A significant corpus of research has shown that occupant behaviour is a key factor of uncertainty when predicting building energy use. Building occupants affect energy use directly and indirectly by regulating their indoor environment according to their comfort criteria and a wide range of contextual, psychological or social factors. Increasing research efforts are being dedicated on developing models able to capture the stochastic nature of the human-building interaction in dynamic simulation programs. However, existing models oftentimes do not include information on multi-domain variables and the global environment. The foundation for the investigation and data-driven modelling of occupant behaviour in the built environment remains measured data, and an effective and extensive data collection remains a key challenge towards gaining a better understanding and modelling of occupant behaviour. This paper provides a structured overview of a monitoring framework for open space offices, eCOMBINE (“Interaction between energy use, COMfort, Behaviour and the INdoor Environment in office buildings”), aimed at capturing an extensive set of subjective and objective multi-domain variables likely to drive building occupants to perform actions on environmental controls. Towards this end, this paper presents a survey framework and an ad-hoc mobile application developed to capture motivations behind actions in real-time. Finally, we highlight lessons learned and research opportunities one might envision once the collection of such comprehensive datasets will become more mainstream.