How climate zones drive compliance
California is divided into 16 climate zones (CZ1 through CZ16) by the California Energy Commission. Your project's ZIP code maps to exactly one zone, and that zone determines the prescriptive baseline your design has to meet — wall and ceiling R-values, window U-factor and Solar Heat Gain Coefficient (SHGC), whether you need a cool roof, whether a radiant barrier is required, and which HVAC efficiency tiers apply.
Coastal zones (CZ3, CZ6, CZ7) are mild and put less stress on cooling and heating equipment. Inland and desert zones (CZ12, CZ13, CZ14, CZ15) are cooling-dominated and drive lower SHGC numbers and higher SEER2/EER2 ratings. Mountain zones (CZ16) run cold enough that heating dominates the calculation. The full table is in Title 24 Part 6 Table 150.1-A (2025).
Per-climate-zone cheatsheet
A reference to the climate-zone-specific differences in the prescriptive residential baseline. Envelope R-values, window U-factor, and HVAC efficiencies follow the zone defaults; these are the rules that change between zones.
| Zones | Rule |
|---|---|
| CZ1, CZ16 | No radiant barrier required. |
| CZ10–CZ15 | Cool roof required; radiant barrier suppressed (the assembly conflicts with cool-roof standard-design expectations). |
| CZ8, CZ9 | R-19 below-deck attic insulation; asphalt shingle + radiant barrier. |
| CZ3, CZ5, CZ6, CZ7 | R-30 ceiling and 2x4 walls. All other zones: R-38 ceiling and 2x6 walls. |
| CZ1, CZ3, CZ5, CZ16 | Window SHGC 0.25 (heating-dominated). All other zones: 0.23 or lower. |
| CZ12 | Tightened cooling tier — SHGC 0.18, HSPF2 9.0 / SEER2 22 / EER2 16. |
| CZ8, CZ9, CZ10 | SHGC 0.20. CZ8/CZ9 cooling: SEER2 20 / EER2 15. CZ10 cooling: SEER2 18.5 / EER2 14.5. |
Source: Title 24 Part 6 Table 150.1-A (2025).
Looking up your climate zone
The fastest way is our free ZIP-code lookup tool — type a 5-digit California ZIP and it tells you which of CZ1–CZ16 applies. The CEC also publishes the official map at the CEC Climate Zone Tool. When you start a project on this site, we auto-resolve the climate zone from your project ZIP as soon as you confirm the address.
Title 24 prescriptive baseline by zone
Every climate zone has its own prescriptive baseline — wall and ceiling R-values, window U-factor and SHGC, HVAC efficiency, and water-heater type. Click through to a zone for the full breakdown:
- CZ1 — North Coast (Crescent City, Eureka, Arcata)
- CZ2 — Wine Country / North Bay (Santa Rosa, Napa, Petaluma)
- CZ3 — Bay Area coast (San Francisco, Oakland, Berkeley)
- CZ4 — South Bay / Salinas Valley (San Jose, Santa Cruz, Salinas)
- CZ5 — Central Coast (Santa Maria, Santa Barbara, San Luis Obispo)
- CZ6 — LA coastal basin (Long Beach, Torrance, Santa Monica)
- CZ7 — San Diego coast (San Diego, Chula Vista, Oceanside)
- CZ8 — coastal Orange County (Anaheim, Garden Grove, Buena Park)
- CZ9 — foothill LA County (Burbank, Pasadena, Glendale)
- CZ10 — Inland Empire west (Riverside, San Bernardino, Redlands)
- CZ11 — north Sacramento Valley (Red Bluff, Chico, Redding)
- CZ12 — Sacramento & north Central Valley (Sacramento, Stockton, Modesto)
- CZ13 — south Central Valley (Fresno, Bakersfield, Visalia)
- CZ14 — high desert (Palmdale, Lancaster, Victorville)
- CZ15 — low desert (El Centro, Indio, Brawley)
- CZ16 — Sierra / mountain (Truckee, Mammoth Lakes, Bishop)
Why your zone matters for cost
The same set of plans can land in three different equipment specs depending on the climate zone. A 2,500 sq ft single-family home in CZ3 (Oakland) might pass with mid-tier windows and a standard heat pump; in CZ12 (Palm Springs / Coachella) the same home needs SHGC 0.18 windows, SEER2 22 cooling, and a cool roof to clear the prescriptive baseline. None of this is optional — picking equipment without knowing the zone risks failing compliance verification.