Ontario: the principal exhaust fan
Table 9.32.3.3 of the Ontario Building Code 2024 sets the normal operating exhaust capacity of the principal ventilation fan, between a minimum and a maximum, by number of bedrooms. Floor area plays no role in Ontario. Houses with more than five bedrooms follow CAN/CSA-F326 or Part 6.
| Bedrooms | Minimum (l/s) | Maximum (l/s) |
|---|---|---|
| 1 | 16 | 24 |
| 2 | 18 | 28 |
| 3 | 22 | 32 |
| 4 | 26 | 38 |
| 5 | 30 | 45 |
Ontario: supply and extra fans
Supply goes to each bedroom and to each storey without a bedroom; if every storey has a bedroom, it also goes to the principal living area. Every kitchen needs a fan of at least 50 l/s, unless the principal fan serves it. A bathroom or toilet that the principal fan does not serve needs at least 25 l/s.
British Columbia: the principal exhaust fan
Table 9.32.3.5 of the BC Building Code 2018 sets the minimum continuous flow of the principal fan by floor area and number of bedrooms, in l/s.
| Floor area (m²) | 0 to 1 bedrooms | 2 to 3 | 4 to 5 | 6 to 7 | more than 7 |
|---|---|---|---|---|---|
| up to 139 | 14 | 21 | 28 | 35 | 42 |
| 140 to 280 | 21 | 28 | 35 | 42 | 49 |
| 281 to 420 | 28 | 35 | 42 | 49 | 56 |
| 421 to 560 | 35 | 42 | 49 | 56 | 64 |
| 561 to 700 | 42 | 49 | 56 | 64 | 71 |
| more than 700 | 49 | 56 | 64 | 71 | 78 |
British Columbia: supply and extra fans
Supply goes to each bedroom and to each storey without a bedroom, through its own ducts when the principal system is a heat recovery ventilator. A kitchen needs its own fan of 47 l/s (intermittent). A bathroom or toilet needs 23 l/s intermittent or 9 l/s continuous, unless the principal fan serves it.
Worked example
Ontario, three bedrooms: the principal fan must deliver between 22 and 32 l/s, and Aira uses 22 l/s. British Columbia, a house of 200 m² with three bedrooms: Table 9.32.3.5 gives 28 l/s (floor area 140 to 280 m², 2 to 3 bedrooms).
How Aira applies it
You choose the province per home. Aira uses the lowest total the code allows and divides it over the rooms that must receive supply, by floor area; bathrooms and toilets share the extract in equal parts, and the kitchen fan is shown as a high setting outside the balance. Aira assumes a system without air heating and a heat recovery ventilator as principal system; the code does not say which room on a storey without a bedroom receives supply, so Aira takes the largest living space. You can adjust every figure in the table before you download the plan.
Source
The Ontario figures are taken from the official Ontario Building Code 2024 (O. Reg. 163/24), section 9.32, checked on 25 October 2026. The British Columbia figures are taken from the official BC Building Code 2018, revision 2.01, section 9.32, checked on the same date.