How To Size An Attic Exhaust Fan

A whole house fan sucks warm house.

How to size an attic exhaust fan. 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. A whole house attic fan is installed in the ceiling between the top floor and the attic as a supplement to air conditioning. Ventilation rate of 10 air changes per hour. Set the thermostat on your attic vent fan so that it cuts on between 100 and 110 f.

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. If your attic requires a 1500 cfm fan then it should also have a 1500 300 5 sq ft air vent. Attic fan size chart for quick reference.

Minimum intake air vent size cfm 300 sq ft. So here the cfm of the fan cfm x 1 15. Intake air vent size. How to size a whole house attic fan.

Your attic fan should be sized to the square footage of your attic. For heating and air conditioning airflow or for other exhaust fan situations see our airflow calculator. Then enter the height at the highest point. Use the chart below as an attic vent fan cfm calculator.

For open blade fans see our ceiling fan calculator. For the exhaust to work properly the attic should have enough intake air vents. Enter the length and width of your attic or ceiling crawl space. Select if your roof is more flat of peaked.