The QuietCool QC-4700 (U. S. Patent #7497774) will help you slash your A/C related electricity costs by 50-90% and pays for itself faster than any other "green energy" product on the market today. This fan motor and self-contained duct system hangs in the attic and the fan's whisper quiet operation is made possible by QuietCool's patented acoustical ducting that provides six feet of separation between the fan motor-head and the ceiling intake grill inside the house. The QC-4700 draws 4757 CFM on high and 3,586 CFM on low and is the perfect fan for homes that want a single-motor central unit combineded with individual fans in the bedrooms for private, zoned control. For vertical wall installations, order a vertical wall adapter (part number : QC-60093).