Located between two main arteries of the city, Zeppelinallee and Bockenheimer Landstrasse, and next to its 19th-century botanical garden, the extension to the KfW Group’s headquarters complements an existing ensemble of administrative buildings. Conceived as a prototypical ecological building, at the time of its opening it ranked amongst the world’s greenest office structures. Despite rising over 50 meters, the new volume acknowledges the presence of the existing towers without blocking their views or aspect from the street. Its sculpted body and polychromatic treatment help it to mediate between two distinct urban realms: its height marks the eaves of the neighboring structure; the flowing form of the four-storeyed plinth defines the edge of the street; on the ground floor a concave recess marks the entrance; and while appearing as a lively volume from the street, it presents a discreet backdrop as seen from the botanical garden. The wind-pressurized double-skin facade, along with its streamlined form, guarantees natural ventilation combined with high insulation and solar screening. Radiant floor slabs and geothermal heating are among the other measures that contribute to the building’s low energy consumption...   [+]