Forced Air vs Boiler Ontario 2026: When Each Wins and What It Costs to Switch

Forced Air System Basics

A forced air system moves conditioned air through a single network of sheet metal or flexible ducts. The heat source is usually a natural gas furnace, an electric furnace, or a cold-climate heat pump paired with an electric or gas backup. The same ductwork carries cool air from an air conditioner evaporator coil mounted above the furnace in summer.[1]

The core components are the furnace or air handler, the evaporator coil, the supply and return duct network, a blower motor, and a filter. Sizing follows the ACCA Manual J load calculation, which replaced the old square-foot shortcut and is now the ANSI recognized standard for residential load sizing across North America.[6] For a typical Ontario home, Manual J results land near 30 to 45 BTU per square foot for heating and 20 to 25 BTU per square foot for cooling, but the full calculation accounts for window area, insulation, orientation, and infiltration rather than pure floor area.

Forced air dominates Ontario new construction because one distribution network delivers heating, cooling, filtration, and fresh air in one install. Builders also prefer it because ducts are easier to rough in before drywall than a hydronic loop with radiators sized and placed room by room.

Boiler System Basics

A boiler heats water, then circulates it through a loop of pipes to emitters in each room. The emitters transfer heat into the space and the cooled water returns to the boiler to be reheated. The loop uses a sealed, pressurized system with a circulator pump, an expansion tank, and zone valves for room-by-room or floor-by-floor temperature control.

There are four common emitter types in Ontario homes:

• Cast iron radiators. Tall, heavy standing units, typical of pre-1945 homes. They run at 70 to 80 C water temperature and retain heat for hours after the boiler cycles off.
• Baseboard convectors. Low-profile fin-tube units along the wall, common in 1960s and 1970s additions to hydronic systems. They heat up and cool down faster than cast iron.
• Panel radiators. Modern flat steel panels mounted on the wall, popular in European-style builds and in hydronic heat pump retrofits because they can run at lower water temperatures when sized generously.
• Radiant floor loops. PEX tubing embedded in a concrete slab or stapled to the underside of a subfloor. Water typically runs at 32 to 45 C, well below radiator temperatures, which makes radiant floors the best match for air-to-water heat pumps.

Modern condensing gas boilers hit 95 percent AFUE efficiency, comparable to the best modern furnaces. Older cast iron boilers from the 1970s and 1980s typically run at 60 to 75 percent efficiency and are often the highest-return replacement target in an older Ontario home.

Pros and Cons of Each

Neither system is universally better. They solve different problems and the right answer depends on the house, the existing infrastructure, and what the homeowner values.

The most common reason Ontario homeowners prefer boilers is comfort. Radiant heat warms objects and occupants directly rather than mixing room air, and there is no blower cycle that kicks cold air across the floor on startup. The most common reason people prefer forced air is that one system solves both heating and cooling, with filtration and ventilation options that hydronic systems cannot match without adding a parallel air distribution network.[5]

Why Older Ontario Homes Have Boilers

The pre-war and post-war split in Ontario housing stock is the single biggest predictor of what kind of heating system a home has. In Toronto, Hamilton, Ottawa, and older parts of London and Kingston, homes built before roughly 1945 almost universally have hydronic heat, typically with cast iron radiators fed by a boiler that was originally coal or oil fired.

Three factors drove this:

• Balloon framing and solid masonry construction left very little room for duct chases. Running 6 inch round supply ducts through a 4 inch wall cavity was not practical, so heat was pushed through narrow 3/4 inch and 1 inch iron pipes that fit anywhere.
• Central air conditioning did not exist in residential form until the 1950s. There was no second reason to install a duct network, and the labour of opening plaster walls for ducts only to use them for heat was uneconomic.
• Cast iron radiators are extremely durable. Ontario homes from the 1910s and 1920s commonly still have their original radiators, which is why so many boiler systems have simply been rebuilt around the same distribution loop for a century.

Post-war construction flipped the math. By the early 1950s, builders were framing with 2x4 platform construction (easier duct chases), central air conditioning was becoming available, and the integrated furnace-plus-AC package was cheaper to install than a hydronic loop plus a separate cooling system. From 1955 onward, forced air became the default in Ontario subdivisions, and it has stayed that way. A home built in Mississauga, Markham, or Oakville in the 1970s, 1980s, or 1990s almost certainly has forced air. For a deeper dive on how heating decisions interact with old-home quirks, see our guide to century home HVAC in Ontario.

Cost of Switching Between Systems

Conversions go both directions, though one is far more common than the other in practice.

