From the very start, the focus of this project was on energy efficiency. The base heating load is covered by geothermal heating using separate, reversible heat pumps via ground water and deep probes and activated concrete core (400 kW). Peak load coverage is guaranteed by a gas boiler plant (780 kW). In order to guarantee an ecologically and economically sustainable building operation, a central stratified load buffer has been designed to be able to feed in any waste or recovered heat energy. In addition, the waste heat from the chiller unit can be fed back into the heating circuit. The basic load for cooling operation is done geothermally using free cooling employing ground water in three source wells and a ground/water heat pump via deep bores and the activated base plate (400 kW). Peak load is covered by a power- controlled screw compressor (847 kW) installed with dry glycol return coolers that is also used to cool the server and LAN rooms in winter months. The 9 ventilation intake and exhaust systems equipped with sustainable and highly efficient heat recuperation units move an air volume of approx. 135,000m2/hr.