What should I know about ductwork before buying an older Toronto home?

Before buying an older Toronto home, you should know that the ductwork is one of the most expensive and disruptive systems to replace, and older homes across the GTA have duct systems that range from functional but aging to completely inadequate for modern HVAC equipment. Understanding what you are inheriting with the ductwork can save you thousands of dollars in unexpected costs after closing.

Pre-war homes (before 1945) in neighbourhoods like the Annex, Riverdale, Cabbagetown, High Park, and Roncesvalles often have remnants of gravity-fed octopus furnace systems. These featured large, round trunk ducts with minimal branching, designed for natural convection rather than forced air. When previous owners replaced the furnace with a modern forced-air system, the old ductwork was often kept in place. The problem is that modern furnaces operate at much higher static pressures and airflow rates than gravity systems were designed for, resulting in poor air distribution, noise, and uneven temperatures. If you see oversized round ducts with few branches in the basement, that is a gravity system adaptation, and complete duct replacement may be needed — budget $5,000 to $18,000 depending on house size and complexity. Also be aware that pre-1990 duct tape and insulation may contain asbestos, which requires professional abatement costing $2,000 to $5,000 before any duct work can proceed.

Post-war homes (1945 to 1975) across Scarborough, North York, Etobicoke, and the inner suburbs typically have galvanized steel duct systems that are now 50 to 70 years old. These were designed for heating only — air conditioning was added later. The original ductwork is commonly undersized for cooling loads, since cooling requires approximately 400 CFM per ton versus 300 CFM per ton for heating. The telltale sign is a home that heats reasonably well in winter but has rooms that never cool properly in summer. Return air is frequently undersized in these homes, often limited to a single return grille on the main floor. Adding return air ducts to bedrooms and the basement — at $300 to $800 per register — is one of the most impactful upgrades you can make.

During the home inspection, ask your inspector to specifically evaluate the ductwork. Look for visible rust on duct surfaces, disconnected joints in the basement or crawlspace, duct tape holding connections together (which means those joints have already failed), sagging flex duct in attic spaces, and any signs of moisture or mould on duct insulation. Check whether bathroom exhaust fans are ducted to the exterior or dumped into the attic — venting into the attic is a code violation that causes mould and wood rot, and it is extremely common in older GTA homes.

Pay attention to the furnace age and duct compatibility. If the furnace is nearing end of life (15 to 20 years old), you will likely replace it within a few years of buying the home. That furnace replacement is the ideal time to address ductwork deficiencies, since the system is already being redesigned. A new furnace installed on inadequate ductwork will underperform, cycle excessively, and may void the equipment warranty.

If you are seriously considering an older Toronto home, getting a separate ductwork assessment from a qualified HVAC contractor — beyond the standard home inspection — is money well spent. Budget $200 to $400 for an airflow and duct assessment that includes static pressure testing. This gives you real data to negotiate the purchase price or budget for post-closing upgrades. Find ductwork professionals through the Toronto Construction Network directory to get a thorough evaluation before you commit.