A window is a great source of fresh air. However, in the Canadian climate, it can be too cold to open a window just for ventilation, especially in winter. But are windows necessary in modern Canadian bathrooms?

The short answer is no. Under the National Building Code of Canada (NBC), a bathroom must have a source of ventilation, and the builder can choose between a window and mechanical ventilation. However, it is important to check and comply with provincial building codes, as they are the primary source of authority.

Regarding windows, provincial codes do not require one. However, if no window is present, a mechanical ventilation system must be installed. In some provinces like British Columbia, mechanical ventilation is often required even if a window is present.

The preference for mechanical ventilation over windows can be easily explained. First of all, some bathrooms are located in basements where installing a window is impossible. Even if a window is installed, mechanical ventilation is a better option for preventing heat loss. A continuously operating fan keeps humidity levels down and helps prevent mold. The minimum exhaust fan rates in Canada are approximately 24–25 L/s (50 cfm) for intermittent use, and approximately 9 L/s for continuous use. We covered how to determine whether your bathroom fan is powerful enough in this guide.

Check with your local building codes to find the actual requirements and the required bathroom exhaust rates, and if you have questions regarding bathroom ventilation, feel free to contact us.