Attic Insulation & Air Sealing in Oakland, CA

Attic insulation and air sealing usually give the best return in an older East Bay house. Houses from the 1920s and earlier often have a few inches of old insulation in the attic, or none, and plenty of gaps in the ceiling: around chimneys, along balloon-framed wall tops, at light fixtures and plumbing vents, and at the hatch. Warm air leaks out through those gaps in cool weather, and attic heat pushes down on hot afternoons.

How much is enough

OpenEI lists Alameda County in climate zone 3C. ENERGY STAR recommends R-49 for an uninsulated zone 3 attic and adding R-38 where three to four inches already exist. In loose fill, that is roughly a foot or more: HomeGuide lists blown fiberglass at R-2.2 to R-2.9 per inch and cellulose at R-3.1 to R-3.8.

The gaps we seal

Top plates of interior walls. Open wall cavities in balloon-framed houses, which can run all the way down to the crawl space. Chimney chases, closed with metal and fire-rated sealant. Plumbing vents and wiring holes. Recessed lights and ceiling boxes. Bath fans that vent into the attic. And the attic hatch.

Old wiring and vermiculite

Knob-and-tube wiring must not be buried in insulation while it is live. If we find it, an electrician needs to check or replace it first. If we find vermiculite, which can contain asbestos, we stop and recommend testing. Both are common enough in older houses that we look for them on every visit.

Hillside and Lamorinda homes

Houses in the hills and in inland valleys like Lafayette and Orinda see hotter afternoons and colder nights than the flatlands. A sealed, deep attic matters more there, and we pay attention to ventilation so the attic stays dry.

Rodents

Attic insulation that has been used by rats or mice should come out before new insulation goes in. See our removal page.

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