Attic fan

When it's hot outside, warm air builds up in the attic. This air has to escape so that your house can cool efficiently. Proper ventilation in the attic releases this excessive heat build-up, saving you money on home cooling. For effective ventilation, you'll have to install a powered ventilator/fan in your attic vents.

An attic fan turns on and shuts itself off automatically based on its built-in thermostat. When the fan's on, it pushes hot air out of the attic while pulling cooler air in through your home's inlet valves, usually set under the eaves.

This project describes the basic steps to install an attic fan in a gable-end wall — the triangular end of an exterior wall above the eaves formed under a gable roof. Choose a model controlled with a built-in thermostat, and if moisture buildup has been a problem, with a humidistat.

Step 1: Find Electrical Source

First, you'll need to figure out where the fan is going to get power. The simplest way is to take power from any available light fixture or outlet in your attic.

Helpful Tips

Always wear a long-sleeved shirt, pants, goggles and a dust mask to protect yourself from the insulation in your attic.

Because the attic is the hottest room in your house, try not to tackle this project on an extremely hot day.

Don't forget a work light and extension cord — you may not have much light up there.

Be careful where you step! That's the ceiling of the room beneath you between the wood joists, so lay a board between the joists as a work floor so you don't accidentally step through.

Step 2: Cut Wall Opening

Working from the top down, remove the siding below the roof peak with a zipper tool, a hand tool for separating and refastening interlocking edges of siding sections. Center and level the template for the louvered vent. Following the manufacturer's instructions, bore a starter hole through the wall sheathing and cut the opening with a portable jigsaw or reciprocating saw. If you have an adequately sized louvered vent, skip to Step 5.

Step 3: Frame the Opening

Provide framing or a plywood mounting board as directed by the manufacturer. You may have to do some additional cutting to the existing framing from the inside.

Step 4: Install the Louver or Shutter

Using the screws provided by the manufacturer, secure the exterior accessory shutter before reinstalling the siding. Siding manufacturers are usually good sources for how-to information on siding installation and repair. Depending on the type of siding you have, you may want to consult the manufacturer for the proper steps.

Step 5: Mount the Fan

Following the manufacturer's instructions, mount the fan to the framing or mounting board with screws.

Step 6: Install the Controller

Remove any knobs and the cover of the controller. This will allow you to secure the controller to the mounting plate or studs with screws, and follow the manufacturer's instructions for locating the unit. Do not use alternative controls (such as solid-state speed controls) that are not approved by the manufacturer.

Step 7: Make Wiring Connections

All electrical work must be done in accordance with local codes. If you are not familiar with basic wiring procedures, you should hire a licensed electrician. Shut off the breaker or remove the fuse for the fan circuit; use a neon circuit tester to verify the power is turned off. Follow the manufacturer's wiring diagram to make the connection to your power supply.

Thermostats and humidistats are adjustable. Follow the manufacturer's guidelines to make the necessary adjustments.

Nice work. Now it's time to turn down your air conditioning and let your new ceiling fans and attic fan do their job. You'll soon start seeing the savings when cooling down your house in summer.

Project Shopping List

Here’s what you’ll need to complete this project successfully.