Attic Fan Installation

Lead Image
What You'll Need
Drill and drill bits
Wire stripper
Sabre saw
Caulk gun
Tape measure
Lighting source, like a plug-in work light
The exhaust fan, thermostat, and louvered cover
Acrylic caulk
1-inch wood screws
2x4 studs
Wire nuts
Electrical tape
Romex wire
Romex connectors and staples
Face mask

Have you ever gone into your attic during the dog days of summer? It gets insanely hot up there! All that heat is trapped above your head, and if you don’t think that it affects your electric bill, you’ve got another thing coming.

One way to control the amount of heat and humidity that collects in your attic is by installing an attic fan. An attic fan works just like the exhaust fan in your bathroom but on a much larger scale. It’s a bigger, more-powerful fan that can cool your entire house substantially without using much energy.

A properly-installed attic fan pulls cool air into the attic through one vent and expels hot air through a vent on the other side. An attached thermostat automatically cycles the fan on and off depending on the temperature in the attic. There are solar-powered fans with photovoltaic panels that power everything and require no wiring at all that can potentially save you even more.

Installing an attic fan sounds harder than it actually is. If you follow these steps in the spring, this summer your house will be more comfortable. What's more, your energy bills will be lower than ever.

Step 1- Put on Your Protective Gear

Be sure to dress for the occasion. A long-sleeved shirt and long pants help protect your skin from the itchy insulation, and the goggles and face mask protect you from breathing it in or getting it in your eyes.

Safety gear

Step 2 - Pick the Location

Determine where you’re going to get an electrical feed for the exhaust fan. In most cases, it’s easiest to branch off of the attic’s light fixture. Before you turn off the power to the attic light, though, get as much as possible done while you still have it working. That means finding a spot in the attic where you can keep everything in one place, so you’re not losing parts in the insulation.

Step 3 - Remove the Old Vent

You will have to remove the existing vent when you decide to install the attic fan. It’s usually screwed or nailed in place. Once it is removed, center the new louvered cover over the hole and trace around its edges with the pencil. Measure 5/8 inch in on each side and mark it again. That will allow enough room for the outer edge of the cover to grab hold.

Step 4 - Cut a Hole and Make the Frame

Use the sabre saw to cut out the new hole for the fan. Follow the lines drawn 5/8 inch in while cutting. Install the louvered cover by screwing it in place and then seal the outside of it with acrylic caulk. Next, cut two pieces of 2x4 to fit between the studs on either end of the louvered cover. Nail them in place, one above and one below the cover, creating a frame on which to mount the fan.

Measure and cut the plywood so that it can easily be mounted to the frame. In many exhaust fan kits, a traceable template of the fan is included. Place the template (or the fan itself if the kit didn’t come with one) directly centered on the plywood. Trace around the perimeter. Use the sabre saw to cut out the hole.

Step 5 - Install the Fan

Center the fan over the hole and screw the housing to the plywood. Give the blades a spin to make sure they turn without hitting any obstacles. When installing the plywood, be sure to make note of which part of the fan is supposed to be the top side. It will be marked on the housing. Hold the mounted fan up against the frame and screw it into the studs, one screw in each corner. Then, check to make sure it is level. Once it is, add a few screws to each side so it’s held down tight.

Step 6—Mount the Thermostat

The thermostat should come in a metal box that can easily be mounted to the plywood. Remove the cover and the controller. Place the back of the thermostat box at one of the lower corners of the plywood, level it, and screw it in place. If the fan doesn’t already have metal sheathing covering its wires, you will need to buy some. The metal sheath gets connected to both the fan and the thermostat box with metal conduit connectors.

Installing the thermostat.

Step 7 - Run the Electrical

Now that the fan is mounted on the plywood and the plywood is mounted to the frame, it’s time to run the electric. Of course, if you went with the solar-powered fan, you can skip this. Make sure you have a second source of light to work with before you turn the power off to the attic light.

Turn the power to the light off once everything is in place. Wear protective gloves to help avoid being shocked. Remove the attic light and knock out one of the available knockouts on the junction box. Strip away about eight inches of sheath from the romex wire. Use a romex connector to connect the romex to the junction box.

Run the romex wire from the light fixture to the exhaust fan, stapling it securely in place at every stud or, if possible, every 12 inches. Remove the same amount of sheathing at the other end of the romex once you have it at the thermostat box and use a romex connector on that end as well.

At the thermostat, strip ¾ inch of the insulation and connect all the white wires together with a wire nut. Wrap the ground wire around the green, grounding screw inside the box. The black wire coming from the light gets connected to the black wire on the thermostat. The red wire on the thermostat gets connected to the black wire coming from the motor. Wrap all wire sets with electrical tape. Replace the cover and set the thermostat for 95 degrees.

Back at the light fixture, cut 6-inch lengths of black, white, and ground wire from the spool of romex. Connect the white wires together with a wire nut to make a “pigtail.” Do the same with the black wires and the ground wires. The pigtail wires get connected to the light fixture exactly the same way as you removed them. Reinstall the light fixture and turn on the power.