What ventilation design works best for a Toronto home with a large open kitchen and island?

For a large open-concept kitchen with an island in a Toronto home, the best ventilation design combines a high-performance island range hood (600–1,200 CFM depending on cooking style) with a properly engineered make-up air system — because once you exceed 75 litres per second (approximately 159 CFM) of exhaust, Ontario Building Code requires make-up air to replace what you're pulling out.

Getting this right in a Toronto home involves more than just picking a hood that looks good over your island. Open-concept kitchens present a specific challenge: without walls to contain cooking exhaust, grease, steam, and odours migrate freely into adjacent living and dining areas. A hood that might be adequate in a closed kitchen is often undersized for an open plan, where cross-breezes from HVAC supply registers, ceiling fans, and foot traffic constantly disturb the capture zone directly above the cooktop.

Hood sizing for island installations follows a different rule than wall-mounted hoods. Because island hoods have no back wall to help direct rising exhaust plumes, they need to be wider than the cooktop on all four sides — typically 6 inches of overhang on each side minimum. For a 36-inch cooktop, that means a minimum 48-inch hood. CFM requirements depend on your cooking style: gas ranges produce significantly more heat and combustion byproducts than electric or induction, requiring higher airflow. A general rule is 100 CFM per 10,000 BTU for gas, but for open-concept spaces, add 25–30% to account for the lack of containment. A 60,000 BTU gas range in an open kitchen realistically needs 750–900 CFM to capture effectively.

The make-up air requirement is where most Toronto homeowners get surprised. At 75 L/s (159 CFM), you're already into OBC make-up air territory — and most island hoods run at 400–1,200 CFM. Without make-up air, running a powerful hood creates negative pressure in the home. This causes backdrafting in gas appliances (furnace, water heater, fireplace), pulls cold air through every gap in the building envelope in winter, slams doors, and dramatically reduces the hood's actual capture efficiency. The make-up air system must be interlocked with the hood so it activates automatically, and in Toronto winters, the incoming air must be tempered — either through a heating coil or by mixing with conditioned air — so you're not blasting -15°C air into your kitchen every time you cook.

Duct routing for island hoods is one of the more complex sheet metal challenges in residential construction. The duct must rise through the ceiling, navigate between floor joists or through a soffit, and reach an exterior wall or roof penetration — all while maintaining adequate duct diameter to keep air velocity below 900 FPM (feet per minute) to minimize noise. For a 900 CFM hood, you need a minimum 10-inch round duct (or equivalent rectangular). Longer duct runs require larger diameters. Every elbow adds resistance — a 90-degree elbow is equivalent to 15–20 feet of straight duct for friction loss purposes. This is why duct routing should be planned before the kitchen is designed, not after the cabinets are in.

GTA-specific considerations matter here. Toronto's cold winters mean any duct penetrating an exterior wall or roof needs a proper insulated cap with a motorized damper that closes when the hood is off — otherwise cold air backdrafts through the duct constantly, and condensation forms inside the duct during cold snaps. Grease accumulation in a duct that experiences freeze-thaw cycling is also a fire hazard that needs annual inspection.

For a project like this, you're looking at $1,500–$4,500 for the exhaust duct and exterior termination, plus $2,000–$5,000 for a make-up air system — costs that are separate from the hood itself. An ESA-Licensed Electrical Contractor handles the hood wiring and make-up air controls; a TSSA-registered contractor handles any gas connections if the make-up air system uses a heating coil.

This is a project that requires a sheet metal contractor experienced with residential ventilation and make-up air systems, not just a general HVAC company. Toronto Ductwork can match you with local ventilation contractors through the Toronto Construction Network — browse the directory at torontoconstructionnetwork.com/directory?trade=hvac or get matched for a free estimate.