In consequence, there is an enormous energy saving potential and the European Union requires from all
EU member states to save energy in this sector. Hence, reducing the energy consumption of buildings represents an essential component of environmental protection efforts. Furthermore, the new European directive 2010/31/EU requires that the member states tighten national standards and draw up national plans to increase the number of "nearly zero-energy buildings". Well-planned energy-saving strategies presume knowledge of specific characteristics of the current national building stock. Therefore, the imple- mentation of a process to support systematic data collection, classification and analysis of the energy consumption of buildings will become increasingly important during the coming years