Re-Stuccoing a House: Does Title 24 Require Wall Insulation?
Title 24 sets no percentage of wall removed that triggers insulation, unlike the 50 percent test for roofing. What matters is whether taking off stucco and lath opens the framing and the wall is then insulated or rebuilt. In that case Section 150.0(c) applies: U-0.095 for 2x4 framing, U-0.069 for 2x6.
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No threshold for walls
Section 150.2(b)1 lists items A through N for alterations. Roofing carries its own more-than-50-percent test in item I, and walls have no item at all. They are reached through Section 150.0(c), which applies to the altered component. Plaster over sheathing you leave untouched is not something Part 6 names.
What bare studs change
The compliance manual's Example 9-3 observes that opened exterior walls are a chance to insulate them, but that such upgrades are unlikely to earn credit without third-party verification of the existing conditions. If the cavity is insulated, the target is R-15 in 2x4 framing or R-21 in 2x6 at 16 inches on center, unless an existing 2x4 wall already has R-11. Section 150.2(b)1 also carries the applicable parts of Section 150.0(a) to (l) into alterations, and 150.0(g)2 asks for a Class I or II vapor retarder on the conditioned side of wall insulation in zones 14 and 16.
Plaster as the air barrier
The manual lists Portland cement and sand parge or gypsum plaster of at least 5/8 inch among materials that qualify as an air barrier. That matters in one case. For a conversion that makes an addition over 700 square feet, window and door header insulation and air sealing are waived while the existing air barrier stays and the exterior cladding is not removed (Section 150.2(a)1Av, Example 9-8). Strip the stucco and the waiver is gone, and any replaced wall meets all of quality insulation installation.
What to settle with the department
Ask whether the permit scope is cladding only or includes the wall cavity, and have the answer in writing before the lath comes off. Wall assemblies and their U-factors are on wall insulation. The sibling topic is re-siding a house, and the inspection step is on quality insulation installation. Our residential Title 24 reports cover alterations. Garage walls are on garage conversions.
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
Part 6 does not name it. The department decides whether the scope is an energy-regulated alteration.
The Standards place no requirement on stucco as cladding. It appears as an air barrier material and in the cladding-removal waiver for conversions.
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View all Insulation guides → · Windows and Building Envelope · Title 24 guide