Boiler to Forced Air

This is the harder, more expensive conversion. A typical 1920s Toronto semi-detached with cast iron radiators on two floors and a basement needs a full duct network added from scratch, which means opening closets, soffits, and parts of the ceiling to run supplies and returns, then patching the plaster. Costs in 2026:

• Furnace, coil, and AC equipment: $8,000 to $14,000 installed for a mid-efficiency pair sized for the home.
• Ductwork fabrication and installation: $10,000 to $25,000, highly dependent on home layout and access.
• Drywall, plaster, and paint repair: $5,000 to $15,000 depending on scope and finishes.
• Boiler and radiator removal and scrap-out:$2,000 to $5,000. Cast iron is heavy and awkward to move.
• Electrical upgrades: $1,500 to $4,000 for the new furnace circuit, AC disconnect, and any panel work.

Total range is $25,000 to $60,000, with most projects landing between $35,000 and $50,000. The cost is mostly the renovation work, not the HVAC equipment itself. In a gutted renovation the incremental duct cost drops sharply because walls are already open.

Forced Air to Boiler

Going the other direction is rare in Ontario and usually only done as part of a major renovation that adds radiant floor heat. A full hydronic retrofit in a 2,000 sq ft home runs $28,000 to $55,000, depending on whether the original ductwork is kept for cooling and fresh air or torn out entirely. The most common version is a hybrid: keep the ductwork for the AC, add a boiler and radiant floor loop in a basement renovation or main floor addition for comfort, and run both systems off a smart thermostat.

Keeping the Boiler, Adding Cooling

For most Ontario homeowners with an older boiler-heated house, the sensible move is not to convert at all. Keep the boiler, which is quiet and long-lived, and add a dedicated cooling system:

• Ductless mini-split heads: $3,500 to $6,000 per zone installed. A three-zone setup for main floor, primary bedroom, and second-floor hallway is typical and runs $10,000 to $16,000. Heads also provide supplemental heat in shoulder seasons.
• High-velocity small-duct systems (SpacePak, Unico): $18,000 to $30,000 installed for a whole-home retrofit. 2 inch flexible supply tubing snakes through wall cavities, existing bulkheads, and closet chases without major demolition.
• Central ducted AC with full new ductwork:equivalent cost to the boiler-to-forced-air conversion above, and rarely worth it unless the plan was to scrap the boiler anyway.

Heat Pump Compatibility with Each

Heat pump retrofits are the single most important HVAC decision in Ontario right now, and the existing distribution system determines which heat pump makes sense.[2]

Forced air homes can drop in a cold-climate air-source heat pump at the next AC replacement cycle. The heat pump replaces the outdoor condenser, a matching indoor coil sits above the existing furnace, and the furnace becomes backup heat for the coldest days. Installation cost is typically $10,000 to $16,000 including the coil swap. The Canadian Home Builders' Association has integrated heat pump sizing into the Net Zero program technical requirements, which makes heat pumps the default primary heat source in new net zero construction.[3]

Boiler homes have two paths. The simpler one is to leave the boiler as backup and add a ductless mini-split or two for cooling plus shoulder-season heating, covering 60 to 80 percent of annual heat load with the heat pump. The more ambitious path is a full air-to-water heat pump that replaces the boiler, paired with lower-temperature emitters. Air-to-water units run water at 45 to 55 C in heating, not the 70 to 80 C of a traditional radiator boiler, so the emitters usually need upsizing. Cast iron radiators are often oversized enough that they still work at 55 C in a reasonably insulated home, but panel radiators and baseboards typically need replacement or doubling up.

A retrofit guide to running a heat pump alongside existing radiators is covered in our heat pump with radiators in Ontario guide. If you are starting from a basement renovation or a slab addition, our radiant floor heating guide covers the design decisions for lower-temperature hydronic distribution, which pairs best with air-to-water heat pumps.

When Each Wins

The short version:

• Forced air wins for new construction, post-war Ontario homes that already have ducts, homeowners who want cooling and filtration in one system, and anyone planning a cold-climate heat pump retrofit. It is the cheaper path by a wide margin when the ductwork already exists or the walls are open.
• Boilers win for pre-war Ontario homes that already have radiators (don't pay to rip them out), for people who prioritize silent, even heat, for new builds with radiant floors in the design, and for air-to-water heat pump retrofits where the emitters can be sized for lower water temperatures from day one.
• Hybrid wins for most older Ontario homeowners. Keep the boiler, add ductless mini-splits for cooling and shoulder-season heat, and reassess when the boiler eventually needs replacement in 15 to 20 more years. By then air-to-water heat pump technology will likely be mature enough in Canada to justify a full swap.

The wrong move in 2026 is spending $40,000 to convert a working boiler system to forced air just to get central AC, when a three zone ductless install does the same job for $14,000 and leaves the 30-year-old cast iron radiators in place doing what they do best.[4]

Frequently Asked Questions