How to Safely Install an Attic Fan

Guide for Installing an Attic Exhaust Fan Attic fans are not a subject a lot of people give much thought to, but if you own a home, you should give the subject of buying and installing one serious thought. Inadequate venting of an attic can lead to high attic temperatures in the summer and low attic temperatures in the winter. These extremes translate into reduced comfort inside the home, higher utility bills, and a shorter lifespan for you roofing materials.

The good news is that by adding a few vents, there is often a significant improvement in the problem. And for even greater effectiveness, you might want to seriously consider installing an attic fan as well.

Attic fans are not only inexpensive, but are also relatively easy to install. You could have the installation in your home done by a professional, or if you are proficient in the use of a few basic hand tools, you could do it yourself. If you’re not sure how, fear not. This article will give you all the information you need to successfully install your attic fan.

Does Your Attic Need Ventilation Fans?

During the hot summer, an attic can easily reach temperatures of 150 degrees F or higher. This kind of heat can affect the rest of your home and make it hot and miserable. And if you try to offset that extra heat by turning on the AC, you’ll spend a lot more money in energy costs. If you want to fix all of these problems, a good start is to install an attic ventilation fan. Most can be installed by a professional for about $400. Attic fans can be purchased that are equipped with humidistats as well as thermostats. These control excess attic humidity as well as temperature.

Ventilation Basics

Before you run out to buy an attic fan, you should take some time to check out what ventilation features you already have on your house. The number and type of vents you have on your home will vary often on the design of your roof, the location of your house, and the amount of sun that directly shines on your house. At a minimum, your venting system should consist of 1 sq ft of roof vent area for every 300 sq ft of attic space.

When it comes to vents and venting, more is almost always better. It is also important to remember that for every vent mounted high on a roof there should also be a vent on the lower roof, usually under the eaves in the soffit, which is the underside of an arch, balcony, or overhanging eave.

With a set-up like this, hot air rising through the upper vents will suck cooler air into the attic that is taken in through the soffit vents. Unless you have soffits, it would be like trying to cool your house by opening the windows on only one side of your house. And speaking of soffits, check to make sure that those smaller vents are clear of debris. On hot days, when the air circulation is strong, light seeds and other material from trees and other sources can be sucked into the vent screens, making it impossible for clean air to enter. Your vents should always be kept clear for your fan to work at maximum efficiency.

Choosing the Correct Attic Fan

How to Choose the Best Attic Fan Attic fans can be broken into two basic designs: those that are made for roof installation and those that are created for mounting on a gable wall. Most roof-mounted fans are mounted on a base that is made of either plastic or sheet metal. These bases serve as the flashing for the fan. Making matters easier, most manufacturers of attic fans sell their products accompanied by a template that should be used for cutting.

Before you pick an attic fan for your home, you need to check the construction of your roof to determine the best type for you. An attic fan should be located near the center of your roof, whether on the top or in a gable to the side. A fan on the roof doesn’t usually present a sizing problem, but if you want to install your fan on a gable, you will need to take careful note of the area available. Gable sizes vary a lot. Fortunately, so do the sizes of attic fans, so finding one that fits is usually not a problem. In some cases, you might be able to use an opening in your roof or a gable that is already there, which makes the job much easier, even if you have to adjust the size of the opening to fit. In cases such as this, the template will come in handy again.

A high-quality attic fan will likely include the following features: a thermostat that operates your fan automatically; durable, all-metal construction; a heavy-duty screen to keep pests and debris out; an automatic shutter, and a permanently sealed and lubricated motor. In many instances, to avoid causing a house fire, your attic fan thermostat should be set to turn the fan off when it detects temperatures in your attic that indicate a fire.

If you want to help your home be greener, you can also choose to buy a solar attic fan. The fans use a solar panel in order to power the fan instead of electricity, so it can help save you money over time as your fan is running.

How to Install an Attic Fan

While an attic fan may seem straightforward now, there is still a lot to remember when it comes to choosing the right fan and installing it.

Select the Correct Fan Size

How to Choose the Right Size Attic Fan In order to choose the correctly sized fan, you first need to know how many square feet your attic is. When you have that number, multiply it by .7 to get the minimum number of cubic feet of air that the fan should be able to move per minute. Step roofs will need an extra 20% added to this number because of the shape of the attic. Once you have the number, finding the right fan for your attic will be a lot easier.

Position the Fan

After you open the attic fan box, you should find the installation template. Where you place your fan will have a huge influence on how effective it is, so be sure to know the right place to put it. Using the template, position the template over the space where you want to install the fan, whether it be on the roof or the wall of a gable. Make sure that you use this template before you cut anything. These templates are designed by engineers who know their products intimately. By not using these templates and adding your own “guesstimates,” you are inviting trouble that can often result in not only an attic fan that does not operate correctly, but leaks in your roof as well.

