Expert Guide to 2024 Ontario Building Code Duct Construction & Installation for London Homes
Sarah's Expert Insight
OBC Compliance Specialist
"At empcontracting.ca Inc., we see many HVAC failures in London and Muskoka renovations due to improper sealing in unheated crawlspaces and the direct nailing of trunk ducts to joists. Following the 2024 OBC thickness and firestopping standards is not just a legal requirement—it is critical for maximizing energy efficiency and ensuring fire safety between garage and living spaces."
Navigating the complexities of the 2024 Ontario Building Code (OBC) is essential for any residential renovation or new build. As empcontracting.ca Inc. your construction contractor in London, Ontario, we ensure every HVAC component meets or exceeds provincial standards for safety and efficiency.
OBC Table 9.33.6.5: Minimum Metal Thickness for Ducts
The thickness of your ductwork is regulated based on the material (Galvanized Steel vs. Aluminum) and the shape of the duct. Proper gauge selection prevents noise, buckling, and airflow resistance.
Round and Rectangular Duct Specifications
- Round Ducts: Single dwelling units (125mm or less) require a minimum thickness of 0.254mm for steel.
- Rectangular Ducts: For enclosed ducts over 350mm, a minimum thickness of 0.41mm (Steel) or 0.41mm (Aluminum) is mandatory.
- Clearance Requirements: Thickness requirements increase for rectangular ducts that are not enclosed with clearances exceeding 12mm to provide structural integrity.
9.33.6.6. Standards for Construction of Ducts and Plenums
Proper construction prevents air leaks and fire hazards. Key requirements include:
- Firestopping: Spaces between heating supply ducts and construction material in walls or floors must be firestopped with noncombustible material.
- Mechanical Supports: Ducts must be secured by metal hangers or straps. Wooden brackets are only permitted where zero clearance is specifically allowed.
- Joint Integrity: Round joints must lap at least 25 mm, while rectangular connections require S and drive cleats or equivalent mechanical fasteners.
- Stiffness: Rectangular panels wider than 300mm must be shaped (cross-broken) to provide sufficient stiffness and prevent "oil-canning" noise.
9.33.6.7. Critical Installation Rules for Ontario Dwellings
How ducts are positioned and connected impacts the health and safety of the home:
Safety and Air Quality Compliance
- Garage Separation: Air duct systems serving garages must never be interconnected with the living areas of a dwelling to prevent carbon monoxide infiltration.
- Airtight Sealing: Ducts passing through unheated spaces, common in Muskoka cottages or London crawlspaces, must be taped and sealed to be completely airtight.
- Support: Trunk supply ducts cannot be nailed directly to wood members; they require proper suspension to allow for thermal expansion.
Disclaimer: This content is generated from the Ontario Building Code for educational purposes. Always consult with a licensed professional engineer or your local building department before starting any construction project in London, Ontario.