Buildings are made for people. In the post-war period of time it was the idea of collective and stable identities of groups of people that dominated our thinking in design. The results were mono-functional and rigid buildings and areas. Nowadays this idea has been left. We realize that we have to deal with an individualized and dynamic demand, due to large demographic changes and to technological developments. This has an enormous impact on the existing built environment. Because this existing stock satisfies more than 99% of existing and new demand for all kinds of housing. Open building is based on this point of view of ever changing individual demand. Therefore the future of open building resides in the renovation and transformation of the existing built environment.