Quick Answer: Attic insulation in the Bay Area costs $1,500–$5,000 for a 1,500–2,000 SF attic (blown-in fiberglass or cellulose at R-38 to R-49). Spray foam insulation costs $3,000–$9,000 for the same space. California Title 24 requires R-38 minimum for attic insulation in most Bay Area climate zones; R-49 is recommended for energy savings. The payback period for Bay Area attic insulation is typically 3–7 years through PG&E savings of $300–$700/year. PG&E and Bay Area cities offer rebates of $250–$1,000 for insulation upgrades through the Energy Upgrade California program.
Attic Insulation Cost by Type — Bay Area 2025
| Type | Cost per SF | 1,500 SF Total | R-Value per Inch |
|---|---|---|---|
| Blown-in fiberglass | $1.00–$1.75 | $1,500–$2,600 | 2.2–3.0 |
| Blown-in cellulose | $0.85–$1.50 | $1,275–$2,250 | 3.2–3.8 |
| Fiberglass batts | $0.75–$1.25 | $1,125–$1,875 | 2.2–3.0 |
| Rockwool/mineral wool | $1.50–$2.50 | $2,250–$3,750 | 3.0–3.3 |
| Open-cell spray foam | $1.50–$2.50/in | $3,375–$5,625 | 3.5–3.7 |
| Closed-cell spray foam | $3.00–$5.00/in | $6,750–$11,250 | 6.0–7.0 |
Question: What R-value do I need for attic insulation in the Bay Area? Bay Area climate zones (most of the Bay Area falls in CEC Climate Zones 3, 4, and 12) require R-38 minimum under California Title 24. The Department of Energy recommends R-49 to R-60 for maximum energy savings in mild climates like the Bay Area. In practice, most Bay Area contractors install R-49 (about 13 inches of blown-in cellulose or 15 inches of blown-in fiberglass) as the cost difference between R-38 and R-49 is small ($200–$400 for a 1,500 SF attic) while the lifetime energy savings are significant. If your attic has any existing insulation, a contractor will measure it and add to reach target R-value — you only pay for the added material and labor.
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