The GSW headquarters in Berlin is an assemblage of five building volumes that extend an office tower from the 1950s. A prototype at the time of completion, this project embodies the paradigm of ecological architecture of the 21st century in an exemplary manner.

The building's individual components reflect the characteristic traces of its urban environment's episodic development and make them visible. At street level a gently curved volume redefines the public space and forms a plinth – with its position and height referring to the earlier baroque city. Seen from the east, the slender high-rise slab acts as a backdrop for the existing tower, while emerging with an assertive presence to the west. As a compositional counterpoint, the so called pillbox balances on the eastern end of the plinth, with its height referring to the buildings of the Gründerzeit. This strategy of retrospective integration embeds the previously solitary tower into the urban fabric while acknowledging the historically evolved conglomeration of Berlin as a structural principle.

The slender layout of the new high-rise optimises the use of daylight and ensures cross-ventilation for all offices. Room-high movable screens of perforated metal define the entire west façade and provide effective solar protection. These are fitted in a cavity of the double-façade that functions as a convection shaft allowing natural ventilation on the high-rise floors. An aero-dynamic wind roof enhances this effect. With various shades of pink, orange and red the solar shades make the building recognisable from afar. The individually operable elements respond to daily and seasonal changes, generating new colour compositions again and again. Thus, the west façade illustrates the ecological aspects of the building while, in addition, turning into a perpetually changing kinetic image.

To understand the history of the site on Kochstrasse one needs to be familiar with the history of Berlin. The city has experienced an extreme variety of different urban ideas since approximately 1700. The Baroque city extensions of northern and southern Friedrichstadt were transformed into the dense “stony Berlin” of the late 19th and early 20th centuries. The bombardments of 1945, the postwar reconstruction in East and West, the incision of the Wall and the International Building Exhibition in the 1980s finally led to the heterogeneous urban structure we found at the start of this project. The simultaneous traces of the various stages of development reveal Friedrichstadt as a rich urban landscape that embodies the social, cultural and political history of this city and its inhabitants.

The whole site is treated as a single public field on which a number of “mats” mark out significant places. Towards Markgrafenstrasse there is a grove of plane trees; towards Charlottenstrasse lies a timber terrace. The entrance hall was conceived as a covered street.

The low-rise building is clad with a solid and heavy material analogous to the mass of its horizontal volume. The terracotta tiles with their graphite-coloured glazing were developed especially for this project.