Quick Answer: Insulating a garage conversion in San Jose for California Title 24 2022 energy code compliance requires: (1) Wall insulation — R-15 minimum in 2×4 framed walls (high-density fiberglass batts or mineral wool); (2) Ceiling/roof insulation — R-38 minimum in the ceiling (blown-in fiberglass or mineral wool); (3) Floor insulation — garages have concrete slabs that must be insulated underneath flooring; R-10 rigid foam board under a sleeper floor or new slab-on-grade is the typical approach. Additionally, the garage door opening must be replaced with an insulated wall, insulated door, or combination — this is the most critical envelope upgrade since the garage door is a major thermal loss point. Windows must meet ENERGY STAR minimum U-factor (0.30 or better) and SHGC requirements. Insulation for a 2-car garage (400-500 sq ft) conversion costs approximately $4,000-$12,000 total including all of the above.
Garage Conversion Insulation Requirements — San Jose Title 24 2025
| Location | Minimum R-Value (Title 24 2022) | Typical Product | Cost (400 sq ft garage) |
|---|---|---|---|
| Walls (2×4 framing) | R-15 | HD fiberglass batt or mineral wool batt | $800 – $2,000 |
| Ceiling (flat) | R-38 | Blown-in fiberglass or mineral wool | $1,000 – $2,500 |
| Floor (slab-on-grade) | R-10 (rigid foam under sleeper floor) | 2″ XPS foam + sleeper + subfloor | $2,500 – $5,000 |
| Windows | U-factor ≤ 0.30, SHGC ≤ 0.23 | ENERGY STAR dual-pane vinyl | $1,500 – $4,000 |
| Door (former garage door opening) | Insulated exterior door, U ≤ 0.20 | Insulated steel or fiberglass door | $800 – $2,500 |
Quartz Construction installs Title 24-compliant insulation in all garage conversion projects in San Jose. We include a Title 24 energy compliance report with all ADU and garage conversion permits. Learn about garage conversions. CSLB #1003436 | Call (650) 749-7436.
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