Ventilative cooling in a school building: evaluation of the measured performances

The test lecture rooms of KU Leuven Ghent Technology Campus are one the demonstration cases of IEA EBC Annex 62: Ventilative Cooling. This nZEB school building is realised on top of an existing university building and contains 2 large lecture rooms for maximum 80 students with a floor area of 140m² each. An all air system with balanced mechanical ventilation is installed for ventilation, heating and cooling. The building is cooled by three techniques of ventilative cooling: (1) natural night ventilation (opening the windows at both sides of the building) (2) a modular bypass in the AHU and (3) indirect evaporative cooling (IEC). 
This paper aims to evaluate thermal comfort in this nZEB school building and the performances of its ventilative cooling system. Therefore, long term measurements of internal temperatures, occupancy, opening of windows, operation of IEC, airflow of AHU, etc. were carried out from May to September 2017 (i.e. cooling season). In addition, the airflow rates through the windows in cross ventilation and single sided ventilation mode were measured on several days in March and April 2017. Both tracer gas concentration decay tests as air velocity measurements were used for this purpose. 
The results show that a good thermal summer comfort was measured in the test lecture rooms at the Technology campus Ghent of KU Leuven (Belgium). Only during heat waves and/or periods with high occupancy rates, high indoor temperatures were monitored. Both nighttime ventilation and indirect evaporative cooling operate very well. IEC can lower the supply temperature by day significantly compared to the outdoor temperature. The ACR of the night ventilation depends a lot on wind direction and velocity. Furthermore, two key lessons learned from the operation phase are: (1) the data monitoring system was essential to optimize the performance of the ventilative cooling and (2) the users have to informed about the operation of automated systems.