Title 24 Reports in Butte County

Valley floor and the rise east

Zone 11 covers the valley: Chico, Oroville, Paradise's lower surroundings, Gridley, Biggs and Durham — fourteen of the twenty ZIP codes we derive for the county. Zone 16 covers the higher ground to the east, six ZIP codes in the foothills and mountains.

The county sits on the eastern edge of the Sacramento Valley, so the terrain climbs steadily from west to east. The zone boundary is that climb rather than any single landmark.

Zone 11 is a hot-summer climate

This is the northern Sacramento Valley, and summer here is hot and dry. Cooling drives the calculation, which means glazing area and orientation, duct location and equipment efficiency carry weight. Winter nights get genuinely cold, so the design is not a single-season problem.

The mountain minority

Zone 16 is the coldest assignment in the state, and in this county it applies to a real but modest share of addresses. Because zone 11 covers most of the population, a Butte County project is usually zone 11 — and the exceptions are in the higher communities, where the requirements change substantially.

That asymmetry is the argument for checking rather than assuming. The default is right most of the time here, which is exactly the condition under which an unchecked assumption eventually produces a wrong report.

Example ZIP codes and their zones

Derived from the Energy Commission's ZIP-to-climate-zone table, with county membership taken from the U.S. Census Bureau's 2020 ZCTA-to-county relationship file:

• Climate zone 11 — 95926, 95928, 95965, 95966, 95969 and 9 more
• Climate zone 16 — 95916, 95942, 95954, 95978 and 2 more

ZIP codes that cross the county line

A ZIP code is a postal boundary, not a county boundary, and several here fall on both sides of one. Where that happens we do not treat the county as settling the question:

• 95973 — about 61% within Butte County, the remainder in Tehama 39%
• 95930 — about 85% within Butte County, the remainder in Yuba 15%
• 95941 — about 85% within Butte County, the remainder in Yuba 15%

For an address in one of these, the climate zone still comes from the ZIP code, which is assigned by the Energy Commission regardless of the county line. What the split affects is which jurisdiction issues the permit — worth confirming before a submittal.

Finding the zone for your own project

The zone is set by the project's location and confirmed from the ZIP code against the Energy Commission's published table — not from the county name and not from the nearest large town. Because Butte County contains more than one zone, that check decides which set of numbers a report is written against.

Give us the project address and we determine the zone as part of preparing the report. It is the first thing established, because every insulation, glazing and equipment figure downstream depends on it.

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 is statewide — what changes locally is the climate zone the site falls in and how the jurisdiction wants the compliance documents presented.

Climate zones in Butte County

Butte County contains California climate zones 11 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.