Comparison Checklist
Mechanical room constraints
Ductwork condition and size
Venting type and code compliance
Insulation and air sealing level
Electrical panel capacity
Budget and rebate eligibility
| Option | Best For | Watch For | Fit |
|---|---|---|---|
| High-efficiency gas furnace | Homes with existing gas service and ductwork that can accept a modern direct-vent or sidewall-vent furnace. | Mid-efficiency to high-efficiency venting conversion can require new PVC piping, chimney liner removal, and sometimes a permit. | The most common upgrade path for older Toronto homes with functional ductwork. |
| Cold-climate heat pump with gas backup | Homeowners interested in reducing gas use and qualifying for Greener Homes or Enbridge rebates. | Electrical panel capacity is the first thing to check. Many older homes have 100-amp service, which may not support a heat pump without an upgrade. | Growing choice for pre-war and post-war Toronto homes with recent panel upgrades. |
| Ductless mini split (zoned) | Homes without ductwork, homes with hot or cold additions, or second-floor bedrooms that central systems cannot reach. | Indoor wall units are visible and not every homeowner likes them. Concealed ducted mini splits are an alternative but cost more to install. | Strong fit for Toronto homes with radiant heating, converted attics, or finished basements. |
Why older Toronto homes are harder to size
A 1920s brick semi in Riverdale has balloon-frame walls with minimal insulation, single-pane or replacement windows of varying quality, a shared party wall, and an uninsulated basement. Standard sizing tables assume a level of air sealing and insulation that these homes do not have.
Oversizing the furnace seems like the safe bet, but it leads to short-cycling, uneven temperatures, and wasted gas. A proper heat loss calculation takes insulation condition into account and sizes the equipment to the actual building, not the square footage.
Ductwork limitations in older layouts
Many older GTA homes have undersized return air, fewer supply runs per room, and ductwork routed through uninsulated spaces. Adding a modern high-output furnace to undersized ducts creates noise, static pressure problems, and rooms that are still uncomfortable.
Before quoting equipment, a contractor should inspect accessible ductwork for sizing, condition, and leakage. Sometimes a $500 duct modification solves the comfort problem more effectively than a $6,000 furnace swap.
Venting changes when upgrading from mid-efficiency
Mid-efficiency furnaces vent through a chimney with hot exhaust gases. High-efficiency furnaces produce cooler, acidic condensate that damages masonry chimneys. Switching to high-efficiency means installing PVC venting — either through the side wall or with a chimney liner.
This is a code-required change, not optional. Some older Toronto homes have shared chimneys serving both the furnace and water heater, which adds complexity. A contractor should address venting in the quote, not as a surprise at installation.