How Many Attic Fans Are Needed

Use only soffit vents as fresh air intakes for powered attic ventilators.

How many attic fans are needed.

Ft of attic space for example 20 x 50 to be effective. According to the home ventilating institute hvi powered attic ventilators need to move a minimum of 700 cubic feet per minute cfm for 1 000 sq. 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. A minimum of one square foot of inlet area for every 300 cfm of hvi certified fan capacity is required for proper fan operation.

There should also be a 50 50 balance of attic venting and roof venting. Note that these two feet would not need to be one large opening. These fans are designed to remove excess heat from your attic which in theory is supposed to lessen the load on the air conditioning in your home. The uniform building code requires that the amount of venting area in the attic be equal to 1 150 of the area of the floor and in most circumstances it allows a ratio of 1.

Vent fan location locate roof mounted fans on the back of the roof below the ridge but not so high as to be visible from the front of the house in the middle of the main part of the attic. When the attic becomes part of the home to be heated and cooled open wall gable vents and. Ideally there should also be plenty of soffit intake space their calculations recommend 336 net square inches of open soffit ventilation to supply 700 cfm. If your roof is 1200 sq ft soffit floor space you will need 4 sq feet of roof ventilation.

Use the calculator below to find out how many exhaust and intake vents you will need on your house. Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation for every 300 square feet of attic floor space evenly split between intake and exhaust. So if your fan is rated at 1500 cfm you will need about two feet of totally open space in your attic. It doesn t matter if the ventilation openings are spread out as long as there is sufficient space for all the air to escape.

With square foot living space at a premium many homeowners turn to their attics for a little extra room. Because what happens is attic fans are so strong that they actually reach down into the conditioned space of your house and they do that by using the wall cavities and where the outlets and pipes come through the walls as places where they draw air from the inside of your house it s that air conditioned air and it ll pull it right up into the attic and exhaust it outside. Ok i would definitely not recommend an attic fan. According to their requirements you should have 1 square foot of attic ventilation per 300 sq ft of attic floor space.