Do you need to know how to install an exhaust fan in the bathroom?  Bathroom exhaust fans aren’t just for eliminating unpleasant odors. They’re important for removing steam and residual moisture that can cause troublesome mold and mildew problems as well as warping of cabinetry and doors. A ceiling exhaust fan will also minimize fogging on windows and bathroom mirrors during showering.

When shopping for a bathroom exhaust fan, here are seven basic things to keep in mind:

1. Features
Bathroom exhaust fans are available in many styles and configurations. Some come with built-in lights. Some have heaters or heat lamps. And some specialty fans are designed to be installed with a remote motor to minimize the sound. Do your research and visit your favorite home center or hardware store to evaluate all your options.

2. Fan Location
The optimal location for a ceiling exhaust fan is between the shower and the toilet. This will draw both moisture and odors from the room in the most efficient manner.

3. Venting
Bathroom exhaust fans must vent to the outdoors. Never vent a fan to an attic, a crawl space or other interior space as this will trap moisture in enclosed spaces and promote mold where you can’t see it.

4. Fan Sizes
Bathroom exhaust fans are rated by how many cubic feet of air they can move in one minute, known as “CFM.” In order to figure out what size fan you need, multiply your bathroom’s square footage by 1.1.  For example, a 100 square-foot bathroom requires a 110 CFM-rated fan.

5. Fan Noise
In addition to CFM, bathroom exhaust fans are also rated by the amount of noise they generate, which is called “sones.” Fans range from .5 sone up to 6.0 sones. Look for both the CFM and sone ratings which should be clearly printed on the box.

6. Fan Mounting
Keep in mind that you’ll need to mount the fan securely to a joist in the ceiling. Most fans come with mounting brackets that are adjustable so you should be able to position it close to your desired location.

7. Electrical Requirements
You’ll need to run power to the unit in the ceiling and to a switch in the wall to operate the fan. Replacing an existing ceiling light with a fan/light combination unit is sometimes the simplest solution since the wiring and switches are already in place.

NOTE: Whenever working with electricity, be sure to turn the power off at the circuit box. Then check the wires with an electrical tester to make sure you’ve turned off the correct circuit. Locking the box will ensure that someone else in your household doesn’t turn it back on by accident.

Now you’re ready to install the exhaust fan. Because of the many variations in bathroom configuration, we’ll focus on a simple installation of a basic ceiling exhaust fan, venting through an attic or crawl space to an exterior wall or gabled roof. Knowing these basics, you can modify your installation based on your specific requirements.

Also, before commencing work, check with your local building authorities to see if any permits will be required. And it’s always best to have your work checked by a building inspector when completed. This isn’t just for safety but it can avoid costly delays when selling your home if the home inspector finds a problem or asks to see a permit.

Step 1: Tools & Materials
You’ll need the following tools:

• Drill
• Drywall saw
• Screw drivers: both Phillips head and straight blade
• Wire strippers
• Electrical tester
• Tape measure
• Pencil

In addition to the fan unit itself, you’ll also need:

• Flexible dryer ducting and clamps    
• Exterior vent cap for either wall or roof
• Electrical cable with grounding wire
• Wire nuts

Step 2: Positioning
Begin by drilling a small reference hole in the ceiling where you want the fan. Then go to the attic and see how close your hole is to a joist. Also check for pipes or electrical conduits that may affect the location. Make sure you have enough exhaust hose to reach an exterior wall or roof and the appropriate wall or roof cap for the vent exterior.

Using the actual fan unit, determine the final positioning over your reference hole and measure the vent opening in relation to your reference hole.

Step 3: Cut Opening
Returning to your bathroom, transfer those measurements to the reference hole and cut an opening just large enough for the intake vent.

Step 4: Mounting
Back in the attic, lay the unit in place with the intake vent protruding through the hole into the bathroom. Once in place, attach the unit to the joist using the hardware provided.

Step 5: Ducting
Now attach the duct hose and run it to an exterior wall or roof where you want the exhaust vent. Drill a small reference hole. From the outside, find your reference hole and cut a larger hole large enough for the exhaust vent.  Then mount the wall cap. If you’re drilling through a roof, you’ll need to remove a few shingles and make sure there’s adequate flashing when replacing them.

Step 6: Electrical
Now you’re ready to make the electrical connections, making sure the power is turned off at the electrical panel. Consult a licensed electrician if in doubt.

With a successful installation of a bathroom exhaust fan, you’ll find odor and moisture problems under control and your bathroom more enjoyable to use.