Duct Sealing Cost Calculator
Duct Sealing costs $1,100 to $1,650 for a typical 1,800 sq ft job in 2026, against a national benchmark of $1,350. Labor runs 7 crew hours at $42.44 an hour. Enter a ZIP code to apply that area's measured wages for this work and its regional price level.
Get in touch with a duct sealing contractor
Talk to a duct sealing contractor serving your area. Give them a call or request an estimate, and connect with a local firm that fits your project.
We are still adding duct sealing contractors. Call the number below to talk to a contractor about your project.
Call (800) 152-1235Listings are supplied by the contractors themselves. We check a license number where one is given, which is not an endorsement of the work. Always confirm the license and insurance directly before signing anything.
What makes up the price
Cost by size
National averages, before any local adjustment. Computed from the same model as the calculator above, so the two always agree.
| Home size | Sq ft of conditioned area | Typical | Range |
|---|---|---|---|
| 1,000 sq ft | 1,000 | $1,000 | $825 to $1,225 |
| 1,400 sq ft | 1,400 | $1,175 | $950 to $1,450 |
| 1,800 sq ft | 1,800 | $1,350 | $1,100 to $1,650 |
| 2,400 sq ft | 2,400 | $1,600 | $1,325 to $1,975 |
| 3,100 sq ft | 3,100 | $1,900 | $1,575 to $2,375 |
The cheapest real improvement most houses can buy
A typical American duct system leaks 10 to 30% of the air it carries. Where the ducts run through an attic or a crawl space, that air is lost outdoors altogether — you are paying to cool the attic and to pull unconditioned air in through every gap in the house to replace it.
Against that, the arithmetic is unusually favorable:
| 1,800 sq ft house | |
|---|---|
| Mastic by hand, tested | $1,350 |
| Aerosol sealing, tested | $2,700 |
| Mastic, no test | $1,175 |
| Mastic, tight crawl or attic | $1,600 |
Recovering a fifth of a system's airflow for $1,350 does more for comfort and running cost than the step from a 14.3 to a 15.2 SEER2 condenser, which costs more than twice as much. It is the first thing to do in a house where the rooms are uneven and the bills are high, and it is the right thing to do before buying new equipment, so the new system can be sized against a house that is not leaking.
Insist on the test
The most important thing on this page, and it is the card worth paying 15% for.
A duct blaster pressurizes the duct system and measures how much air escapes, expressed as a percentage of the system's airflow. A reading before and after turns "we sealed it all up" into a number. Good practice for a retrofit is to get total leakage under about 6%, and a bad system commonly starts north of 25%.
Without a test, you have bought an afternoon of somebody's time and have no way to know what it achieved — and duct sealing is exactly the kind of work where that matters, because none of it is visible when the panels go back.
The aerosol process produces a live readout as it runs, showing leakage falling in real time. That is one of the honest arguments for paying more for it.
Mastic or aerosol: a question of reach
Not a question of quality. Both seal well; they reach different leaks.
| Mastic by hand | Aerosol | |
|---|---|---|
| 1,800 sq ft, tested | $1,350 | $2,700 |
| Seals | Every joint somebody can touch | Gaps anywhere in the system, from inside |
| Reaches buried duct | No | Yes |
| Measurement | Separate duct blaster test | Live readout as it runs |
| Availability | Any HVAC contractor | Licensed dealers only |
If your ducts are in a basement or an open crawl space, start with mastic. Most of the leakage in such a house is at the plenum, the trunk joints and the takeoffs, and every bit of that is reachable by hand. Paying double to seal from the inside buys very little.
If the ducts disappear into walls, floors or finished ceilings, the aerosol process is what the extra money buys, because nobody can touch those joints at all.
Where the leaks actually are
Worth knowing, because it tells you whether a quote is addressing the problem:
- The plenum and the equipment connections. The biggest single leak in most systems is where the duct meets the air handler, and it is also the easiest to reach.
- Returns built out of building cavities. This is the one nobody mentions. Many houses use a wall cavity or a floor joist bay as a return — a "panned" return, with sheet metal nailed across joists — and that assembly pulls air out of the wall, the crawl space or the attic. It can be the largest leak in the house by a wide margin, and sealing it properly sometimes means lining it or replacing it with actual duct.
