Most of these are the big propellers with shutters – You will find them with direct drive and belt drive – belt drives reduce the fan speed and make them quieter.
Air Vent, Dayton/Grainger, Invisco, LL Building Products (GAF/MasterFlow), Marley, Triangle Engineering, TPI and Ventamatic are sources for these big fans. Note – on average, the 24 inch is 5500 CFM, 30 is 6000, 36 is 10,000, 42 is 14,000, 48 is 18,000. BD is belt drive, DD is direct drive, VS designates that the fan has a continuously variable speed control instead of a 2 speed motor)
Air Vent (24, 30 DD and 30, 36 BD)
Dayton/Grainger (24, 30, 36, 42 BD and 24, 30 DD)
Invisco has ceiling mounted machines ranging from 24 inches to 48 inches similar to Triangle. The primary difference is that all Invisco whole house fans have infinitely variable speed motors.
In addition, Invisco is bringing out the new SmartSpeed(tm) automatic speed control.
LL Building Products/GAF/Master Flow (24 DD and 30 BD) Note- some Master Flow 30BDs at Home Depot have been found to be manufactured with a defect – the motor pulley and the driven fan pulley cannot be properly aligned – See Invisco for the solution.
Marley Engineered Products/QMark (20,24,30 DD and 24, 30, 36 BD)
Triangle Engineering (24, 30, 36, 42, 48 BD and 24, 30 DD)
TPI has 24, 30 and 36 belt drives.
Ventamatic/Cool Attic (24, 30, 36 BD and 24, 30 DD)
THERE ARE A FEW SMALLER INSULATED HALL CEILING MOUNTED FANS WITH DOORS THAT OFFER EXCELLENT INSULATION.
These designs are smaller fans in boxes that mount right in the ceiling between joists.
Tamarack has the only R38 and R50 insulated motorized door system. Available in 1000, 1450, 1600 and 3400 CFM.