Ventilation through building walls:Wind tunnel studies

The usual way of extracting the waste air in a multi-storey residential building is to conduct the air above the roof. The purpose of this research program was to examine whether exhaust air from each apartment could be discharged outdoors via exhaust vents mounted on the outer wall in such a way that no odours or other harmful effects are caused. This would facilitate the use of apartment-based mechanical ventilation using wall ventilators which would be of great help specially in renovating old multi-storey apartment houses. A wind tunnel investigation was carried out using tracer gas measurements with models of three multi-storey buildings to determine how much waste air from a wall outlet is carried into the intakes on the same wall. Also full-scale experiments were performed and for comparison some of full-scale test wind conditions were reproduced in wind tunnel tests. Several parameters were varied in wind tunnel investigations, for example: exhaust jet-to-wind velocity ratio, the distance between outlet and intake openings and the position of the wall outlet. The results showed that the exhaust jet-to-wind velocity ratio is a suitable parameter for determining dilution rates and the tests can be carried with different absolute velocity values. Owing to the turbulence caused by the building itself and near-by buildings the trajectories of the exhaust plumes are much more complicated with wall ventilators than with roof ventilators. Near exhaust vents on the open wall, the measured dilution was usually much more higher than that predicted by the minimum dilution theory for roof exhaust. Thus, the theory could be useful when dimensioning exhaust vents on an open wall. In niches and corners the theory does not function reliably