For the exhaust to work properly the attic should have enough intake air vents.
How to size an attic exhaust fan.
How to size a whole house attic fan.
A whole house fan sucks warm house.
Attic fan size chart for quick reference.
For open blade fans see our ceiling fan calculator.
A whole house attic fan is installed in the ceiling between the top floor and the attic as a supplement to air conditioning.
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.
Then click on calculate.
Your attic fan should be sized to the square footage of your attic.
Then enter the height at the highest point.
Minimum intake air vent size cfm 300 sq ft.
Humidity sensors are also available that cut the fan on if moisture in the attic becomes too high.
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.
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.
Ventilation rate of 10 air changes per hour.
Set the thermostat on your attic vent fan so that it cuts on between 100 and 110 f.
Enter the length and width of your attic or ceiling crawl space.
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.
So here the cfm of the fan cfm x 1 15.