Insulation requirements in California
Short answer
California spans climate zones 2, 3, 4, 5, 6. For most of the state (zone 3), the DOE recommends about R49–R60 of attic insulation, with more in its colder areas.
Climate zones
2, 3, 4, 5, 6
Most of the state
Zone 3
Recommended R-values for California
Based on zone 3, which covers most of California. Colder parts of the state (higher zones) need more — enter your ZIP for your exact numbers.
| Area | Recommended R-value | Blown fiberglass |
|---|---|---|
| Attic / ceiling | R49–R60 | 24.0" |
| Exterior walls | R20–R21 | 8.4" |
| Floors | R19–R25 | 10.0" |
| Crawlspace / basement wall | R5 | 2.0" |
Californiarebates & tax credits
The federal 25C tax credit (30% of insulation materials, up to $1,200/yr) applies everywhere. California's IRA rebate programs are administered by the state and rolling out on their own timeline. Check the official finder for California's current status and how to apply.
Find California's rebate programs →Last verified 2026-07-07.
Your exact numbers
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Frequently asked questions
How much insulation do I need in California?
California is in IECC climate zones 2, 3, 4, 5, 6. For most of the state the DOE recommends about R49–R60 in the attic, with more in colder areas. Enter your ZIP for the exact zone.
Are there insulation rebates or tax credits in California?
Yes — the federal 25C tax credit covers 30% of insulation materials (up to $1,200/year), and California's IRA HOMES/HEAR rebate programs (up to $1,600 for insulation) are administered by the state. Check the official finder for current California status.
What climate zone is California in?
California spans IECC climate zones 2, 3, 4, 5, 6; most of the state is zone 3. Your exact zone depends on your county — enter your ZIP to check.