How much does it cost to reline existing ductwork instead of replacing it in Toronto?

Relining existing ductwork in a Toronto home typically costs $3,000 to $8,000 for a whole-house treatment, which is roughly 40 to 60% less than complete duct replacement. The exact cost depends on the total linear footage of ductwork, the condition of the existing system, accessibility, and which relining method is used.

Duct relining involves applying a new interior surface to existing ductwork rather than tearing it out and installing new ducts. This approach makes the most sense when the existing duct system is properly sized and routed but has deteriorated from the inside — rusted galvanized steel, deteriorating fibreglass duct board, or old ductwork with interior mould contamination that can't be adequately cleaned. It's also valuable when the ducts are buried in finished walls, ceilings, or concrete slabs where physical replacement would require significant demolition and reconstruction.

The most common relining methods available in the GTA market include spray-applied polymer coatings, which cost $2,500 to $6,000 for a typical home. A technician cleans the ductwork thoroughly, then sprays a flexible antimicrobial polymer coating onto the interior surfaces using specialized equipment. The coating seals small leaks, encapsulates residual contaminants, and provides a smooth new interior surface. This method works well for galvanized steel ducts with minor rust and for fibreglass duct board where the interior fibreglass surface has deteriorated. The coating adds a negligible reduction in duct diameter — typically less than 1/16 of an inch — so airflow impact is minimal.

Aeroseal duct sealing at $1,500 to $3,500 is sometimes confused with relining but serves a different purpose. Aeroseal seals leaks at joints and connections by blowing polymer particles through the system, but it does not coat or reline the interior duct surfaces. If your primary concern is air leakage rather than interior surface deterioration, Aeroseal may be all you need and costs significantly less than full relining.

Relining is not always the right choice. If your existing ductwork is severely undersized for your current HVAC equipment — a common problem in post-war GTA homes across Scarborough, North York, and Etobicoke where heating-only ductwork was never upgraded when air conditioning was added — relining won't fix the fundamental sizing problem. Similarly, if duct runs are crushed, disconnected, or have major structural damage, replacement is the only real solution. And if asbestos insulation or tape is present on older ductwork, it must be professionally abated before any relining work can begin, adding $2,000 to $5,000 to the project.

Compare relining costs against full replacement to make an informed decision. Complete duct replacement for a typical 1,500 to 2,500 square foot GTA home runs $5,000 to $18,000 including removal of old ductwork. If your ducts are properly sized and routed but just showing their age, relining at $3,000 to $8,000 saves considerable money and avoids the disruption of tearing out ceilings and walls. But if the system has fundamental design problems — undersized trunks, inadequate returns, excessive flex duct — spending money on relining is putting lipstick on a problem that needs a real solution.

Get matched with a ductwork contractor who offers relining services through Toronto Ductwork — it's free to connect through the Toronto Construction Network.