How to Install & Properly Vent a Bathroom Fan

Have a licensed electrician run wire from the bathroom's light switch to the attic.

Turn off the power to the bathroom. Put on your goggles. Mark the ceiling where you want to install the fan. The fan should go between the toilet and shower for optimum performance. Drill a reference hole through the mark and into the attic.

Climb into the attic and clear the area around the hole. Measure the vent fan housing and position the fan between two joists near your reference hole. Climb out of the attic.

Measure the inside dimensions of the fan's intake port. Draw the outline of the intake port onto the ceiling and cut along the line with your saw. Support the cut-out piece with your other had before you complete the cut so that it does not fall. Climb back into the attic.

Attach the four-inch duct elbow to the outlet port vent fan housing, and secure it with duct tape. Slide the four metal brackets into the tabs protruding from the sides of the vent fan, and center the fan on the ceiling hole and lower it into place. Extend the brackets to the joists and secure each bracket end with a drywall screw. Slip one end of the flexible duct over the elbow and secure it with duct tape. Feed the electrical cable through the connector, and tighten the connector screw to secure the cable. Select a spot on the sidewall for the duct to exit the house. Mark and drill a reference hole through the sidewall. Exit the attic and go outside the house.

Cut a four-inch duct hole through the exterior wall using the drill's hole saw. Attach the connector duct to the wall cap (the vinyl piece that covers the vent hole) with duct tape. Apply several beads of silicone adhesive to the siding around tthe hole. Press the wall cap against and secure it with four stainless steel screws. Go back into the attic. Run the duct as straight as possible. Attach the free end of the duct to the wall cap connector and secure with duct tape. Return to the bathroom.

Unscrew the fan motor from the vent fan housing and set it aside. Unscrew the built-in receptacle from inside the housing to expose its wiring. Use wire nuts to join the fan wires with same color wires from the cable connected earlier. Wrap the bare copper wire under the green ground screw and tighten the screw. Reattach the receptacle, plug the fan motor into the receptacle and screw the motor in place. Slide the fan grille's mounting wires into the fan's housing. Push the grill tight against the ceiling.

Turn on the power and test the fan.