How much does it cost to seal leaky ductwork in a Toronto home?

Professional duct sealing for a Toronto home typically costs $1,500 to $4,000 for conventional mastic-and-tape sealing of accessible joints, or $1,500 to $3,500 for Aeroseal technology that seals ducts from the inside. The investment pays for itself surprisingly quickly — the average home with unsealed ductwork loses 20 to 30 percent of conditioned air through leaks at joints, connections, and failed seals before it ever reaches living spaces.

Conventional duct sealing involves a technician accessing every visible joint and seam in your duct system and applying duct mastic — a thick, water-based sealant that remains flexible and does not degrade with temperature cycling — followed by UL 181-rated foil tape over the mastic for a belt-and-suspenders approach. This method works well in homes with unfinished basements and accessible ductwork, but it cannot reach joints hidden inside walls, ceilings, or enclosed chases. A typical GTA home with an unfinished basement and accessible trunk lines falls in the $1,500 to $2,500 range for full sealing of all accessible connections.

Aeroseal is the better option when significant portions of your ductwork are inaccessible. This patented process involves sealing off all registers and then pressurizing the duct system with a polymer aerosol. The tiny particles travel through the ducts and accumulate at leak points, building up a seal from the inside that closes gaps up to 5/8 inch. The system measures leakage in real time before and after, giving you documented proof of improvement. Aeroseal typically reduces duct leakage by 90 percent or more. For homes with ductwork buried in walls and ceilings — common in two-storey GTA homes from the 1970s through 1990s where branch runs pass through wall cavities and floor systems — Aeroseal is often the only practical option short of tearing open finished spaces.

The return on investment for duct sealing is compelling. A home losing 25 percent of conditioned air through duct leaks is essentially heating and cooling air that never reaches the rooms. With GTA natural gas and electricity costs, homeowners typically see $200 to $500 in annual energy savings after sealing, meaning the project pays for itself in three to seven years. Beyond energy savings, sealed ducts deliver more consistent temperatures room to room, reduce dust circulation, and decrease the workload on your furnace and air conditioner, extending equipment life.

If you want to test before committing, ask a contractor about a duct leakage test (also called a duct blaster test), which costs $200 to $400 and quantifies exactly how leaky your system is. This tells you whether sealing is worth the investment for your specific home. Toronto Ductwork can match you with local ductwork professionals for free estimates on sealing your system.