Quick answer
New ductwork is priced by how much sheet metal has to be fabricated and hung and by how hard the space is to work in, not by the size of the house. Adding two supply runs in an open basement is a day's work. Re-trunking a 1950s bungalow so a modern variable-speed furnace can breathe is a much larger project, and it needs a measured quote.
New ductwork costs whatever the metal and the access cost, which is why the honest answer is a number written after someone has been in your basement with a tape measure. There is no per-square-foot rate that survives contact with a real house. What there is, is a short list of things on the quote — and knowing what belongs on it is how you compare two prices fairly.
What you are paying for in a duct quote
- Trunk — the main supply and return lines, usually rectangular sheet metal fabricated to suit your joist spacing and headroom.
- Runs — the individual branches out to each register, in round pipe or flex, plus the boots and takeoffs.
- Returns — the item most retrofit quotes are short on. A house with one hallway return and none in the bedrooms will never balance properly.
- Sealing — mastic or foil tape rated for ducts on every joint, not cloth duct tape, which lets go within a few years and leaves you paying for the leak on the gas bill.
- Insulation — on any duct passing through an unconditioned attic or a cold crawl space.
- Balancing dampers, and the time to set them once the system is running.
- Drywall and finish repair where the route crosses a finished ceiling, which is often the single largest line on the page.
At the bottom of the scale is two or three new branch runs off an exposed trunk in an unfinished basement — a day's work in round pipe with no finish repair. At the top is a full re-trunk of a finished bungalow: new supply and return trunks, a return in every bedroom, and a ceiling opened and repaired along the whole route. Most jobs sit between, and the finish repair line is what usually decides which end you are closer to.
Why 1950s bungalows and 1970s two-storeys price differently
In the post-war bungalows through Aldershot, Roseland and the lower city in Hamilton, the original layout was gravity or early forced air: a fat trunk, short runs, and a return system that amounts to one grille in a hallway. Those houses usually need return capacity added more than supply, and the trunk hangs low enough that a finished-basement plan runs straight into it.
The 1970s–90s two-storeys in Millcroft, Glen Abbey and River Oaks have the opposite problem. Supply is adequate but the second floor is fed by long runs with one undersized return, which is exactly why the upstairs bakes in July — see why the second floor is so hot. The fix there is targeted: a larger return, a couple of re-routed runs, sometimes a zone damper. Not a new system.
The 2000s+ builds in Alton Village, the Orchard and Waterdown are usually ducted adequately but to the minimum. Complaints in those houses are almost always about balancing and register sizing rather than missing metal — builder-grade HVAC upgrades covers what is worth changing and what is not.
Ductwork is sized, not guessed
A proper quote follows a heat loss and gain calculation for the house and a duct design for the airflow that comes out of it. Undersized ducts on modern equipment announce themselves as noise first: whistling registers, a roaring return, a blower that never settles. Whistling vents are usually the first symptom of a duct system fighting the furnace it was paired with.
That matters more with each equipment generation. A variable-speed blower and a heat pump move more air at lower supply temperatures than the 1980s furnace your ducts were built around. Starve the return and the system short-cycles, ices its coil in summer, and never delivers the efficiency you paid a premium for.
Cleaning is not the same as replacing
If the complaint is dust, the answer is usually not new metal. Professional duct cleaning for a typical GTA house runs $300–$700, and $700–$1,000 or more for a larger home with heavy loading — a fraction of a rebuild and often the right first step. What duct cleaning costs in the GTA breaks that down by home size.
Modify or replace ducts when the problem is capacity or distribution: rooms that will not hold temperature, a new addition, a basement finish that needs its own supply and return, or a furnace upgrade the existing trunk cannot support.
Common questions about ductwork cost
- Can I add air conditioning without ducts? Yes — air conditioning without ductwork covers ductless options and when they beat retrofitting metal.
- Do ceilings have to be opened? Sometimes. We map the route first and show you exactly where before anything is cut — in a 1970s two-storey the second-floor runs usually go up inside a closet or an existing return chase, which keeps the drywall work to one or two openings.
- Is a permit needed? For a heating system change, usually. Municipal permit fees typically run $100–$300.
- Can flex be used everywhere? No. Short, straight, properly supported runs only — long sagging flex is where airflow goes to die.
- Should the ducts be sealed before a heat pump goes in? Yes. A heat pump moves more air at a lower supply temperature than a furnace, so every leaking joint in the basement costs it more than it cost the old furnace. Mastic on the accessible joints is cheap the day the new equipment goes in.
ZK Mechanical designs and fabricates ductwork for basement finishes, additions and equipment upgrades throughout Burlington, Oakville and Hamilton. See ductwork installation. Call (647) 801-1252 or book a measure and quote.