How To Size An Attic Exhaust Fan

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 an attic exhaust fan.

How to size a whole house attic fan. Humidity sensors are also available that cut the fan on if moisture in the attic becomes too high. 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.

Use the chart below as an attic vent fan cfm calculator. Ventilation rate of 10 air changes per hour. So here the cfm of the fan cfm x 1 15. 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 the exhaust to work properly the attic should have enough intake air vents. If your attic requires a 1500 cfm fan then it should also have a 1500 300 5 sq ft air vent. For open blade fans see our ceiling fan calculator. 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. 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. A whole house fan sucks warm house. Intake air vent size.

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. Then click on calculate. Then enter the height at the highest point. 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.