Duct Sealing
Closing the leaks in supply and return ductwork so conditioned air reaches rooms instead of the crawlspace. Leaky ducts can waste a large share of the heating and cooling you pay for, and duct condition is a standard checkpoint before any equipment upgrade.
The longer answer
Duct leaks occur at joints, connections, and aging tape — especially in crawlspaces and attics where temperature swings accelerate material failure. Mastic (brush-on sealant) is the durable fix; duct tape is not (it fails in a few years). A blower-door duct test quantifies leakage before and after sealing.
In mid-century Seattle ramblers with 50-year-old ducts, sealing often reclaims 10–20% of system capacity per ENERGY STAR — capacity that changes the equipment sizing recommendation. Skipping the duct test and installing new equipment on leaky ducts is how systems underperform their rated efficiency from day one.
The Seattle angle
WA code brings duct testing into HVAC replacements — ~15% leakage is the action threshold. Sealing before a heat pump install reclaims capacity the old furnace never delivered.
Guides that use this term
Where this decision happens
Nearby in the glossary
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