How much does ductwork replacement cost?

Ductwork replacement costs $2,500–$6,500 for partial replacement (1–2 zones) and $5,000–$15,000 for a full-house replacement in a typical 1,500–2,500 sq ft home. Cost per square foot of home is $3–$8 for flexible duct and $5–$12 for sheet metal. Labor accounts for 50–60% of total cost; material access difficulty is the biggest price variable.

When should ductwork be replaced?

Replace ductwork when it is 20–25+ years old (especially flexible duct, which degrades faster than metal), when ducts have visible mold, when asbestos insulation is present on old metal ducts, when the system has major leaks that can't be sealed, or when you're upgrading to a significantly larger HVAC system that requires resizing. Duct sealing alone solves most minor leakage issues — full replacement is for structural failure or contamination.

What is the difference between flexible duct and sheet metal duct?

Flexible ductwork uses a corrugated plastic tube wrapped in insulation. It costs $1–$2 per linear foot installed (less labor) and is ideal for short runs, but bends and sags reduce airflow. Sheet metal (galvanized steel) is rigid, lasts 25+ years, has better airflow efficiency, but costs $3–$6 per linear foot and requires more labor to install and cut. Fiberboard duct is a middle option — low cost but absorbs moisture and can harbor mold. Sheet metal is the gold standard for main trunks; flexible is acceptable for branch runs.

Does old ductwork have asbestos?

Homes built before 1980 may have asbestos insulation on metal ductwork, or asbestos in the duct tape used to seal joints. If you suspect asbestos, do not disturb it — have a certified asbestos inspector test before any duct work begins. Asbestos abatement typically adds $1,500–$5,000+ to a duct replacement project. Any contractor working on pre-1980 ductwork should follow EPA NESHAP regulations.

What is duct sealing vs. duct replacement?

Duct sealing (with mastic or Aeroseal) repairs leaks in existing ductwork for $500–$2,500. It is the right choice when ducts are structurally sound but just leaky. Duct replacement is needed when ducts are physically damaged, collapsed, moldy, asbestos-containing, or so old they can't be sealed effectively. A blower door or duct blaster test can measure leakage and help you decide. Sealing first often eliminates the need for full replacement.

Home / Home Maintenance Calculators / Ductwork Replacement Cost Calculator

🔄 Ductwork Replacement Cost Calculator

Estimate the cost to replace existing ductwork — partial or full house — based on material type, access difficulty, and home size

Who Should Use This

Homeowners with older ductwork (20+ years), mold or asbestos concerns, persistent hot/cold rooms despite HVAC repairs, or those bundling duct replacement with a new furnace and AC installation.

Purpose

Calculate duct replacement cost by material type, extent (partial vs. full house), access difficulty, and add-ons like mastic sealing and insulation — including cost per square foot.

Example

Replacing full-house flexible ductwork in a 1,800 sq ft home with a crawlspace (moderate access) typically costs $6,500–$11,000. Adding mastic sealing and insulation wrap adds $800–$1,500 but extends the new system's lifespan and efficiency.

Ductwork Details

Home Size (sq ft)

New Duct Material

Replacement Extent

Access Difficulty

Condition of Old Ductwork

Add-Ons

Mastic Sealant on All Joints

Professional mastic application for airtight seals (+$400–$800)

Insulation Wrap (R-8)

Wrap ducts in unconditioned spaces — attic, crawlspace (+$600–$1,200)

New supply and return air grilles (+$200–$500)

💡 Pro Tip: Before replacing all ducts, get a duct blaster test ($100–$300). If leakage is under 15%, mastic sealing alone ($500–$2,000) may solve the problem without full replacement. Replacement is justified when ducts are physically collapsed, moldy, asbestos-containing, or so old they cannot be effectively sealed.

Replacement Cost Estimate

Total Replacement Cost

$— – $—

Full house replacement including all selected options

Cost Per Sq Ft of Home

$— – $—

Total project cost divided by home square footage

Cost Breakdown

Duct Materials$—

Labor (Removal + Installation)$—

Old Duct Disposal$—

Asbestos Abatement$—

Mastic Sealant$—

Insulation Wrap$—

How It Works

4 Steps to Your Ductwork Estimate

Enter Home Size

Select your home's square footage to estimate the total linear footage of ductwork needed.

Choose Material & Extent

Select flexible, sheet metal, or fiberboard duct and whether you need partial or full replacement.

Set Access Difficulty

Access difficulty (basement vs. crawlspace vs. finished walls) is the biggest labor cost driver.

Add Options

Include mastic sealing, insulation wrap, and new registers for a complete project budget.

Ductwork Replacement Cost Factors

Access difficulty is the single biggest cost variable in ductwork replacement. Ducts in an open unfinished basement can be replaced for 30–40% less than the same ducts in a finished ceiling or tight attic space, because labor time is the dominant cost.

Material choice matters for longevity. Flexible ductwork is cheaper and faster to install but degrades more quickly — inner liners crack after 20–25 years and bends restrict airflow. Sheet metal is the premium choice: better airflow, 30+ year lifespan, easier to clean, and more resistant to pest damage.

Home size determines linear footage. A 1,500 sq ft single-story home typically needs 100–150 linear feet of trunk and branch ductwork. A 2,500 sq ft two-story home may need 200–280 linear feet.

