| Primary value | 0.37 m² |
| Applies to | Bathrooms · WCs · Combined bath + WC |
| Exceptions | Internal bathrooms (no external wall) → Mechanical exhaust required |
| Measured as | Openable window or fixed vent area connecting to outside air. |
| Source | NBC 2016 — Part 4, Clause 4.3 ✓ Verified |
Bathrooms generate moisture that breeds mould and damages finishes. 0.37 m² of ventilation removes daily steam and odours when sized for typical residential use.
Most bathrooms provide a 0.45-0.60 m² high-level window plus an exhaust fan. The combined approach handles peak humidity quickly.