How to Add a Bathroom Fan


If you do not have any windows in your bathroom, then you should install a bathroom ventilation fan. A fan will cut down on a lot of the moisture build up that causes foggy mirrors, mildew and mold. When allowed to grow out of control, mold and mildew will damage wood structures and drywall in your home. Mold can also cause health problems to the occupants of the home.

Things You'll Need

  • Power drill
  • 3/8-inch drill bit
  • Tape measure
  • Pencil
  • Straight edge ruler
  • Drywall saw
  • 4-inch 90 degree elbow
  • Foil duct tape
  • Hammer
  • 1 1/2-inch drywall screws
  • 4-inch hole saw
  • Wall cap kit
  • Silicone caulk
  • 1 1/2-inch steel screws
  • Wire connectors
  • Turn off the breaker giving power to the bathroom. Locate an area on the ceiling between the shower and the toilet where you would like to put the ventilation fan. The fan should be located within 6 feet of an outside wall. Use a 3/8-inch drill bit and drill a hole through the ceiling, into the attic.

  • Use a tape measure to measure the dimensions of your fans intake port. The intake port is the part underneath that will be placed into the ceiling. Use a straight edge ruler to draw these dimensions onto the ceiling.

  • Use a drywall saw to cut out the square intake port hole in the ceiling. Hold onto the square you are cutting out until it is entirely released from the ceiling to avoid ripping the surrounding drywall.

  • Take the vent housing into the attic and place it in the square you just cut out. Use foil duct tape to attach a 4-inch round 90 degree elbow to the outlet port in the side of the fan. Make sure the elbow is pointing up towards the roof before securing it.

  • Locate the knock-out hole on the side of the vent housing and use a hammer to hit it out. Put your existing electrical cable for the bathroom into this hole. Pull out the side brackets until they meet the ceiling joists on either side of the vent housing. Use 1 1/2-inch drywall screws to mount the brackets to the ceiling joists.

  • Mark a place on the siding outside your home for ventilation. This hole should be no more than 6 feet from the vent fan. Use a 4-inch hole saw to cut the hole. Push a wall cap into this hole.

  • Place one end of a 6-foot long piece of flexible duct over the elbow you mounted to the vent housing and the other end to the end cap in the wall. Use foil duct tape to hold it in place.

  • Go back outside. Remove the wall cap and apply a strip of silicone caulk around the edges. Push it back into the wall and screw 1 1/2-inch steel screws into all four corners.

  • Go to the bathroom and temporarily remove the blower motor and cover for the wiring inside the vent housing. Use wire connectors to connect the wires of the existing electrical cable to the blower motor. Only connect wires that are the same color.

  • Put the motor back into the vent housing. Mount the fan grille to the ceiling by putting the mounting wires over the vent housing's side clips. Turn the breaker for the bathroom back on and test out your fan.

Tips & Warnings

  • Have a friend help you to cut back on the trips you need to make in and out of the attic. This will save you a lot of time.
  • If not familiar with electrical wiring, consult with a licensed electrical contractor.

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  • Photo Credit View of Hotel Bathroom image by TekinT from
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