What maintenance should I do on my Toronto home ductwork before summer cooling season?

Before switching to cooling mode each spring, a few key ductwork maintenance tasks will help your air conditioning run efficiently, prevent condensation problems, and improve indoor air quality throughout the GTA's hot, humid summer months. Most of these tasks are straightforward and can be done by a capable homeowner in an afternoon.

Start with your furnace filter. Replace or clean it before the cooling season begins, even if you changed it recently. A dirty filter restricts airflow across the evaporator coil, reducing cooling capacity, increasing energy consumption, and potentially causing the coil to freeze. For the GTA's humid summers, a pleated filter rated MERV 8 to MERV 11 strikes the best balance between filtration and airflow — higher-rated filters can restrict airflow in older duct systems that were not designed for the added resistance. Plan to check or replace your filter monthly during peak cooling season (June through September) when the system runs frequently.

Clean all supply registers and return air grilles. Remove them from the wall or floor, wash with warm soapy water, dry thoroughly, and reinstall. Dusty, clogged registers restrict airflow and distribute dust and allergens throughout your home when the air conditioning starts up. While the registers are off, look inside the duct opening with a flashlight — if you see significant dust buildup, debris, or visible mould, professional duct cleaning may be warranted. Legitimate duct cleaning in the GTA costs $300 to $700 from reputable NADCA-certified companies using truck-mounted equipment. Be extremely wary of companies advertising $99 whole-house specials — these are bait-and-switch operations.

Inspect any visible ductwork in your basement, utility room, and attic for damage from the winter season. Look for disconnected joints, sagging flex duct, crushed sections, rust spots, water stains, and gaps at connections. Toronto's 50-plus freeze-thaw cycles per winter cause expansion and contraction that loosens duct joints over time. Any visible gaps or disconnections should be resealed with duct mastic or UL 181-rated foil tape — never grey cloth duct tape, which fails quickly in GTA temperature extremes. Sealing accessible duct joints with mastic is a manageable DIY task in an unfinished basement — a gallon of mastic costs $15 to $30 and covers 30 to 50 joints.

Check your condensate drain. Your air conditioning evaporator coil produces condensation that drains through a condensate line. If this line is clogged with algae or debris, water backs up and can overflow onto your furnace, into your ductwork, and onto your basement floor. Pour a cup of white vinegar down the condensate drain to clear biological buildup, and verify that water flows freely through the drain when the system runs.

Open all supply registers throughout the home. If you closed registers in unused rooms during winter, open them before starting air conditioning. Closing too many registers increases static pressure in the duct system, which can damage the blower motor, cause air leaks at duct joints, and reduce overall cooling performance. If you want room-by-room temperature control, ask a ductwork professional about a zoning system with motorized dampers — this is the proper way to control airflow without stressing the system.

Finally, if your home has ductwork running through the attic, inspect the duct insulation for damage, compression, or displaced vapour barrier. Summer cooling creates the worst condensation conditions in attic ducts — cold supply air at 12 to 15 degrees Celsius running through ducts in a 50-degree attic will sweat heavily if insulation is inadequate. R-8 minimum duct wrap insulation is essential in GTA attics.