Duct Sealing in San Rafael, CA

Duct sealing in San Rafael homes

One room never warms. The furnace runs long. Crawlspace smells drift up at startup. Usually that is leakage, not capacity. In pre-1940 Marin houses the old gravity system was converted to forced air, and the sheet metal trunk still sits in a vented crawlspace. Joints were wrapped in cloth or asbestos tape. Tape lets go. Boots drop off the subfloor. The register is then heating dirt.

Flex has a different failure. On 1970s-90s tract and condo systems the flex tears right at the takeoff collar. The outer jacket stays inflated, so nothing looks wrong from the attic hatch. Inner core is split. We pull back the insulation and check each collar individually.

Return leaks matter more than supply leaks to most people. A leaky return in a crawlspace pulls in damp air and rodent droppings. Oak and grass pollen drift in each spring. That is the musty foggy-morning odor. Sealing the return path often fixes the smell complaint by itself.

Mastic on cleaned metal, mechanical fastener first. Tape alone on a dusty crawlspace joint will fail again. If a trunk is rodent-contaminated or the flex is crushed flat, sealing is wasted money (replace that run instead). We will say so rather than seal around a problem.