Analyses in this study focus on characteristics of three different clusters of ventilation for office buildings. These comprise natural, mechanical and hybrid ventilation. In a major project study, extensive data was collected from 27 office buildings. Besides physically measurable parameters, psycho-social-oriented surveys of building users and information about building-specific constructional or building technology were compiled. In a selection, results of indoor air quality (IAQ) and indoor

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... environment quality (IEQ) were compared with current standards. Thom's Discomfort Index (DI) suggested that, for all three clusters, populations feeling discomfort are to be expected during the summer months. Responses for certain aspects corresponding to IEQ and IAQ showed a remarkable seasonal divergence of satisfaction with air temperature for naturally ventilated buildings. The appearance of stagnant air is found to occur in its strongest form in naturally and hybrid ventilated buildings. Mechanically ventilated buildings were reported as having the lowest values for satisfaction with air humidity in winter. Each ventilation system comprises characteristic advantages and disadvantages. A tendency might favour, at least seasonally, mechanically or hybrid ventilated buildings. Differences between these two systems are not significant in this sample. The result raises the question of how much technical effort is actually necessary to provide satisfactory ventilation.