Adding or replacing an exhaust fan in your bathroom is easy when you buy an exhaust fan and light combination package. You can install one fixture that powers both your fan and the light for your bathroom, decreasing the work required to install two separate fixtures. In one afternoon, you can replace an existing fixture with one of these combination fixtures. Look to buy combination bathroom light and exhaust fan fixtures at your local home improvement store.
Turn off power to the bathroom where you will work. Handling electrical wires as you install the bathroom light and fan is dangerous if you leave the power on. Access your circuit breaker box and flip the appropriate breaker "Off" to disconnect power to that room. Make sure it is off by checking the existing light fixture in the bathroom.
Measure the location where you want to install your bathroom fan and light. If you want to install it in the area of your existing light fixture, you can skip this step. If you want to install it in a different location to add additional lighting to your room, run a stud finder across the ceiling and mark the location of the studs. Your bathroom fan installs between the ceiling joists.
Drill a long screw in the centre of the area where you want to conduct your bathroom light installation. When you work up in the attic, the long screw helps you identify the location easier, because the screw sticks up and you can feel it when you run your hands through the insulation.
Lay a plastic dust sheet on your bathroom floor to protect it as you install your light/fan combination. Place a bucket under the area where you will work to catch falling debris.
Climb up into your attic to the area where you will install the bathroom light and fan. Sweep away the insulation until you find the long screw sticking up, and sweep the insulation to the side so it doesn't fall to the floor when you cut out your bathroom fan hole.
Measure the size of the hole required for your bathroom fan and mark the area you will cut out. Drill ½-inch holes in each corner of the square you will cut, and then cut out the hole using a reciprocating saw.
Cut a 2-by-4 piece of wood so it runs from stud to stud over the area where you will install the bathroom light and fan. Secure the wood to the studs using wood screws.
Mount the light/fan combination into the ceiling. It may help to have a helper in the bathroom while you're in the attic so you both can work to install the bathroom fan and light. Insert the fan into the hole you cut out. Use 3-inch deck screws drilled through the bathroom light and fan into the mounting board that runs over the fan.
Connect the electrical components of your bathroom light and fan to the wiring in your house. Your light and fan will have one green ground wire, one white neutral wire, one red hot wire and one black hot wire. There are two hot wires because one powers the light and one powers the fan. Connect the green ground wire on your fan unit to the green ground wire in your house. Press the ends together, insert them in a wire nut then screw the wire nut to connect the wires together. Do this to connect the white neutral wires, red hot wires and the black hot wires. Tuck the wires into the electrical box and screw on the cover to protect your connections.
Slide a 90-degree elbow onto five feet of 4-inch diameter exhaust duct. Slip the other end of the elbow on the exhaust port on your bathroom exhaust fan. Tape the seams using metal foil tape for a secure seal. Set your exhaust duct in place in the attic, leaving the other end open. Anything vented from your bathroom into your attic will vent out of your attic through its built-in ventilation system. You may also choose to allow the exhaust to vent directly outside, by connecting the duct to a vent on the outside wall of the house.
Add a bead of caulk around your light/fan combination to seal any gaps between your drywall and the fixture.
Install light bulbs into the light fixture and place the light cover on the fixture. Restore power to the room by flipping your circuit breaker "On."
To turn on the light and the fan separately, install a dual light switch in place of your existing light fixture switch. Turn on one switch and it will power the light; turn on the other switch and it will power the fan. This would require you run a separate wire for the light and the fan to each individual switch.
Don't use flexible duct to vent your bathroom exhaust fan. Its irregular surface reduces the efficiency of the fan because it creates too much air flow resistance. Always be especially careful to shut off the electricity at the circuit breaker. Check to make sure the power is indeed off by checking the existing light fixture in the bathroom or using an electricity tester or multimeter.