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Install a Bathroom Exhaust Fan
Level of difficulty: Intermediate

If you don't have an exhaust fan in a bathroom with a tub or shower, you should add one to alleviate the spread of mildew and other moisture-related problems. The good news is that fans are inexpensive and usually easy to install. Typically, bathrooms are located on outside walls so it's easy to vent to the outside. And the wiring (or at least some of it) is often in place in the form of an existing ceiling light operated by a switch. If you are experienced with wiring a wall switch or a light, you can handle the electrical work yourself.

Tools and Materials:
Exhaust fan or fan/light

Drill or drill/driver

1/8-inch twist bit, 1/2-inch spade bit

Hammer and nails

Jigsaw and blades

4-in. roof cap, roofing nails

4-in. wall cap or soffit vent

4d common galvanized nails

Siliconized acrylic caulk or roof cement

Caulking gun

Flexible vent duct with clamps or...

Aluminum ductwork (straight, elbows)

Tin snips

Utility knife

Drywall saw

Torpedo or other very small spirit level

Phillips and standard screwdrivers
Wiring:

2- or 3-wire w/ground-type NM cable

Wire connectors (wirenuts)

Single or double switch as req'd.

Long-nose pliers

Wire strippers

Cable staples

1. Plan Duct

Consider whether you want a fan or fan/light combination, and how you will wire it (see Step 5). Determine the number of cubic feet in the room (length x width x height) and choose an appropriately sized fan (see guidelines on fan package). Also compare the sound ratings of various units and choose the quietest unit that fits your budget. Installing a fan in the ceiling, the topic discussed here, requires access from above. If you don't have access above, you should consider wall-mounted units.

2. Install Housing

Tap on the ceiling to find approximate stud locations and drive a nail through the ceiling from below at the desired location between joists. From above, adjust the location so it is unobstructed and within a joist bay. Cut the hole in the ceiling from below with a utility knife or drywall saw. Attach the unit to the framing so it is flush with the ceiling, using screws through the housing or the mounting brackets provided with the fan. The housing must be perfectly level and secure or else the fan may make excessive noise.

3. Install a Wall, Soffit, or Roof Cap

Always vent to the outdoors (preferably through a wall or soffit). Take the shortest possible route for venting pipes using the minimum number of elbows. Drill a very small hole through the wall, soffit, or roof from inside at the approximate vent location and insert a nail so you can locate it outdoors. Drill a starter hole in the exterior and complete cutting with a jigsaw. Slip the flange of the roof cap under the shingles above it, nail it to the roof, and seal the nailheads with roofing cement. Caulk the underside of a wall or soffit flange before you press it into place, and secure it with 4d galvanized nails or screws.


	Tip:

		A wall cap will be easier to seal if it sits on a flat surface. Working from the outside, adjust the location so the top edge of the wall cap will fall just below a siding course.

4. Connect the Vent

Attach the duct collar to the fan's discharge opening as directed. Then connect a 4-inch round duct to the duct collar and to the vent cap with clamps.


	Tip:

		Aluminum duct is smooth and, therefore, most efficient. It is easily cut with tin snips. Flexible aluminum or plastic is more convenient and acceptable for short runs.

5. Wire the Unit

You'll need to provide a switch, and wire from the switch to the unit and a power source. If you are working with an existing light/switch the wiring is usually a simple matter. Before you begin, shut off the power at the breaker. If you must connect to a power source, especially a circuit panel, you may require the services of a licensed electrician. If you are knowledgeable about electric wiring and related codes, and want to do the work yourself, follow the manufacturer's wiring diagram. If you are replacing a light with a fan/light, you need to run new wiring for the additional switch if you want to operate fan and light independently. You can replace the existing single-light switch with an approved fan timer or with a multiswitch device.


	Caution:

		Caution: Never place a switch where it can be reached from a tub or shower, per electrical code. Remember, always shut off power at the breaker before working on wiring.

6. Complete the Installation

Insert the fan unit into the housing and attach it with the screws provided. Plug the fan (and light if applicable) into the wiring box receptacle(s). Screw in a light bulb and install the decorative grill. Restore power to test operation.