Attic insulation in Berkeley

Berkeley has written down more about attic insulation than any other city on our list. Its building department has a form for attics with old wiring, its energy office lists attic insulation as a credit toward a point-of-sale ordinance, and its municipal code even says what insulation may contain. That paperwork exists because the houses are old: the city's Housing Element says nearly half of Berkeley's homes were built before 1939.

Old houses, old wiring: Form 146

Berkeley's 2023–2031 Housing Element puts the median construction year of the city's housing at 1942, and owner-occupied homes are older still, with a median before 1939. In an attic that old, knob-and-tube wiring is a real possibility, and Berkeley handles it with a specific document: Form #146, the Knob-and-Tube Wiring Safety Report, last revised March 25, 2026.

The form's rule is short: attics with knob-and-tube wiring "may not be insulated" unless an electrical contractor submits a certification letter. The electrician checks one of three findings: the wiring is in good condition; it is not in good condition and can't be covered without repair or rewiring; or it is disconnected or removed. Then:

• copies of the signed form are posted in the attic before inspection, and the original goes to the building inspector at final;
• warning signs in English and Spanish go up at every attic access where the wiring is concealed by insulation;
• under the electrical code section the form quotes, the insulation must be noncombustible and contain no conductive material.

We don't do the electrical survey ourselves. We refer you to an electrician, and the insulation date waits for the signed form. The knob-and-tube guide explains the electrical code exception line by line.

Permits at the Permit Service Center

Berkeley's Form #140, Permit Requirements and Exemptions (revised January 23, 2026), lists work that needs no permit: small sheds, low fences, finish work such as painting and tiling, and a handful of minor electrical and plumbing items. Insulation is not on it. The BESO measure sheet, below, also treats a permit and final inspection as the proof that attic insulation was done. That points one way, but neither document states an insulation-permit rule in so many words, so confirm the permit type for your scope with the Permit Service Center at 510-981-7440. The written quote says who handles it.

One more local rule: Berkeley Municipal Code 11.62.050 bars installing building insulation that contains or uses an ozone-depleting compound, and asks for a written statement saying so with the permit application. It matters most for spray foam, where the blowing agent is the question; we name the product on the quote so its data sheet can be checked.

BESO: attic insulation as a resilience credit

The Building Emissions Saving Ordinance requires 1–2 unit homes to have an energy assessment at the time of listing, and resilience upgrades within 2 years of sale. The city's measure sheet for attic insulation, updated April 21, 2026, lists it as a resilience upgrade worth 2 credits. Its installation criterion is to add insulation across the entire attic surface area, and the verification it asks for is:

• a permit with an approved final inspection, with "for BESO compliance" written in the scope of work on the permit application;
• a contractor invoice describing the insulated areas.

If you are buying or selling, the assessment report is a useful starting point for the inspection. Questions about the ordinance go to BESO@berkeleyca.gov (opens in a new tab).

Zone 3 in practice

Every Berkeley ZIP code sits in climate zone 3. Under Table 9-8 of the 2025 Compliance Manual, an altered attic that starts below R-19 goes to R-49, with recessed cans covered and the ventilation checked; at R-19 or more the row asks for the ventilation check only, and air sealing isn't a zone 3 requirement. Knob-and-tube that stays in the attic is one of the listed exemptions from those upgrades. Note that BESO's "entire attic" criterion is the city's own, separate from the code. The Title 24 page has the full table.

The hills and the 2025 fire map

In 2025 the City Council adopted CAL FIRE's updated Fire Hazard Severity Zones by Ordinance 7,958-N.S. and added to them. Panoramic Hill and the streets around it were designated Very High, citing narrow spacing between houses and a single evacuation route. A High zone was drawn west of the state's Very High area, along boundary streets including Arlington Avenue, Spruce Street, Gayley Road, Warring Street and Claremont Avenue, citing major fires in 1905, 1923, 1970, 1980 and 1991. Sellers in both zones must make a natural hazard disclosure.

If your house is in either zone, the attic vents are where embers get in. Ember-resistant vents are the attic-side fix, and we cut roof openings for them.

Utilities, rebates and our visits

Ava Community Energy supplies Berkeley's electricity by default; PG&E delivers it and supplies the gas. Neither lists an attic insulation rebate open to every customer; see the rebates page. We are based in Redwood City and come to Berkeley for a free inspection, or work from photos you send. The quote lists the R-value, depth and each measure, nothing is installed before you sign, and you have 5 business days to cancel.