How much does ductwork cost for a Toronto laneway suite or garden suite?

Ductwork for a Toronto laneway suite or garden suite typically costs $3,000 to $8,000 as part of the overall HVAC installation, depending on the size of the unit, the heating and cooling system chosen, and the complexity of the layout. Since the City of Toronto legalized laneway suites in 2019 and expanded permissions for garden suites in 2022, these secondary dwelling units have become increasingly popular across established neighbourhoods — and getting the HVAC and ductwork right in these compact spaces requires thoughtful design from the start.

The ductwork scope depends heavily on which HVAC system is selected. A ducted mini-split heat pump system — the most popular choice for Toronto laneway and garden suites — uses a compact air handler with short duct runs to supply and return registers. Because these units are typically 400 to 1,000 square feet with an open-concept layout, the duct system is small: a compact supply plenum, 4 to 8 short branch runs, and 2 to 4 return air paths. Material and installation for this scale of ductwork runs $2,000 to $5,000. The mini-split air handler itself and outdoor condenser unit add another $4,000 to $8,000 installed, bringing total HVAC costs for a laneway suite to $6,000 to $13,000. Alternatively, a ductless mini-split system eliminates ductwork entirely using wall-mounted indoor units — this costs $3,500 to $7,000 installed for a one or two-head system, but some homeowners prefer ducted systems for the cleaner aesthetic without wall units.

If the laneway suite uses a small high-efficiency furnace with central air conditioning, the ductwork scope is more traditional — a supply plenum, trunk line, branch runs, return air system, and all associated fittings. For a 600 to 800 square foot suite, this runs $3,500 to $8,000 for ductwork plus $3,000 to $6,000 for the furnace and air conditioner. This approach requires gas service to the suite (TSSA-registered contractor for installation), a flue venting path, combustion air supply, and condensate drainage — all of which add cost and complexity compared to an electric heat pump system.

There are several GTA-specific considerations for laneway and garden suite ductwork. Since these are new construction, the Ontario Building Code requires engineered duct design using Manual D calculations, and all ductwork must meet current energy efficiency standards including proper sealing and insulation. If ducts run through unconditioned spaces (unlikely in a well-designed suite but possible in attic or floor assemblies), R-8 minimum insulation is required. The suite needs its own independent mechanical system — it cannot share ductwork with the main house. An HRV or ERV is strongly recommended and often required under the OBC energy provisions for new airtight construction, adding $2,500 to $5,000 for the unit and dedicated ventilation ductwork.

Building permits are mandatory for laneway and garden suites, and the mechanical portion of the permit covers the HVAC and ductwork installation. Toronto permit fees for laneway suites typically run $5,000 to $15,000 total (covering building, mechanical, electrical, and plumbing), with the mechanical portion being $500 to $1,500. Budget $3,000 to $8,000 for ductwork specifically, and discuss HVAC system options with your contractor early in the design process — the system choice drives the ductwork design. Toronto Ductwork can help you find qualified HVAC contractors experienced with laneway suite projects through the Toronto Construction Network.