Remodel With New Insulation and Windows: Title 24 Checklist
Windows and insulation are separate alterations that meet at one choice: show compliance prescriptively or by modeling. Replacement glass up to 75 square feet gets relief, added glass up to 16 square feet skips the area caps, and added insulation must reach its mandatory value. Quality insulation installation is not an alteration requirement.
- Choose your report
- Upload your plans
- Pay securely
- Permit-ready report by email
The two glass thresholds
Replacing up to 75 square feet of vertical glass lets the new units meet U-0.40, and SHGC 0.35 in zones 2, 4 and 6 to 15. Zone 15 still needs SHGC 0.23. Adding up to 16 square feet of new glass is exempt from the total and west-facing area limits; beyond that, the total glass must stay within 20 percent of floor area, with 5 percent facing west in zones 2, 4 and 6 to 15. Across the house, the weighted average U-factor of all windows cannot exceed 0.40, with up to 10 square feet or 0.5 percent of floor area excused.
The insulation floors
Added wall insulation reaches U-0.095 in 2x4 framing or U-0.069 in 2x6, which R-15 and R-21 batts meet at 16-inch spacing. Existing 2x4 walls already at R-11 are excepted. Raised floors take R-19 or U-0.037, unless the crawlspace is controlled-ventilation or unvented and meets the conditions of Section 150.0(d).
Where QII stops
Quality insulation installation, verified by an ECC-Rater, is a prescriptive item for new buildings and for additions over 700 square feet. It is not on the alteration list in Section 150.2(b)1, and the compliance manual says it does not apply to altered spaces even inside a large addition. See quality insulation installation.
Credit depends on proof
Without third-party verification, the standard design for altered insulation is the mandatory level and for altered glass the prescriptive level of Section 150.1(c)3A, so upgrading only to those levels earns nothing. With an ECC-Rater verifying existing conditions, the baseline becomes what is really there, and a verified single-pane metal operable window is modeled at U-1.28. That check must happen before construction and before the CF1R is registered, so photograph and measure before demolition.
Opened exterior walls are the moment to insulate, as the manual's loft example notes. The pieces are covered on wall assemblies, windows and older homes with unknown insulation. Combined jobs belong in the whole-house checklist.
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
No. QII is prescriptive for new buildings and additions over 700 square feet. It does not appear in the alteration requirements of Section 150.2(b)1.
Exception 1 is written for replacement of vertical fenestration no greater than 75 square feet, and the manual counts the area replaced. Beyond that, the zone values in Table 150.1-A apply; ask the building department how it totals a multi-wall job.
Explore Windows and Doors
- Remodel With New Windows and HVAC: Title 24 Checklist
- Replacing One Window: Does Title 24 Apply?
- Sealing Around Replacement Windows: What Section 110.7 Requires
- Sliding Glass Door Replacement: Title 24 Requirements
- Title 24 Aluminum Windows: Do They Comply?
View all Windows and Doors guides → · Windows and Building Envelope · Title 24 guide