How To Size An Attic Exhaust Fan

Ventilation rate of 10 air changes per hour.

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. Enter the length and width of your attic or ceiling crawl space. Select if your roof is more flat of peaked. Your attic fan should be sized to the square footage of your attic.

A whole house attic fan is installed in the ceiling between the top floor and the attic as a supplement to air conditioning. 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. A whole house fan sucks warm house.

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. How to size a whole house attic fan. 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.

Minimum intake air vent size cfm 300 sq ft. Use the chart below as an attic vent fan cfm calculator. Humidity sensors are also available that cut the fan on if moisture in the attic becomes too high. 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. Attic fan size chart for quick reference. So here the cfm of the fan cfm x 1 15. Then enter the height at the highest point.