How Many Attic Fans Should I Have

The air being exhausted must be replaced by outside air drawn through vents under the eaves in the soffit.

How many attic fans should i have.

The result is a cooler attic space with plenty of air exchange. Multiplying the total square footage of the attic by 0 7 will provide the rate required. This is done because you need one square foot of ventilation area for every 750 cfm that your fan can push. Attic x 0 7 700 cfm minimum fan rating add an additional 20 cfm x 1 20 if you have a steep roof and 15 cfm x 1 15 for a dark roof.

As a general rule unless a homeowner has a highly qualified person to evaluate their house i think its safe to say that attic fans should be avoided. Attic ventilation fans whether hard wired or powered by their own solar panels seem like a low cost and effective way to help keep your house cool. Attic fans reduce heat dramatically. These include the following.

Powered attic ventilators should provide at least 10 air changes per hour. Any whole house fan that you buy should have this figure listed somewhere on the packaging. Attic fans perform this ventilation by pushing hot air out into the environment while also pulling fresh cool air into the attic. With square foot living space at a premium many homeowners turn to their attics for a little extra room.

Now take that number and divide it by 750. You place the fans on the gable walls of your attic. With an attic fan many attics have a temperature that is the same as the outside air or just a few degrees warmer. The temperature in attics without attic fans can climb to as high as 150 degrees f.

Dwight barnett is a certified master inspector with the american. When the attic becomes part of the home to be heated and cooled open wall gable vents and. If the home already has a fan roof vents or gable vents these should be blocked and sealed from the attic side of the home. Like so many other plug in solutions attic fans certainly have the potential to make things worse rather than better.

So if your fan is rated at 1500 cfm you will need about two feet of totally open space in your attic. There are many benefits of attic fans. Powered attic ventilator fans designed to cool your attic by drawing the hot and humid air out of the attic and bring in a flow of chilly air from outside. Your article does a great job of outlining how this happens.

The downside of attic ventilation fans. Attic vent fans are commonly rated from 800 to 1 600 cfm making one fans suitable for attics of up to around 2 200 square feet.