- Boots at the register, where the duct meets the drywall or the floor. The gap around a boot leaks conditioned air into the ceiling or the floor cavity continuously, and it is sealed with mastic or foam from above.
- Takeoffs and branch collars, especially on flex, where a single drawband was used where two were needed.
- The filter slot. Often a wide open gap pulling attic or basement air straight into the supply side — and it should be gasketed, not taped shut.
If a quote talks only about "sealing the joints" and the house has panned returns, it has missed the main event.
What sealing does not fix
Honest limits:
- Undersized ducts. Sealing a system that is too small to carry the air makes it marginally better and leaves it undersized.
- Missing insulation. A sealed but uninsulated duct in a 130°F attic still delivers warm air. Sealing and R-8 wrap go together, and if the attic duct is bare the wrap is the bigger win.
- A bad design. A house with one central return and no path from the bedrooms is a design problem, and sealing does nothing about it. See ductwork installation for what that costs to put right.
- Dirty ducts. Sealing is not cleaning; they are different jobs with different purposes, and the second one is far more often sold than needed.
Doing some of it yourself
If the ducts are in a basement or an accessible crawl space, this is one of the few jobs on this site where an afternoon of your own work captures a real share of the value.
What you need: a tub of duct mastic ($20 to $30), a cheap brush, fiberglass mesh tape, and a headlamp. Total under $40.
Where to put it: every joint you can reach, starting at the air handler and working outwards. The plenum seams, the takeoff collars, the joints between trunk sections, and around any boot you can get to from below.
Two rules: do not use duct tape, which dries out and peels within a few years — the name is a historical accident. And do not seal the filter slot shut; it should be gasketed so the filter can still be changed.
What you cannot do yourself: reach the buried joints, and measure the result. If the house has panned returns or duct in the walls, a professional with instruments is buying you something you cannot get with a brush.
Rebates
Duct sealing is one of the most commonly rebated measures there is, because utilities like it for the same reason this page does: it is cheap and it works.
- Utility rebates frequently cover a substantial share, sometimes conditional on a before-and-after test — which is another reason to insist on one.
- Home energy audit programs in many states include duct testing free or at low cost, and the audit report is a useful second opinion on whether sealing is the right priority.
- Ask your utility before booking, and ask the contractor which programs they are certified for, since many rebates require a participating contractor.
What you are paying for
An 1,800 square foot house sealed by hand with mastic, tested before and after, at $1,350:
| Labor, about 7 hours | around $414 |
| Mastic, mesh tape and fasteners | $270 |
| The visit and the setup | $180 |
| Before-and-after testing | +15% on the work above |
| Overhead and margin | the balance |
Note the shape of that: the material is cheap and the labor is the job, which is the opposite of most of this site. What you are buying is somebody finding the leaks, which is the skill, and then reaching them, which is the unpleasant part.
Questions worth asking
- Will you test the leakage before and after, and give me both numbers?
- What leakage figure are you aiming for?
- Does this house have panned or cavity returns?
- Are the register boots being sealed to the drywall?
- What about the filter slot?
- Mastic or aerosol here, and why?
- Is the attic duct insulated to R-8, and should that be done at the same time?
- Which utility rebates apply, and are you a participating contractor?
- Should this happen before the equipment is replaced?
- Which joints can I not reach myself?
Common questions
How much does duct sealing cost?
About $1,350 for an 1,800 square foot house sealed by hand with mastic and tested before and after, or $1,175 without the test. The aerosol process is $2,700 tested. A 1,200 square foot house is $1,075 by hand and a 3,000 square foot house $1,875, with aerosol at $2,050 and $4,000 respectively. A tight crawl space or attic adds about 20%.
Is duct sealing worth it?
In most houses it is the cheapest real efficiency improvement available. A typical duct system leaks 10 to 30% of the air it carries, and where the ducts run through an attic or crawl space that air is lost outdoors entirely. Recovering a fifth of a system's airflow for $1,350 does more for comfort and running cost than stepping up a SEER2 tier, which costs more than twice as much — and it should be done before new equipment, so the system can be sized against a house that is not leaking.
Should duct sealing be tested?
