The idea of designing Zero Energy Buildings (ZEBs) has been gaining international interest in recent times because it seems the perfect solution to make buildings more independent of the electric grid considering the growing energy demand and the climate change. Either way, before being completely introduced in the national building regulations and international standards, the ZEB concept claims a solid and clear definition and a shared energy calculation methodology by all the Member States of the EU. In a period of significant climate change and awareness, the improving of technologies and materials for constructions and the Energy Performance of Building Directive (EPBD), that sets the standards for new and renovated buildings across Europe, might play a key role for the improvement of the building stock and to reduce the greenhouse gas emissions in the atmosphere.