This paper presents the results of a field study concerning indoor conditions in an office space in Grieskirchen, Upper Austria. The office is equipped with a displacement ventilation (DV) as well as personal ventilation (PV) systems. The space can also be naturally ventilated through the manual operation of windows (NV). The main objective of the study was to assess the functionality of the mentioned ventilation systems with regard to indoor air quality and thermal comfort. The configuration of the indoor climate control system in this office allows for the performance evaluation of the ventilation systems through different methods. In fact, the monitored data and short-term user surveys provide a basis to document the indoor conditions and their implications for the occupants. Our study also illustrated the utility of calibrated CFD models toward a better understanding of the airflow phenomena and estimation of the airflow velocity as an input data for calculation of predicted mean vote (PMV) values. The results suggest that the combined operation of the above mentioned systems provides in general acceptable indoor environmental conditions. However, optimal operation of the systems installed requires the continuous and comprehensive monitoring of indoor conditions, systems states, and occupants’ feed-back.