A blower assembly for advancing the flow of air in an air flow device at a selected one of a plurality of air flow rates. The blower assembly includes a blower housing defining a body thereof and a wall of the blower housing moveably secured to the body, a blower wheel rotatably mounted to the blower housing and a motor for rotating the blower wheel at a selected one of a plurality of rotational speeds. The blower assembly further includes a motion device secured to the body and to the wall. The motion device moves the wall relative to the body to a selected one of a plurality of distinct wall positions. The motor rotates the blower wheel at a selected one of a plurality of rotational speeds. A controller calculates an optimum wall position and rotational speed to provide for minimal energy usage rate.