Powered Attic Fan Wiring Information

Incomplete electrical wiring on an unfinished wall.
  • 6-8 hours
  • Intermediate
  • 150-600
What You'll Need
Attic Fan Kit
Drill & Bits or Hole Saw
Wire Strippers
Wire Connectors
Electrical Tape
Caulking and Gun
Roof Vent Flashing
Ceiling Escutcheon

A powered attic fan can provide attic ventilation all year round. It will lower your cooling bills in the summertime by removing superheated air from your attic, where temperatures can reach up to 160 degrees.

In the winter, a powered attic fan helps keep the air drier by removing humidity that can damage the wood and your roof. A powered attic fan effectively acts as an exhaust fan for your whole house.

Installing Power Attic Fans

Wiring powered attic fans is usually as simple as running power from the existing attic light fixture. If you need to create a new hole for the fan, the wiring may actually be the easiest part.

It is critical to install the fan in such a way as to seal openings and leaks around the fan itself. Installing the fan in a preexisting hole is your best bet and can often be accomplished by removing a plain grate vent and installing the fan in its place.

Installing a power attic fan can be a dirty job. Take safety precautions, such as wearing goggles to keep dust and debris out of your eyes. You'll also want to wear long sleeves to protect yourself from insulation.

Fortunately, many powered attic fans come in a kit that includes everything you'll need to install the fan, including a traceable template that will assure a good fit between the fan and the hole.

Fan Thermostat

Like your heating and cooling system, an attic fan comes with a thermostat. The thermostat is mounted with the fan and can be set to automatically turn the fan on when certain air temperatures are reached.

It may also have a remote control that allows you to turn the fan off and on at will. Using automatic settings to run the fan when the temperature climbs is a no-worry way of controlling your energy costs and preventing roof damage.

Wiring Power Attic Fans

If you have any doubts about wiring, hire a professional to install your fan.

If you're familiar with wiring, first cut the power to your attic light and then connect Romex wire that's been stripped of about 8 inches of covering at the end to an available knockout in the junction box. Then, run the wiring to your attic fan, strip another 8 inches at that end, and connect the wire to the thermostat.

Strip away about 3/4 inch of the insulation and use a wire nut to connect all the white wires. Then, wrap the green wire around the grounding screw inside the thermostat box. Connect the black wire coming from the light fixture to the black wire on the box and then connect the red wire on the thermostat to the black wire that comes from the fan motor.

Rewire the Light

Take the spool of Romex and cut 6-inch lengths of the black, white, and ground wire. Make a "pigtail" of each of the white, black, and ground wires by using a wire nut for each of them. Then, install these pigtailed wires to the light fixture in the same way the wires you removed were installed.

For safety's sake, take the Romex wire coming from the light fixture and staple it to the ceiling joists at 12-inch intervals. When you're finished with the wiring, wrap all the wires with electrical tape. Now, set the thermostat to 95 degrees and your powered attic fan will turn on to keep your attic at a safer and more energy-efficient temperature.