How to Invoice After an HVAC Ductwork Job: Feet and Drops

Short answer: How to invoice after ductwork job HVAC work: bill trunk and branch by the linear foot, count boots, drops, and returns each, and print the insulation R-value per run — R-8 for attic ducts 3 inches and larger, R-6 below that under the 2021 IECC. Quantities come from a measured as-built, not from the takeoff. Close the invoice with two numbers the customer can keep: total external static pressure before and after, and a duct leakage result at 25 Pa.

A duct job is invoiced in a completely different currency from the service call that probably preceded it. On a service ticket the unit is a failed component; here it is feet of duct, a count of openings, and a pressure reading. The general field list is in what to include on an invoice, and the ticket that got you into the attic in the first place works the way how to invoice after an HVAC service call describes. This is the other document.

Where do the linear feet on the invoice come from?

From a measured as-built taken after the last connection, walked with a tape, not copied out of the bid. Attics and crawlspaces are where takeoffs go wrong: a run that measured 18 feet on paper became 24 because it had to go around a truss web and a bath fan.

Three quantities do the work. Trunk length by size, because a 20-inch trunk is not priced like a 10-inch branch. Branch length by diameter, measured along the actual routed path including sag allowance on flex. And openings counted — every boot, register, return grille, and balancing damper.

Reconcile before you bill. Flex comes in known box lengths, and what you consumed should line up with what you measured plus normal waste. If the delivery ticket says six boxes of R-8 flex and your as-built says 90 feet, one of the two numbers is wrong, and it is better to find that in the driveway than in an email three weeks later.

What gets billed by the foot, and what gets billed each?

Keep the units honest. Mixing them is the fastest way to make a duct invoice look like a guess.

Item	Unit	Note
Supply and return trunk	Linear foot, by size	Price per size, not one blended rate
Branch runs	Linear foot, by diameter	Measured along the routed path
Plenums, supply and return	Each	Fabricated, not bought by the foot
Transitions, tees, takeoffs, elbows	Each	Fittings are hours, and hours do not scale with footage
Boots and register drops	Each	Ceiling, wall, and floor boots are different labor
Return drops and filter grilles	Each	Undersized returns are the most common reason a system underperforms
Balancing dampers	Each	With the set position noted
Duct sealing	By the system or by the joint count	Mastic gallons and labor hours
Duct insulation	Linear foot at a stated R-value	Print the R-value on the line
Duct leakage test	Each test	Rough-in and final are two tests
Old duct removal and disposal	Lump or by the foot	Attic tear-out is real labor
Attic or crawlspace access premium	Hours	Say it out loud rather than hiding it in the per-foot rate

The fitting count is where duct jobs quietly lose money. Two houses with the same total footage can differ by twenty fittings, and every fitting is fabrication time, sealing time, and a hanger. A per-foot price with fittings buried inside it prices the easy house correctly and the hard one at a loss.

What does the sealing and insulation line have to say?

Enough that an inspector and a homeowner can both read it. Under the 2021 IECC, supply and return ducts in attics are insulated to at least R-8 for ducts 3 inches in diameter and larger and R-6 for smaller ones, while ducts elsewhere outside conditioned space run R-6 and R-4.2 on the same size split. Adopted code editions differ by jurisdiction, so state the R-value you actually installed and let it match what your inspector holds you to.

Sealing gets its own line and its own words. Joints are sealed with mastic or a listed closure product — the UL 181A and 181B listings are the ones the code points at — and ordinary cloth-backed duct tape is not an approved closure regardless of what it is named. If you pulled and replaced a system that was taped with it, that is worth a sentence, because it is the reason the old ducts leaked. The EPA’s ENERGY STAR duct sealing guidance, which tells homeowners outright never to use duct tape, is the plain-language version you can point a skeptical customer at.

One warning that belongs on any tear-out invoice: duct wrap and tape in older homes can contain asbestos. That is not a line item on your invoice. It is a stop, a test, and a separate abatement scope by someone licensed for it.

