How To Size An Attic Exhaust Fan

Then click on calculate.

How to size an attic exhaust fan.

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

For heating and air conditioning airflow or for other exhaust fan situations see our airflow calculator. 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. 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.

How to size a whole house attic fan. For the exhaust to work properly the attic should have enough intake air vents. 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.

Select if your roof is more flat of peaked. Attic fan size chart for quick reference. 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.

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. 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.