I pulled a return duct out of a 1970s ranch last spring and a family of mice had turned it into a condo. The homeowner had been running her AC full blast all summer, wondering why the back bedrooms never dropped below 80. The ducts were crushed, disconnected in the attic, and leaking about a third of the air into the crawlspace.
She thought she needed a new AC. She did not. She needed new ductwork, which nobody had ever mentioned in three separate service calls. That is the part of an HVAC system most people never think about, and it quietly wastes money on every single cycle.
So let me walk you through what ductwork replacement actually costs, when you truly need it, and where contractors love to pad the bill.
What Ductwork Replacement Costs in 2026
For a typical single-family home, full ductwork replacement runs $3,000 to $12,000. Most of my jobs land somewhere around $6,000 to $8,000 for a 1,800 square foot house with a standard layout.
The spread is huge because no two houses run their ducts the same way. A single-story home with an accessible attic is cheap labor. A two-story with finished basements, tight chases, and returns buried in walls is a different animal entirely.
| Home Size | Typical Duct Replacement | What Drives the Price |
|---|---|---|
| Under 1,200 sq ft | $2,500 - $5,000 | Single story, easy attic access |
| 1,200 - 2,000 sq ft | $5,000 - $9,000 | More runs, a few tight spots |
| 2,000 - 3,000 sq ft | $8,000 - $14,000 | Two stories, wall returns, longer trunk lines |
| Over 3,000 sq ft | $12,000 - $20,000+ | Multiple zones, custom fabrication |
Those numbers assume flex duct and sheet metal trunk lines, which is standard for most residential work. Fully rigid metal ductwork costs more, sometimes 30 to 50 percent more, but it lasts longer and seals up cleaner.
What You Are Actually Paying For
Labor is the big line item. Crawling through an attic in July or a nasty crawlspace in the rain is slow, miserable work, and it is most of your bill.
Here is roughly how the money breaks down on an average job:
- Labor: 50 to 60 percent. Two guys, two to four days.
- Materials: 25 to 35 percent. Duct, boots, plenums, mastic, insulation.
- Permits and disposal: 5 to 10 percent. Old duct hauling is not free.
If a quote is way below everyone else, they are either skipping the permit, reusing your old plenum, or planning to leave half the leaks in place. Cheap duct work always costs you twice.
When Your System Actually Needs New Ducts
Not every house with weak airflow needs a full replacement. I turn down duct jobs more often than I sell them, because a lot of problems are just leaks and bad connections that seal for a few hundred bucks.
You genuinely need replacement when you see a few of these together:
- Ducts are 20+ years old and made of that gray flex that crumbles when you touch it.
- Rooms furthest from the unit never heat or cool right, no matter the thermostat setting.
- Visible mold inside the ducts, or a musty smell every time the system kicks on.
- Rodent or water damage, torn insulation, or sections that have collapsed.
- Your energy bills climbed for no clear reason and the AC itself is fine.
If a contractor pushes duct replacement in the same breath as a brand new unit and cannot show you the actual damage in the attic, get a second opinion. Bundling the two is a classic way to inflate a sale.
Repair or Replace: How to Decide
Before you spend five figures, get the ducts tested. A blower door or duct blaster test measures how much air you are actually losing. Anything over 20 percent leakage is a real problem, and honestly most old homes test worse than that.
If the leaks are at joints and connections, sealing with mastic and new tape is cheap and effective. That might run $500 to $2,000 and buy you years. Replacement only makes sense when the duct material itself is failing or the layout was wrong from day one.
This is also the moment to look at whether your ducts are even sized correctly. Undersized returns are one of the most common issues I find, and no amount of new supply duct fixes a system that cannot breathe. Our hvac sizing guide walks through how to check that your ducts and equipment actually match.
Doing Ducts With a New System
The one time full replacement almost always pays off is when you are already replacing the furnace or AC. The crew is in there anyway, the old equipment is out of the way, and matching new ducts to a new unit means the whole system works the way it was engineered to.
If you are pricing out a full changeout, factor ducts into the conversation early. I break down equipment pricing separately in our rundown of new hvac system cost, and ductwork is the piece most homeowners forget to budget for until the quote lands.
Ask your contractor to price the job two ways: equipment only, and equipment plus ducts. Seeing both side by side tells you fast whether the duct work is being fairly priced or quietly buried in the total.
Surprise Line Items That Blow the Budget
Here is where the estimate and the final invoice tend to part ways. None of these are scams, but they catch people off guard.
Asbestos. Older duct tape and insulation can contain it. If we find it, work stops and an abatement crew comes in. That can add $1,500 to $4,000 and it is not optional.
Access. If your ducts run through finished walls or ceilings, we have to open drywall, then you pay to patch and paint. That is a separate trade and it adds up quick.
Code upgrades. Pull a permit and the inspector may require sealed returns, new supports, or better insulation to meet current code. Right thing to do, but it is money you did not plan on.
Keeping the Cost Down Without Getting Burned
The best savings come before the crew ever shows up. Get at least three quotes, and make sure each one lists duct sizing, sealing method, and whether the plenum is included. If you want a checklist for reading estimates line by line, our guide to honest hvac quotes shows exactly what a clean bid should spell out.
Once the new ducts are in, sealing and insulation are where you actually recover money on your bills. Tight, well insulated duct runs can cut a heating and cooling bill by 15 to 20 percent, which is a real chunk. There is more on that in our piece on how to lower hvac bills after the work is done.
Full duct replacement usually runs $3,000 to $12,000, most often around $6,000 to $8,000. Replace when the material is failing, mold or rodents are present, or you are already swapping the unit. Otherwise, test first and seal the leaks.
Getting the Timing Right
If your ducts are limping but not dead, plan the replacement around your next system upgrade. Doing both at once saves a full day of labor and avoids paying a crew to come out twice.
And if a room has been hot or cold for years while everyone blamed the thermostat, get someone in the attic with a flashlight before you spend a dime on new equipment. Half the time the answer is up there.
How long does ductwork replacement take?
Most homes take two to four days for a two-person crew. Bigger or two-story houses with wall runs can push to a full week, especially if drywall has to be opened and patched.
Can I replace just part of my ductwork?
Yes, and sometimes that is the smart move. If only the attic runs are damaged and the trunk line is solid, replacing the bad sections costs far less than a full tear-out. Have it tested first so you are not guessing.
Does new ductwork lower my energy bills?
It can, meaningfully. Sealed, properly sized ducts stop the 20 to 30 percent air loss common in old homes, and that often trims a heating and cooling bill by 15 to 20 percent.
Ductwork is the least glamorous part of any HVAC job and the one that quietly decides whether the rest of your system does its job. Get the ducts tested, fix what is actually broken, and time the big replacement around your next equipment change. Do that, and you will spend your money where it counts instead of heating the attic all summer.
