4500 CFM 24 In. Direct Drive Whole House Fan with Shutter
4500 CFM 24 In. Direct Drive Whole House Fan with Shutter. Airflow (CFM) 4500. The GAF Master Flow 4500 CFM 24 in. A minimum 1100 sq. ft. of attic space with a minimum of 1008 sq. in. of net free area attic exhaust is required for proper operation.