How to Install an Attic Ventilation Fan
If you are not afraid of cutting a hole in the roof and climbing a ladder to the top of your home, putting in an attic fan is a rather simple home-improvement project that will take two people about a day to complete. With temperatures in excess of 120 degrees Fahrenheit on hot summer days, attics are -- for most homes -- unused areas that waste energy and money. Putting in an attic fan is not only cost-effective, it is an important part of an ecologically efficient home, too. Does this Spark an idea?
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Things You'll Need
- Drill
- Utility knife
- Keyhole or saber saw
- Hammer
- Roofing nails
- Screwdriver
- BX cable
- Switch
Instructions
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1
Choose a fan powerful enough for the job. Attic fans are rated by the amount of air they move in cubic feet per minute (cfm). To calculate the size you will need, multiply the square footage of your attic by 0.7. If your roof is dark, add 15 percent to this number. The result is the number of cfm the fan will have to pull.
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2
Mark the location for the fan on the inside of the attic. The fan should be as close to the peak of the attic as possible to minimize the hot air above it and close to the center of the roof between two rafters. With a long bit, drill a hole through the roof and shingle. Stick a piece of wire through the hole so you will be able to locate it from the outside.
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3
Cut away the roofing materials around the drill hole by first using the manufacturer's shingle template to mark which shingles have to be removed. Use the square sheathing template provided by the manufacturer for cutting through the rest of the roofing material. Use a utility knife for the shingles and a saber or keyhole saw for the rest of the roofing materials.
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4
Install the exhaust vent by first coating the vent's square flashing with roofing cement and sliding it under the shingles adjacent to the fan hole. Nail the flashing into place with roofing nails. Attach the vent cover to the flashing according to the manufacturer's directions.
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5
Screw the fan's thermostat to a stud or rafter inside the attic.
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6
Connect the electric cables to complete a circuit containing the fan, thermostat, override switch, and power supply. If the manufacturer did not include wiring instructions, use two-wire metallic sheathed BX cable from the thermostat to the fan, and three-wire cable running from the power supply to the override switch and from the switch to the fan. The black and white wires of the fan will connect to the thermostat. Connect the white wire from the power supply to the silver screw on the switch. Connect both hot wires (black and red) at the switch to the brass screws. At the power supply, use electrical connectors to join the wires: red-to-red, black-to-black, and white-to-white. At the thermostat, connect the remaining black wire to the red wire.
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