Title 24 Reports in Contra Costa County

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Mostly inland, with a coastal edge

The bulk of the county — Walnut Creek, Concord, Danville, San Ramon, Lafayette, Moraga, Orinda, Antioch, Pittsburg, Brentwood and Martinez — sits in an inland valley zone, the same one the Tri-Valley and the Sacramento area share. The western edge along the bay, including Richmond, El Cerrito and Hercules, sits in the milder zone instead.

That is the reverse of the pattern people expect from a Bay Area county. Contra Costa is largely on the hot side of the hills, and its climate has more in common with Sacramento than with San Francisco.

The line is the ridge, again

The same Oakland-Berkeley hills that split Alameda County continue north through Contra Costa. Orinda and Lafayette sit immediately east of the ridge and are firmly in the inland zone, despite being a short drive from Oakland. Richmond, north of the ridge and on the water, is not.

For anyone working across the East Bay this is the practical takeaway: proximity to Oakland is a poor guide to which zone applies, and the ZIP code is the only reliable one.

City and unincorporated permitting

A project inside a city's limits is permitted by that city. A project on unincorporated land is permitted by the county instead, and the two can run different submittal processes even where the energy requirements are identical. The California Energy Code itself is statewide — what changes locally is the climate zone the site falls in and how the jurisdiction wants the compliance documents presented.

Because the county contains more than one zone, the requirements are confirmed from the project ZIP code rather than from the county name.

Climate zones in Contra Costa County

Contra Costa County contains California climate zones 3 and 12. The zone drives the insulation, glazing and equipment performance a report has to demonstrate, and it is confirmed from the project ZIP code against the Energy Commission's published table.