Attic insulation, measured before it's quoted

What attic work usually involves

A Bay Area attic rarely needs just "more insulation". Usually something else is going on up there too, and the order of the work matters as much as the material. In roughly this sequence:

• Clear out what shouldn't be there. Old fill that has packed down, gotten wet or filled up with droppings comes out first, and the attic gets cleaned. See insulation removal and attic cleaning.
• Close the doors. Gaps at the eaves, loose vent screens and holes around pipes are how rats and mice get in. Rodent proofing closes them with metal mesh and sealant.
• Seal the leaks. Top plates, wire holes, recessed lights and the hatch get air sealed before anything new covers them, because nobody will see them again.
• Insulate. Blown-in fiberglass or cellulose goes in to the depth written on the quote. Batts fit the spots where loose fill won't stay put.
• Let it breathe. Baffles at the eaves keep the soffit vents clear, and attic ventilation balances the air coming in with the air going out.

Not every attic needs every step. A clean attic with thin insulation may only need sealing and a top-up. One that has hosted a family of roof rats needs the full list.

What the energy code adds to the job

Under California's 2025 Energy Code (Title 24, Part 6), adding or replacing attic insulation makes the ceiling an "altered ceiling", and attics already at R-38 or more are exempt from its upgrades. The zone-by-zone rules, and which zone each of our 30 cities sits in, are on our Title 24 attic insulation page; the inspection is where we work out which of them apply to your attic.

What it costs

The numbers on this site are Bay Area market ranges, not Attic WISE prices: ranges that Bay Area contractors and cost guides published, collected in October 2026, with every source listed on the cost page. Blown-in attic insulation runs about $1.20 to $4.50 per square foot installed. Taking old insulation out first adds roughly $1.00 to $3.00 per square foot.

What moves a price: the size of the attic, how hard it is to get around in, how deep the new insulation goes, and whether old material, droppings or leaks have to be dealt with first. The estimator turns your answers into a range in a minute. The written quote after the inspection sets the actual price.

Droppings, vermiculite and old wiring

Some things in an attic call for caution before anyone starts working.

• Rodent droppings. The California Department of Public Health says not to sweep or vacuum them; are rodent droppings dangerous? has its guidance, quoted with the source.
• Vermiculite. The EPA advises assuming it contains asbestos and not disturbing it, so we refer you to an asbestos consultant first. More in our vermiculite guide.
• Knob-and-tube wiring. Insulation can go over it only under strict conditions, starting with an electrician's survey; the knob-and-tube guide has the details.

Start from what you're noticing

Most people don't arrive here wanting "insulation". They arrive with a symptom, and the attic is often where it starts.

• Bedrooms that bake on summer afternoons, mostly an inland story in San Jose, the Tri-Valley and Walnut Creek: see why the upstairs is too hot.
• Scratching overhead at night, more often a roof rat than a ghost: see rats in the attic.
• A house that never warms up on a gray fog-belt winter day: see a cold, drafty house.
• Not sure what's up there at all? A flashlight and a ruler from the hatch tell you a lot: see how to check your attic insulation, or let us look at the free attic inspection.

Who does the work

Attic WISE is a new company based in Redwood City, and the work is done by our own crews. Nobody likes going up into the attic. That's what we're for. More on who we are and how a job runs.