How To Size An Attic Exhaust Fan

For the exhaust to work properly the attic should have enough intake air vents.

How to size an attic exhaust fan.

Ventilation rate of 10 air changes per hour. 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 fan sucks warm house. Minimum intake air vent size cfm 300 sq ft.

Then click on calculate. Attic fan size chart for quick reference. Then enter the height at the highest point. Select if your roof is more flat of peaked.

For open blade fans see our ceiling fan calculator. Set the thermostat on your attic vent fan so that it cuts on between 100 and 110 f. 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. 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. If your attic requires a 1500 cfm fan then it should also have a 1500 300 5 sq ft air vent. Enter the length and width of your attic or ceiling crawl space.

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