Attic insulation in San Francisco

San Francisco's housing is the oldest of any city we serve, by a wide margin. That, the fog, and a time-of-sale ordinance that names attic insulation make the city its own case. Below: what the code asks, what DBI says about permits, what RECO means if you're selling, and what we look for in an old attic before adding anything.

Nearly half the city predates 1940

The Census Bureau's 2019–2023 estimates put about 45% of San Francisco's housing units in buildings from 1939 or earlier. The 1940s add another 9%. Nowhere else on our list comes close. California's first residential energy standards date from 1978, so most of these buildings went up long before anyone required insulation, and many got their first attic insulation decades later, if at all.

Not every San Francisco building has an attic. Flats and row houses can have a shallow space under a low-slope roof, reachable only through a small hatch or a roof access, and some top-floor ceilings sit directly under the roof deck. At the inspection we look for a cavity we can work in and say plainly when there isn't one; insulating from above during a reroof is a roofer's job.

What old attics hide

Age changes the inspection more than the insulation. Before anything new goes in, we look for:

• knob-and-tube wiring, common in pre-war buildings, which shouldn't be buried in insulation without an electrician's assessment; we refer that out (knob-and-tube guide);
• vermiculite, a pebbly loose-fill that may contain asbestos; we don't disturb it and refer you to an asbestos consultant (vermiculite guide);
• droppings, nesting and debris, which come out before new insulation goes in (attic cleaning);
• fans venting into the attic instead of outdoors, which matters in a damp climate; we route bath and kitchen fan ducts out through the roof or a wall.

Noise is a San Francisco concern too. If street or neighbor noise is the problem more than cold, soundproofing is a separate conversation.

Climate zone 3 in the fog

San Francisco is in Title 24 climate zone 3. Cool, foggy summers mean the attic's main job is keeping heat in, much of the year. For an altered attic ceiling, the 2025 Energy Code splits on what's there now:

• less than R-19: R-49, recessed-can covers, attic ventilation;
• R-19 or more: attic ventilation only.

Zone 3's row in that table has no air-sealing requirement, but in a drafty old building, sealing the ceiling's gaps is often the most useful part of the job. The Title 24 page has the exceptions.

What DBI says about permits

DBI's page on whether a construction project needs a permit lists the work that doesn't. One item is reroofing without the installation, repair or removal of roof material, if no more than 25% of the roof's surface is reroofed in any 12-month period. The rest of the list covers finish work, small sheds and fences, and similar minor items, with the complete version in Section 106A.2 of the San Francisco Building Code. Insulation isn't mentioned.

DBI's reroofing page adds that you need a permit before installing, repairing or removing roofing material, and that online reroofing permits are only for work that needs no plans and doesn't replace structural parts such as framing or decking. Bigger jobs go over the counter.

For insulation, then, there's no stated rule on the city's page. Ask at a DBI permit counter about your scope. The written quote says who handles the permit, and that's decided before work starts.

RECO: if you're selling

San Francisco's Residential Energy Conservation Ordinance ties energy work to a sale. The city's environment department says owners preparing to sell must obtain an inspection, install basic energy and water conservation devices or materials, and then obtain a certificate of compliance. "Insulating attic space" is one of the energy measures it lists, alongside weather stripping, water heater insulation and duct insulation. DBI publishes a list of RECO inspectors. The environment department's page carries no date, so confirm the current rules with DBI before you list. If the inspection points at the attic, our written quote gives the R-value and depth an inspector will look for.

CleanPowerSF, PG&E and rebates

CleanPowerSF is a not-for-profit program of the San Francisco Public Utilities Commission. Customers are enrolled automatically and can opt out; PG&E still delivers the power, sends the bill and supplies gas. CleanPowerSF's Electrify Your Home credits cover heat pump water heaters, heat pump heating, electric cooking and dryers, not insulation. The rebates page tracks it.

Wildfire maps

On the state's 2025 Local Responsibility Area maps, almost all of San Francisco is mapped as non-wildland. The State Fire Marshal's viewer confirms any address.

Scheduling an inspection

We drive up from Redwood City for a free inspection, or estimate from photos or video. You get a photo report, then a written quote with every measure, R-value and depth listed. Nothing is installed before you sign, and you have 5 business days to cancel. Bay Area market ranges are on the cost page.