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.

For open blade fans see our ceiling fan calculator. For the exhaust to work properly the attic should have enough intake air vents. A whole house fan sucks warm house. 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.

Use the chart below as an attic vent fan cfm calculator. 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. Ventilation rate of 10 air changes per hour.

A whole house attic fan is installed in the ceiling between the top floor and the attic as a supplement to air conditioning. How to size a whole house attic fan. Minimum intake air vent size cfm 300 sq ft. Your attic fan should be sized to the square footage of your attic.

Attic fan size chart for quick reference. Intake air vent size. Then click on calculate. 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.

Then enter the height at the highest point. Humidity sensors are also available that cut the fan on if moisture in the attic becomes too high. 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. 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.