The use of cooling towers for concrete-core-cooling in building technology enables energy saving possibilities, which are based on evaporative cooling. Therefore, the necessity of separate cooling devices is obsolete in this type of buildings. This technique may only be realized with use of dynamic simulation tools that support the design of the system. The operation concept for these systems works in a way that they cool down the concrete-core during night time and use this potential for cooling the building during day time. Besides the principle, examples that demonstrate the energy saving capacity are presented.