The building sector has a key role in the fight against the climate change, since it is responsible of the largest share of energy consumption and CO2 emissions both at global and at European levels. In Europe, the existing building stock represents a huge problem since its almost entire share is energy inefficient. Therefore, a green retrofit action is needed, that is not only meeting the minimum energy performance requirements and being financially beneficial to the building owners, but that also has a low environmental impact. The aim of this Master's Degree thesis is to identify how the researchers have been figuring out a methodology for the economic evaluation of a green retrofit scenario in a life cycle perspective in the European context.