Information · NFRC & ENERGY STAR
NFRC & ENERGY STAR
What is the NFRC?
The National Fenestration Rating Council (NFRC) is the independent, nonprofit organization that runs the standard rating and labeling system for windows, doors and skylights in the United States. Its ratings describe the whole product, frame and glass together, at a standard size and under standard conditions, so products from different manufacturers can be compared fairly.
U.S. energy codes, including the IECC and ASHRAE 90.1, rely on NFRC ratings to show that fenestration meets their requirements, and ENERGY STAR is based on them.
How a product is rated
- Simulation. An NFRC-accredited simulation lab models the frame sections and glass in LBNL THERM and WINDOW, following NFRC 100 (U-factor) and NFRC 200 (SHGC and visible transmittance).
- Validation testing. A physical sample is tested in a hot box at an accredited test lab to confirm the simulation.
- Certification and inspection. An independent inspection agency certifies the product, lists it in the NFRC Certified Products Directory, and inspects the factory to make sure what is shipped matches what was rated.
What the NFRC label shows
| Rating | Standard | What it tells you |
|---|---|---|
| U-factor | NFRC 100 | Rate of heat loss through the whole window, in Btu/h·ft²·°F. Lower is better. |
| Solar heat gain coefficient (SHGC) | NFRC 200 | Fraction of solar heat admitted, 0 to 1. Lower keeps out more sun. |
| Visible transmittance (VT) | NFRC 200 | Fraction of visible light admitted, 0 to 1. Higher means more daylight. |
| Air leakage (optional) | NFRC 400 | Air passing through the unit, in cfm/ft². Lower is better. |
| Condensation resistance (optional) | NFRC 500 | Resistance to interior condensation, 1 to 100. Higher is better. |
Ratings are for a standard size of each product type, for example 1200 × 1500 mm for fixed and dual action windows and 600 × 1500 mm for casements, so a window’s rating is not the value for every size you order. Commercial projects can also use the NFRC Component Modeling Approach (CMA), which rates the actual frames and glass of a specific project. The Key to NFRC Codes explains the product codes on the label.
NFRC and European ratings are not the same
Europe and the Passive House Institute rate windows under EN ISO 10077, with different standard sizes, temperatures and calculation rules. The same window will have a different U-value under each method, so a European Uw cannot be compared directly with an NFRC U-factor. Phius accepts either route through its own window program. See U-Value & SHGC.
Our ratings
NFRC and CSA certification of our F-Series windows is in progress. Until each label is issued, we publish whole-window values calculated in LBNL THERM 8.1 and WINDOW 8.1 to NFRC 100 at NFRC standard sizes, and label them Calculated. Our GR85 fixed window with ZERO 04 glass calculates at 0.085 Btu/h·ft²·°F. Every system is on the performance page.
ENERGY STAR
ENERGY STAR is the voluntary U.S. efficiency label for residential windows, doors and skylights. Products must be NFRC-certified and meet U-factor and SHGC limits for each of four climate zones. Many utility rebates and some state programs reference it.
| ENERGY STAR Version 7.0 zone | Window U-factor | Window SHGC |
|---|---|---|
| Northern | ≤ 0.22 | ≥ 0.17, a minimum, to admit winter sun. Equivalent options allow U up to 0.26 with a higher SHGC. |
| North-Central | ≤ 0.25 | ≤ 0.40 |
| South-Central | ≤ 0.28 | ≤ 0.23 |
| Southern | ≤ 0.32 | ≤ 0.23 |
The program continues: Congress funded it for 2026, and its administration is moving from the EPA to the U.S. Department of Energy during 2026. In Canada, ENERGY STAR is run by Natural Resources Canada with its own climate zones, and products can qualify by U-factor or by Energy Rating (ER) under CSA A440.2.
ENERGY STAR criteria are summarized from the Version 7.0 specification; confirm the current specification and any equivalent-performance options with ENERGY STAR before specifying.