How To Size An Attic Exhaust Fan

For open blade fans see our ceiling fan calculator.

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. Use the chart below as an attic vent fan cfm calculator. 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. Intake air vent size.

Then click on calculate. So here the cfm of the fan cfm x 1 15. 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. For the exhaust to work properly the attic should have enough intake air vents.

How to size a whole house attic fan. Enter the length and width of your attic or ceiling crawl space. Select if your roof is more flat of peaked. Set the thermostat on your attic vent fan so that it cuts on between 100 and 110 f.

Humidity sensors are also available that cut the fan on if moisture in the attic becomes too high. Minimum intake air vent size cfm 300 sq ft. A whole house attic fan is installed in the ceiling between the top floor and the attic as a supplement to air conditioning. A whole house fan sucks warm house.

If your attic requires a 1500 cfm fan then it should also have a 1500 300 5 sq ft air vent. 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. For heating and air conditioning airflow or for other exhaust fan situations see our airflow calculator. Ventilation rate of 10 air changes per hour.