There are several actors involved in the planning, constructing and operating of buildings. Each one of these stakeholders is - more or less - capable of taking influence in the implementation of sustainable strategies that are composed of economical, ecological and social aspects. The question arises, who the key actors concerning sustainability are and therefore determine the impact on the environment, the economy and the society. Key actors are identified by analyzing their personal aims, their roles within the actors' network and their involvement in significant decisions. Inspecting the actors' professional training and further education it becomes obvious that there is a considerabel need for pertinent classes and teaching-moduls ñ aligned with each professional's education and requirement. Another strong factor in the decision making process is the application of certain technics and conventional methods that often don't allow to install specific parameters dealing with sustainability matters.