Replacement vs. Sealing — Making the Call

Not every leaky duct system needs full replacement. A duct blaster test measures total leakage and helps you decide:

Under 15% leakage: Mastic sealing ($500–$2,000) is usually sufficient
15–25% leakage: Aeroseal ($1,500–$3,500) or partial replacement of worst zones
Over 25% leakage or physical damage: Full replacement is the right call
Mold present: Replace affected sections; sealing over mold is not a solution
Asbestos-containing materials: Must be abated before any duct work proceeds

The payback period for duct replacement is typically 8–15 years through reduced energy waste. Leaky ducts in unconditioned spaces (attic, crawlspace) waste 20–30% of heating/cooling energy.

Buyer's Guide

Ductwork Replacement — What to Know

Materials, sealing, access, and energy savings

🌬️

Flexible Duct

Most common in modern homes. Corrugated plastic inner liner wrapped in fiberglass insulation. Cost: $1–$2/linear ft material. Lifespan: 15–25 years. Key weakness: bends and sags restrict airflow. Keep runs short and straight for best performance.

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Sheet Metal Duct

Galvanized steel — the gold standard. Cost: $3–$6/linear ft material. Lifespan: 30+ years. Best airflow efficiency, easier to clean, more pest-resistant. Requires more labor to cut and fit. Best choice for main trunk lines.

🏗️

Access Difficulty Impact

Easy access (open basement): labor cost baseline. Crawlspace: 30–40% labor premium. Finished walls or tight attic: 60–100% labor premium. Some ducts in finished walls require opening drywall — factor in drywall repair costs.

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Asbestos Awareness

Homes built before 1978 may have asbestos wrap on metal ducts or asbestos duct tape. Do NOT disturb without testing. Certified testing: $200–$400. Abatement if needed: $1,500–$5,000+. Always disclose suspected asbestos to contractors.

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Mastic Sealing

Mastic is a brushed-on elastomeric sealant applied to all duct joints. More durable than duct tape (which dries out in 2–5 years). Cost: $400–$800 for a full house application. Should be specified in any duct replacement project for maximum efficiency.

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Insulate Ducts in Unconditioned Spaces

Any duct running through an attic or crawlspace should be wrapped with R-6 to R-8 insulation. Without insulation, conditioned air loses heat/cool to the surroundings. Insulation wrap adds $600–$1,200 but can reduce duct heat loss by 50–70%.

Common Questions

Ductwork Replacement FAQ

Full house ductwork replacement by home size:

Under 1,000 sq ft: $3,000–$7,000
1,000–1,500 sq ft: $4,000–$9,000
1,500–2,000 sq ft: $5,500–$11,000
2,000–2,500 sq ft: $7,000–$13,000
2,500–3,500 sq ft: $9,000–$16,000

Partial replacement (1–2 zones): $2,500–$6,500 for most homes.

Key cost drivers: Sheet metal vs. flexible (+40–60%), access difficulty (+30–100% for finished walls), and asbestos abatement (add $1,500–$5,000).

Duct lifespan by material:

Flexible duct: 15–25 years (inner liner degrades, bends loosen)
Sheet metal: 30–50 years (rusts if moisture present)
Fiberboard: 15–20 years (absorbs moisture, can harbor mold)

Signs ductwork needs replacement (not just sealing):

Visible collapse or kinking in flexible runs
Disconnected or separated sections
Mold growth inside ducts
Physical deterioration of flexible duct inner liner (flaking)
Asbestos-containing materials present
New HVAC system requiring larger duct sizing

Seal first, replace only if necessary. Decision guide:

Seal with mastic ($500–$2,000): Ducts are structurally sound, just leaky at joints; under 15 years old; no mold or contamination
Aeroseal ($1,500–$3,500): Ducts are mostly intact but have hard-to-reach small leaks; up to 30% duct leakage rate
Partial replacement ($2,500–$6,500): 1–2 zones with physically damaged or collapsed ductwork; isolated mold growth
Full replacement ($5,000–$15,000): 20+ year old flexible duct throughout; widespread mold; asbestos; new HVAC requires resizing

Get a duct blaster test first: Costs $100–$300 and gives you data to make the right decision. Many HVAC contractors offer this for free when bidding a full replacement.

DIY duct replacement is possible but not recommended for full projects.

Where DIY is feasible: Replacing one or two flexible duct runs in an easily accessible basement with visible connections. Materials are available at home improvement stores.

Why professional installation matters:

Proper sizing requires Manual D calculations — wrong sizes reduce efficiency
Pressure balancing (supply vs. return) requires HVAC expertise
Most jurisdictions require a permit for full duct replacement
Asbestos risks require certified abatement contractors
HVAC contractors typically warranty labor for 1–2 years

What you can DIY: Sealing accessible joints with mastic yourself is safe, effective, and saves $300–$600. Use UL 181B-rated mastic paste, not standard duct tape.

Yes — leaky ducts are one of the biggest energy wasters in a home.

Typical leaky duct system loses 20–30% of conditioned air before it reaches rooms
In attics and crawlspaces, this means you're conditioning the outdoors
Replacing and sealing ducts can reduce HVAC energy use by 20–25%
A 2,000 sq ft home spending $2,400/year on heating/cooling could save $480–$600/year
Payback period: 10–15 years for full replacement; 2–5 years for sealing alone

Best ROI approach: Test with duct blaster → seal with mastic if possible → replace only sections that can't be sealed effectively. Full replacement gives best long-term performance but sealing provides faster payback.

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