What is the exact value of a building? These days sustainable buildings do not get a perceivable higher value relative to unsustainable buildings. This due to the lack of sustainability within valuations. It are only a building’s users that benefit from the positive aspects of a sustainable building like the increase in productivity and decrease of absenteeism. There are no perceptible benefits for the building owners, therefore making existing real estate more sustainable is stagnating. Using the Fuzzy Delphi Method (FDM) a consensus among property appraisers about the most important physical aspects of an office building is made. The results of the FDM are included in the renewed valuation model. Sustainability is expressed in four aspects: energy costs, maintenance costs, productivity an absenteeism. Due to the incorporation of sustainability in valuations sustainable buildings will get a perceptible higher value relative to unsustainable building. In addition, all stakeholders will benefit from the positive effects of sustainable buildings.