Question 1

How long should I run my bathroom fan after a shower?

Accepted Answer

Run your bathroom fan for 20-30 minutes after showering to properly remove moisture and prevent mold growth. This gives the fan enough time to clear humid air from the bathroom and surrounding areas.

The key is removing all the moisture that gets absorbed into walls, ceilings, and fixtures during your shower. Even after you can't see steam, humidity lingers in materials and air pockets. A good rule of thumb is to keep the fan running until mirrors are completely clear and surfaces feel dry to t

Question 2

Can I vent a bathroom fan into the attic?

Accepted Answer

No, you should never vent a bathroom fan directly into the attic. This creates serious moisture problems that can lead to mold growth, wood rot, and insulation damage.

Proper bathroom fan venting requires the exhaust to terminate outside your home - either through the roof, an exterior wall, or a soffit. The ductwork should run from the fan location directly to the exterior termination point without any breaks or connections to attic spaces. In Ottawa's climate, this is especially critical beca

Question 3

Do I need a bathroom fan if I have a window?

Accepted Answer

Yes, you still need a bathroom fan even with a window. The Ontario Building Code requires mechanical ventilation in all bathrooms, regardless of natural ventilation sources like windows.

Why both are necessary: Windows provide natural ventilation when open, but they're not reliable year-round in Ottawa's climate. During winter months, you're unlikely to open a window in your bathroom, leaving you without proper moisture removal. Bathroom fans provide consistent, controlled ventilation that oper

Question 4

Where should I vent my bathroom exhaust fan?

Accepted Answer

Bathroom exhaust fans must be vented directly to the exterior of your home - never into an attic, crawl space, or other interior area. This prevents moisture buildup that can cause mold, rot, and structural damage.

The best venting locations are through the roof or an exterior wall. Roof venting is often preferred as it provides the shortest duct run and natural updraft, but requires proper flashing and weatherproofing. Wall venting works well for upper floors and is easier to seal, but may be

Question 5

What CFM exhaust fan do I need for my bathroom?

Accepted Answer

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

Question 6

What is a humidity sensing bathroom fan?

Accepted Answer

A humidity sensing bathroom fan is an exhaust fan equipped with a built-in sensor that automatically detects moisture levels in the air and turns on when humidity rises above a preset threshold. These smart fans eliminate the need to manually operate a switch, ensuring your bathroom is properly ventilated even when you forget to turn on the fan.

The sensor typically activates the fan when humidity levels reach around 60-70% and continues running until moisture drops to normal levels, usually ta

Question 7

Can a bathroom fan be too powerful?

Accepted Answer

Yes, a bathroom fan can definitely be too powerful. An oversized fan can create negative pressure that interferes with proper ventilation and may even cause backdrafting of combustion appliances.

Proper sizing is crucial for effective bathroom ventilation. The standard calculation is 1 CFM (cubic feet per minute) per square foot of bathroom space, with a minimum of 50 CFM for bathrooms under 50 square feet. For example, a 60 square foot bathroom needs a 60 CFM fan. However, if your bathroom has

Ventilation