This paper presents initial research outcomes of a longitudinal study which was initiated in 2013/2014 to determine the real added value of sustainable buildings for end-users. The focus of this research is on the added value of sustainable buildings to organisations – specifically the added value thereof to user-experience, comfort, well-being and perceived performance. The sustainability of a newly constructed or refurbished office building is often used extensively in marketing the sustainable goals and ambitions / achievements of organisations. Being the start of a longitudinal study, the objectives of this research is firstly, to establish a proper theoretical framework according to which the added value of sustainable office buildings to both end-users and organisations can be studied, and secondly, using case studies to validate the theoretical knowledge. The development and initial research discussed in this paper was executed as a bachelor graduation project in the IREFM (International Real Estate and Facility Management) programme at the Academy of Hotel and Facility Management at the NHTV Breda University of Applied Sciences in the Netherlands. The methodology employed was based on the development of a theoretical framework according to literature sources in the field of sustainability and the impact thereof on end-users and organisations. Subsequent to the development of the theoretical framework, interviews and questionnaires were used to further develop the framework for application as a conceptual framework for the longitudinal study. Preliminary results of the case study indicate that users of sustainable office buildings are more satisfied and perceive themselves to be more productive. However, employees still suffer from physical complaints whilst being in the office building, which indicates that sustainable buildings do not directly increase physical well-being of employees. For many employees, the indoor climate is affecting daily tasks, which might result in stressful situations and therefore in decreased psychological well-being. Although employees feel safe in the office building and experience enhanced social interaction because of the available workspace, it can be concluded that overall well-being of employees is not increased due to sustainable office buildings. The study provides a first-draft approach to developing a comprehensive framework for longitudinal research into the real added value of sustainable office buildings.