS2.pdf
Krestmark energy performance data:
Table below is from http://www.efficientwindows.org/energystar.php with the required properties for a product to be Energy Star Rated.
|Southern Zone Required Properties (mostly cooling)|
|U-factor||Solar Heat Gain Coefficient (SHGC)||Visible Transmittance (VT)||Air Leakage (AL)|
Skylights: U?0.60EWC Recommendation: A low U-factor is useful during cold days when heating is needed. A low U-factor is also helpful during hot days when it is important to keep the heat out, but it is less important than SHGC in warm climates.
Skylights: SHGC?0.28EWC Recommendation: A low SHGC is the most important window property in warm climates. For superior energy performance, use windows with a SHGC of 0.25 or less.
|Windows: VT=No Requirement
Skylights: VT=No RequirementEWC Recommendation: Select windows with a higher VT to maximize daylight and view.
Skylights: AL?0.30EWC Recommendation: Select windows with an AL of 0.30 or less.
U=U-factor in Btu/hr-sf-°F
SHGC=Solar Heat Gain Coefficient in fraction of incident solar angle
VT=Visible Transmittance in fraction of incident visible radiation
AL=Air Leakage in cfm/s