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Ventilation rate requirements for Canadian buildings
Canadian homes are far more airtight than they once were, so fresh air no longer arrives by leakage alone. Section 9.32 of the building code requires mechanical ventilation in new houses and lists CSA F326 as one compliance route. Without enough outdoor air, moisture, carbon dioxide and pollutants from cooking, cleaning and building materials build up indoors.
ASHRAE 62.2 covers low-rise residential buildings of up to three storeys, and ASHRAE 62.1 covers most other buildings, including offices, schools, retail and larger multi-family buildings. Both aim for acceptable indoor air quality, but use different methods suited to their building types.
The ASHRAE 62.2 whole-building formula
The required continuous rate is Qtot = 0.03 × floor area (ft²) + 7.5 × (bedrooms + 1) in CFM. In metric the same formula reads 0.15 × floor area (m²) + 3.5 × (bedrooms + 1) in L/s, as NIST writes it in its study of ventilation controls. A studio counts as 0 bedrooms. A 2,000 ft² home with 3 bedrooms needs 60 + 30 = 90 CFM, about 42.5 L/s. The result excludes local exhaust in kitchens and bathrooms, and the standard's credit for measured infiltration.
Running the fan part of the day
A fan that runs only part of the day must move more air while it runs. The schedule options use the simple minimum: 24 divided by the hours of operation, so a 12-hour schedule needs at least twice the continuous rate. ASHRAE 62.2 adds a ventilation effectiveness for intermittent fans that depends on the on-time fraction and the cycle length, which can push the requirement higher, so use the result as a floor and check the standard for the final size.
The ASHRAE 62.1 Ventilation Rate Procedure
Commercial zones use two terms: a people term (Rp × occupancy) and an area term (Ra × floor area), which sum to the breathing zone outdoor airflow, Vbz. Dividing by the zone air distribution effectiveness, Ez, gives the zone outdoor airflow, Voz. An office of 1,500 ft² with 20 people has Vbz = 5 × 20 + 0.06 × 1,500 = 190 CFM (about 90 L/s). The presets come from the standard's Table 6.2.2.1 and the Ez options from Table 6.2.2.2, but always check the edition your local code adopts. A multi-zone system also needs a system ventilation efficiency, which the outdoor air calculator applies.
How the Canadian code differs
The code sets principal ventilation for houses with its own rules rather than the 62.2 formula, so the two rates can differ. Before you finalize a design, check the figure against the requirement your authority applies, which the ventilation code calculator works through.
From rate to equipment
Once you have the rate, size the recovery ventilator to deliver at least that flow at the operating schedule. The HRV calculator sizes the core, and the HRV and ERV selection calculator helps you choose between the two.
Frequently Asked Questions
The required rate is Qtot = 0.03 × floor area (ft²) + 7.5 × (bedrooms + 1) in CFM, or 0.15 × floor area (m²) + 3.5 × (bedrooms + 1) in L/s. For a 2,000 ft² home with 3 bedrooms that is 60 + 30 = 90 CFM, or about 42.5 L/s, running continuously. Kitchen and bathroom local exhaust is required in addition, and the standard allows a credit for measured infiltration in some cases, which this tool does not apply.
ASHRAE 62.1 covers commercial, institutional and larger multi-family buildings, using the Ventilation Rate Procedure with a people-based rate (Rp) and an area-based rate (Ra) for each space type, corrected by the zone air distribution effectiveness. ASHRAE 62.2 covers low-rise residential buildings of up to three storeys, using a whole-building formula based on floor area and bedroom count. A house or townhouse is a 62.2 building, while an office, school or high-rise apartment is a 62.1 building.
Yes, but the fan must be larger. Running a fan for 12 hours a day needs at least twice the continuous rate, so 90 CFM becomes at least 180 CFM. The schedule options in this tool give that minimum, using 24 divided by the hours of operation. ASHRAE 62.2 applies a ventilation effectiveness for intermittent fans that can raise the requirement further, so confirm the final fan size against the standard.
Not necessarily. Canadian houses are normally designed to the mechanical ventilation provisions of the building code, which list CSA F326 as one compliance route and require a principal ventilation exhaust fan or ducted central system, so the code rate can differ from the ASHRAE 62.2 figure. Treat this result as the ASHRAE value, and compare it with the whole-house ventilation calculator and your local authority's accepted method.