Comfort strategies became a decisive parameter for a possible retrofit of buildings. Lacking flexibility of mechanical systems and/or lacking comfort often make a renovation or retrofit expensive and sometimes even impossible. This can be related to spatial issues such as mechanical rooms and shafts. Often a horizontal distribution of systems lead to insufficient height of spaces. Particularly the post war building stock doesn’t provide the necessary flexibility. Lacking floor to floor height, combined with perceived inacceptable comfort conditions and often underutilized land use are main arguments for a complete replacement of buildings. The architectural aesthetic of that time doesn’t cause any public nor heritage resistance. Before design for circular material use it is essential to re-think the current economically and technology driven building design towards an architecture, which provides true program flexibility based on robust comfort strategies.