Pick your city and see which California Title 24 climate zone you sit in — and what that zone actually changes about insulation, windows, roofing and ducts.
Every result is a planning estimate, not a quote or an engineering determination. Real numbers depend on site conditions, existing structure, engineering requirements, and your jurisdiction’s current fee schedule. For structural and engineering work we coordinate with a licensed engineer — we do not perform or stamp engineering ourselves. Get a project-specific estimate before committing to a budget.
California is divided into 16 Title 24 climate zones, drawn by ZIP code rather than county line. The zone is the first input in every energy calculation, because it sets the heating and cooling loads the software assumes for your building. Change the zone and the required insulation, window performance and roofing all shift with it.
The Bay Area spans three of them in a remarkably short drive. Most of Santa Clara County and the mid-Peninsula sit in Zone 4, a mild zone with a real but modest cooling season. The East Bay flats — Fremont, Union City, Hayward, Castro Valley — fall into Zone 3, the coolest and most coastal-influenced of the three, where summer cooling load is small enough that prescriptive solar heat gain limits relax. Push past the hills into the Tri-Valley and Dublin and Pleasanton land in Zone 12, an inland zone with genuinely hot summers, cool roof expectations and tighter duct requirements.
That is why a set of drawings that sailed through in Hayward can come back with corrections in Pleasanton. It is the same code, but a different zone with different prescriptive targets.
Assuming the city equals the zone. Zones follow ZIP boundaries, and a few Bay Area cities straddle a line. San Jose is large enough that the far east foothills and the flats do not always behave the same in the modeling. We always run the energy report off the project address, never the city name.
Specifying windows before the zone is confirmed. In Zone 3 there is generally no prescriptive solar heat gain limit, so a homeowner can order clear high-visible-transmittance glass. The same order in Zone 4 or Zone 12, where a SHGC cap applies, fails the prescriptive path and forces a redesign or an energy model.
Ignoring cool roof in the inland zones. Re-roofing a Pleasanton or Dublin house often carries a prescriptive cool roof expectation that does not apply in San Jose or Fremont. That is a material selection decision, and it is cheaper to make it before the roofer is on site.
Once your zone is set, the rest of the report follows. We prepare registered Title 24 CF1R energy calculations and coordinate the numbers with the permit set so the window schedule, insulation callouts and mechanical notes all agree with the energy report.
By ZIP code, not by county or city limits. The California Energy Commission publishes the ZIP-to-zone mapping, and the compliance software uses it to pull the weather file that drives the whole calculation. Because a few large cities cross a boundary, we always confirm the zone from the exact project address.
They sit on opposite sides of the East Bay hills. Fremont is in Zone 3, cooled by coastal air, with a small summer cooling load. Pleasanton is in Zone 12, inland and genuinely hot in summer. Zone 12 carries a solar heat gain limit on glazing, cool roof expectations and tighter duct insulation that Zone 3 does not.
No. They are typical prescriptive targets to help you plan a design and a materials budget. Actual compliance is demonstrated on a registered CF1R for your specific building, using the code cycle in force when you apply for the permit.
Yes. The insulation R-values, window U-factor and SHGC, roofing reflectance and duct sealing requirements that come out of your zone all have to appear on the drawings and match the CF1R. Plan checkers compare the two documents directly, so a mismatch is one of the most common reasons a set comes back.
Tell us what you're building and we'll get back to you with next steps — usually within one business day.
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