Duct Sealing

Despite the name, cloth-backed duct tape fails on ducts. Its adhesive dries out in attic temperatures within a few seasons and the tape peels off. Mastic — a brushable, water-based sealant — bonds to metal and flex-duct connections and stays sealed for the life of the duct system. California code requires mastic (or equivalent) for duct sealing, not tape.

Pre-2000 systems commonly test at 20–30 percent duct leakage to the outside — meaning that fraction of your conditioned air never reaches the rooms. A properly sealed system targets single-digit leakage. The energy and comfort difference is substantial.

Duct work performed as part of an HVAC changeout triggers Title 24 requirements including a duct-leakage test by a third-party HERS rater. Standalone duct sealing on an existing system without equipment replacement generally does not require a permit, but we document the work either way.

Homes with weak airflow at the far registers, large room-to-room temperature differences, or an HVAC system that runs constantly often see the biggest change. Homes that already perform well won't see as much. We assess leakage before quoting the work.