Air Duct Repair in San Jose, CA

The back bedroom gets no air and the attic feels conditioned

That is usually a disconnected boot. The flex pulled off the ceiling register collar. Mastic dried, the strap slipped, and supply air now feeds the attic. Many San Jose homes from the 1950s and 60s still carry original galvanized trunk and branch, with flex spliced on later. Those transitions fail first. We pull the register and look up with a light before quoting anything.

Crushed flex is the other common cause. Attic storage boxes sit right on the run. A kink at a tight turn halves the opening. The gray and black flex from the 1970s through the 90s has baked brittle up there, and the inner liner tears when you move it. That is replacement, not tape. When several runs are that far gone, patching each one wastes labor.

Returns matter just as much. Older homes used panned joist returns. Unsealed, the plenum drags in attic air, pulling insulation fiber and rodent droppings along with remodel drywall dust. Undersized slots with 1-inch filters bypass at the edges, so registers keep graying even after a cleaning.

Mold is uncommon in attic duct here; the air is too dry. Crawlspace runs under Willow Glen and Naglee Park-era houses are different, and so are coil and drain pan areas. Smell it at the register, not the thermostat.