Replacing a home’s ductwork runs $1,400–$7,000 for most residential jobs. The right number for your situation depends on whether you’re doing a full system replacement, replacing a section, or whether sealing is actually the better call.
Before you approve ductwork
- 1How did you measure the leakage — a duct blaster test, or a visual estimate?
- 2What’s actually being sealed or replaced, and what’s being left alone?
- 3Can you show me before/after airflow numbers, not just “it’ll feel better”?
- 4Is insulation included where ducts run through unconditioned space?
- 5What’s the warranty on the sealing method or materials used?
- 6Will this change my system’s static pressure, and did you check for that?
Before any ductwork replacement quote, get a duct leakage test. It’s the only way to know if the structure is still sound and sealing can do the job, or if replacement is genuinely necessary.
What ductwork replacement costs
| Scope | Typical cost |
|---|---|
| Full duct replacement, 1,500–2,500 sq ft home | $1,400–$5,600 |
| Full duct replacement, larger home or complex access | $4,000–$7,000 |
| Partial replacement (1–3 runs) | $800–$2,500 |
| Per linear foot (flex duct) | $25–$35 |
| Per linear foot (sheet metal) | $35–$55 |
| Per run (trunk to register, including branch and register) | $270–$500 |
Labor accounts for 40–60% of the total. Homes with attic ductwork in tight spaces, or ductwork in finished areas requiring access cuts, run toward the top of the range.
When replacement is the right call
Replacement makes sense when the duct structure itself is failing, not just leaking at joints. Specific signs:
- Flex duct with collapsed or deteriorated sleeves. The outer sleeve of flex duct degrades over time, particularly in hot attics. When the sleeve collapses around the wire core, airflow is permanently restricted. This isn’t fixable with sealing.
- Ductwork over 25–30 years old throughout. Sheet metal from the 1970s–1990s may have corroded joints, failing insulation, and multiple disconnections. At a certain age, the cost of sealing every problem section adds up to more than replacement.
- Connections that have completely separated. A duct branch that’s fully detached from the trunk is dumping conditioned air into an attic or crawlspace. Reconnection is a repair; if this has happened in multiple locations, it indicates systemic failure.
- Asbestos insulation on older ducts. Ducts in pre-1980 homes may have asbestos-containing insulation. Disturbing it requires abatement; replacing the duct system with new insulated ductwork is often the practical solution.
When sealing is the better option
If the duct structure is intact (no collapsed flex, no separated connections, no major deterioration) and the problem is air leakage at joints and seams, sealing extends duct life significantly at a fraction of replacement cost.
Manual sealing with mastic sealant and foil-backed tape runs $400–$1,900 for a professional job covering accessible sections. For inaccessible leaks in attic runs or hidden connections, Aeroseal (an injected polymer sealant) runs $1,300–$3,000 and can seal 85–95% of duct leakage in a single visit.
The decision point: if a leakage test shows 20–30% leakage and the duct structure is otherwise intact, sealing will recover most of that. If a visual inspection shows collapsed flex runs and multiple disconnected joints throughout, sealing is treating symptoms of a structural problem.
See duct sealing cost and options for the full comparison.
What a ductwork replacement job includes
A complete replacement bid should cover:
- Removal of old ductwork (labor and disposal)
- New trunk lines (sheet metal is standard for main runs)
- Branch runs to each register (flex duct acceptable for short runs; specify maximum bends per run)
- Insulation (R-6 minimum in attics, R-8 in hot climates per IECC)
- Sealing at all joints with mastic and foil tape (not standard duct tape)
- Registers and grilles (replacement or reuse of existing)
- Permit (required in most jurisdictions; if omitted, ask why)
- Post-replacement duct leakage test to verify the work
If a contractor’s bid doesn’t mention the leakage test, ask for one. Without it, there’s no independent verification that the new duct system achieves the target leakage rate.
Before you sign: 3 questions for this job
For the full contractor-vetting checklist, see The HVAC Quote Checklist. For ductwork replacement specifically:
- “Will you do a duct leakage test before and after, and share the numbers?” Good answer: yes, targeting less than 10% leakage post-installation. Bad answer: “we’ll seal everything tight.”
- “What material are you using for trunk lines vs. branch runs?” Good answer: sheet metal trunk, short flex branches. Bad answer: all flex, no further detail.
- “Is the permit included?” It should be.
For the broader context of what this job costs compared to equipment repairs, see the HVAC repair and replacement cost index. For guidance on whether your airflow problem is a duct problem at all, start with how ductwork works.
