Attic Insulation Requirements for California Remodels
A remodel brings in attic insulation rules only when the ceiling below a vented attic is altered or a new duct system is installed there. Then R-49 applies in zones 1 to 4, 6 and 8 to 16, with air sealing, recessed light covers and ventilation by zone. Existing R-38 or better excuses all of it.
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What counts as altering the ceiling
The manual lists replacing existing attic insulation, adding new attic insulation and replacing the ceiling plane, and adds installing an entirely new duct system in the attic. Installing two new recessed lights in a kitchen is a lighting alteration and does not count.
What you already have decides the rest
- R-38 or more: every requirement is excused.
- R-19 or more: R-49 is still required except in zones 1, 3 and 6. Air sealing is skipped, and recessed lights need covering only in zones 11 to 16.
- Less than R-19: the full set applies. R-49 or U-0.020 in zones 1 to 4, 6 and 8 to 16, air sealing of the ceiling plane in zones 2, 4 and 8 to 16, and recessed lights insulated to the same depth in zones 1 to 4 and 8 to 16.
Attic ventilation to the residential code applies in every zone whenever the ceiling is altered. Atmospherically vented combustion appliances inside the home excuse the air sealing alone.
Four conditions excuse the whole set
Existing R-38, asbestos the work would disturb, knob and tube wiring in the attic, or a shared attic over a unit whose ceiling is not altered. When one is claimed, record the existing condition on the certificate of compliance. Anyone taking responsibility may sign it, and the building official verifies it on site.
When the attic is too shallow
If the accessible space cannot hold the required R-value, fill all of it, as long as the residential code ventilation clearance in Section R806.3 is kept.
Who checks it
An ECC-Rater is not needed for these items; the building department inspects them. A remodel that also changes ducts is on HVAC Title 24, and the roof side is on roof replacement and insulation. The overall list is on insulation requirements, and a living-space conversion is on attic conversions. Order from residential Title 24 reports.
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
Yes. The manual says a ceiling is altered when new attic insulation is added, so the R-49 requirement applies unless an exception such as existing R-38 covers the attic.
Not the R-49 step. Zones 5 and 7 are not on the R-49 list in Section 150.2(b)1J, so only the mandatory R-19 minimum for an altered ceiling and attic ventilation apply.
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