As the energy demand of new office buildings has been reduced during the last years, there is a rising interest for heating and cooling systems based on renewable sources of energy. While conventional office buildings requires complex technical devices which associate a high energy demand, the reduced energy demand of low-energy office buildings can be supplied mostly by natural heat sources in winter and summer. Low-energy office buildings can successfully use passive cooling concepts in summer. If solar and internal heat gains are minimised and the building's thermal inertia is utilised, the reduced and smoothed heat gains can be counterbalanced only by the cool night air. This thesis analyses the realised passive cooling systems in four low-energy office buildings using the wide data pool from a two years' monitoring and short-term measurements in each building. This thesis aims to enhance the design and operation of passive cooling concepts. A comprehensive data analysis shows the night ventilation potential in realised buildings and how design tools should be used in order to accurately design and operate the passive cooling concept.
