Whole house fan

A whole-house fan adapted for installation in an opening in a ceiling above a pair of adjacent, parallel ceiling joists, without cutting either of said joists, said fan comprising a fan impeller having blades for drawing air through said opening in said ceiling, said fan impeller having a vertical axis of rotation, said fan impeller having a diameter of at least two feet, so that said blades extend over both said adjacent joists when said fan is in operation, a motor for driving said fan impeller, frame means for supporting said fan impeller and said motor on upper surfaces of said adjacent joists, said frame means comprising a pair of spaced apart, generally horizontal frame members, and a fan housing above said frame members for defining an air path through said assembly, each of said frame members being U-shaped, said fan housing being secured to up-turned arms of said members and said motor and said fan impeller being supported by horizontal reaches of said members, and mounting means on said frame members spaced apart sixteen inches and twenty-four inches on centers, for mounting said frame members to said upper surfaces of said adjacent uncut joists at right angles to said adjacent uncut joists, regardless of whether said adjacent uncut joists are spaced apart sixteen or twenty-four inches.