Title 24 Reports in San Bernardino County
San Bernardino County is the largest county in the United States by area, and it contains four climate zones — valley, mountain, high desert and low desert.
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Four zones across an enormous county
The southwestern corner, where almost all the population is, sits in an inland-valley zone: Ontario, Rancho Cucamonga, Upland, Fontana, Rialto, Colton and the City of San Bernardino. It is the same zone as western Riverside County next door.
North of that the San Bernardino Mountains rise steeply into the mountain zone. Beyond them the Mojave opens out into a high-desert zone covering Victorville, Hesperia, Apple Valley, Barstow and Yucca Valley. Further east and lower, toward the Colorado River, the county reaches a low-desert zone.
Why the size matters here
Because most of the county's area holds very little of its construction. The great majority of projects are in that southwestern corner, in one zone, and the practical question for most applicants is simply whether their site is below or above the mountain line. For the minority working in the desert, the requirements are substantially different, and assuming valley figures would be a serious error.
Elevation, not distance, is what moves a site between zones in this county.
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 San Bernardino County
San Bernardino County contains California climate zones 10, 14, 15 and 16. 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.