A blower has a blower housing of clamshell construction, including two housing members having a scroll back wall molded with radial draft, an impeller and a motor within the housing, and a static tap connected to the housing. The impeller has a backplate with a backplate back surface region of substantially the same radially converging shape as that of a front surface region of the scroll back wall formed by the radial draft, providing a substantially uniform axial gap between the backplate back surface region and the scroll back wall. The impeller has a ring connected by a skirt to the back plate to define a stepped area behind the ring. The impeller includes impeller blades extending forwardly from the impeller backplate and the ring and back fins extending rearwardly from the ring. The blower has a scroll width of about twice an impeller exhaust width.