How to Estimate an HVAC Duct Replacement | Reddit & LinkedIn

To estimate an HVAC duct replacement, measure the total linear feet of trunk and branch runs, count registers and returns, choose duct type, then price material, labor per run, sealing, and disposal, and add markup. Full-home replacements in 2026 commonly run $3,500 to $12,000. The rest of this guide walks the estimate step by step so your number holds up when the client compares bids. Estimate the same way every time and your win rate and your margin both get more predictable.

Sketch the trunk and branch layout, measure total linear feet, and count supply registers, return grilles, and boots. The count and footage are the backbone of the estimate.

Decide between rigid sheet metal, insulated flex, or ductboard based on the layout and the client's budget. Each has a different material cost and a different install time per run.

Price the duct, fittings, plenum, insulation, and mastic, then set a labor rate per run and per register. Access in a tight attic or crawlspace multiplies those hours.

Include mastic or aeroseal sealing, a duct-leakage test if code requires it, and removal and disposal of the old system. These lines are often forgotten and eaten as loss.

Add your markup for warranty and callbacks, then present duct type, sealing, and disposal as separate lines so the client can compare bids on equal footing.

Duct estimates live and die on footage, register count, and access. A ranch with a walk-in attic and short runs is quick, while a two-story home with runs buried in chases and a low crawlspace can double your labor hours on the same footage. Duct type is the other lever: rigid sheet metal costs more in labor but lasts and seals well, flex is faster but needs careful support, and ductboard sits in between. Finally, code: many jurisdictions now require a duct-leakage test on replacement, so build the test and the sealing to pass it into the number from the start.

Even a good estimator loses margin to a few repeatable errors. Watch for these before you send the quote.

• Estimating footage from the thermostat instead of actually mapping the runs.
• Using one labor rate for an easy attic and a tight crawlspace.
• Forgetting old-duct removal and disposal, which is real time and dump fees.
• No line for a new plenum or return drop when the old one is undersized.
• Skipping the leakage test the local code requires, then eating the re-test.

A 1,900 square foot home with 9 supplies and 2 returns in flex might price as 260 linear feet of duct and fittings, per-register labor across 11 openings, a new plenum, mastic sealing, a leakage test, and haul-off, then markup, landing around $6,800. Grouping it this way makes the bid auditable.

You can run this whole estimate by hand, but doing it on paper at night is how quotes go out late and lose. On ContractShield you record the measurements and choices on your phone at the site, the AI drafts the line items with your own rates, and you send a signable, itemized quote in about 25 minutes. When the client accepts, the quote becomes the project plan, and milestone billing plus automatic collections gets you paid for 2% per job (1% each side), capped at $250, no per-lead fees.