How To Size An Attic Exhaust Fan

Then click on calculate.

How to size an attic exhaust fan.

Set the thermostat on your attic vent fan so that it cuts on between 100 and 110 f. For the exhaust to work properly the attic should have enough intake air vents. 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.

Intake air vent size. Ventilation rate of 10 air changes per hour. How to size a whole house attic fan. 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.

Attic fan size chart for quick reference. Humidity sensors are also available that cut the fan on if moisture in the attic becomes too high. Enter the length and width of your attic or ceiling crawl space. Use the chart below as an attic vent fan cfm calculator.

A whole house fan sucks warm house. Then enter the height at the highest point. 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 example a 1 000 square foot attic needs to have a fan that can handle at least 460 cubic feet per minute of airflow.

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. 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. Select if your roof is more flat of peaked.