Yes, and it is the thing to insist on. A duct blaster pressurizes the system and measures leakage as a percentage of airflow, so a before-and-after pair turns "we sealed it up" into a number — good practice for a retrofit is under about 6%, where a bad system often starts above 25%. Without a test you have bought an afternoon of somebody's time with no way to know what it achieved, and none of this work is visible once the panels go back.
What is the difference between mastic and aerosol duct sealing?
Reach, not quality. Mastic by hand seals every joint a technician can physically touch, which in a basement or open crawl space covers the plenum, the trunk joints and the takeoffs — where most leakage usually is. The aerosol process masks the registers, pressurizes the system and injects an atomized sealant that collects at gaps from the inside, which is the only way to reach a joint buried in a wall or above a finished ceiling. Accessible ducts: mastic. Buried ducts: aerosol.
Where do ducts leak the most?
The plenum and the connections at the air handler are the biggest single leak in most systems, and the easiest to reach. After that: returns built out of building cavities — a wall or a joist bay used as a return, which pulls air from the wall, the crawl space or the attic and can be the largest leak in the house; the gap where a boot meets the drywall at each register; branch takeoffs where one drawband was used instead of two; and the filter slot, which is often wide open.
What is a panned return and why does it matter?
A return built from the building structure rather than from duct — typically sheet metal nailed across floor joists, or a stud cavity used as a chase. It is extremely common in older American houses and it is often the single largest leak in the building, because it pulls air directly out of a crawl space, a wall or an attic. Sealing it properly can mean lining the cavity or replacing it with actual duct, and a quote that talks only about joints has missed it.
Can I seal my own ducts?
If they are in a basement or an accessible crawl space, yes — and it is one of the few jobs here where an afternoon of your own work captures real value. You need duct mastic at $20 to $30, a brush, fiberglass mesh tape and a headlamp. Seal every joint you can reach, starting at the air handler. Two rules: no duct tape, which dries and peels within a few years, and do not seal the filter slot shut — it should be gasketed so the filter can still be changed.
Why not use duct tape on ducts?
Because it fails, and the name is a historical accident. The adhesive dries out in the temperature swings a duct sees and the tape peels within a few years, which is why taped joints in attics are routinely found hanging open. Mastic — a thick paste brushed on, with mesh tape in wider gaps — stays flexible and lasts. UL 181 foil tape is acceptable on metal-to-metal joints and is a different product from the hardware-store roll.
What does duct sealing not fix?
Undersized ducts, which stay undersized once sealed. Missing insulation — a sealed but bare duct in a 130°F attic still delivers warm air, so sealing and R-8 wrap belong together. A bad design, such as one central return with no path from the bedrooms, which is a ductwork problem rather than a sealing one. And it is not duct cleaning: different job, different purpose, and far more often sold than needed.
Should I seal ducts before or after replacing my HVAC system?
Before, for two reasons. A sealed house has a lower load, so the new equipment can be sized correctly rather than sized for the leaks — and oversizing is the commonest cause of a system that short-cycles and never dehumidifies. And if the ducts are in an attic that is also getting insulation, seal before the duct gets buried under blown fiberglass, because afterwards it is a far worse job.
Are there rebates for duct sealing?
Very often, because utilities like it for the same reason this page does: it is cheap and it works. Rebates frequently cover a substantial share and are sometimes conditional on a before-and-after test, which is another reason to insist on one. Many state home energy audit programs include duct testing free or cheaply. Ask your utility before booking and ask the contractor which programs they are certified for, since several rebates require a participating contractor.
How long does duct sealing take?
About seven hours for a hand-sealed 1,800 square foot house, including the leak survey and the testing, so most of a working day. The aerosol process is around nine and a half hours because of the masking and the equipment setup, and it is usually a single visit as well. Most of the time on either method goes into finding and reaching the leaks rather than applying the sealant.
Where these numbers come from
Nothing here is copied from a contractor directory. Labor is priced from what the trades are actually paid, materials from published producer prices, and both are adjusted to your area using federal cost-of-living data.
- Plumbing, heating and air-conditioning contractors, United States: $42.44/hour, August 2026 (BLS CES CES2023822003)
- Mastic, mesh tape and fasteners: $0.15 per sq ft of conditioned area (price recorded October 2026, not index-adjusted)