Attic Fan Installation

by Dave Donovan

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, then you’ve got another thing coming. Not to mention, if you’re like most people you probably have things stored up there like clothing, odds and ends or maybe pictures. In the summertime, the temperature in your attic can reach over 150 degrees. You can imagine what the heat is doing to your valuables!

One way to control the amount of heat and humidity that collects in your attic is with the installation of 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 substantially cool your entire house without using much energy doing it.

If you notice, your house probably has vents on each end of the attic. The vents allow cooler air to flow into the attic while the hot air escapes. This is a nearly useless method of cooling the attic, mainly because the attic vents are positioned much lower than the point in the gabled roof. This enables the hot air to rise and collect above the vents, causing the temperature to increase throughout the attic.

A properly installed attic fan pulls cool air into the attic through one vent, forcing the cool air across the attic and expelling the hot air out of the other side of the attic, effectively getting rid of the super-heated air. A thermostat is usually installed that automatically cycles the fan on and off depending on the temperature in the attic. Installing an attic fan is a job that sounds harder than it actually is, so if you follow these easy steps, this summer your house can be more comfortable and your energy bills lower than ever.

The tools you will need for this installation include:
• Screwdrivers
• Drill and drill bits
• Hammer
• Wire Strippers
• Sabre Saw
• Caulk Gun
• Tape Measure
• Level
• Lighting Source like a plug-in work light

Materials you will need include:
• The Exhaust Fan, thermostat and louvered cover
• Acrylic Caulk
• 1” Wood screws
• Plywood
• 2 x 4 studs
• Wire Nuts
• Electrical Tape
• Pencil
• Romex Wire
• Romex Connectors and Staples
• Goggles and Face Mask

First step will be to 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 go and turn off the power to the attic light, get as much done while you still have the light working. So, that means finding a spot in the attic where you can call “parts central”. That’s where you can keep everything in one place so you’re not losing parts in the insulation.

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. It is best to do this installation in cooler weather!

You will have to remove the existing vent where you decide to install the 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” in on each side and mark it again. That will allow enough room for the outer edge of the cover to grab hold.

Use the sabre saw to cut out the new hole for the fan. Follow the lines drawn 5/8” 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 2 x 4 to fit in between the studs on either end of the louvered cover. Nail them in place, one above and one below the cover, creating a frame for the fan to be mounted to. 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.

Center the fan over the hole and screw the housing to the plywood. Give the blades a spin to make sure they meet no 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 so keep that in mind. Hold the mounted fan up against the frame and screw it into the studs that make up the frame. One screw in each corner, then check to make sure it is level. If it is, then add a few screws to each side so it’s held down tight.

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 then you will need to buy some. The metal sheath gets connected to both the fan and the thermostat box with metal conduit connectors.

Now that the fan is mounted on the plywood and the plywood is mounted to the frame, it’s time to run the electric. 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. Remove the attic light and knock out one of the available knockouts on the junction box. Strip away about 8 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” 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” 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. Re-install the light fixture and turn the power back on.

When it gets above 95 degrees, your attic fan will automatically turn on to help cool things down. For even more energy saving tips or information how to do a home energy audit, click HERE.

Dave Donovan is a freelance copywriter living in Atco, N.J. An electrician for 15 years, an injury forced him to pursue his true passion - writing.