What Happens If a Window Has No NFRC Label?
The window is rated from default tables, not by what it actually does. Tables 110.6-A and 110.6-B assign a U-factor and SHGC from frame type, pane count and tint, and they are set so that they do not give any significant number of products a better figure than a tested rating. No default reaches the 0.40 mandatory U-factor, so the fix is an NFRC-rated product.
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What the default costs
A double-pane operable window with clear glass defaults to U-0.79 and SHGC 0.70 in a metal frame, U-0.66 and 0.63 with a thermal break, and U-0.58 and 0.65 in a nonmetal frame. The targets are 0.27 or 0.30 and 0.23. The Commission requires the tables to be set so that they do not give any significant number of products a lower figure than the NFRC procedure would; the Multifamily Compliance Manual's commentary calls them the least efficient possible values, to encourage ratings.
How it plays in the calculation
- Prescriptive: the U-factor and SHGC are area-weighted averages, so a small unrated window can be carried by better ones. The manual says no default-table product meets 0.40 by itself.
- Mandatory 0.40 average: the first 10 square feet or 0.5 percent of floor area is exempt; a whole unrated house is not.
- Performance: the default is modelled as installed, so it costs energy budget that must be recovered elsewhere.
What still has to be on the product
A default is not a free pass: the product needs a temporary label showing "CEC Default U-factor" and "CEC Default SHGC". With no label at all, the manual tells inspectors to stop further installation until proof is produced, and the appendix checklist for installers says to confirm with the responsible person that the product meets the specification.
How to avoid it
Ask the supplier for the NFRC Certified Product Directory listing before ordering. Custom windows are usually manufactured products and can be rated, because ratings are issued by product line. Field-fabricated windows must use the defaults, and unrated site-built ones may use the Appendix NA6 alternative instead. The label itself is explained on NFRC labels and window approval.
For frame-material questions read Title 24 aluminum windows; for jobs in progress see the replacement checklist and new windows and Title 24. Our residential reports show the effect of each option.
Common Title 24 Questions
- When is Title 24 required for a home?
- Does a remodel need Title 24?
- Does a room addition need Title 24?
- What plans are needed for a residential Title 24 report?
- How much does a residential Title 24 report cost?
- How long does a residential Title 24 report take?
Frequently Asked Questions
Not if it carries a CEC Default label and the defaults still meet the project's calculation. A window with no label at all cannot be verified by the inspector.
Custom windows delivered to the site are normally manufactured products, so they can be rated; only windows assembled on site from loose parts are field-fabricated.
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