Ductwork replacement and installation cost

This Old House also lists material-only prices per linear foot, before labor:

The gap between material price and installed price shows where the money goes. Most of a ductwork bill is labor.

• Length and layout. Bigger homes need longer runs and more vents. Two-story homes and long branch runs add labor.
• Access. Ducts in an open basement or a roomy attic are easy to reach. Ducts in a tight crawlspace or behind finished walls and ceilings take much longer, and you may need drywall repair afterward.
• Material and insulation. Sheet metal costs more than flex duct. Ducts in attics, garages and crawlspaces need insulation.
• Removal. Contractors usually charge extra to remove and dispose of old ducts.
• Hidden problems. This Old House notes that asbestos abatement or mold remediation can add upwards of $2,000.
• Permits. This Old House puts permit fees at under $100 to several hundred dollars, depending on where you live.

Installing ducts in a home that never had them is a different project from replacing existing ducts, because the installer has to create paths through framed walls and floors. The central air installation cost guide covers pricing with and without existing ducts.

Many duct problems do not call for full replacement. ENERGY STAR says about 20 to 30 percent of the air that moves through a duct system is lost. It lists high utility bills, rooms that are hard to heat or cool, stuffy rooms, and tangled or kinked flexible ducts as signs of trouble. Sealing joints, reconnecting a fallen run, replacing one crushed section and adding insulation fix many of these for far less than new ducts.

Replacement makes sense when ducts are collapsing, rusted through, contaminated, or badly sized for the equipment. It also makes sense to price duct work when you replace your furnace or AC, since new equipment on undersized or leaky ducts will not perform as rated.

• Linear feet of supply and return duct, and the number of registers and returns.
• Duct material, insulation value and how joints will be sealed.
• Whether the design is based on a load and duct calculation or copied from the old layout.
• Removal and disposal of old ducts.
• Permit, plus any drywall or patching work and who does it.
• A leakage or airflow test after the job, if offered.

Compare quotes on the same scope. One contractor may be pricing a full replacement and another only the accessible trunk lines. More prices are in the HVAC cost guides.