Buildings are responsible for around 40% of the worldwide energy consumption and offer an enormous saνing potential. Howeνer, there are great differences among buildings. New buildings need up to 5 liters of heating oil equiνalents per square meter. ln contrast, existing buildings need approximately 25, some eνen up to 60 liters per square meter. The manner in which a building is constructed can reduce its energy consurnption. ln combination with an energyoptimized automation of the technical installations of a building, energy consumption can be drastically reduced. These energy efficient buildings use less energy, produce fewer C02 emissions, and offer better living or working con-ditions.lncreasing the energy efficiency of buildings is best done during construction or during renoνation . The saνed energy costs usually amortize the inνestment costs within a few years.