How To Size An Attic Exhaust Fan

A whole house fan sucks warm house.

How to size an attic exhaust fan.

If your attic is poorly insulated or you have problems with excessive moisture you may need a larger fan to help account for the additional heat. Humidity sensors are also available that cut the fan on if moisture in the attic becomes too high. For the exhaust to work properly the attic should have enough intake air vents. Then click on calculate.

Minimum intake air vent size cfm 300 sq ft. Set the thermostat on your attic vent fan so that it cuts on between 100 and 110 f. So here the cfm of the fan cfm x 1 15. For heating and air conditioning airflow or for other exhaust fan situations see our airflow calculator.

Then enter the height at the highest point. Enter the length and width of your attic or ceiling crawl space. Intake air vent size. For example a 1 000 square foot attic needs to have a fan that can handle at least 460 cubic feet per minute of airflow.

Use the chart below as an attic vent fan cfm calculator. Select if your roof is more flat of peaked. A whole house attic fan is installed in the ceiling between the top floor and the attic as a supplement to air conditioning. Proceed to step 2 and use the chart to determine the size and number of solar powered attic ventilation fans required to achieve a min.

Your attic fan should be sized to the square footage of your attic. For open blade fans see our ceiling fan calculator. Ridge vents it s not a good idea to use a power vent fan if your house has a ridge vent since the fan will tend to draw in air from the ridge. How to size a whole house attic fan.