This AF-30  Whole House Fan solution uses your attic space as a plenum ! So if you have a very shallow-low clearance attic or if your attic has a lot of clearance this fan will provide a lot of through put !This cooling solution will act as an attic fan when the plenum opening is closed and a whole house fan when the plenum is open.Some of our customers just open their attic hatch when they want the fan to operate as a whole house fan and close the hatch when they want to run their AC.Some of our customers purchase a separate low profile ceiling grate/s and place it in a central hallway or in bedroom/s.This attic fan / roof fan EXHAUSTS CONTINUOUSLY whether the electric motor is ON or OFF. When the fan is off, outside air moving against the Aura Ventilator causes the Venturi effect, thereby creating an exhaust. The exhaust is created without the use of electricity or moving parts. On the days when the fan is not needed, the Aura Vent will still operate passively; this increases the life of the motor since it is not in constant use. The Aura Fan Ventilator reduces energy consumption.Inside Dia =30   Outside Dia=36  Head Height=12  L&W=37  Roof Pitch=3/12  Height TTL=18 Weight 75HP-1  Amps=11.8  RPM=1075  Motor Type PSC * Open Ventilation - 30" Roof opening