Install a bathroom fan

Preventing a slew of steamy problems

By Douglas Thomson


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A bath fan gets rid of odours and keeps mirrors from fogging up–but the best reason to install a bath fan is to remove humid air from your home. Moisture that fills the air while you shower or bathe eventually ends up as water on your walls; nourishing mildew and causing paint and wallpaper to peel.

Although installing a fan is fairly simple, before you begin you must accept three things.

1. You’re going to make a mess of your bathroom.

2. You’re going to have to cut a hole in your outside wall (or roof).

3. It’s a job that’s going to take you a full day to complete.

How you choose to route the duct for your vent is up to you. Our contractor, Jacques Doiron, suggested that since the fan was located in the second-floor bathroom of our three-story home, venting through the attic and roof was not an option. If your installation leaves the through-the-attic option open, it’s worth considering as an alternative–working with ducting in a reasonably sized attic space can sometimes be the easier choice. Be sure to wrap attic venting duct with insulation to prevent moisture from the cool attic air from condensing on the duct. Since venting through the attic may also allow you to tap into an existing attic junction box for power, you may find that running wires is ultimately less intrusive to your finished walls.

If you’re going through-the-wall like we did, you’ll have to access power in a junction box that powers your overhead fixture. You’ll likely find the junction box mounted on the joist next to the fixture when you cut the hole to mount the fan. Because bath fans require very little power, you should be safe tapping into almost any existing electrical circuits.

A word of caution is in order here. If you’ve never done electrical work before, consider doing only the rough work yourself and hire a licensed electrician to do the electrical connections.

You’re also going to need to buy the fan itself. To determine the size of fan, measure the square footage of the bathroom first. In our installation, the bathroom was 60 sq.ft. (to determine the Cubic Feet per Minute [CFM] you require, multiply the square/feet by a factor of 1.1). In our case there were only two options readily available: a 50 CFM, or an 80 CFM. We decided to err on the side of caution and purchased the larger unit.

What you’ll need:

Renting is your best option to obtain the large drill you’ll need to drive the masonry hole-saw, as well as the large corded drill to drive the 14″-masonry bit. Other necessary tools are: a drywall saw, cordless drill, tape measure, pencil and safety glasses.

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