California’s 16 building climate zones, explained
The California Energy Commission divides the state into 16 building climate zones based on weather. Every Title 24 energy calculation uses the climate zone of the project’s physical location, which changes requirements such as insulation levels, window performance and how cooling- or heating-heavy the analysis is.
How to find your zone
Use the CEC’s official climate zone lookup by address or ZIP code. ZIP codes can contain more than one zone; local jurisdictions may designate one zone for a whole ZIP code.
Why it matters
A home in Palm Springs (Zone 15) and one in Arcata (Zone 1) face very different conditions. The Energy Code adjusts requirements accordingly.
Browse our climate zone directory for zone-by-zone guidance.
Sources & official references
Related reading
This article is general information, not professional or legal advice. Always confirm requirements with your building department.
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