Electric gable attic fans are used to increase fresh airflow through an attic. Insufficient attic ventilation can cost the homeowner by increasing cooling costs. Additionally, improper attic ventilation will reduce the life span of your roof. With proper ventilation, the gable attic fan will pull fresh air from the opposing gable vent, as well as soffit vents. It is crucial to determine that all vents are clear of debris to ensure maximum efficiency.
Step 1 - Determine Shutter Size
With an existing installation, if the vent is large enough to accommodate the gable attic fan, this step can be skipped. In new construction, you must cut the hole required to suit the fan you have purchased. For an existing vent, if the vent is too small, you must enlarge the hole in the gable to accommodate the new fan and shutter.
Step 2 - Prepare Opening for Fan and Shutter
From the outside, hold the shutter up to the face of the gable where the fan will be installed. Use a pencil to trace around the edges of the shutter. To determine hole placement for the attachment screws, measure in 5/8 inches inside the drawn square. This will determine the size and placement of the new opening for the gable attic fan.
Step 3 - Prepare Opening
If you are working with a flat surface such as plywood siding you can attach the shutter directly to the siding. If you have lapped siding, cut away siding to create a flat surface for mounting. Use 1x4 boards to frame a surface to mount the shutter for the gable attic fan. If there is an existing opening, you may need to remove any framing inside the attic with a reciprocating saw.
Step 4 - Cut Opening
Clear the opening of all obstructions. With a saber saw, cut the smaller opening drawn in Step 2 from the outside. This is the size that is 5/8 inches inside the flange.
Step 5 - Install Shutter
Certain that the gable attic fan shutter is plumb and level, nail it to the outside of the gable. If a base is required as in with lapped siding, attach the shutter to the base first, then nail it to the house. Caulk around the shutter and at all nail penetrations to prevent leakage. To support the fan mount, replace any framing that was cut out during shutter installation.
Step 6 - Mount Fan on Plywood
Cut 1/2-inch plywood to accommodate the framing in Step 5. Using a circle template equal to the diameter of the fan, draw a circle in the center of the plywood. This will be the fan opening. Setting the fan on the plywood will ensure that the fan blades will not be obstructed by walls.
Drill a hole into the perimeter of the circle just drawn on the plywood using a saber saw and cut out the circle. Center the gable attic fan over the hole and attach the mounting brackets with screws. Use washers with screws so the heads don’t pull through the plywood. Nail the entire fan assembly in the correct orientation to the framing from Step 5.
Step 7 - Wire the Fan
Be absolutely certain to meet local electrical codes. You will need at least 5 amps service to run the typical vent fan. Determine whether you have an existing source from attic lights or outlets with enough room (5 amps) to add the fan to the circuit. If not, you will need to run a new circuit to the panel. Attach the fan thermostat control box to the panel. If using an existing circuit, use the closest access point, such as a light or outlet. Disconnect power to the fixture you are using to power the fan. Bore 5/8 inches holes in the center rafters as required for running the wire to the fixture. Pull the wire to access both the fan and the fixture. Secure the wire with clamps and staples within 8 inches of both termination points. Strip, twist and using wire nuts at each connection, complete the terminations at both ends. Close up the fixture and thermostat box. Set the thermostat on your new gable attic fan to about 105 degrees Fahrenheit.