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HRV and ERV Size Calculator: Required Airflow for a BC Home

Rates and rebates last verified October 9, 2026

Find the minimum continuous airflow the BC Building Code asks for from the principal ventilation fan in a new house, based on floor area and bedrooms. Use it to check that an HRV or ERV quote is big enough, in litres per second (L/s) and CFM.

Heated living area. Ask your building official how finished basements count.

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. 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.

Estimate only. Your designer or building official decides which code edition and floor area definition apply to your permit. This tool uses the 2018 code table.

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.

Related guides

Frequently asked questions

How much airflow does the BC Building Code require for a house?

The 2018 code sets a minimum continuous airflow for the principal ventilation exhaust fan from a table of floor area and bedroom count. It runs from 14 L/s for a home under 140 square metres with 0 to 1 bedrooms up to 78 L/s for the largest homes. Enter your numbers to see your row.

Does an HRV or ERV have to be installed in a new home?

The code requires a principal ventilation system in a new house, and a heat or energy recovery ventilator is a common way to provide it in an airtight home. The code table sets the airflow, not the type of equipment.

Is a bigger HRV always better?

No. The table is a minimum, and an oversized unit can cost more, use more fan power and be louder. The code limits the principal fan to 1.0 sone at the required airflow, so ask for the sound rating too.

What airflow rating should I compare?

The code rates the fan at 50 Pa of external static pressure, using the HVI 916 or CAN/CSA-C260 test method. Compare your unit published airflow at that pressure, not its maximum boost.

Does this cover kitchen and bathroom fans?

It shows the code minimums for them too: 47 L/s for a kitchen fan, and 23 L/s for each bathroom fan unless the bathroom is served by the principal fan. Your designer confirms what applies to your permit.