How is the principal ventilation fan sized by number of bedrooms in Ontario?
Required whole-house ventilation capacity scales with bedroom count: roughly 32 L/s for a one-bedroom home, rising to about 51 L/s (108 cfm) for three bedrooms. In Ontario new homes this duty is typically performed by an HRV or ERV.
Paraphrased for clarity — open this provision in the BUILDAiD Library for the exact wording.
Bedroom count is the code's proxy for how many people breathe, cook and shower in the house, so the ventilation table steps up with each bedroom. In Ontario practice, energy efficiency requirements make a heat or energy recovery ventilator the standard principal ventilation appliance, ducted either fully independently or simplified into the forced-air system. Sizing errors usually come from measuring rated airflow instead of installed airflow: duct restrictions can cut delivered capacity dramatically, so commissioning and balancing at final inspection matter as much as the nameplate.
The more bedrooms a house has, the more fresh-air capacity its ventilation system must provide, since bedrooms roughly equal people. A typical three-bedroom Ontario home needs about 50 litres of fresh air per second, usually via an HRV.
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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.