Office employees are exposed to a variety of environmental and contextual stimuli that might drive them to perform control actions, such as operating windows or window blinds. These actions have a significant impact on building energy use and increase uncertainty when predicting building performance. Despite the advancements in the understanding of separate fields of comfort (thermal, olfactory, visual, and acoustic), the combined effect of Indoor Environmental Quality (IEQ) factors on user perception and behaviour in real buildings merits further explorations. In this context, the eCOMBINE framework ("Interaction between energy use, COMfort, Behaviour and the INdoor Environment in office buildings") aims to create new knowledge on human-building interactions in office environments, with a dedicated focus on open plan offices. This paper provides initial results of the eCOMBINE monitoring campaign performed during a two-week period in winter (February 2020) in Switzerland. The main subjective drivers behind interactions with windows and window blinds were analysed based on self-reported actions collected with a dedicated mobile application called OBdrive, which was installed close to windows and window blinds to capture employees' motivations in real-time. The subjective feedback was supplemented with environmental data, such as operative temperature, air quality, lighting levels, and sound pressure levels. Environmental and subjective data were evaluated jointly to gain insights into the relationship between global environmental stimuli and human-building interactions. The results showed discrepancies between perceived air quality and motivation to open windows, which confirms that occupants might not always correctly interpret actual air quality. While the primary motivations for windows and blind control actions were rather logical (e.g., opening windows when it is too warm, closing blinds in case of glare), occupants' actions were often triggered by multiple motivations at a time, suggesting that a single criterion is not necessarily enough to capture occupant's action.