A ducted heat pump is only as good as the ducts it has to breathe through.
That is why two quotes with the same outdoor unit can feel completely different after installation, and why "duct improvements: TBD" is one of the more expensive three words a quote can contain.
Quick answer
Ask whether the contractor tested duct leakage and static pressure, or is assuming the existing ducts are fine. Below is a priced breakdown of the seven duct-scope items that most often turn into a change order: leakage testing, sealing, a new or enlarged return, a resized trunk, crushed flex repair, insulation, and static-pressure testing. If a quote reuses ducts without naming which of these it checked, it is skipping the part that decides comfort.
Duct scope items and 2026 US prices
Ranges below are national estimates checked September 2026 from cost aggregators, HVAC diagnostic providers, and this site's own hidden-costs research (see Sources). Your actual price depends on house size, access, and duct material.
| Duct scope item | 2026 price range | When it applies | What to name on the proposal |
|---|
| Duct leakage testing (duct blaster test) | $115-$500 per HVAC system, most commonly $150-$450 | Should happen before any duct-reuse decision on a ducted retrofit; often skipped on a phone or photo estimate | "Duct leakage test, percent leakage to outside reported" |
| Duct sealing, mastic (accessible runs) | $500-$4,000, averaging around $2,250 depending on joint count and access | Common wherever ducts are reachable in a basement, crawlspace, or attic | "Mastic sealing, linear feet or joints sealed named" |
| Duct sealing, aerosol (Aeroseal, sealed cavities) | $1,500-$4,000 typical, up to $6,900 on large systems | Used when ducts run inside finished walls or floors that mastic cannot reach | "Aerosol duct sealing, pre/post leakage percentage reported" |
| New or enlarged return | $200-$750 for a simple added vent; $400-$1,200+ for a longer or harder run; $1,500+ on difficult access | Common in homes with one central return and multiple bedrooms, or rooms added after the original ductwork | "New return, size and location named" |
| Trunk resizing (undersized sheet-metal trunk) | $35-$60 per linear foot installed for sheet metal, close to this site's general duct-replacement range | Needed when the existing trunk is undersized for the new equipment's airflow, found by a static-pressure or duct-design check, not by tonnage alone | "Trunk resize, from-size to to-size and linear footage named" |
| Replacing crushed or damaged flex duct | Roughly $7-$35 per linear foot depending on insulation; general duct replacement runs $35-$55 per linear foot | Situational, found only when a technician physically accesses the attic or crawlspace | "Flex duct replacement, linear footage and R-value named" |
| Insulating ducts in an unconditioned attic or crawlspace | $4-$8 per linear foot for R-8 jacketed insulation; can move a full duct job by $200-$1,700 | Common in attic and crawlspace duct runs in older homes | "Duct insulation, R-value and linear footage named" |
| Static pressure / airflow testing | Often bundled into a $90-$200 general diagnostic visit; a standalone test can run roughly $250-$400 (lower-confidence figure, confirm with your contractor) | Should apply to every ducted job, in principle; in practice it is inconsistently performed | "Static pressure test, reading in inches w.c. against the equipment's rated maximum" |
A duct leakage test and a static-pressure test measure two different things and are not interchangeable. The leakage test pressurizes the duct system with a calibrated fan (a duct blaster) and reports what percentage of air escapes before it reaches a register. The static-pressure test uses a manometer at the supply and return plenums to check whether the ducts resist airflow more than the equipment is rated for. A contractor can pass one and fail the other.
Ducts built for a furnace may not be fine
A heat pump can run longer and at different supply temperatures than the old system. Ducts that were barely acceptable before may show their weakness after the swap.
That does not mean every home needs new ducts. It means the quote should tell you what was checked, and which of the seven items above it covered.
What a "duct improvements" allowance hides
A lump-sum "duct improvements" or "duct repairs as needed" allowance can bundle any combination of the seven items above into one number with no way to tell what you are actually paying for. That is the same red flag as any other unexplained line when you read a heat pump quote: it protects the contractor's margin, not your ability to compare bids.
Convert the allowance into named line items before you sign:
- Ask which of the seven scope items above the allowance is meant to cover, and get each one priced separately or capped individually rather than folded into one number.
- Ask whether the allowance number came from an actual leakage or static-pressure test, or from a visual walk-through. A number with no test behind it is a guess dressed as a quote line.
- If the allowance has no stated cap, ask for one in writing. An allowance without a cap is a blank check for a change order later.
For how these seven items sit alongside the other things a heat pump quote commonly leaves out, electrical work, permits, condensate, and removal, see heat pump hidden costs. Put the priced items next to the rest of a bid using the heat pump bid comparison template.
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Ductless may be cleaner in some homes
If ducts are terrible, a ducted replacement can become expensive fast. A ductless or hybrid approach may fit some homes better, especially additions, basements, bonus rooms, and houses with no existing duct system. The tradeoff is mapped out in ducted vs mini-split.
The right answer is the one that heats and cools the house, not the one that preserves the old layout by default. If two bids treat your ducts completely differently, our free quote review can tell you which one did the homework.
Quote red flags
- A lump-sum "duct improvements" allowance with no cap and no named scope.
- No mention of a leakage or static-pressure test, on a house where the ducts have never been tested.
- Tonnage or trunk size chosen without checking existing duct capacity.
- A price for "duct sealing" that does not say whether it is mastic, aerosol, or both.
- "Ducts are fine" stated without measurement, especially on a home over 20 years old.
Frequently Asked Questions
Do I need new ducts for a heat pump?
Not always. You need the ducts evaluated against the seven items above. Some need sealing or a return, some need a trunk resized, and some are fine.
Why did one quote include ductwork and another did not?
Because one contractor may have tested leakage or static pressure and priced what they found, and the other may be assuming the existing ducts work.
Can bad ducts ruin a heat pump?
They can make it noisy, inefficient, uncomfortable, or unreliable. The equipment may be fine while the system disappoints.
What should the quote say?
It should state whether ducts are reused as-is, tested, sealed, resized, insulated, or redesigned, with each item named and priced rather than folded into one allowance.
Is duct leakage testing the same as a static-pressure test?
No. A leakage test measures how much conditioned air escapes the ducts before reaching a register. A static-pressure test measures how hard the equipment has to work to push air through the ducts. A contractor can quote one without the other, so ask which was actually done.
What we could not verify
- A single national price for trunk resizing as its own line item. Sources price sheet-metal duct installation by the linear foot, but no source separates "resize an existing undersized trunk" from a full duct replacement job, so the range above is the general sheet-metal installed rate, not a resizing-specific figure.
- Your specific price. Every range above is a national estimate checked in September 2026. Get a written, itemized quote for your actual house.
Sources
All sources checked September 2026.
