Title 24 for Window Installers
On a window job the inspector checks a label, not a test result. That makes the sticker on the glass the most important paperwork you handle.
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No ECC-Rater tests windows: none of the field-verified measures listed in the Residential Appendices is a window (Tables RA2-1 to RA2-7). The building inspector checks the product against the CF1R instead, using the label on the glass and your installation certificate. We prepare the CF1R, and its values are the ones your products have to show.
What matters for your projects
Leave the label on
Each manufactured window and glazed door carries a temporary label with its U-factor, SHGC and visible transmittance, certifying its air leakage (Section 10-111(a)1), and that label may not be removed before the building department inspects (Section 110.6(a)5). A product without an NFRC rating is labelled with "CEC Default" values from the code's default tables.
Check it against the CF1R
A same-area replacement meets the prescriptive U-factor and SHGC for the climate zone (Section 150.2(b)1B), listed on do new windows need Title 24. Default-rated products rarely get there: the compliance manual notes that none in the default tables meets the mandatory 0.40 U-factor on its own. Glazed doors with 25 per cent or more glass count as fenestration.
The 75 square foot rule
Replacing no more than 75 square feet of windows only needs a U-factor of 0.40 or lower, and an SHGC of 0.35 or lower in zones 2, 4 and 6 to 15 (Exception 1 to Section 150.2(b)1B). Any replacement in zone 15 still needs an SHGC of 0.23.
Repair, replacement or new area
New glass in an existing sash and frame, or new sashes in an existing frame, are repairs if they perform at least as well as the originals. Windows removed and reinstalled are exempt from the certification rules of Section 110.6(a). A new or enlarged opening is added fenestration, which also has to meet the area limits, with up to 16 square feet exempt (Section 150.2(b)1A).
Your certificate
The single-family set has a CF2R-ENV-01-E for fenestration installation and a CF2R-ALT-05-E for alterations that need no field verification. The licensed person responsible for the installation signs it and a copy is posted on site (Section 10-103(a)3). On a replacement with no field verification the building department may waive it or use a simplified form of its own (Section 10-103(a)3D), so ask which it wants.
Site-built glazing and apartments
Field-fabricated windows must use the default values of Tables 110.6-A and 110.6-B, and be caulked and weatherstripped (Section 110.6(b)). Apartment buildings follow Table 180.2-B instead; see apartment window replacement.
Every project includes
- Permit-ready documentation for your scope
- Registration where your project requires it
- Unlimited revisions until you comply
- Direct contact with the analyst on your file
Frequently Asked Questions
No. Section 110.6(a)5 says the temporary label may not be removed before inspection by the building department. It is how the inspector checks the product against the CF1R.
No. The repair note in Section 150.2(b)1B covers only new glass in an existing sash and frame, or new sashes in an existing frame. An insert brings its own frame, so it is replacement fenestration and has to meet the replacement values.
Not for the windows. No window measure appears in the Residential Appendices' lists of field-verified measures. A rater is needed only if other work on the permit, such as an HVAC changeout, calls for one.