How do I choose between flex duct and rigid metal duct for my Toronto home?

For most Toronto home applications, rigid galvanized steel duct is the superior choice for trunk lines and main supply runs, while flex duct is acceptable only for short branch connections from the main duct to individual registers. The choice between the two significantly affects airflow, energy efficiency, noise levels, and long-term performance — especially in the GTA's demanding climate with its extreme temperature swings.

Rigid galvanized steel duct is the industry standard for good reason. Its smooth interior surface creates minimal friction, allowing air to flow efficiently with low static pressure drop. It is fire-resistant, does not support mould growth, maintains its shape permanently, and lasts the life of the home — 50 years or more with proper installation. In Toronto's climate, where ducts must handle temperature differentials exceeding 55 degrees Celsius between winter and summer extremes, rigid steel holds up without degradation. It is available in round, rectangular, and oval profiles. GTA pricing runs $8 to $20 per linear foot for round and $12 to $30 per linear foot for rectangular, including installation. Spiral round duct — a factory-made option with a continuous spiral seam — is particularly strong, has fewer air leaks than snap-lock duct, and has become popular in GTA basement renovations where an industrial aesthetic is desired, at $10 to $25 per linear foot installed.

Flex duct has its place, but it is frequently misused. It consists of a plastic inner liner with a wire helix for structure, wrapped in insulation and a vapour barrier. Its advantage is ease of installation in tight spaces and for making connections where rigid duct would require multiple fittings. The problems begin when it is installed improperly — which happens far too often. Flex duct must be pulled taut and supported every 4 feet. When it sags, kinks, or is compressed, airflow drops dramatically. A single 90-degree kink in flex duct can reduce airflow by 50 percent or more. Maximum recommended length is 25 feet with no more than 180 degrees of total bends. GTA pricing is $8 to $18 per linear foot installed.

For Toronto homes specifically, consider these factors. In unconditioned attic spaces — common in 1970s to 1990s suburban homes across Mississauga, Brampton, Markham, and Vaughan — flex duct is especially problematic. Over time, the support straps loosen, the duct sags between supports, and the insulation compresses at contact points, creating condensation issues during humid GTA summers. Rigid metal duct with external R-8 insulation wrap is far more reliable in attic installations. In basement renovations, rigid duct gives a cleaner look and better long-term performance. The only scenario where flex duct makes sense is for the final 4 to 6 feet of a branch run connecting a rigid trunk or branch to a register boot — this short flex connection allows for easier alignment and absorbs vibration from the air handler.

The practical recommendation for most GTA homeowners is to use rigid steel for all trunk lines, main branches, and any runs longer than 6 feet, and limit flex duct to short final connections only. If a contractor proposes using flex duct extensively throughout your home because it is faster and cheaper to install, understand that you are trading long-term performance and efficiency for lower upfront cost. Properly designed and installed rigid duct systems cost more initially but deliver better comfort, quieter operation, and lower energy bills for decades. Get matched with a ductwork contractor through the Toronto Construction Network for quotes on your specific project.