Attic Fan Info Center > Attic Fan Frequently Asked Questions

Check out Attic Fan Faq's Section for common questions and answers about attic fans:

Commonly Asked Questions:

1) What size fan do I need?

ANSWER: An attic fan should be sized to provide 10 attic air volume changes per hour.

To figure out what flow rate this works out to, figure out the volume of your attic in cubic feet. Multiply your attic volume x 10 air changes per hour to get the total flow required per hour.

Since fans are sized in terms of their cfm (cubic feet/minute) output, divide your total flow per hour by 60 to get cubic feet per minute.

Required flow rate in cfm = (attic volume x 10) / 60

Now check the fan specifications to find the fan or combination of fans required to meet your ventilation needs.

It is also very important to make sure there is enough air inlet area in your attic to allow fresh air to enter and replace the hot air being exhausted. A minimum of 1 square foot for every 360 cfm of exhaust is required. Typically soffit vents are used as inlets.

2) How long will an attic fan last?

ANSWER: Attic fans are designed to provide many years of trouble free operation. The length of manufacturers' warranties are a good indicator of the high standards these fans were designed to:

Broan - Info Available Soon!

Marley - Info Available Soon!

TPI - Info Available Soon!

3) How is an attic fan controlled?

ANSWER: A thermal switch is often used to control an attic fan. This switch only allows the fan to run when the attic is warmer than 80-90 degrees F. Running the fan only when the attic is hot extends the life of the fan motor and results in less heat loss to the attic in winter, but does not allow the fan to reduce moisture build-up in the attic at all times and does not allow the fan to prevent ice dams during the winter.

4) Where can I find more information and pricing on attic fans?

ANSWER: Follow this link: Attic Fans

5) Can my attic have too much Ventilation?

ANSWER: The amount of ventilation an attic needs is determined by many factors, but in general the more the ventilation your attic has, the better off you will be. As attic air turnover is increased and fresh make-up air is brought into the attic, the attic temperature will begin to approach that of the ambient outside air temperature, which in turn minimizes heat transfer into your home. As long as your attic has plenty of fresh air make-up ventilation, more airflow through the attic will only increase the cooling performance of your attic fan.

7) Why would I want to cool off my attic?

ANSWER: During the summer, as the sun radiates heat onto your roof, your roof's shingles or tile becomes very hot. This heat is transferred through the roof and in turn heats up the air inside your attic. If the hot air stays inside your attic, the heat from this air will eventually enter your home.

While attic insulation slows this process, it does not eliminate the heat transfer process entirely. If your attic is not very well insulated, it will do very little to stop the heat from getting through. Additionally, a hot attic stays hot long after the sun goes down, so the process of heat transfer into your home never really ends.

By removing the hot air from your attic, the process of heat transfer into your home is minimized. The less attic heat that is transfer into your home, the less your air conditioner will need to work. If your air conditioner unit doesn't need to run as much to keep your home cool, you save energy and money.

8) What are the cost benefits of installing a attic fan?

ANSWER: How much money you will save is greatly dependent on the price of electricity in your area, the amount of attic space in your home, the efficiency of your attic insulation, and the amount of ventilation your attic vent is able to provide. In our experience, a typical installation will usually pay for itself in savings within 1-2 summers of use.

9) How are ridge vents, turbine vents, or gable vents different from a attic vent?

ANSWER: Ridge vents, gables vents, and dormer vents work by passive (natural) draft air convection. This means that as hot air rises in your attic, it should flow out from these vents creating a natural draft through the attic. However, as you have probably noticed if you currently have any of these vents installed on your home, they are not very effective at reducing the temperature of your attic.

Turbine vents are designed to pull hot air out of your attic when the wind blows. These vents are equally ineffective at removing attic heat due to frequent mechanical problems, low air moving capability, and a dependence on the wind to supply the power needed to induce a draft through the attic.

10) Are these attic fans very loud when operating?

ANSWER: No, not at all. You can barely hear them running when you're standing right next to one. The fan blades used in these attic vents are specially designed for whisper quiet operation.