How Much Does Ductwork Repair or Replacement Cost?

How much does ductwork repair cost?

A typical duct repair costs $200 to $700, and most homeowners pay around $450 for a pro visit that fixes one or two problems. Reconnecting a duct that has fallen off its boot or trunk line runs about $150 to $400. Replacing a damaged section of flex duct costs $150 to $650 depending on length and access. Swapping a crushed or rusted boot (the fitting behind each register) runs $100 to $300 per boot. Patching holes and resealing joints with mastic is usually billed hourly at $75 to $150 per hour.

Access drives the price more than the part does. A duct lying in plain sight in a basement is quick work. The same repair in a 100-degree attic, an 18-inch crawl space, or behind finished drywall takes longer and costs more, and anything that requires opening a ceiling adds drywall repair on top. If a single room stopped cooling and the rest of the house is fine, a broken or disconnected branch duct is a prime suspect; work through why your AC is not cooling to rule out the cheap stuff first.

How much does it cost to replace ductwork?

Full duct replacement costs $25 to $55 per linear foot installed, which works out to $2,400 to $6,600 for most single-family homes with 100 to 150 feet of duct runs. The national average lands near $4,000. Flex duct is the cheaper material; rigid sheet metal costs more per foot but lasts longer and flows air better. Add $300 to $600 per vent if the new layout adds supply runs, and more if the plenum or return trunk needs rebuilding.

Difficult access changes the math fast. Ducts buried in finished walls and ceilings, multi-story layouts, or a crawl space too tight to work in can push a replacement past $10,000. If your ducts are that far gone and the AC is also old, price the whole project together; see how much a new AC costs. In some houses the honest answer is to skip ducts entirely and go ductless, which is the comparison covered in mini split vs central air.

How do you know if your ducts need repair or replacement?

The classic signs of failing ductwork are rooms that never match the thermostat, weak airflow at some registers, rising energy bills, whistling or rattling when the blower runs, and dust that comes back days after cleaning. One starved room usually means a local problem: a disconnected, kinked, or crushed branch run. Whole-house symptoms (every room weak, bills climbing year over year) point to systemic leakage or undersized trunk lines.

Age decides repair versus replace. Sheet metal ducts last 20 to 25 years; flex duct is closer to 15 to 20 before the inner liner and insulation degrade. If your ducts are past that age, sections are rusted or rotted, the insulation is falling off, or there is mold inside the runs, patching one leak at a time is throwing money at a dying system. A duct system under 15 years old with a few specific failures is almost always worth repairing instead.

Is sealing leaky ducts cheaper than replacing them?

Yes, by a wide margin, and it is the right call when the ducts are structurally sound but leaky. ENERGY STAR estimates the typical home loses 20% to 30% of the air moving through its duct system to leaks, holes, and bad connections. Professional hand-sealing with mastic and metal-backed tape runs $1,000 to $2,500 for a whole house. Aerosol-based sealing (Aeroseal is the common brand), which blows sealant particles through the system to plug leaks from the inside, typically costs $1,500 to $3,000.

Sealing accessible joints yourself costs almost nothing: a tub of duct mastic and a roll of UL-181 foil tape run under $50 combined. Skip the cloth-backed gray duct tape entirely; it dries out and falls off ducts within a few years. Sealing pays off fastest in homes where ducts run through unconditioned attics or crawl spaces, because every leaked cubic foot of cooled air is fully wasted there. Sealed and insulated ducts also let a correctly sized system do its job; if you are replacing equipment anyway, size it with the BTU calculator rather than upsizing to overpower leaky ducts.

Can you repair ductwork yourself?

Some of it. Sealing exposed joints with mastic, re-strapping a sagging flex run so it does not kink, reattaching a duct that slipped off its boot with a proper clamp and tape, and adding insulation around accessible runs are all reasonable owner jobs. The materials are cheap, nothing is pressurized or electrified, and a careful afternoon of sealing in the attic genuinely cuts bills. Work in the morning before attic heat builds, watch your footing on the joists, and wear a mask around fiberglass.

Full replacement is a different animal. Duct systems are engineered: trunk and branch sizes come from a Manual D calculation matched to the equipment's airflow, and a layout that just copies the old ducts often copies the old problems. Undersized returns and long, kinked flex runs are the two most common reasons a brand-new system underperforms. Replacement also means working with sharp sheet metal in tight spaces, and in older homes it can disturb asbestos-wrapped runs that legally require abatement. Hire it out, and put the savings into sealing and insulating what the pros install.

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