Cities & areas in CZ10
Riverside, San Bernardino, Redlands, and the surrounding ZIP codes mapped to Climate Zone 10 by the California Energy Commission. If you're not sure which zone applies to your project, the ZIP-code lookup tool will tell you.
Prescriptive baseline for CZ10
These are the values your project's design has to meet, or beat, under the Title 24 Part 6 prescriptive path. Your Title 24 report (CF1R) can also satisfy compliance through the performance path; the values below are what the code book sets as the baseline for CZ10.
| Component | Value |
|---|---|
| Ceiling | R-38 (R-38 Ceiling Below Attic) |
| Walls | R-21+R5 CI, 2x6, Synthetic Stucco |
| Roof assembly | Asphalt Shingle, R-19 Below Deck, No RB, cool roof required |
| Radiant barrier | Not required |
| Window U-factor | U-0.30 |
| Window SHGC | 0.20 |
| Heating & cooling | Heat pump · HSPF2 9.0 / SEER2 18.5 / EER2 14.5 |
| Water heating | Heat-pump water heater (Tier 3 50-gallon HPWH) |
What this means for your design
In practice, walls go up at 2x6 with R-21 cavity insulation plus continuous-insulation sheathing on the outside, the roof needs a cool-roof finish (high solar reflectance) and skips the radiant barrier, windows must hit SHGC 0.20, meaning low-solar-gain glazing, the heat pump needs HSPF2 9.0 / SEER2 18.5.
ADUs and additions in CZ10
Accessory Dwelling Units, additions, and addition+alteration projects in CZ10 run against the same per-zone baseline shown above, with scope-specific adjustments, newly-constructed dwellings get full PV sizing; additions and alterations on a permitted residence are exempted from PV. The flow on this site picks the right scope automatically based on the details you confirm.
Title 24 reports in CZ10 cities
Detailed pages for the largest cities in CZ10, same prescriptive baseline as above, plus the local building department that will receive your submitted Title 24 report:
Title 24 in Riverside · Title 24 in San Bernardino · Title 24 in Fontana · Title 24 in Moreno Valley · Title 24 in Rancho Cucamonga · Title 24 in Ontario · Title 24 in Corona · Title 24 in Escondido
The three design options for CZ10 projects
Whether your design lands in CZ10 or anywhere else in California, you'll choose between three pathways: Prescriptive (matches the baseline above), 2x4 Performance (lighter framing, compensated by upgraded windows and roof), and 2x6 Enhanced (heavier framing, easier equipment specs). Full breakdown on the Title 24 explained page.
Other California climate zones
Title 24 prescriptive values change zone by zone. Browse the full set:
CZ1 · CZ2 · CZ3 · CZ4 · CZ5 · CZ6 · CZ7 · CZ8 · CZ9 · CZ11 · CZ12 · CZ13 · CZ14 · CZ15 · CZ16