How to Install a Bathroom Exhaust Fan

Installing a bathroom exhaust fan requires cutting a ceiling hole, running electrical wiring, and connecting ductwork to vent moisture outside your home.

  1. Size and locate your fan. Choose a spot between ceiling joists, at least 3 feet from the shower or tub. Use a stud finder to locate joists and mark your fan location. Most fans need 6-8 inches clearance above the ceiling, so check your attic space. The fan should be sized for your bathroom - calculate 1 CFM per square foot of floor space.
  2. Kill power, run cable. Shut off power at the breaker box. Run 14-gauge cable from your electrical panel or an existing circuit to the fan location. If you're connecting to a light switch circuit, you'll need to run cable from the switch box to the fan location. Leave 8 inches of cable hanging down through the ceiling for connections.
  3. Carve ceiling opening. Use the fan housing template to mark the ceiling opening. Drill pilot holes at the corners, then cut along the lines with a drywall saw. Work slowly to avoid damaging surrounding drywall. Clean up debris before proceeding to keep dust out of your electrical connections.
  4. Mount housing to joists. Feed the electrical cable through the housing knockout. Position the housing between the joists and secure it to the ceiling joists using the provided brackets and screws. The housing should sit flush with the ceiling drywall. Some units have adjustable mounting bars that span between joists.
  5. Route duct to exterior. Attach 4-inch or 6-inch flexible duct to the fan outlet using duct clamps or foil tape. Run the duct to an exterior wall or roof vent, keeping the run as straight and short as possible. Avoid sharp bends that reduce airflow. Secure the duct every few feet to prevent sagging.
  6. Connect wires safely. Connect the electrical wires using wire nuts - black to black, white to white, and green or bare copper to the ground screw. Follow the manufacturer's wiring diagram exactly. Tuck all connections into the housing junction box and replace the cover plate.
  7. Verify airflow works. Snap or screw the fan grille into place over the housing. Turn the power back on and test the fan operation. Check that air is flowing properly through the ductwork by holding tissue paper near the grille - it should be drawn up strongly.