Department of Energy clarifies that ENERGY STAR product specifications apply only to residential windows, doors, and skylights meeting specific criteria, excluding assembled products or nonresidential installations for ENERGY STAR certification.
Quick Answer
For ENERGY STAR-qualified windows, measure the opening and confirm it's a residential window type. Exclude assembled products or nonresidential installations. Department of Energy's ENERGY STAR website provides product specifications and efficiency ratings.
What Makes a Window ENERGY STAR-Qualified?
ENERGY STAR's product specifications require windows to meet specific residential criteria, such as being installed in homes and not assembled on-site. Products like sash packs or sash kits are excluded from ENERGY STAR certification, according to the Department of Energy. This means contractors must verify the window type matches the definition before quoting it as ENERGY STAR-qualified.
Some windows sold by government agencies like the General Services Administration (GSA) may not be labeled as ENERGY STAR-qualified, even if they meet the standards, according to the Department of Energy.
All other residential windows, doors, and skylights types are excluded, including but not limited to products that are assembled on site, sash packs or sash kits. Windows, doors, or skylights that are intended for installation in nonresidential buildings; and window, door, or skylight attachments that are not included in a product's National Fenestration Rating Council (NFRC)-certified rating.
- Confirm the window is installed in a residential building.
- Ensure it's not assembled on-site (e.g., sash packs or sash kits).
- Verify it's included in the product's NFRC-certified rating.
How to Measure for a Proper Fit
The U-factor - a measure of heat flow through glazing - should be low for energy efficiency, according to the Department of Energy. A lower U-factor means less heat escapes, which is vital for residential windows. Contractors must measure the opening precisely to ensure the new window fits without obstructions.
ENERGY STAR product specifications exclude windows intended for nonresidential buildings, so the measurement must reflect a residential context, according to the Department of Energy. The DLA ENAC for residential window, door, and skylight models is "DZ".
Environmental Protection Agency (EPA) provides residential window, door, and skylight efficiency levels and product specification information on its ENERGY STAR website for contractors to review.
- Ensure the window is intended for residential use, not nonresidential installations.
- Check the DLA ENAC code for residential windows, doors, and skylights (DZ).
- Review ENERGY STAR product specifications on the EPA website for efficiency ratings.
Why Some Windows Don't Meet ENERGY STAR Standards
Not all windows qualify for ENERGY STAR, especially those that are assembled on-site or designed for nonresidential buildings. This means contractors must carefully review the product's specifications to avoid quoting windows that don't meet the criteria.
Some windows sold by government agencies may not be labeled as ENERGY STAR-qualified, even if they meet the standards, according to the Department of Energy. Residential Window, Door, and Skylight Schedules and Product Codes indicate that not all windows sold by GSA are ENERGY STAR-qualified, and some products that do qualify may not be indicated as such.
Windows, doors, or skylights that are intended for installation in nonresidential buildings; and window, door, or skylight attachments that are not included in a product's NFRC-certified rating.
- Check if the window is assembled on-site (e.g., sash packs).
- Confirm it's not intended for nonresidential buildings.
- Verify the product's NFRC certification status.
Key Metrics for Window Efficiency
Window efficiency is measured using the U-factor and Solar Heat Gain Coefficient (SHGC). A lower U-factor indicates better insulation, while SHGC measures heat transmission, according to the Department of Energy. For residential windows, a higher SHGC value means more heat is retained, which is beneficial in colder climates.
The Visible Transmittance (VT) metric indicates how much daylight is transmitted through a window, according to the Department of Energy. A higher VT value means more natural light enters the space, improving energy efficiency and occupant comfort. These metrics help contractors select windows that balance heat retention and light transmission.
- U-factor: Lower values mean better insulation.
- SHGC: Higher values retain more heat in cold climates.
FAQ
Why might a window not be ENERGY STAR-qualified?
ENERGY STAR product specifications exclude windows assembled on-site, such as sash packs or sash kits, and those intended for nonresidential buildings, according to the Department of Energy. Contractors must verify the window meets residential criteria and has NFRC certification.
How do I check if a window is ENERGY STAR-qualified?
Ensure the window is installed in a residential building, not assembled on-site, and has NFRC certification to meet ENERGY STAR standards.
Primary Sources
Everyday Fit Check provides general measurement and planning information. The exact product manual, seller terms, building rules, and qualified installer guidance control the final decision.