Duct Sealing in Irvine, CA

Why one room never cools, and what sealing actually fixes

The common symptom is a back bedroom that stays warm while the hallway runs cold. Usually the flex branch has pulled partway off its boot collar in the attic. Conditioned air dumps above the ceiling instead of through the register. Sometimes the inner liner is still attached but kinked where it crosses a truss. Either way the register feels weak at the hand.

Sealing starts at the connections, not the middle of the run. Collars get mastic, a screwed strap on the inner core, then the outer jacket pulled back over and banded. Cloth duct tape left by earlier installers is removed, since it dries out in attic heat and lets go. Ductboard plenums need attention at the cut edges and at the air handler cabinet seams. Return drops leak hardest because they are under suction, pulling attic dust and insulation fiber straight into the blower.

Leaky returns are why registers streak gray. Compressed insulation on a cold supply line causes sweating and ceiling stains. In foothill and canyon-adjacent neighborhoods we also find rodent damage to the outer jacket.

Badly torn flex is replaced, not patched. Sealing a crushed or undersized run only moves the complaint elsewhere.