How To Size An Attic Exhaust Fan

Enter the length and width of your attic or ceiling crawl space.

How to size an attic exhaust fan.

Intake air vent size. Humidity sensors are also available that cut the fan on if moisture in the attic becomes too high. Attic fan size chart for quick reference. A whole house attic fan is installed in the ceiling between the top floor and the attic as a supplement to air conditioning.

For open blade fans see our ceiling fan calculator. For the exhaust to work properly the attic should have enough intake air vents. Ventilation rate of 10 air changes per hour. 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.

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. A whole house fan sucks warm house. 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. How to size a whole house attic fan.

For heating and air conditioning airflow or for other exhaust fan situations see our airflow calculator. So here the cfm of the fan cfm x 1 15. If your attic requires a 1500 cfm fan then it should also have a 1500 300 5 sq ft air vent. Select if your roof is more flat of peaked.

Then enter the height at the highest point. Your attic fan should be sized to the square footage of your attic. Use the chart below as an attic vent fan cfm calculator. Minimum intake air vent size cfm 300 sq ft.