Which numbers prove the job is finished?

Ductwork is invisible once the access panel goes back on, so the invoice closes with measurements instead of adjectives. Three of them.

Measurement	What it shows	Where to put it
Total external static pressure, before and after	The blower is no longer fighting the duct system	On the invoice, both readings
Duct leakage at 0.1 in. w.g. (25 Pa)	The system is as tight as the code requires	On the invoice, with the test method named
Supply airflow at the problem rooms	The complaint that started the job is fixed	On the invoice, room by room

Static pressure is the one homeowners never hear and always benefit from. Many residential air handlers are rated at 0.5 in. w.g. total external static, and a system reading well above its blower table is being strangled by the duct, not by the equipment. A before-and-after pair on the invoice turns an invisible job into a measured one.

For leakage, name the test and the number. The 2021 IECC’s rough-in total leakage limit is 4.0 CFM25 per 100 square feet of conditioned floor area with the air handler installed, and 3.0 without it, tested per the referenced standards. Print your measured result next to the limit that applied. Some jurisdictions require a third-party test, in which case the report number goes on the invoice and the test itself may be a pass-through cost.

What changed between the estimate and the invoice?

Something almost always did, because the estimate was written by someone looking at a ceiling and the invoice is written by someone who has been above it.

What was found	What it added
Return capacity far short of the supply	A new return drop, filter grille, and the wall opening for it
Joist bay unusable as a return path	A hard-piped return replacing a panned bay
Trunk size undersized for the airflow	Larger trunk, more fittings, more insulation footage
Framing in the way	Additional elbows and offsets, each of them hours
Old duct wrap suspect for asbestos	Stop work, testing, and a separate scope by others
Ceiling opened for a new boot	Drywall patch and paint — usually excluded, so say by whom
Rough-in leakage test failed	Additional sealing labor and a retest

Each one gets a dated line with the quantity, who approved it, and how. “Added return drop, 14 in., plus filter grille — approved by text 7/09” reads as accounting. The same amount folded into the base footage reads as a price increase.

Two exclusions belong on every duct invoice because they are the two things homeowners assume are included: drywall repair and paint around new openings, and any electrical work for a zone panel or a damper motor.

Does the design belong on the invoice?

Reference it, briefly, because it is what separates a duct system from a pile of flex. The chain runs Manual J for the load, Manual S to select equipment against that load, and Manual D to size ducts and registers so each room gets the airflow the load calculation says it needs. Capacity never comes from square footage — 1 ton is 12,000 BTU/h, and which tonnage the house needs is a calculation, not a rule of thumb.

One line naming the design basis is enough: the Manual D duct design the runs were sized from, with the design airflow. It is what a home inspector, a rebate program, or the next contractor asks for, and it is the answer when someone claims a room is short.

Permits work the same way. Duct alterations and new systems usually require one, and it goes on the invoice as a pass-through at cost with the number printed, plus a note for the inspection trip. Do not use a scheduled inspection as payment leverage; the permit was pulled under your license.

How do I build a per-foot price that is mine instead of borrowed?

Cost it up, then price it. A per-foot number from a forum belongs to a different attic in a different market.

1. Take material off the as-built, not off memory: trunk by size, branch by diameter, boots, plenums, fittings, hangers, mastic, tape, and insulation footage at your required R-value.
2. Add a waste factor to flex and wrap, because sag allowance and trim are real consumption.
3. Price fittings as hours, not as feet, from your own crew’s fabrication and sealing pace.
4. Add an access factor. Hours in a 120-degree attic or a 30-inch crawlspace are not basement hours, and the price should reflect a crew that works slower because it must.
5. Multiply by your loaded hourly cost — wage, payroll burden, insurance, truck, tools, and the sheet metal shop if you have one — then add overhead across the hours you actually sell.
6. Then add margin, and get the arithmetic right. A 30 percent markup on $6,000 of cost bills $7,800 and keeps $1,800, which is a 23 percent margin. To keep 30 you divide by 0.70 and bill $8,571. On a trade where material is a large share of the ticket, that difference compounds across every job of the year.

