Bank Tower in Frankfurt-on-Main
Reversing the idea of a central core, the design locates a triangular, light-filled atrium at the heart of the building, with the office spaces laid out about it and three access/ service spines at the corners. The spines also form the main supporting structure between which the eight-storey office segments are hung. The segments alternate vertically with four-storey garden spaces, which wind in a series of steps up the three faces of the building. These nine garden spaces are set back from the outer façades and overlook the atrium internally. They are used by the staff as areas for relaxation and discussion. As a result of this layout, it was possible to situate office areas along both faces of the segments, with internal views to the atrium and the gardens. To avoid wind currents and any build-up of smoke, the atrium is divided every 12 floors by a glass roof. Openable windows mean that the offices on the atrium face are in protected contact with the open air, which obviates the need for mechanical ventilation on most days. The same applies to the offices along the external faces of the building, where a second glazed skin with ventilation slits allows fresh air to enter the storey-height façade cavities. The solar screening is also housed in these spaces. In the event of extreme temperatures or storms, a central control unit closes all windows and sets a conventional air-conditioning plant in operation. The rooms are cooled by a chilled-water ceiling installation that avoids any sensation of draughts.