ENERGY STAR® Windows
The Department of Energy (DOE) and the Environmental Protection
Agency (EPA) have developed an ENERGY STAR designation for products
meeting certain energy performance criteria.
Since energy efficient performance of windows, doors, and skylights varies by climate, product recommendations are given for four U.S. climate zones. For making comparisons among ENERGY STAR products, use the NFRC label or the NFRC Certified Products Directory.
Incentives and rebates for energy-efficient windows and other efficient products»
| Northern Zone Required Properties (mostly heating) | |||
| U-factor | Solar Heat Gain Coefficient (SHGC) | Visible Transmittance (VT) | Air Leakage (AL) |
|
Windows: U≤0.30 (up to 0.31 if SHGC≥0.35, up to 0.32 if SHGC≥0.40) Skylights: U≤0.55 |
Windows: SHGC=No Requirement (if U-factor≤0.30) Skylights: SHGC=No Requirement |
Windows: VT=No Requirement Skylights: VT=No Requirement |
Windows: AL=No Requirement Skylights: AL=No Requirement |
| EWC Recommendations | |||
| If air conditioning needs are minimal, windows that give good access to winter solar heat gain (Solar Heat Gain Coefficient 0.40 or higher) are also energy efficient with U-factors as high as 0.32. | If air conditioning is not a concern, look for a high SHGC (0.30-0.60) so that winter solar heat gains can offset a portion of the heating energy need. If cooling is a significant concern and no shading is available, select windows with a SHGC less than 0.40. Select skylights with a SHGC of 0.40 or less. | Select windows with a higher VT to maximize daylight and view. | Select windows with an AL of 0.30 or less. |
| North/Central Zone Required Properties (heating & cooling) | ||||||||||||||||||||||||||||||||||||||||||||
| U-factor | Solar Heat Gain Coefficient (SHGC) | Visible Transmittance (VT) | Air Leakage (AL) | |||||||||||||||||||||||||||||||||||||||||
|
Windows: U≤0.32 Skylights: U≤0.55 |
Windows: SHGC≤0.40 Skylights: SHGC≤0.40 |
Windows: VT=No Requirement Skylights: VT=No Requirement |
Windows: AL=No Requirement Skylights: AL=No Requirement |
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| EWC Recommendations | ||||||||||||||||||||||||||||||||||||||||||||
| The larger your heating bill, the more important a low U-factor becomes. | If you have significant air conditioning costs or summer overheating problems, look for SHGC values of 0.30 or less. If you have moderate air conditioning requirements, select windows with a SHGC of 0.40 or less. Windows with lower SHGC values reduce summer cooling and overheating but they also reduce free winter solar heat gain. | Select windows with a higher VT to maximize daylight and view. | Select windows with an AL of 0.30 or less. | |||||||||||||||||||||||||||||||||||||||||
| South/Central Zone Required Properties (heating & cooling) | |||
| U-factor | Solar Heat Gain Coefficient (SHGC) | Visible Transmittance (VT) | Air Leakage (AL) |
|
Windows: U≤0.35 Skylights: U≤0.57 |
Windows: SHGC≤0.30 Skylights: SHGC≤0.30 |
Windows: VT=No Requirement Skylights: VT=No Requirement |
Windows: AL=No Requirement Skylights: AL=No Requirement |
| EWC Recommendations | |||
| The larger your heating bill, the more important a low U-factor becomes. 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 during warm seasons. | Select windows with a SHGC of 0.30 or less. While windows with lower SHGC values reduce summer cooling and overheating, they also reduce free winter solar heat gain. | Select windows with a higher VT to maximize daylight and view. | Select windows with an AL of 0.30 or less. |
| Southern Zone Required Properties (mostly cooling) | |||
| U-factor | Solar Heat Gain Coefficient (SHGC) | Visible Transmittance (VT) | Air Leakage (AL) |
|
Windows: U≤0.60 Skylights: U≤0.70 |
Windows: SHGC≤0.27 Skylights: SHGC≤0.30 |
Windows: VT=No Requirement Skylights: VT=No Requirement |
Windows: AL=No Requirement Skylights: AL=No Requirement |
| EWC Recommendations | |||
| 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. | A low SHGC is the most important window property in warm climates. | Select windows with a higher VT to maximize daylight and view. | 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/sf
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