What is the best location to install a make-up air intake on a Toronto home exterior wall?

The best location for a make-up air intake on a Toronto home is on an exterior wall facing away from prevailing winds, at least 600mm (24 inches) above grade, well away from exhaust outlets, gas meters, and any combustion appliances — typically on the north or east wall of most GTA homes.

Placement is one of the most consequential decisions in a make-up air installation, and it directly affects system performance, combustion safety, and long-term durability in Toronto's climate. Getting it wrong means pulling contaminated air into your home, freezing the intake in winter, or creating backdrafting conditions that allow carbon monoxide to enter the living space.

Separation from Contamination Sources

Ontario Building Code Part 6 requires make-up air intakes to be separated from exhaust outlets, gas meters, dryer vents, and any combustion appliance venting by a minimum of 1,800mm (6 feet) horizontally and 600mm (24 inches) vertically. In practice, experienced contractors push this further — aim for 3 metres (10 feet) or more from any exhaust point. This matters enormously in Toronto because homes are often close together and exhaust from a neighbour's dryer vent or gas furnace flue can easily reach your intake if placement is careless. Never locate the intake near a garage — vehicle exhaust and carbon monoxide are a serious risk.

The intake must also be positioned away from areas where snow drifts accumulate. Toronto's freeze-thaw cycles and heavy snowfall events can bury a low-mounted intake, blocking airflow entirely and potentially damaging the tempering coil or motorized damper. A north-facing wall in a sheltered corner of the home is particularly vulnerable to drifting — factor in your home's specific snow accumulation patterns before finalizing placement.

Wind Direction and Pressure Dynamics

Toronto's prevailing winds come predominantly from the southwest, especially in winter when cold air masses push in from Lake Huron and Georgian Bay. Locating the intake on the north or east wall keeps it in a lower-pressure zone, which reduces the risk of wind-driven rain and snow entering the duct and reduces the static pressure the system must overcome. An intake on the southwest wall faces direct wind loading in winter, which can overwhelm the motorized damper and force cold air into the home even when the system is off — a serious comfort and energy problem.

Homes near Lake Ontario (Beaches, Mimico, Port Credit, Lakeshore communities) face additional wind considerations from lake-effect weather patterns. In these neighbourhoods, a sheltered north-facing location is almost always the best choice.

Height, Termination Cap, and Insulation

The intake termination cap should be at least 600mm above finished grade — higher if you're in an area with significant snowfall accumulation or if the wall faces a driveway where snow is ploughed and piled. Use a hooded intake cap with a bird screen (minimum 6mm mesh, maximum 13mm to prevent bird nesting). The duct penetrating the wall must be insulated with minimum R-8 duct wrap from the exterior wall to the point where it connects to the air handler or tempering unit. In Toronto winters, an uninsulated make-up air duct running through a cold basement wall cavity will sweat with condensation every time the system runs, causing water damage and mould inside the wall.

The motorized damper — which closes when the system is off to prevent cold air infiltration — must be installed on the warm side of the insulation, not in the cold zone near the exterior wall. This is a common installation error that causes the damper actuator to fail prematurely in GTA winters.

This Is Professional Work

Make-up air system installation requires a TSSA-registered contractor when the system is interlocked with gas appliances, and an ESA-Licensed Electrical Contractor for the control wiring and interlock connections. Improper make-up air installation is one of the leading causes of combustion appliance backdrafting — a carbon monoxide hazard. This is not a DIY project.

If you're installing a high-CFM range hood (400+ CFM) that triggers the OBC's 75 L/s make-up air requirement, get a contractor who will do a proper combustion safety test after installation to confirm no backdrafting is occurring.

Need help finding a qualified ductwork and ventilation contractor for your make-up air project? Toronto Ductwork can match you with local professionals through the Toronto Construction Network — browse contractors at torontoconstructionnetwork.com/directory?trade=hvac.