How can one define sustainability in architecture? And what are the consequences for the design process of architects and engineers? There are lots of different definitions for sustainability in the world. Nowadays, in the world of architecture, there are enormous personal and respectively various definitions for sustainability. The procedure of development caused a big increase of so called certification systems for sustainable buildings. And all of these systems are trying to define sustainability in different ways in order to merchandize a reliable standard for green construction and respectively protecting nature base on their local technologies and conditions. The intention of this work is to compare eight existing sustainable building certification systems (LEED, BREEAM, DGNB, HQE, Green Star, CASBEE, BCA Green Mark, TERI GRIHA) from America, Europe, Asia and Australia in a theoretical way in order to answer the questions above. A common and worldwide definition of sustainability is one of the results of this comparison that on one hand shows the differences in topics and weighting of these systems, on the other hand presents the necessary materials, decisions and steps for the design process of planners and architects. In a further step, a green building will be designed that documents decisions taken during design process by monitoring the questions such as: when do I need to decide what? How easy is this process? And who has to take the decision?