Ductwork Cost Calculator

A 1,500 sq ft home usually has about 10 supply runs (~160 ft of duct). Replacing it with insulated flex in the attic, mastic-sealed, prices around $6,331 installed (roughly $5,065–$8,547 including old-duct haul-away) — inside HomeGuide's $2,400–$6,600 whole-house band and well under Fixr's $9,293 national average, which is pulled up by full sheet-metal systems.

Cheaper, yes: on the same 160-ft attic system our model prices flex at $6,091 versus $10,480 for galvanized metal — about 72% more for metal. Angi's material prices explain why: flex runs $1–$4 per linear foot versus $7–$13 for rigid metal. Flex sags and collects dust if strung without support every 4 ft, so crews often build metal trunks and plenums with flex branches — the durable middle path.

Hand-applied mastic on accessible joints adds about $440 on a 160-ft system in our model — consistent with Angi's $500–$1,500 typical hand-sealing range. Most duct systems leak a meaningful share of their air into attics and crawl spaces before sealing, so in a hot-attic install the sealing usually pays back in lower summer bills. Injected aerosol sealing ($1,600 here; $1,500–$3,500 is the typical single-family quote range published by aerosol-sealing vendors) reaches joints you can't touch, but mastic covers the accessible 90% for a fraction of the price.

Energy-code guidance calls for R-8 on ducts running through unconditioned attics and R-6 in other unconditioned spaces like crawl spaces and garages; ducts inside conditioned space need no wrap at all. Insulated flex ships with roughly R-6 already on it — upgrading to R-8 wrap on flex only costs the delta, while bare metal or duct board needs the full wrap job (about $880–$1,600 per 160 ft in our tables, matching Angi's $1,000–$2,700 pro duct-wrap range).

Yes — the duct and registers cost the same, but labor doesn't. On our reference 160-ft metal system, attic access adds about $774 over a basement install and crawl-space access about $1,548 — Angi quotes crawl-space labor at $30–$60 per linear foot versus $25–$55 for installs generally. Crawl-space systems total $2,600–$7,300 per Angi, and top quotes climb further when access is tight.

Most jurisdictions require a mechanical permit when ducts are extended, rerouted, or replaced as part of an HVAC change — a like-for-like swap sometimes slides under the original system's permit. The model carries a $250 allowance that scales with your state's labor rates: roughly $200 in low-wage states up to $363 in the highest-cost markets. Your contractor usually pulls it — confirm who does, because unpermitted duct work can complicate a home sale.

A ducts-only replacement in an accessible attic or basement typically takes a 2-person crew 1–3 working days; HomeGuide times full HVAC-plus-ductwork installations at 3–5 days. Two things in this calculator stretch the schedule: tear-out — removing old ducts adds about $560 on a 160-ft system and all of it happens before anything new goes up — and crawl-space access, where the same system prices at $11,254 versus $10,480 in an attic because every drop is fitted by hand in the dark.

Usually the cheapest moment to do it — the equipment crew is already on site, so you pay duct labor once. HomeGuide prices combined HVAC-plus-new-ductwork installations at $7,000–$16,000, and notes ductwork itself lasts 10–20 years, so ducts installed with a 15-year-old furnace are often due exactly when the furnace dies. Price the systems with the HVAC replacement calculator, then add this tool's duct line to see the combined number.