Company Headquarters Tower in Essen
The requirements of the brief for an energy-saving design are reflected in the form and construction of this tower block. In terms of the ratio between the area of the outer skin and the volume, as well as aspects such as wind pressure, heat losses, structural costs and daylighting, the cylindrical shape represents an optimal form. Despite the continuous glazed skin, the different uses – entrance hall, office storeys, service floors and roof garden – remain legible. Vertical access is via a separate linked lift tower, which also facilitates orientation on the individual floors. The working storeys are laid out with a core zone for group and communicational uses (sometimes with linking staircases between levels), a circular access corridor and an outer zone of offices. The form of the floor slabs, which taper towards their outer edges, maximizes the penetration of daylight. Clerestory windows also allow light to enter the core zone. The windows in the inner skin of the two-layer glazed façade can be opened, permitting all workplaces to be naturally ventilated. The façade is also extended up at the top of the tower to protect the roof garden against strong winds. The building is designed to allow users to control their own environment. When weather conditions prevent the opening of the windows, ventilation is provided by an air-conditioning plant with a minimum air-change capacity. The concrete floors are clad with perforated metal sheets to enable their mass to be exploited for thermal storage.