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.

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. Then enter the height at the highest point. For open blade fans see our ceiling fan calculator. Ventilation rate of 10 air changes per hour.

Use the chart below as an attic vent fan cfm calculator. A whole house attic fan is installed in the ceiling between the top floor and the attic as a supplement to air conditioning. 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.

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. Intake air vent size. Enter the length and width of your attic or ceiling crawl space.

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

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. Set the thermostat on your attic vent fan so that it cuts on between 100 and 110 f. For the exhaust to work properly the attic should have enough intake air vents. Attic fan size chart for quick reference.