What Title 24 Now Requires of Your Replacement Windows

Most homeowners meet Title 24 as a line on a quote, or as a reason a contractor gives for a price. It is worth understanding for one practical reason: the number changed at the start of 2026, and a quote built on the old figure is a quote for a window that no longer complies where you live.

The requirement, as it stands

The 2025 Building Energy Efficiency Standards — Title 24, Part 6 — apply to work whose permit application is submitted on or after 1 January 2026. Replacing windows in an existing home is an alteration, and the prescriptive requirements for altered fenestration are:

Every market we work in sits in the group where the maximum U-factor moved from 0.30 to 0.27. If you are outside these cities, the California Energy Commission publishes an address lookup tool and a climate zone list by ZIP code.

The two figures measure different things. U-factor is how much heat passes through the whole window assembly — lower is better, and it matters most on cold mornings. SHGC is how much of the sun's heat comes through the glass — lower blocks more, which is what matters through a Sacramento Valley summer. There is no SHGC requirement in San Francisco or at Tahoe because the cooling load there does not justify one.

The small-job exception, which most homeowners qualify for

This is the part that rarely gets mentioned and often saves money. Replacing 75 square feet or less of vertical fenestration may be done at a maximum U-factor of 0.40 and a maximum SHGC of 0.35.

Seventy-five square feet is a meaningful allowance — a typical bedroom window is somewhere around 12 to 15 square feet, so this covers roughly five or six average windows. If you are replacing a handful rather than the whole house, ask whether your job falls inside the exception before accepting a specification written for a full-house replacement.

Two caveats worth stating. The exception is about the prescriptive standard; the window still has to meet the mandatory requirements. And if you are likely to do the rest of the house within a few years, matching may matter more to you than the saving.

How to check a quote

1. Ask for the product's NFRC label or spec sheet. Not the brochure — the certified figures for the exact product and configuration quoted.
2. Find U-factor and SHGC. Our guide to reading an NFRC label covers what each number on it means.
3. Compare against your zone, using the table above.
4. Ask which compliance path is being used — prescriptive or performance. Both are legitimate; the answer tells you whether the numbers above are the test.

Be wary of "Title 24 compliant" as an unqualified claim. Compliance is zone-specific, so the phrase without a zone tells you nothing. A contractor who cannot say which zone your house is in has not checked.

Why this catches people out

Because the requirement is fixed by the permit application date rather than the installation date, a quote prepared from a specification written in 2025 can be for windows that were compliant when the document was drafted and are not now. This is not usually dishonesty — it is a stale reference sheet. It is also why a great deal of published guidance still says 0.30, including, until recently, several pages on this site. We corrected ours; it is reasonable to ask a contractor to confirm theirs.

Permits

Replacement windows generally require a permit, and the permit is where compliance is demonstrated. Our page on permits for retrofit windows in California covers the process. For the wider regulation, see what Title 24 is. If you manage an apartment community rather than a house, the multifamily version is at Title 24 compliance for multifamily window replacement.

Sources

Figures on this page are from the California Energy Commission: the 2025 Building Energy Efficiency Standards for the effective date, the Single-Family Residential Compliance Manual for the 2025 standards (CEC-400-2025-005) for the alteration requirements and the 75-square-foot exception under Section 150.2(b)1A, and the Commission's Building Climate Zones by ZIP Code list for zone assignments. Requirements change each code cycle — confirm the current standard with your building department before specifying.

Working with Heritage Exteriors

We specify replacement windows to the current standard for your zone and pull the permit as part of the job, and our quotes show the performance figures rather than asserting compliance. Licensed in California, CSLB #1055919. Call (916) 546-2991.