A heat recovery device such as an EGHR device includes a bypass valve, a gas/liquid heat exchanger and a flow duct. The flow duct has an open top and an open bottom. A top surface of the duct seals to a surface surrounding an opening of a gas flow conduit, such as an exhaust pipe. A duct wall extends from the top surface to the bottom surface, to which the heat exchanger is secured. The flow duct provides a passage through gas flows between the gas flow conduit and the heat exchanger. The bypass valve is mounted in the flow duct and is movable between a bypass position and a heat exchange position. The bypass valve may be mounted adjacent to the top or bottom of the duct, and may be a butterfly-type valve, a one-sided flap valve, or a pair of one-sided flap valves.