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Cost guide

Ductwork Replacement Cost

Removing and replacing deteriorated, undersized, or leaking supply and return ductwork in a home.

Typical range
$1,500–$10,000
Most people pay
$4,500
Service life
20–30 years for sheet metal; 10–15 for flex duct in hot attics

National cost range

National range, per home

$1,500 – $10,000

Most homeowners pay around $4,500. The spread is real, not hedging — the drivers below determine which end of it you land on.

Low end
$1,500
Simple access, like-for-like
Typical
$4,500
What most jobs come in at
High end
$10,000
Upgrades, difficult access, code work

What you are actually paying for

Find the row that matches your situation. Quotes that differ wildly from each other usually differ in scope, not in price.

ScenarioTypical cost
Attic trunk and runout replacementAccessible attic — the most common partial replacement.$1,500–$4,000
Whole-house duct replacement, attic and crawlspaceFull supply and return system in accessible spaces.$4,000–$8,000
Duct replacement with drywall accessDucts inside walls require opening and repairing finished surfaces.$6,000–$12,000
Return duct addition to fix pressure issuesAdding return capacity without full replacement.$800–$2,500
Duct sealing and insulation only (no replacement)Aeroseal or manual mastic sealing when ducts are sound but leaky.$500–$1,500

What moves the price

In descending order of impact. These are also the questions worth asking a contractor whose quote sits outside the range above.

  1. Extent of replacement

    Replacing a section of trunk duct in an accessible attic is far cheaper than a whole-house duct replacement that requires opening walls and ceilings.

  2. Duct material

    Sheet metal trunk with flex runouts is standard. All sheet metal costs more but lasts longer. Duct board is cheaper but more fragile.

  3. Insulation and sealing

    Ducts in unconditioned spaces (attic, crawlspace) must be insulated to R-8 or better. Mastic sealing at every joint is code in most jurisdictions and adds labor.

  4. Accessibility

    Attic ductwork is accessible. Ducts inside walls or between floors require drywall removal and repair.

  5. Return duct adequacy

    Many replacements address undersized returns — adding return duct capacity often requires new wall or floor grilles and additional trunk routing.

Can you do it yourself?

Limited DIY scope

A homeowner can replace accessible flex duct runouts in an attic with basic tools. Trunk duct sizing, return adequacy, and mastic sealing at code level require HVAC knowledge. Improper ductwork wastes the investment in new equipment.

Permits and inspection

A mechanical permit is required for duct replacement in most jurisdictions. Duct leakage testing may be required at inspection in energy-code jurisdictions.
Run the DIY vs. pro decisionCheck a quote you already have

When this cannot wait

  • Rooms that never get enough airflow despite a running system
  • Visible disconnected or collapsed flex duct in the attic
  • Energy bills high with a system that runs constantly
  • New HVAC equipment performing below its rated efficiency due to duct losses

Common questions

How much does ductwork replacement cost?
Partial attic duct replacement runs $1,500 to $4,000. Whole-house replacement in accessible spaces runs $4,000 to $8,000. Replacement requiring drywall access runs $6,000 to $12,000.
How do I know if my ducts need replacing?
Signs: rooms that are always too hot or cold, flex duct that is crushed or disconnected in the attic, visible mold on duct insulation, and systems over 25 years old with original ductwork. A duct leakage test quantifies the problem.
Should I replace ducts when I replace my AC?
If the ducts are undersized, leaking, or deteriorated, yes — new equipment on bad ducts performs 20 to 30% below its rating. At minimum, seal and insulate existing ducts. Full replacement is worth it when flex duct is brittle or returns are inadequate.
How much does duct sealing cost?
Manual mastic sealing of accessible ducts runs $500 to $1,500. Aeroseal duct sealing (from inside) runs $1,500 to $2,500 for a typical home. Sealing alone can reduce energy loss 15 to 30% if ducts are otherwise sound.
One room never gets cold air — duct problem replacement cost?
A single disconnected or crushed duct run repair runs $200 to $600. If the entire attic duct system is deteriorated, partial replacement runs $1,500 to $4,000. Whole-house duct replacement runs $4,000 to $8,000. A duct leakage test ($200 to $400) identifies the problem before quoting.
AC running but weak airflow from vents — duct replacement cost?
Weak airflow with a running system usually means crushed flex duct, disconnected joints, or undersized returns. Sealing runs $500 to $1,500. Partial replacement runs $1,500 to $4,000. If flex duct is brittle throughout the attic, full replacement at $4,000 to $8,000 restores 20 to 30% lost capacity.
Mold smell from vents when the AC turns on — duct replacement cost?
Mold in ductwork requires removal and replacement of affected sections ($500 to $2,000) or full replacement ($4,000 to $8,000) if widespread. Duct cleaning alone ($300 to $500) does not kill mold in porous flex duct — replacement is the correct fix.
New AC installed but house still not cool — bad ducts cost to fix?
New equipment on leaking or undersized ducts performs 20 to 30% below rating. Duct sealing runs $500 to $1,500. Modification or replacement runs $1,500 to $5,000. This is the most commonly omitted item in HVAC quotes — insist on a duct evaluation before blaming the new unit.
Rats in the attic chewed through ductwork — replacement cost?
Replacing rodent-damaged sections runs $500 to $2,000 depending on extent. Full attic duct replacement runs $1,500 to $4,000. Seal attic entry points ($200 to $500) before replacing ducts or the problem recurs. Contaminated insulation should be removed ($1,000 to $3,000).
House built in 1970 with original ducts — are they still good, and what does replacement cost?
Ductwork over 25 years old with original flex duct is typically deteriorated even if not visibly damaged. Replacement runs $4,000 to $8,000 for a whole house. Pair with a new HVAC system for one mobilization — doing ducts separately costs 30% more in labor.

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