Ductwork Installation & Replacement — Toronto GTA

Manual D-designed, sheet-metal preferred, sealed to UL 181

Ductwork installation and replacement in Ontario is governed by OBC 2024 Section 6 (mechanical) and Manual D (ACCA duct design standard). RenoHouse coordinates new and replacement ductwork through HVAC partners with the right tools (snap-lock sheet metal brake, duct-sealing mastic, flow hood), Manual D drawings, and Building Permit when required. Pricing $2,400 – $11,500 installed Q2 2026 GTA.

Quick answer

Ductwork is often the silent cost in a HVAC retrofit — undersized ducts make a brand-new heat pump or AC underperform. Manual D resizing during a furnace/AC/heat-pump swap is the right answer when airflow tests show static pressure > 0.5" w.c. or zones don't balance.

What's included

• Manual J + Manual D duct design (by certified HVAC partner)
• Tear-out of existing ductwork where applicable (asbestos consideration — see below)
• New sheet metal trunk lines (rectangular or round spiral, galvanized 26 ga / 28 ga)
• Branch runs (round spiral or rectangular tap-ins)
• Return air paths (often the bottleneck — many old homes have undersized returns)
• Duct sealing per UL 181 / SMACNA (mastic or aerosolized sealant, NOT duct tape)
• Insulation wrap (R-6 minimum on supply ducts in unconditioned spaces)
• Boots, registers, grilles (Tuttle & Bailey, Hart & Cooley standard; premium aluminum / brass available)
• Final airflow balancing with flow hood; written commissioning report

Toronto-specific scenarios

1. Heat pump retrofit airflow upgrade — heat pumps deliver air at lower temps (~38-43°C vs 49-54°C from a furnace) and need ~20-30% more CFM. Most pre-2010 Toronto homes have undersized supply trunks built for furnaces — they whistle, short-cycle, and underperform after a heat pump swap. Manual D + trunk resize is the fix.

1. Asbestos-wrapped duct insulation (1950s-1970s Toronto homes) — Tar paper, white wrap, or grey/brown lagging on old steel ducts may contain asbestos. Cannot be torn out without HCRA Type 1/2 abatement specialist. We coordinate certified abatement before duct work; budget +$2,500 – $8,000 for typical home. Required by Ontario Reg 278/05 (Asbestos on Construction Projects).

1. Basement finishing — adding finished basement often requires duct rework: lower trunk lines to gain head height, add supply registers for the new rooms, add return path for the new zone. Common in coordination with our Basement Finishing and Basement Underpinning services.

1. Multiplex conversion (Bylaw 474-2023) — each dwelling unit needs independent supply + return for OBC compliance and unit-by-unit metering. Adds 3-5K per unit on the duct side.

1. Pre-1960 homes (Cabbagetown, Riverdale, Annex, Beach, Parkdale) — many were built without central air ducting at all (hydronic radiator systems). Adding ductwork is a major project — $11,500 – $25,000+ if entire home, often paired with a deep retrofit. We frequently recommend ductless mini-split as a less-invasive alternative.

Sheet metal vs flex — what we install

Sheet metal (rectangular trunk, round spiral branches): default in all our installs. Snap-lock or pittsburgh-seam joints, sealed with mastic. Long-life (50+ years), best airflow (lowest friction losses), ESA & OBC preferred.

Flex duct: permitted in residential only ≤5 ft per run per OBC 6.2.3. Use cases: final connection from trunk to register boot through tight ceiling cavity, retrofit through joist bays where sheet metal won't fit. Insulated R-6 minimum. We use M-K-T or Atco brand only.

Fiber-board duct (fibreglass): NOT used by us. Cheap, but mould risk and structural fragility issues.

Permits & compliance

• Toronto Building Permit required when duct work breaches fire-rated assemblies (floor/ceiling fire separations) or affects egress
• ESA permit for any duct-mounted equipment with electrical (heater coils, booster fans, electronic air cleaners, dampers with 24V motors)
• TSSA permit NOT required for ductwork itself (no gas involvement)
• HCRA Type 1/2 abatement contractor for asbestos-wrapped ducts (mandatory, not RenoHouse direct)
• OBC 2024 Section 6 compliance — airflow, static pressure, return-air paths, fire dampering at penetrations
• SMACNA Standards for sheet metal fabrication and sealing

Pricing reality by job type

FAQ

Q: My new heat pump doesn't feel as warm as the old furnace. Is it the ducts? A: Almost always. Heat pump supply air is 38-43°C (lukewarm to your hand) vs furnace 49-54°C (hot). The way to deliver the same heat is more airflow — which means the ducts must be sized properly. Common fix: replace the main supply trunk to a larger size, add return-air capacity, balance registers. $2,400 – $5,800 typical retrofit. Manual D shows where the bottleneck is.

