How Big Should My Attic Fan Be

To determine the size of your attic multiply the width by the length of the attic floor in feet.

How big should my attic fan be.

Watch these helpful videos about exhaust fans and how to vent them out of roofs. References international code. Divide the cubic feet measurement by the cfm rating assigned to the fan. It helps to cool your home temperatures and the attic by approximately 30 degrees.

If your attic floor has a vapor barrier you will need one square foot of nfa per every 300 square feet of attic floor area half of that will be intake half for exhaust. Measure the length and width of each floor of your home with the tape measure. This means that a fan must have the ability to move 14 400 cubic feet of air in an hour. The minimum requirements say that this air should be changed 15 times an hour.

You now need to multiply 960 x 15. The whole house fan is installed inside the attic between the living space and ceiling. Next multiply the square feet of attic space by 0 7 to get the minimum number of cubic feet of air per. What this means is that every eleven minutes the air in the home is being exchanged by a fan of this rating along with having windows open in each room.

Multiply the total air volume in cubic feet by 30 which represents a complete air change every 2 minutes. It must be large enough to allow for removal of the largest piece of equipment in the attic. The warm air escapes through the attic and to the attic vents allowing the circulation of chilly air from the windows. Multiply length times.

Find the overall air volume of your home. Your soffit ventilation actually needs to be considerably more than 336 net square inches to supply a 700 cfm fan system or the fan is going to pull the air it needs through unsealed holes and gaps in the attic floor from the conditioned living space. This opening must provide clear access of at least 20 by 30 inches. If there is no vapor barrier double it to one square foot of nfa for every 150 square feet of attic floor space half for intake half for exhaust.

How to size attic exhaust vent fans for your home attic size. How to size a whole house attic fan.