Frame the Opening

In most cases, you will need to cut an opening in the roof, normally near the peak, and attach the fan over the opening you have just cut. Once the fan is secured to the surface of the roof, you will need to move the shingles over the flashing and use a sealant to make sure that no water enters through the opening. Most roof-mounted fans do not include a shutter, but others do. A shutter is normally installed on the opposite side of the wall or roof to prevent creepy-crawlies and debris from entering the attic when the fan is shut off.

Mounting an attic fan in a gable is slightly different. First, there are no shingles to disturb, which makes the possibility of causing a leak virtually nonexistent. In the case of a gable-mounted fan, the fan needs to be positioned and the opening cut. Again, make sure you use the template to make your marks before you cut. Center the automatic shutter on the outside of the opening, using wood screws that are only in about half-way until you determine that everything is positioned correctly. Next, go inside to place the fan inside the gable and make sure that it is properly aligned with the shutter.

Install the Attic Fan

How to Install an Attic Exhaust Fan Once you have gotten the fan into this position, you will need to make sure that the frame of your roof is correctly positioned with the fan. Once you determine that the fan is level, nail blocking in place just below the bottom of the fan. Remember to replace any blocking that you remove if you enlarge the opening. This blocking will help to support the fan after it is mounted.

As an extra bit of insurance, it is usually a good idea to include a piece of plywood as a mounting panel. This will keep the fan blades away from the surface of the roof or the wall and will enable you to center the assembly securely, without undue concern over the underlying framing.

Using a sabre saw, cut the hole in the mounting panel to fit the fan as well as the opening in the blocking. Again, having a good template will solve a lot of problems at this stage, but it’s still not difficult to complete this part even if there is no template. Ccenter the fan onto the panel and screw the bracket to the plywood. It’s also a good idea to back your screws with washers to prevent the screws from pulling through. Now it’s time to nail or screw the panel assembly into the attic behind the shutter. With that complete, go outside to tighten down the screws that are holding the shutter in place.

Finally, to wire your fan you will need to determine the requirements of your local codes. You will also need to determine if you have a circuit in your attic that has enough reserve capacity to handle the motor of your fan. If you don’t have the capacity on an existing circuit, you will need to create a new circuit dedicated to the fan. If you decide to do this, you will need to have your work inspected by a code official.

Install the Thermostatic Fan Regulator

The thermostat is normally already installed in a box attached to your fan via a flexible conduit. You need to screw this box to the plywood panel so that it is in a direct path of the airflow coming through the fan.

Next, go to the circuit box, or if you have a fixture nearby, open it and bring the wiring from the fan to the box. You might need to drill holes from the fan to the circuit box in order to prevent using an inordinate amount of cable. Regardless, make sure that you use insulated staples to keep the cabling in place and prevent waste.

Once you get the wiring to the box, strip the insulation about eight inches from the end, and use a box connector on the cable and feed all the wires into the box. Tighten down the fastening nut on the box connector, and connect the ground wire to the terminal inside the box.

Now connect the circuit wire to the fixture lead and the circuit wire to the black fixture lead. You can use twist connectors to do this easily. Tuck all the wiring inside the box and replace the box cover. Now set the thermostat in order to activate the fan at about 105 degrees F.

You can now finish your wiring by going back to the circuit box and attach the two eight-inch lead wires to the pull-chain fixture. Connect the black lead wire to the terminal screw and white wire to the silver screw. Now join the like-colored wires with twist connectors and mount the fixture in the box.

Test the Fan

If you follow these instructions precisely, you should have an attic fan that operates correctly, but now it’s time to make sure everything works. Just turn on your fan and enjoy your hard work. If your fan does not come on, recheck your wiring and connections. You might also need to make sure there isn’t something blocking the movement of the fan. If the fan does not work or it doesn’t spin correctly, you might need to add some powdered graphite or spray some WD-40 into the mechanism to loosen it.

How Much Does Attic Fan Installation Cost?

The Price of Installing an Attic Fan If you decide that installing your attic fan isn’t for you, you might want to consider hiring a professional for help. No doubt, a professional will probably be more expensive, but without some knowhow, you might be well served to make the sacrifice. A large amount of the final bill for a professional will take several things into consideration: the workmanship in the area, the complexity of the job, and other factors. The average cost of an attic fan installation can be upwards of $600 or more. Many homeowners expect to pay between $400 and $900 for a complete installation, and if you opt for any add-ons, a final project can run between $200 and $1,300.


When all is said and done, adding an attic fan to your home isn’t cheap, but when you consider the cost savings and improvement in the livability of your home during the year, an attic fan doesn’t cost—it pays. Even if you opt to forego the work yourself and let a professional make the installation, you are likely to see considerable energy savings in your bills in the years to come. There is also no accounting for the improved environment you will enjoy regardless of the time of year you use your fan.