Q: How do I know if my existing ductwork is undersized? A: Static pressure test at the air handler. > 0.5" w.c. = system fighting the ducts. We do this measurement free at the consultation. Also watch for whistling registers, large temperature variation between rooms, or short-cycling at the air handler — all classic undersized-duct symptoms.

Q: Can you reuse existing ductwork during a furnace/AC swap? A: Often yes. We pressure-test and inspect at the consultation. About 60-70% of pre-2010 Toronto homes have reusable trunk lines that just need new boots, sealing, and balancing — $480-$1,800 cleanup vs $5K+ replacement.

Q: What about duct cleaning vs replacement? A: Duct cleaning ($300-$600) is a separate service — useful for allergen control or post-renovation dust, but doesn't fix airflow problems. Ductwork replacement is a structural fix. We refer duct cleaning to specialist partners (Modernistic, Stanley Steamer).

Q: How long does duct work take? A: Partial replacement (one trunk): 1-2 days. Full system (existing home): 3-7 days. New construction / addition: 2-5 days. Asbestos abatement adds 5-10 days lead time and 2-3 days site work.

Q: Do I have asbestos in my ducts? A: If your home was built 1950-1980 AND has white/grey/brown insulation wrap on the supply trunks (especially in the basement), assume YES until tested. Do not disturb. $80-$180 test by HCRA-licensed sampler before any work begins.

Q: What's the warranty? A: 2-year RenoHouse labour. Lifetime warranty on sheet metal duct material (galvanized 26 ga from Hart & Cooley / Tuttle & Bailey). Manufacturer warranty on installed equipment (dampers, booster fans) per spec sheet.

Q: Can you do zoning while you're at it? A: Yes — adding zone dampers + zone control board + extra thermostats ($1,800 – $4,500 added) lets you heat/cool different areas independently. Most common: separate upstairs / downstairs zone in 2-storey home. We coordinate the controls with the HVAC partner.

Q: What's the difference between flex and sheet metal — does it matter? A: Sheet metal: longer life, better airflow, no mould risk, OBC preferred for trunk lines. Flex: only for ≤5 ft final connections per OBC. We use sheet metal everywhere we can; flex only at the boots. Pricing comparable for the same job; flex is sometimes cheaper labour but doesn't last as long.

Q: Can you do ductwork during FIFA 2026 work-window restrictions? A: Yes — ductwork is not gas-fired and doesn't trigger Enbridge restrictions. ESA inspection scheduling for duct-mounted electrical may have minor delays in late June through July if downtown core.

Toronto/GTA neighborhood considerations

• Forest Hill / Rosedale / Lawrence Park (heritage): Pre-1940 octopus-gravity coal-furnace conversion stock — original galvanized round trunk on 1.5-storey balloon framing; Manual D redesign mandatory with R-8 mineral wool external wrap (Owens Corning SoftR) on attic-run plenums. Typical full-house re-duct $9.5K-$15K including TSSA-permit gas-line resize.
• North York / Scarborough / Etobicoke (60s-70s): Post-war 1960s flex-duct R-4.2 attic spaghetti with bird-cage register layout — common to retrofit galvanized rigid takeoff at plenum + Aeroseal sealant ($1.8K-$2.8K add) to fix 30%+ leakage. Standard scope $4.8K-$7.5K.
• Mississauga / Brampton / Vaughan (90s+): 1990s metal trunk + flex branch already-conforming to OBC 6.2 minimum; scope is typically R-6 attic wrap upgrade + Aeroseal pass $2.4K-$3.6K, or trunk extension for finished-basement bonus zone.
• Caledon / King City / Aurora (rural well): Rural propane-furnace or geothermal heat-pump duct sizing — Manual D recalc mandatory at heat-pump conversion (lower delta-T = larger duct). Typical $6.5K-$11.5K for full reseal + R-8 plenum wrap on cathedral-ceiling main floor.
• Downtown condos: Vertical-stack fan-coil units — no central ductwork; horizontal supply within 8-inch concrete-slab bulkhead. Scope is grille-and-diffuser swap, condensate-line clean, plus VAV box rebalance $480-$1.2K per suite.

Permit + license: TSSA G2/G1 gas fitter for furnace reconnect, ESA 309A electrician for line-voltage swap, Toronto Building Permit at any new appliance install or relocation. Manual D + Manual J load calc on permit submission. CSA B149.1 gas code, SMACNA HVAC Duct Construction Standard. Greener Homes Grant up to $5K + HRS pre/post EnerGuide ($600 incentive).