Ductwork replacement cost

Replacing ductwork costs $10 to $35 per linear foot, and a typical house carries 150 to 350 feet of it. That puts a whole-house replacement at $3,500 to $12,000, with most jobs landing near $5,800.

Ducts are the part of a heating and cooling system nobody looks at and everybody pays for. A leaky duct system in an unconditioned attic can lose a quarter of the air the equipment moves before it reaches a room, which means you have bought capacity you never receive.

Cost by material

Most modern residential systems use rigid metal trunks with flexible branch runs, which balances cost against durability. Flex duct is not the problem people think it is when it is installed properly: supported every four feet, pulled tight, and not bent past its radius. Badly installed flex duct, sagging and kinked, is a real problem and extremely common.

Whole-house cost by house size

Access drives the labor more than the footage does. A single-story house with a walkable attic is straightforward. A two-story house where runs are buried in finished ceilings and walls can double the price, because getting to the duct means opening and repairing drywall.

Repair, seal or replace

Full replacement is rarely the first answer. In order of cost:

Sealing. Mastic on the joints of an otherwise sound system costs $500 to $2,000 and often recovers most of the lost airflow. This is the highest return per dollar in the entire trade. Aerosol sealing from inside the ducts, sold under various brand names, costs $1,500 to $4,000 and reaches joints nobody can get to.

Insulating. Uninsulated or poorly insulated ducts in an attic or crawl space lose heat before the air arrives. Adding insulation costs $2 to $6 per linear foot.

Partial replacement. Replacing the runs that are crushed, disconnected or undersized while leaving sound ones. Common and sensible.

Full replacement. Justified when the system is asbestos-wrapped, has been water damaged, has mold through it, or was so badly designed that sealing a fundamentally wrong layout is throwing money away.

Signs your ducts are the problem

• Rooms at the end of a run that never reach temperature
• A large temperature difference between floors that balancing does not fix
• Dust that reappears within days of cleaning
• Visible sagging, disconnected or crushed flex duct in the attic or crawl space
• Utility bills out of line with neighbors in similar houses
• Whistling or roaring at registers, which usually means undersized returns

That last one is worth its own paragraph. Return air is undersized far more often than supply air, because it is invisible and cheaper to skimp on. A system that cannot get air back to the furnace runs at high static pressure, which is hard on the blower, noisy, and reduces capacity everywhere.

What a good quote includes

A duct quote should say what the design airflow is and how it was calculated, not just what will be replaced. Manual D is the industry method for sizing duct runs, as Manual J is for sizing equipment. Very few residential quotes include it, and that is precisely why so many duct systems underperform.

It should also state whether the work will be pressure tested afterwards. A duct leakage test costs $150 to $400 and is the only way to know whether you got what you paid for. Some jurisdictions require it on new duct systems.

Frequently asked questions

Is duct cleaning worth the money?

Usually not for air quality. Studies have not found consistent health benefits in ordinary houses, and aggressive cleaning can damage flex duct and dislodge fiberglass. It is worth doing after construction work, after a rodent infestation, or if there is visible mold. Duct cleaning is not a substitute for sealing.

Can I replace ductwork without replacing the equipment?

Yes, and it is often the better order. New ducts on old equipment improve comfort immediately. New equipment on bad ducts disappoints people constantly.

How long does ductwork last?

Sheet metal can last the life of the house. Flex duct is typically 15 to 25 years before the inner liner degrades. Duct board fails early if it ever gets wet.

Should the ducts be inside the conditioned space?

Ideally yes. Ducts in an unconditioned attic lose energy to a space that reaches 130°F in summer. Moving them inside is expensive in an existing house, but sealing and insulating them well recovers most of the benefit.

Will bigger ducts make the system quieter?

Often, yes. Noise at registers is usually a symptom of air moving too fast through passages that are too small. Correctly sized ducts and adequate return air are the cure, not closing vents, which makes the pressure problem worse.