Published per-foot ranges are a sanity check and nothing more. They move with duct material, access, region, code, and season. Use them to notice you are off by half, never to set the number.

What do I show at handover, and how do I get paid that day?

Walk the house with the system running. Hand over four things: before-and-after photos of each area you worked in, the static pressure pair, the leakage test result against the limit that applied, and the damper positions you set so nobody moves them in October and blames you. Add your workmanship warranty in one sentence, with what voids it.

Then collect while you are both standing at the thermostat. Build the invoice on the phone, let them scan the payment link as a QR code, and hand back a receipt if they pay on the spot. On general contractor and new construction work you are on their terms instead, usually with retainage and a lien waiver traded for the check, and reading which waiver you are signing is worth the two minutes.

What goes in the file after the ductwork invoice?

The as-built sketch with footage by size, the delivery tickets, the change-order texts, the permit and inspection record, the leakage test report, the static pressure readings, the photo set, and the numbered invoice. That set answers a warranty question years later and supports the deduction — the categories are laid out in Schedule C line items explained.

Keel is an iOS app that holds it on the device, with no account, no bank connection, no cloud, no login, and an App Store privacy label reading Data Not Collected. In practice the invoice is built in the hallway before the ladder comes down, in about a minute, with your numbering, logo, and brand color, the footage-by-size lines you just measured, and a payment link the homeowner scans as a QR code. Supply house tickets for flex, sheet metal, boots, and mastic get photographed at the counter and read on-device by Apple Intelligence, so the material figure behind a change order has paper attached instead of curling in a door pocket. The ledger is append-only and hash-chained, so what you billed and when does not quietly change. Year end exports as a single file, or as the Accountant Pack: a CSV plus a one-page summary PDF. Free is $0 with unlimited invoices, receipts, and mileage; Keel Pro is a one-time $249.99 Lifetime purchase, not a subscription.

Frequently asked questions

How is a ductwork job billed — by the foot or by the register?

Both, on separate lines. Trunk and branch are billed by the linear foot at a rate that varies by size or diameter, measured from an as-built after installation. Boots, register drops, return drops, plenums, transitions, and balancing dampers are each. Fittings priced as footage is the single most common way a duct job with a difficult layout ends up unprofitable.

What R-value should be on the duct insulation line?

Whatever you installed, stated explicitly. Under the 2021 IECC, attic supply and return ducts are insulated to at least R-8 at 3 inches in diameter and larger and R-6 below that, while ducts in other unconditioned spaces run R-6 and R-4.2 on the same split. Your jurisdiction may be on a different code edition, so match the number your inspector enforces.

Should a duct leakage test result be on the invoice?

Yes. Print the measured total leakage at 0.1 in. w.g. next to the limit that applied — 4.0 CFM25 per 100 square feet of conditioned floor area at rough-in with the air handler installed under the 2021 IECC, 3.0 without it. The number is proof the work was done to spec and it is what a rebate program or a future buyer’s inspector will ask for.

Why does static pressure belong on a ductwork invoice?

Because it is the only way a homeowner can see what changed inside a wall. Many residential air handlers are rated at 0.5 in. w.g. total external static pressure, and a system reading well above its blower table is being choked by the duct system rather than by the equipment. A before-and-after pair turns an invisible job into a documented one.

Who pays for drywall repair after new duct openings?

Say it on the estimate and repeat it on the invoice, because the default assumption runs against you. Most duct contractors exclude drywall patch, texture, and paint around new boots and return openings and name who is responsible instead. An exclusion written after the ceiling is open is a negotiation; one written before is a term.

What if the old duct insulation might contain asbestos?

Stop, do not disturb it, and do not put it on your invoice as a line you handled. Older duct wrap and tape can contain asbestos, and removal is a separately licensed scope. Document the discovery with photos and a dated note, bill the work performed up to that point, and let testing and abatement proceed as their own contract.

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This article is general information, not professional or tax advice.