Should I install separate ductwork for my Toronto home heating and cooling systems?

No — in the vast majority of GTA homes, heating and cooling share the same duct system, and installing separate ductwork for each would be unnecessarily expensive, space-consuming, and impractical. Modern forced-air HVAC systems are designed to use a single duct network for both heating and cooling, with the furnace and air conditioning coil (evaporator) integrated into one air handler.

The way it works is straightforward. Your furnace heats air and pushes it through the duct system in winter. In summer, the air conditioning evaporator coil sits directly above (or downstream of) the furnace's heat exchanger inside the same cabinet or plenum. The furnace's blower fan pushes air across the cold evaporator coil and through the exact same ducts that carry warm air in winter. The same supply registers deliver conditioned air, and the same return grilles bring air back to be re-cooled. This shared approach is the standard across virtually every forced-air home in the GTA.

The one important design consideration is duct sizing. Heating and cooling have different airflow requirements — cooling typically requires about 400 CFM per ton of cooling capacity, while heating requires roughly 300 CFM per ton equivalent. This means a duct system designed only for heating may be undersized for cooling. Many post-war Toronto homes built in the 1950s and 1960s across Scarborough, Etobicoke, and North York originally had heating-only systems. When central air conditioning was added later, the existing ductwork was often left as-is, resulting in undersized ducts that cannot deliver adequate cooling airflow. If your home has this history and you experience uneven cooling, the solution is not separate ductwork — it is resizing the existing system to handle the higher cooling airflow demand. A qualified contractor will evaluate your current ductwork against Manual D requirements for both heating and cooling loads.

There are a few situations where separate or dedicated ductwork does make sense. An HRV (Heat Recovery Ventilator) or ERV (Energy Recovery Ventilator) system has its own independent duct network — typically small 6-inch supply and return ducts — that brings fresh outdoor air into the home and exhausts stale air. This ventilation ductwork is completely separate from the heating and cooling ducts and is required by the Ontario Building Code in new construction. HRV installation with dedicated ductwork typically costs $2,500 to $5,000. Similarly, exhaust systems for bathrooms and kitchens use their own dedicated ducts that must terminate outside the building envelope — never connected to the heating and cooling ductwork.

Another scenario is radiant floor heating combined with forced-air cooling. Some GTA homeowners install hydronic radiant heating in basement floors or throughout the home, then use a separate forced-air system solely for cooling and air filtration. In this case, the duct system is sized specifically for cooling loads, which can actually allow smaller ducts since heating is handled by the radiant system.

For the typical GTA homeowner replacing or upgrading their HVAC system, one properly sized duct system serving both heating and cooling is the right approach. Budget $3,000 to $15,000 for a complete new duct system designed for both functions. If your current ducts seem inadequate for cooling, get a professional airflow assessment before assuming you need additional ductwork — often the issue is leaky joints, crushed flex duct, or an undersized return, all of which can be corrected within the existing system.