Ventilation flows generated by a localised heat source within a room connected to the ambient environment via two openings (a doorway and high-level vent) are examined. In all cases considered, a steady two-layer stratification of well-mixed fluid is established within the room. Classical displacement ventilation flow is observed when the interface between the two layers is above the height of the doorway. Displacement ventilation flow can persist when the interface within the room is below the height of the doorway; in general, however, an unbalanced exchange flow forms across the doorway and the ventilating flow is found to be dependent on the effective area and aspect ratio of the doorway, the effective area of the high-level vent and the entrainment coefficient of the plume. An analytical model is presented which predicts the ventilation rates and temperature structures within the room for these flows. Results from laboratory experiments demonstrate good agreement with the model for a wide range of the parameter space relevant to the full-scale application.