Together with the architects, HVAC and structural designers, Transsolar has developed the desired energy-optimized and naturally ventilated concept for the administration building from competition through building completion. The eleven-story building on a triangular plot has the shape of a prism: Two massive and one double-glazed office wing enclose a central atrium. It meets the German low energy standard , is comfortable for the users and ecologically designed. The ventilation concept primarily uses natural ventilation and night ventilation. Essential for this are the atrium and double façade with the possibility to reverse the direction of airflow to allow summer or winter operation. In winter, the supply air enters the double façade from the outside, flows through the rooms and passes through tubes in the concrete ceiling as exhaust air into the atrium. The driving force behind this is the natural chimney effect in the atrium. In summer, the air from the shaded, cooler atrium is channeled into the offices and vented through the warmer double façade. For this purpose, the atrium is supplied mechanically with air through a tempering earth channel. This creates a slight overpressure and ensures supported by the chimney effect in the double façade for d-aeration. In addition, the building is "flushed" and cooled during summer nights with cool nighttime air using the chimney effect the atrium with cool night air. Transsolar has performed numerous thermal and hydraulic simulations, making additional comfort measurements in the segment mock-up, for implementing natural ventilation as much as possible. Transsolar also worked on daylight performance with computer simulations, analyzed a 1:100 scale physical mock-up to determine the distribution of light in the atrium under an artificial sky, designed the combined system of shading and light baffles on the glass roof and guided the distribution of workplaces throughout the office spaces.