Can squirrels or raccoons damage ductwork in a Toronto home attic?

Absolutely — wildlife damage to attic ductwork is a surprisingly common problem in the GTA, and raccoons in particular can cause thousands of dollars in duct damage in a remarkably short time. Toronto has one of the densest urban raccoon populations in North America, and squirrels are equally persistent about finding warm nesting spots in residential attics across every GTA neighbourhood.

Raccoons are the more destructive of the two. They are strong enough to tear apart flex duct completely — ripping through the outer vapour barrier, pulling apart the fibreglass insulation, and puncturing or disconnecting the inner plastic liner. They target flex duct because it is soft and easy to manipulate, and they are attracted to the warm air flowing through supply ducts in winter. A raccoon nesting in an attic will often tear open a supply duct to create a warm air source near its den, disconnecting the run entirely. The damage typically affects multiple duct sections because raccoons move through the attic and disturb ductwork along their travel paths. Beyond the physical damage, raccoon feces and urine contaminate duct insulation and can introduce harmful bacteria and roundworm eggs into the air system if the inner duct liner is breached.

Squirrels cause different but still significant damage. They chew through flex duct outer jackets and insulation to access nesting material — the fibreglass insulation inside flex duct is attractive nesting material for squirrels. They also gnaw on duct board and can chew through the foil facing of fiberglass duct board sections, compromising both the air seal and the insulation value. Squirrel entry points into attics often occur at soffit vents, ridge vents, and gable vents — the same locations where exhaust ducts terminate, so bathroom and kitchen exhaust duct terminations are frequently damaged by squirrels enlarging the opening to gain entry.

If you discover wildlife damage to your ductwork, the repair sequence matters. First, the animals must be removed and excluded from the attic by a licensed wildlife removal company — repairing ductwork before sealing entry points guarantees repeat damage. Second, any contaminated insulation and duct sections must be removed and disposed of properly. Raccoon feces require careful handling due to Baylisascaris roundworm risk. Third, damaged duct sections are replaced and reconnected with proper mechanical fasteners, mastic, and UL 181 foil tape. Finally, all duct insulation is replaced and vapour barriers are sealed.

The cost for wildlife-related duct repair in the GTA typically runs $500-$3,000 depending on the extent of damage, with the wildlife removal and exclusion adding another $300-$1,500 as a separate service. If raccoon contamination is extensive, professional cleaning and sanitizing of the remaining duct system is recommended, adding $300-$700 for duct cleaning by a NADCA-certified company. Homeowner's insurance sometimes covers wildlife damage to ductwork — check your policy before paying out of pocket, as the claim may be worthwhile for extensive damage. For the duct repair portion, a qualified ductwork contractor can assess the damage and recommend whether individual sections can be repaired or whether full replacement of the attic duct runs makes more sense given the extent of the problem.