Ductwork Guide: Types, Cost & Installation

Sheet metal: Most durable and efficient. Made from galvanized steel or aluminum. Smooth interior reduces airflow resistance. Cost: $10-$20 per linear foot installed. Lifespan: 20-25+ years. Best for main trunk lines and exposed installations.

Flexible (flex) duct: Insulated plastic tube with wire coil frame. Easy to install in tight spaces. Cost: $5-$10 per linear foot installed. Lifespan: 10-15 years. Best for connecting branch runs to registers.

Fiberboard: Compressed fiberglass with foil facing. Good insulation properties built-in. Cost: $6-$12 per linear foot. Lifespan: 15-20 years. Not recommended for humid climates (mold risk).

Fiberduct (spiral): Spiral-wound sheet metal. Superior air seal at joints. Cost: $12-$25 per linear foot. Common in commercial but increasingly used in high-efficiency homes.

Trunk line: Main duct from HVAC unit, typically 10-16 inches diameter or equivalent rectangular. Sized based on total CFM of system.

Branch runs: Individual ducts to rooms, typically 6-8 inches diameter. Sized based on room square footage and heat load calculation.

Manual D calculation: Professional method for sizing ductwork. Accounts for friction loss, fittings, and total equivalent length. Essential for efficiency.

Common mistakes: Undersized ducts cause high velocity (noisy), restricted airflow, and system strain. Oversized ducts waste materials and can cause low velocity (poor mixing).

New installation (whole house): $2,000-$6,000 for 1,500-2,500 sq ft home. Includes trunk line, branch runs, registers, and insulation.

Replacement: $3,000-$8,000 depending on accessibility. Attic or crawlspace access is easier than in-wall or in-slab.

Duct sealing only: $1,500-$3,500. Professional aeroseal process or manual mastic sealing. Can improve efficiency 20-30%.

Insulation wrap: $1-$3 per linear foot. R-6 or R-8 wrap for ducts in unconditioned spaces (attics, crawlspaces).