What are the requirements for heating and air-conditioning ducts in Ontario homes?
Ducts must be made of noncombustible or code-permitted materials, sealed at joints, supported at regular intervals, insulated where they pass through unheated spaces, and arranged to supply conditioned air and return air per the design without degrading fire separations.
Paraphrased for clarity — open this provision in the BUILDAiD Library for the exact wording.
Leaky, uninsulated ductwork silently wastes the capacity the F280 calculation worked to establish; sealing joints with mastic or foil tape, not cloth duct tape, is baseline practice. Return air cannot be drawn from garages, and rooms like bathrooms and kitchens face return restrictions to avoid circulating odours and moisture. Where ducts pierce a required fire separation, such as between a house and secondary suite, dampers or specific protection apply. Panned joist spaces for returns are limited and must be tightly fitted; supply runs to far rooms need real design, not guesswork.
The metal ducts feeding warm air around your house must be sealed, properly hung, and insulated wherever they cross cold spaces like attics or garages. Sloppy, leaky ducts mean cold rooms and high gas bills.
Get answers like this for any code question
BUILDAiD Assist searches the building code and answers in plain English with exact citations — in seconds.
This page is provided for general information. Building code requirements depend on your specific project, occupancy and municipality, and code editions change. Always verify requirements against the current Ontario Building Code and confirm with your local building department.