Sensing and predicting occupancy in buildings is an important task that can lead to significant improvements in both energy efficiency and occupant comfort. Rich data streams are now available that allow for machine learning based algorithm implementation of direct and indirect occupancy estimation. We evaluate ensemble models, namely random forests, on data collected from an 8x8 PIR matrix thermopile sensor with the dual goal of predicting individual cell temperature values and subsequently detecting the occupancy status. Evaluation of the method is based on a real case study deployed in an IT Hub in Bucharest, for which we have collected over three weeks of ground data, analyzed and used it in order to predict occupancy in a room. Results show a 2-4% mean absolute percentage error for the temperature prediction and >99% accuracy for a threeclass model to detect human presence. The resulting outputs can be used by predictive building control models to optimize the commands to various subsystems. By separating the specific deployment from the system architecture and data structure, the application can be easily translated to other usage profiles and built environment entities. As compared to vision based systems, our solution preserves privacy with improved performance when compared to single PIR or indirect estimation.Index Terms-occupancy prediction, smart buildings, random forests, computational intelligence, data acquisition.