Abstract: A damper assembly in a heat recovery ventilator, comprising a rotor, a bearing, drive means, and sealing means. The rotor rotates about an axis of rotation and includes a pair of end walls in spaced-apart relation to define a substantially open periphery. The rotor also includes an air-deflecting member connected between the end walls. The bearing is associated with one of the end walls and is located at the axis of rotation, to support rotation of the rotor. The drive means rotates the rotor about the axis of rotation and positions the air-deflecting member in first and second orientations. The sealing means is in slide contact engagement with the rotor and seals between the rotor and a surrounding damper compartment of the ventilator. The sealing means isolates the exhaust airstream from the supply airstream in the damper compartment while the air-deflecting member is in the first or the second orientation.