Direct drive whole house fan with white powder-coat finish shutter. 2 speed, thermally protected 1/3 HP PSC (Permanent Split Capacitor) motor. Precision balanced aluminum fan blade assembly. 4 fan blades for greater air movement. Includes 2-speed switch and wall plate. Joist-in or joist-out installation. Ceiling mount application only. Tough steel motor struts. Steel venturi for enhanced durability. 24" whole house fan is appropriate for homes with up to 1800 sq ft (square foot) attics. Requires a minimum of 8 to 10 sq ft of net free air exhaust vent area. 30" whole house fan is appropriate for homes with 2000 to 3000 sq ft attics. Requires a minimum of 10 to 12 sq ft of net free air exhaust vent area. Veins run lengthwise with stationary center vein to allow no-cut joint installation. 10 year limited warranty.