Duct Sealing in San Juan Capistrano, CA

Duct sealing in San Juan Capistrano homes

One bedroom never cools. The hallway vent blasts, the end-of-run room barely breathes. Usually that is not the condenser. Air leaves the duct before it reaches the register, or attic air gets pulled in where it should not. Dust on the register face is another tell. So is a filter that loads fast while the coil still turns gray.

Most leakage here sits at three places. Boots where duct tape was used instead of mastic. The adhesive dries and the cloth curls off the collar. Crushed radius elbows where flex was bent tight against a truss. Platform returns framed out of joist bays, never sealed, drawing attic air straight into the system. On pre-1975 houses with rigid trunks, the fiberglass duct board plenum is often the real problem. Aging binder sheds fiber into the airstream.

Sealing means mastic and mesh tape at collars, boots and plenum seams, flex re-supported so it stops sagging and pooling dust at low points, and filter grille sizing corrected so air stops bypassing the filter edges.

Sealing will not fix a duct that is undersized or already full of debris. Those get cleaned or replaced first, before anyone paints mastic over them.