The possibility of using stored hot water generated during the day by using solar energy to assist in the provision of adequate buoyancy driven natural ventilation flow rates through small theatres during the evening hours has been numerically investigated in a very basic manner. The hot water would be used to heat the air using a plate type heat exchanger system mounted in a roof-top chimney-like air discharge system. A simple building with a given cross-sectional design has been considered. Two-dimensional steady flow has been assumed to exist and the flow has been assumed to be symmetrical about the vertical centre-line through the building. The Boussinesq approximation has been adopted, i.e., the air properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being treated assuming a linear relation between the density changes and the temperature change. Radiant heat transfer effects have been neglected. The standard k-epsilon turbulence model with buoyancy effects being fully accounted for has been used. The heat generation from the audience has been treated as a uniformly distributed heat flux over the floor, the smaller the audience, the lower being this heat flux. The solution has been obtained using the commercial CFD solver FLUENT©. The results, while of a very preliminary nature, indicate that the proposed system could provide an adequate natural ventilation flow rate.