How Big Should My Attic Fan Be

Divide the cubic feet measurement by the cfm rating assigned to the fan.

How big should my attic fan be.

How to size a whole house attic 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. References international code.

How to size attic exhaust vent fans for your home attic size. The whole house fan is installed inside the attic between the living space and ceiling. This means that a fan must have the ability to move 14 400 cubic feet of air in an hour. 17600 cubic feet 1600 11.

It must be large enough to allow for removal of the largest piece of equipment in the attic. 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. 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.

Next multiply the square feet of attic space by 0 7 to get the minimum number of cubic feet of air per. Whole house fans work on the principle of removing the hot and humid air out of the house. Find the overall air volume of your home. This opening must provide clear access of at least 20 by 30 inches.

The warm air escapes through the attic and to the attic vents allowing the circulation of chilly air from the windows. You now need to multiply 960 x 15. Multiply length times. Measure the length and width of each floor of your home with the tape measure.

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. The 537 cfm fan is capable of moving plenty of air through an average sized attic roughly 1 200 square feet.