Learning from innovative climate concepts in schools

Abstract

Newly designed buildings should be energy efficient as well as comfortable. To achieve both, new HVAC concepts are designed. Unfortunately, the introduction of new HVAC concepts is not always successful, leading to discomfort and even health complaints among the occupants. In this paper we describe three cases that we investigated recently: 1) A school with concrete core heating/cooling and natural air supply and mechanical exhaust. 2) A school with an all-air system with VRF units and heat pumps. 3) A monumental school building (secondary school) with pressure regulated ventilation (BaOpt) and ground heat pump. The occupants had the following complaints in the three cases: 1) complains about cold air draught and cold feet in the winter, spring and autumn and heat in the summer season. 2) complaints about air draughts, fluctuating temperatures, bad air quality and unpleasant odours. 3) Complaints concern heat in summer, cold in winter and intermediate season, and stuffy and dry air. The causes found for the indoor climate problems for the three cases: 1) The combination of natural air supply and low temperature heating. A heating pipe was installed in front of the air inlet but was unable to prevent the draught. 2) The central AHU did not have heating or cooling sections. In defrosting mode of the air heat pump, fluctuating air inlet temperatures were measured. When defrosting, the ventilation system switched to recirculation, with implications for the IAQ. Different zoning of the ventilation system and the heating and cooling system exacerbated the problems. 3) Due to the low air tightness of the building envelope, the ventilation system did not perform as intended. Only the classrooms near the air handling unit got fresh air. The ground heat pump did not function due to underground leakages, therefor the school did hardly have heating and no cooling. From these cases we learn that it is crucial to bring together technical / theoretical knowledge, practical expertise and the user perspective when working on innovative solutions. In this way we learn from practical experience which hopefully lead to improved and robust HVAC-systems.