Can I seal my own ductwork or should I hire a professional in the GTA?

You can absolutely seal accessible duct joints yourself if your ductwork is visible and reachable — unfinished basements with exposed ducts are the ideal DIY duct sealing scenario. However, for ducts hidden in walls, ceilings, enclosed chases, or running through attics and crawlspaces, hiring a professional is strongly recommended for both safety and effectiveness.

DIY duct sealing in an unfinished basement is one of the most cost-effective home improvement projects a GTA homeowner can tackle. The materials are inexpensive and the technique is straightforward. You need a gallon of duct mastic ($15 to $30, covers 30 to 50 joints), a roll of UL 181-rated foil tape ($8 to $15), a disposable brush or old paintbrush, and disposable gloves. Work along the trunk duct from the furnace plenum outward, applying mastic to every joint, seam, connection point, branch takeoff, and register boot. Spread the mastic generously — at least an inch and a half on either side of every joint, thick enough that you cannot see metal through it. Pay special attention to the plenum-to-trunk connection, branch takeoff collars, and the seams where rectangular duct sections join. For reinforcement at critical joints, press UL 181 foil tape over the cured mastic. The entire job in a typical Toronto basement takes four to six hours and can reduce total system leakage by 15 to 25 percent if the basement joints are where most of your leaks are concentrated.

Where professionals are necessary is any ductwork you cannot physically reach and see. Many Toronto homes have supply and return ducts running through finished ceilings, interior walls, between floors, and in enclosed soffits. You cannot seal what you cannot access, and tearing out drywall to reach hidden duct joints is neither practical nor cost-effective. This is exactly where Aeroseal excels — sealing ducts from the inside at $1,500 to $3,500 for a typical GTA home. Professional contractors also have duct blaster equipment to measure total system leakage before and after sealing, giving you verified results rather than guesswork.

Attic ductwork should always be handled by professionals. GTA attics are dangerous workspaces — temperatures exceed 50 degrees Celsius in summer, the spaces are cramped with limited footing, and insulation makes it difficult to see where to step. Beyond safety, attic duct sealing must be done correctly because any leaks in attic ducts are the most expensive kind — conditioned air escaping directly to the outdoors. Professional contractors also handle the insulation work that must follow sealing, wrapping attic ducts with R-8 minimum duct wrap and ensuring a continuous vapour barrier to prevent condensation.

One important caution for older homes: if your ductwork has white or grey tape that appears to be made of a cloth-like material wrapped at joints, do not disturb it without having it tested for asbestos first. Many GTA homes built before 1985 have asbestos-containing duct tape or insulation. Professional asbestos abatement costs $2,000 to $5,000 but is legally required — disturbing asbestos without proper containment is both dangerous and illegal in Ontario.

For a combined approach, many GTA homeowners seal the accessible basement joints themselves and then hire a professional for Aeroseal treatment of the enclosed duct runs. This gives you the best of both worlds — significant savings on the DIY portion and professional results for the ductwork you cannot reach.