What CFM exhaust fan do I need for my bathroom?

For most residential bathrooms, you'll need an exhaust fan rated at 50-80 CFM, but the exact requirement depends on your bathroom size and local code requirements.

The standard calculation is 1 CFM per square foot of bathroom area. So a 5x8 foot bathroom (40 sq ft) would need a 40 CFM fan minimum. However, most contractors recommend going slightly higher - around 50-80 CFM for typical bathrooms - to ensure adequate moisture removal and account for ductwork resistance.

Larger bathrooms or those with higher ceilings may need more powerful fans. Bathrooms over 100 square feet often benefit from 80-110 CFM units. If you have a separate toilet room or multiple fixtures, you might need multiple fans or a higher-capacity unit. The Ontario Building Code requires mechanical ventilation in bathrooms without operable windows, and even bathrooms with windows benefit from exhaust fans for moisture control.

In Ottawa's climate, proper bathroom ventilation is crucial to prevent mold, mildew, and moisture damage during our humid summers and cold winters. Look for Energy Star rated fans with low sone ratings (1.5 sones or less) for quiet operation. Features like humidity sensors, timers, and LED lighting can add convenience and energy efficiency.

Installation considerations include proper ductwork sizing (typically 4-inch diameter), insulated ducts to prevent condensation, and venting directly to the exterior - never into attic spaces. The fan should be positioned away from the shower area but centrally located for optimal air circulation.

City of Ottawa requirements may vary - confirm with your licensed contractor. For proper sizing and installation of your bathroom exhaust fan, request a quote from Ottawa Bathrooms for professional assessment and installation.