Windows by the Numbers
Every Energy Star Certified window is tested independently by the NFRC. A sticker will appear on your new window with the results and these number can NOT be altered. It is by far the best way to compare the performance of multiple windows.
The top 3 performance numbers to compare are:
Energy Star Minimum |
Alliance |
Alliance Triple Glass |
|
U-Value | .30 or less (less is better) | .27 | .21 |
Air Leakage | .30 or less (less is better) | .06 | .06 |
DP-Design Pressure | more than 20 | 40 | 40 |