What are the signs that my Toronto home ductwork needs to be replaced?

If your ductwork is more than 30 to 40 years old, has visible rust or deterioration, or your energy bills have been climbing despite a newer furnace, it is likely time for replacement. Many GTA homes — particularly post-war construction across Scarborough, North York, Etobicoke, and the inner suburbs — are running on original galvanized steel ductwork that is now 50 to 70 years old, well past its expected service life.

The most obvious sign is visible physical deterioration. Walk through your unfinished basement and look at the ductwork. Rust holes, corroded seams, separated joints, and crushed or sagging flex duct all indicate a system that is leaking conditioned air into unconditioned spaces. If you can see daylight (or feel warm air escaping) at duct joints when the furnace is running, those leaks are costing you money with every heating and cooling cycle. Minor leaks at a few joints can be sealed with duct mastic for $150 to $600, but widespread deterioration across the entire trunk and branch system usually means replacement is more cost-effective than piecemeal repairs.

Uneven temperatures throughout the house that persist despite a properly functioning furnace are another strong indicator. If some rooms are 3 to 5 degrees warmer or cooler than the thermostat setting and adjusting register dampers does not help, the ductwork is likely undersized, poorly routed, or so leaky that insufficient air reaches distant rooms. This is especially common in homes where air conditioning was added decades after the original heating-only duct system was installed — the ducts were never sized for cooling loads, which require roughly 400 CFM per ton versus 300 CFM per ton for heating.

Excessive dust, musty odours, or allergy symptoms that worsen when the system runs can indicate ductwork problems. Older duct systems with failed joints pull unfiltered air from basements, crawlspaces, and wall cavities — bringing dust, mould spores, and insulation fibres into your living spaces. If your home gets dusty within a day or two of cleaning, leaky ductwork is a likely culprit. Additionally, if your ducts have been contaminated by rodent droppings, mould growth inside the duct walls, or residue from old fibreglass duct liner, cleaning alone may not resolve the problem — replacement is the definitive solution.

Rattling, banging, or whistling noises that have gotten progressively worse over the years suggest that joints are loosening, metal is fatiguing, and the system is losing structural integrity. While some noise is normal due to thermal expansion, increasing noise levels indicate worsening deterioration.

If your home has asbestos-wrapped ductwork or asbestos duct tape — common in Toronto homes built before 1980 — you cannot simply patch or modify the system. Professional asbestos abatement is required before any duct work, adding $2,000 to $5,000 to the project cost. A complete duct replacement for a typical GTA home runs $5,000 to $18,000 including removal and disposal of the old system, but the improvement in comfort, efficiency, and air quality is dramatic. Get matched with a ductwork contractor for a free estimate on your project through Toronto Ductwork.