Windows in a Wildfire Zone: Vinyl, Aluminum and Title 24
A window in a fire hazard severity zone answers to two codes. The California Wildland-Urban Interface Code, Title 24 Part 7, governs how the glazing resists fire and embers. The Energy Code, Part 6, governs U-factor and solar heat gain. The Energy Code rates the whole window rather than its frame, so vinyl versus aluminum comes down to each product's fire listing and energy label.
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Two codes, two questions
Part 7 took over the wildfire construction rules that sat in Chapter 7A of the Building Code and Section R337 of the Residential Code, and its 2025 edition took effect on 1 January 2026. Section 504.8 covers exterior glazing, and the State Fire Marshal has proposed amending it so that, in multilayered glazing, at least the inner pane is tempered. Ask your building department which text applies to your permit, and whether your lot is in a designated zone.
What Part 6 asks
Every window needs an NFRC U-factor and SHGC. The mandatory 0.40 limit on a home's weighted average U-factor has an exception for fenestration in buildings that meet Part 7 and sit in a fire hazard severity zone or WUI fire area designated by the local enforcement agency (Exception 3 to Section 150.0(q)). It lifts only that cap. The prescriptive values in Table 150.1-A, 0.27 or 0.30 by zone, still apply, and a home whose windows cannot reach them complies through the performance approach.
Vinyl, aluminum or wood
Part 6 rates the whole window. An unrated aluminum window takes a poor default, as the aluminum windows page shows, while a rated thermally broken unit can comply. On the fire side, UC Agriculture and Natural Resources reports that the former Chapter 7A allowed any framing material, and it recommends a reinforcing bar in vinyl frames. Check a product's fire listing and its energy label together, because the window must carry both.
Rebuilds and replacements
The energy report must model the window actually chosen, as the wildfire rebuild guide sets out. Replacements follow the window rules, and trade questions are answered at Title 24 for window installers.
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
The Energy Code does not regulate frame material, and UC Agriculture and Natural Resources reports that the former Chapter 7A allowed any framing material. Confirm the specific product against Part 7 with your building department.
No. It lifts only the mandatory 0.40 weighted-average U-factor cap. The prescriptive U-factor and SHGC values, or a performance trade-off, still apply.
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