Ductwork near you

Duct problems usually show up as comfort complaints that people blame on the furnace or the thermostat, so check the ducts before replacing equipment.

Leaky joints are among the most common duct problems, especially at the plenum, the elbows and the branch connections. Natural Resources Canada recommends sealing all plenums and supply and return ducts with aluminum foil duct tape, approved flexible plastic tape or water-based mastic. It also warns against standard vinyl-type duct tape, whether for sealing ducts or holding insulation in place, because the adhesive dries out over time.

Mastic is a thick paste brushed over joints and seams that stays flexible once it cures, while foil tape suits clean, dry, flat seams. The contractor focuses on the exposed runs in the basement, the crawl space and the attic, and seals them before they are insulated or closed in.

Good ductwork design starts from the heating and cooling needs of each room: a qualified designer estimates how much heat each room loses in winter and gains in summer, then sizes the supply runs, the returns and the main trunk to deliver the right amount of air without excessive speed or noise. Ducts that are too small make the blower strain and whistle; ducts that are too large can leave the air moving too slowly to reach the far rooms. A new furnace or heat pump is a good moment to check the sizing, since the new equipment may need different airflow.

Balancing sets how the air is shared among rooms. Most branch ducts have a damper, a small plate inside the duct turned by a lever on the outside. Natural Resources Canada suggests partially closing some dampers in the basement and on the main floor while leaving those on the upper levels fully open, but notes that balancing won't always work if there is insufficient return air ducting or inadequate supply ducts. A technician can measure the airflow at the registers and mark the damper positions.

Every metre of duct that runs through an unheated space loses heat before the air reaches the rooms, and in summer, cold air-conditioning ducts in a warm attic or crawl space can sweat and drip. Natural Resources Canada says heating ducts running through unheated or cool basements and crawl spaces should be insulated, using batt or blanket insulation of RSI 2.1 (R-12) or more.

Seal the ducts first, then insulate them, and protect the insulation from moisture, crushing and animals. Attic ducts sit in the coldest part of the house, so a renovation is a good chance to bring them inside the heated space; when that isn't possible, they need careful sealing and insulation. In a heated, finished basement, the ducts are already inside, so sealing usually comes first.

A forced-air system has to take back as much air as it delivers. Many older homes have only one or two central returns, so a bedroom with its door closed gets little conditioned air, and the whole system can become noisy or strained. Since balancing can't make up for missing return air, adding returns is often part of fixing a comfort problem.

Sheet metal ducts can last a long time, so age alone is rarely a reason to replace them. Repairing and sealing usually make sense when the layout works and only some sections leak, sag or rattle. Replacement is worth considering when ducts have rusted after basement flooding or years of condensation, when flexible ducts are torn or kinked, when the layout no longer matches the rooms after a renovation, or when a new heat pump or air conditioner needs more airflow than the old ducts can carry. Open walls and ceilings are the best time, since new runs can go where they belong rather than wherever they fit.

In older homes, some duct wrap, joint tape and insulation may contain asbestos, and you can't tell by looking. Health Canada says asbestos-containing materials left undisturbed and in good condition pose no significant health risk, and advises hiring professionals trained to handle asbestos if you plan to renovate. If you suspect it, don't cut, sand or strip old duct wrap: have it assessed and, if needed, removed by a qualified specialist before the ductwork begins.

Day-to-day duct care is simple: change or clean the furnace filter as the manufacturer recommends, keep registers and returns clear of furniture and rugs, and check the exposed runs once a year for loose joints or damaged insulation. Duct cleaning is a separate service that helps in specific cases, such as after dusty renovations or water damage, and our duct cleaning page explains when it's worth it. Sealing and balancing fix problems that cleaning can't.