How much does flex duct cost compared to rigid metal duct in the Toronto area?

Flex duct costs $3 to $8 per linear foot for materials or $8 to $18 per linear foot installed, while rigid galvanized steel duct costs $8 to $30 per linear foot installed depending on the profile. On a material-only basis, flex duct is roughly one-third to one-half the cost of rigid metal duct. However, the installed cost gap narrows because rigid duct goes up faster for straight trunk runs, and flex duct's apparent savings can be completely erased by the performance problems that cheap or improper flex duct installations create.

Rigid galvanized steel duct is the industry standard for trunk lines and main supply runs in GTA homes. Round rigid duct runs $8 to $20 per linear foot installed, rectangular (used for trunk lines where vertical clearance is limited) runs $12 to $30 per linear foot installed, and spiral round duct — a premium option with fewer air leaks and a clean aesthetic for exposed installations — runs $10 to $25 per linear foot installed. Rigid duct has a smooth interior that creates minimal friction, meaning air flows more efficiently and the system operates more quietly. It is durable, does not sag, does not support mould growth, and lasts the lifetime of the home with minimal maintenance.

Flex duct has a legitimate role in residential ductwork, but it is limited. Flex duct is appropriate for short branch runs from a rigid trunk line to individual supply registers — typically 6 to 15 feet maximum with no more than 180 degrees of total bends. It is useful in tight spaces where rigid duct cannot make the turn, and it absorbs some vibration and noise from the air handler. However, flex duct that is kinked, compressed, sagged, or run in excessive lengths dramatically reduces airflow. A single 90-degree kink in a flex duct run can reduce airflow by 50 percent or more. When flex duct sags between supports in an attic, the corrugated inner liner creates turbulence that increases friction far beyond what rigid duct produces.

The real cost comparison should factor in long-term performance. A home with an all-flex duct system (common in some builder-grade GTA new construction from the 2000s onward) will use 10 to 20 percent more energy than an equivalent home with rigid trunk lines and short flex branches. Over 15 to 20 years, that energy penalty can easily exceed the initial savings on materials. Flex duct also has a shorter functional lifespan — 15 to 25 years before the outer jacket and insulation degrade — compared to rigid galvanized steel that lasts 50 years or more.

The best approach for most GTA homes is rigid galvanized steel for all trunk lines and main supply runs, with flex duct used only for short final connections to registers. This gives you the durability and efficiency of rigid duct where it matters most, with the flexibility and vibration isolation of flex duct for the last few feet. When getting quotes, ask contractors to specify which sections will be rigid versus flex — a contractor who proposes all-flex duct for a complete system is cutting corners.