Can duct sealing lower heating costs?

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How Leaky Ducts Drive Up Heating Costs

Forced-air furnaces and ducted heat pumps push heated air through a network of metal or flexible ducts to reach every room. When those ducts have gaps at the joints, disconnected sections, or seams that were never properly sealed during construction, a portion of that heated air escapes into attics, crawlspaces, basements, or wall cavities instead of reaching your living space. Your thermostat still reads the same target temperature, so the furnace keeps running longer to compensate, burning more gas or electricity to deliver the same comfort. In many older homes across Metro Vancouver, especially those built before more modern duct-sealing standards became common practice, ductwork was assembled with slip joints and screws alone, with no mastic or foil tape to seal the connections.

This isn't just a comfort issue. Leaky return-side ducts can also pull unconditioned, dusty, or musty air from crawlspaces and attics into your system, which then gets recirculated through your home. Combined with the extra runtime needed to compensate for lost heat, leaky ducts create a double cost: higher energy bills and reduced indoor air quality.

Why This Matters More in Metro Vancouver Homes

Metro Vancouver's climate is generally mild, but our wet winters and periodic cold snaps mean furnaces and heat pumps run for extended stretches over many months rather than in short bursts. That extended runtime magnifies the cost of any duct leakage. Add to that the region's substantial stock of older housing, character homes, and post-war bungalows with ductwork routed through unheated crawlspaces or attics, and duct leakage becomes a more significant factor than it might be in a newer, tightly built home. Condos and townhomes are a different story: duct runs are often shorter and may stay within conditioned space, which can limit (but doesn't always eliminate) the potential savings from sealing.

What You Can Safely Check Yourself

• Look at accessible ductwork in the basement, crawlspace access, or utility room for visibly disconnected joints, torn flex duct, or sections wrapped in old, cracked cloth tape.
• Feel around duct joints and register boots (where the duct connects to a floor or wall vent) for drafts when the system is running.
• Check whether rooms far from the furnace feel noticeably cooler or take longer to warm up than rooms closer to the equipment, which can point to duct losses along the way.
• Note any unusually dusty or musty odor coming from vents, which can indicate return ducts are pulling air from an unconditioned space.
• Check that furniture, boxes, or renovation debris haven't crushed or disconnected flexible ductwork in a crawlspace or storage area.

If any of these checks turn up an obvious problem, especially near the furnace itself, do not attempt to reseal or reroute ductwork close to the flue, draft hood, or combustion air supply. That area needs to stay exactly as a licensed technician installed it.

What Requires a Licensed Technician

Proper duct sealing uses mastic sealant or UL 181-rated foil tape, not standard cloth duct tape, and often requires accessing tight crawlspaces, attics, or sections behind finished walls. A technician will also test airflow and static pressure to confirm the system is balanced after sealing, and will inspect ductwork near the furnace's combustion components to make sure nothing about the venting or gas connections has been disturbed. Under BC's Technical Safety BC framework, any work touching a gas furnace's combustion venting, flue, or gas line must be performed by a licensed gas fitter. A CANRO technician holding Technical Safety BC gas licence LGA0043870 can seal ductwork and safely inspect the connected gas appliance in the same visit.

What to Expect From a Professional Duct Sealing Visit

1. An inspection of accessible ductwork throughout the home, including crawlspaces, attics, and basements, to identify leaks, disconnections, and crushed or damaged sections.
2. A check of airflow at supply and return registers to identify rooms that are underperforming due to duct losses.
3. Sealing of accessible joints and seams with mastic or foil tape rated for HVAC use, along with reconnecting or repairing any disconnected sections.
4. A review of insulation around ducts running through unheated spaces, since insulation and sealing work together to reduce heat loss.
5. A safety check of the furnace's combustion venting and gas connections if ductwork near the appliance was accessed, consistent with Technical Safety BC requirements.
6. A written summary of what was found and sealed, so you know what was addressed and whether any further duct replacement or upgrade might be worth considering.

Duct Sealing vs. Other Ways to Lower Heating Costs

Duct sealing is usually one of the more cost-effective steps because it targets a specific, fixable loss point without requiring a full equipment replacement. It's often worth addressing before or alongside a furnace or heat pump upgrade, since a new high-efficiency system connected to leaky ductwork won't deliver its full potential savings.

Financing and Rebate Considerations

The federal Canada Greener Homes grant closed to new applicants in early 2024, so it's no longer available for new projects. Homeowners planning broader efficiency upgrades, including duct work paired with a furnace or heat pump replacement, may still want to look into the interest-free Canada Greener Homes Loan program (up to $40,000) or the Oil to Heat Pump Affordability (OHPA) program if switching from oil heat. CleanBC, BC Hydro, and FortisBC also run rebate programs from time to time for qualifying equipment upgrades. Program details and amounts change, so confirm current eligibility and figures directly with the program or ask at the time of your quote rather than relying on older information.

Frequently asked questions

Reviewed by the CANRO Heating & Cooling service team — July 11, 2026. CANRO holds Technical Safety BC gas licence LGA0043870 and boiler licence LBP0046450, employs Red Seal certified technicians, and carries WorkSafeBC and liability insurance. 4.9★ from 85+ Google reviews · serving Metro Vancouver since 1999 · (604) 359-1081 · info@canroheat.ca.