TOP DOWN VENTILATION AND COOLING

This paper examines the problems inherent in passively ventilating and cooling low and medium rise urban buildings. We focus on overcoming numerous key issues, such as those of pollutant ingress associated with locating low-level intake openings in passive displacement ventilation systems. A solution is suggested. The concept that is examined is to take ventilation air into the building from the top and to draw it down into the spaces below using the stack effect associated with the difference in temperature between the internal and external environments. Stale air and excess heat from the spaces are discharged via outlet openings into the same external air pressure zone as the inlet. Results of laboratory experiments using the salt-bath technique are reported which substantiate this concept, and two wind-driven devices which may be used to assist the top-down process are described. This paper also discusses methods of occasionally actively cooling the vertical intake ducts of passively ventilated buildings, adopting the top-down system both to boost airflows and to improve internal environmental quality on occasions when solely passively driven ventilation may prove inadequate.