When does an atrium enhance natural ventilation?

This paper investigates passive displacement flows in a simple, two-compartment building that comprises a single storey connected to an atrium. Heat gains in the storey and solar gains in the atrium create a stack pressure which drives a ventilating flow. A model is developed to determine the steady flow rate and thermal stratification for a range of heat gains, storey and atrium heights, and ventilation opening areas. We show that the accumulation of warm air in the atrium serves to enhance the flow rate through the storey only if the upper atrium opening is not too small, and the lower atrium opening is not too large.