The dissertation presented below talks about differences and peculiarities of green rating systems, how they have changed during the last 10 years and how they work. This research describes a self-reporting program, Level(s), and a commercial green building system, WELL. The first one is a non-commercial framework that aims to sensitize all European countries towards sustainability and the concept of the “Life Cycle Assessment” and consequently the importance of those two ideas. On the other hand, Level(s) is compared with WELL (Well Building Standard), which belongs to a new generation of certification programs that stress the importance of occupant satisfaction while maintaining a high standard in design, sustainability and building processes.