How to read your result
The code asks for one fan, called the principal ventilation exhaust fan, to run all the time at no less than the airflow in the result. An HRV or ERV is a common way to provide that continuous ventilation in a tight house, because it recovers heat from the air it exhausts. New homes built to the Step Code are tested for airtightness (a Victoria builder's guide to Step Code levels for new homes explains the targets), and how tight the house is depends partly on how its walls are framed, which a builder's note on Step Code wall assemblies and framing tolerances walks through. If your unit has several speeds, its lowest speed still has to meet the number shown.
The airflow is a minimum, not a recommended size. Installers also look at how the ducts are laid out, how much the unit boosts for showers and cooking, and how loud it is: the code limits the principal fan to 1.0 sone at the required airflow. Compare unit airflow at 50 Pa of external static pressure, the pressure the code uses for the rating.
How we calculate this
- Airflow: BC Building Code 2018 (Revision 2.01), Division B, Section 9.32, Table 9.32.3.5, Principal Ventilation System Exhaust Fan Minimum Air-flow Rate, by floor area band and bedroom band. Checked October 9, 2026. The 2024 edition was not opened; a search of its table showed the same values for the two smallest floor area bands.
- Kitchen and bathroom fans: the same section, Table 9.32.3.6, lists 47 L/s for a kitchen (intermittent) and 23 L/s for a bathroom (intermittent) or 9 L/s (continuous), unless the bathroom is served by the principal fan. Checked October 9, 2026.
- Floor area is converted at 10.7639 sq ft per square metre and airflow at 2.11888 CFM per L/s, then rounded up to a whole CFM.
- Our assumption: the floor area you enter is the code's floor area. We did not confirm how the code counts basements or secondary suites.