Installing a Bathroom Fan

Posted by Woodrow Aames ~ March 15, 2010

Depending on your local building codes, you may be required to have a bathroom fan even if there are windows in the room. Without a fan equipped to handle the job, you're risking mildew, mold, rot, warping doors and window frames, and paint and wallpaper damage. Be sure to read our informative article on the basics of bathroom fans.

Installing a new fan during a bath remodeling project or replacing the one you have can take at least a full day to complete, so plan ahead to work in dry weather.

The most difficult part of the project can be the ducting of the ventilation to the outdoors, which means working through the roof or soffit.

You can also route the ventilation through the attic and out a side wall. Above everything else, don't vent bathroom moisture directly into an attic or sub floor and let it remain there.

Steps for Installing a Bathroom Fan

Home Depot presents a helpful installation guide on its website. In order, the steps are:

    • Cut the hole (from above if you have an attic, from below if there's no attic).

    • Attach the fan (and block insulation from the fan).

    • Cut the roof hole.

    • Cut out shingles.

    • Install a roof cap.

    • Connect the ductwork.

    • Wire the fan, then the switch.

    When shopping for a new or replacement fan, check fan ratings for how many cubic feet of air it moves per minute (CFM). A rule of thumb is to multiply 1.1 against your bathroom square footage to determine the CFM sufficient to move out moisture.

    Replace a Noisy Bathroom Fan

    Fan noise is rated by "sones." The lower the number, the quieter the fan. Reader's Digest has step-by-step instructions for replacing a noisy fan with a better unit. I've never lost sleep because of the sound of a fan, but I don't usually run my fan at bedtime. A fan that sounds like an Air Force bomber can be distracting when shaving or putting on makeup.

    If you're going to do either project, be sure to check with your municipality or county to obtain any required permits and inspections. And if you're uncomfortable with wiring, call in a contractor. When planning any bathroom remodel, it's wise to look over any potential plumbing, fixtures, electrical, or structural changes before picking up the hammer.

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