National baseline
The NBC specifies minimum exhaust ventilation rates for bathrooms, kitchens, and other rooms. Use the applicable section for the building's Part 9 or Part 3 classification.
Canadian building code question
What are the building code requirements for exhaust fan and bathroom ventilation rates in Canada?
Bathrooms, kitchens, and other rooms that produce moisture or contaminants require mechanical exhaust ventilation at rates specified in the building code. The required exhaust rate depends on room type and size, and the ductwork must terminate to the exterior. Provincial adoption and the distinction between Part 9 and Part 3 buildings can change specific requirements.
Exhaust ventilation rates are frequently undersized or improperly installed in residential and small commercial projects. The code specifies minimum exhaust rates by room type, duct sizing and material requirements, and exterior termination rules that prevent recirculation into the building or into adjacent units.
What to check first
- Every bathroom and kitchen requires mechanical exhaust ventilation at code-specified rates. Natural ventilation alone is not sufficient in most conditions.
- Exhaust ducts must terminate to the exterior. Terminating into attics, soffits, or wall cavities is a common code violation.
- The required exhaust rate varies by room type and building classification. Part 9 and Part 3 buildings may follow different ventilation standards.
Jurisdiction notes
Provincial adoption
Provincial amendments may modify exhaust rates or add requirements for specific room types. Confirm the adopted code edition and any provincial supplements.
Energy code interaction
Energy code requirements for airtightness and HRV/ERV systems interact with exhaust ventilation. Ensure the exhaust strategy is coordinated with the overall ventilation design.
Work through it in this order
- Identify all rooms requiring mechanical exhaust ventilation and determine the applicable code section.
- Size exhaust fans to meet or exceed the minimum code-specified rates for each room type.
- Route exhaust ducts to terminate at the exterior with appropriate clearances from openings and property lines.
- Coordinate exhaust ventilation with the overall mechanical ventilation strategy including makeup air and HRV/ERV systems.
Common questions
What is the minimum exhaust rate for a bathroom fan in Canada?
The specific rate depends on the room size and the applicable code section (Part 9 vs Part 3). Do not assume one number applies to all conditions. Check the adopted code tables.
Can I vent a bathroom exhaust fan into the attic?
No. Exhaust ducts must terminate to the exterior. Venting into the attic is a code violation that causes moisture damage and is one of the most common residential inspection failures.
Do I need makeup air for bathroom and kitchen exhaust fans?
In modern airtight buildings, makeup air is typically required to replace the air removed by exhaust fans. The energy code and overall ventilation design determine the specific requirements.