Title 24 Reports in Alameda County
Alameda County holds two climate zones, and the divide is the Oakland-Berkeley hills. The bay side and the Tri-Valley behind it are assessed against different requirements.
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The ridge splits the county
Everything on the bay side sits in the milder coastal-influenced zone: Oakland, Berkeley, Alameda, Emeryville, Piedmont, San Leandro, Castro Valley, Hayward, Union City, Newark and Fremont. Behind the hills, the Tri-Valley — Dublin, Pleasanton, Livermore and Sunol — sits in an inland valley zone instead.
The transition is abrupt because the hills are abrupt. The two portals of the Caldecott Tunnel are in different climate zones, which is about as compact a demonstration of the boundary as the state offers.
Why "Alameda County" is not an answer
Because a builder working both sides is working in two sets of numbers. A design that complies in Livermore has nothing in common with one that complies in Oakland beyond the code it cites, and calculations cannot be moved between them.
Within Oakland itself, by contrast, elevation changes nothing — the hill neighbourhoods carry the same zone as the flatlands, all the way up to the ridge. It is crossing the ridge, not climbing it, that changes the requirement.
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 Alameda County
Alameda 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.