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Installing an Attic Fan

Materials List
Attic fan
Roofing nails
Roofing mastic (tar)
Electrical cable (NM)
Cable clamps
Wire nuts
Self tapping wood screws
Tools List (click item to shop)
Reciprocating saw
Electric drill
Drill bits
Putty knife
Wire cutter/stripper
Tape measure
Work gloves
Safety glasses
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IMPORTANT: Read this before you start


No matter how hot it gets in your home this summer, you can bet that it’s even hotter in your attic. All that heat in your attic gets transferred to the ceiling below, which will in turn heat the interior of your house.

One way to solve this problem is to cool your attic with an attic fan. An attic fan pulls in outside air through the roof vents and forces hot attic air out through the fan. On a hot day, the outside air can be 15 to 30 degrees cooler than attic air, even if your attic is well vented. This exchange of air can make quite a difference in keeping your attic and your house cool in the summer even if your attic is insulated or you have air conditioning.

Choosing a fan is a relatively simple process. Decide how you will mount the fan by reading the steps below, and then choose the appropriate model. You can mount the fan to vent either through the roof or through the gable. Next, choose the correct size fan by comparing the manufacturer’s specifications to the square footage of your attic space. If you have a large house, or will encounter problems mounting a large fan, consider two smaller fans that together will meet the manufacturer’s recommendations for your attic.

Skill Level & Time To Complete
• Beginner - 5 hours
• Intermediate - 4 hours
• Advanced - 3 hours

Make sure you turn off the electrical circuit you will be working on.

Working in a hot attic can lead to dehydration. Make sure you drink plenty of water and take frequent breaks.

When walking through an attic, always step on the ceiling joists, never between them.

Helpful Tips
Make sure your power source can handle at least a 15 amp draw from the fan. If not, you will need to install a new circuit.

Try to purchase an attic fan with a temperature control switch (regulator) so that it turns on and off as the attic heats and cools. This will save money by not having the fan run continuously. It also makes installation easier because no power switch will need to be installed in the house.

Heat rises, so position the fan near the top of the roof for better efficiency.

For the hot air to exit, outside air needs to come in. Make sure that your existing roof vents are large enough and not blocked by anything, such as insulation. To determine if your existing roof vents are large enough, add the total square footage of all intake vents together. The total should be at least double the area of the fan opening.

1. To mount an attic fan on the roof, drill a starter hole out through the roof. Next, with a reciprocating saw, start your cut in the starter hole and cut a circle matching the diameter of the fan. Note: If you have a tile, metal, or flat roof, this portion of your installation should be done by a professional roofer as special tools and techniques are needed to cut through and seal these roofs. Other options are explained in step 4.
2. Slip the flange on the fan housing under the shingles that are above the hole. It may be necessary to remove some of the shingles or cut them back to accomplish this. Refer to the Replacing Damaged Shingles tutorial to replace your shingles. Before putting the fan in place, make sure to spread a generous amount of roofing mastic under the flange to seal against water.
3. Once in place, nail down all four corners of the flange (the top corners can be nailed through the shingles) and put some tar over each of the nails. If necessary, also screw in place any hood or cover at this time.
4. An alternate method of mounting a fan is to mount it in the gable end of older homes. Gable ends should have existing vents set between studs that are 16-inches apart on center. To take advantage of these vents, simply use a fan with mounting brackets that allow it to be mounted across the studs (such fans are a common item). To make the fan work more efficiently, put blocking between the studs, both above and below the fan to direct the flow of air out. Note: If you do choose to use an existing vent for your fan, there must be at least two other vents of similar size to serve as intake vents. If not, you will need to install more vents for the fan to work properly.
5. With the fan in place, remove the regulator cover and secure the regulator to a nearby stud or rafter.
6. Remove a knockout for the power supply cable. Install a cable clamp in the hole, thread the cable through the clamp and tighten the clamp. Remove the sheathing on the cable and strip the wires. Repeat the procedure for the fan cable as necessary.
7. Attach the fan wires to the regulator wires as specified by the manufacturer. Usually, all the white wires will go together, the black wires from the supply line and regulator will go together, the black wire from the fan will go to the red wire from the regulator, and the copper or green ground wires will be connected to each other or a ground screw.
8. When the connections have been made, reinstall the cover to the regulator and set the temperature control to about 95 degrees Fahrenheit. This setting should provide a good compromise between energy efficiency and cooling. Your fan is ready to start keeping your house cool, so turn on the power and see how it works. Remember, if it does not come on right away, it may not be hot enough in the attic. Try turning the regulator down or waiting until the attic gets warmer before concluding that the fan is not working.



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