Air quality, ducts & controls
Ductwork repair and sealing
Leaky, crushed or undersized ductwork is one of the most common reasons a working system still leaves rooms too hot or cold. A contractor measures static pressure and leakage, then seals joints with mastic, repairs or replaces bad runs, and balances airflow.
- Licensed local HVAC contractor
- Diagnosis and price before work
- Same-day appointments when a local contractor has an opening
- Free to call, no obligation
Ducts in attics, crawl spaces and garages lose the most energy when they leak, because they're pulling or pushing air through unconditioned space. Disconnected flex duct in an attic is a frequent, easy-to-miss culprit.
Sealing and repair is different from duct cleaning. Cleaning has its place after renovation dust or pests, but it doesn't fix airflow problems.
Ductwork Repair & Sealing at a glance
- Category
- Air quality, ducts & controls
- Urgent service
- Usually scheduled
- Who does the work
- An independent, licensed HVAC contractor
- Quote
- Given after diagnosis, before work starts
Signs you need ductwork repair & sealing
- One or more rooms never comfortable
- Weak airflow from some vents
- Dusty house even with good filters
- Whistling or rattling ducts
- Crushed or disconnected flex duct in the attic
What the technician does
- 1
Measure
Static pressure and, where available, a duct leakage test show how bad the problem is.
- 2
Inspect
Accessible runs checked for disconnections, crushing, kinks and missing insulation.
- 3
Seal and repair
Joints sealed with mastic or approved tape; damaged runs replaced and supported.
- 4
Balance
Dampers adjusted and airflow rechecked room by room.
What affects the cost
Prices are set by the contractor after diagnosis. These are the factors that move the number most:
- Duct location and access
- Extent of leakage or damage
- Whether runs must be resized or added
- Insulation requirements
Safe to check yourself
- Make sure every supply and return vent is open and unblocked
- Look for obviously disconnected ducts in an accessible basement
Leave to a pro
- Crawling across attic joists near wiring
- Using cloth 'duct tape', which fails on ducts
Ductwork Repair & Sealing FAQ
How much air do leaky ducts waste?
In a typical home, a significant share of the air moving through ducts can be lost to leaks and poor connections, according to ENERGY STAR. Leaks in attics and crawl spaces cost the most.
Is duct cleaning worth it?
Only for specific reasons: renovation dust, pests, visible mold or debris. Routine cleaning isn't shown to improve health or efficiency on its own.
Can ductwork cause high bills?
Yes. Leaky or undersized ducts make the system run longer to deliver the same comfort.
How do I know if my ducts are leaking?
Signs include rooms that never reach temperature, weak airflow at some vents, dusty rooms and high bills. A duct leakage test with a calibrated fan measures it directly.
What is static pressure?
Static pressure is the resistance to airflow in the duct system. High static pressure from undersized ducts or clogged filters makes the blower work harder and reduces comfort.
Is mastic better than tape for sealing ducts?
Mastic or UL-listed foil tape is the right choice. Cloth duct tape fails on ductwork as the adhesive dries out.
Should ducts in the attic be insulated?
Yes. Ducts in unconditioned attics and crawl spaces should be sealed and insulated to avoid losing heating and cooling to outside air.
Can ductwork cause one room to be too hot?
Yes. Undersized, crushed, leaky or poorly balanced ducts are among the most common reasons for uneven temperatures.
Last reviewed . General information, not a diagnosis of your system.
Popular cities for ductwork repair & sealing
Get ductwork repair & sealing from a local pro
One call connects you with an independent, licensed HVAC contractor who serves your ZIP code. It's free to call, and you get a quote before any work starts.
Free · No obligation