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Article from issue 3/1999 »Solar Architecture«

Conversion of Reichstag Building into German Bundestag in Berlin

Drafts
Detail of dome glazing 1:5
First floor plan/Third floor plan/Fourth floor plan, West elevation/South elevation, Sections 1:1000
Part section through dome 1:100
Sectional detail through dome structure 1:20
Site plan 1:10000
Vertical section through light cone

The conversion of the old Reichstag building into a modern seat of parliament is one of the main symbols of the Bundestag’s move from Bonn to the capital. The steel dome structure, with a diameter of 38 m at the base and a height of 23.5 m, is a token of the renewal of a building that is otherwise little changed outwardly. From a public viewing platform 16 m above the base of the dome and reached via a double helical ramp, visitors have a view through the glass roof of the debating chamber. Within the dome is a conical steel structure with mirrors. It has a maximum diameter of 15 m and serves to deflect daylight into the chamber beneath. It also acts as a central element for the heating and ventilating system (see technical report, p. 455). A 12-metre-high revolving shading element around the conical structure protects against glare. A central opening surmounted by a wind deflector facilitates the ventilation of the dome space and the assembly hall.
The 24 triangular, tapering ribs to the dome are supported by a circular box girder on the roof and are welded to a ring beam at the top. The ramps are suspended from alternate ribs and are lined with acoustic insulation on the inside. Within the dome structure, they function as an additional ring beam. New welding technology and computer-aided fabrication allowed the load-bearing structure to be manufactured with a quality finish, thus obviating subsequent working or additional cladding.
The entire outer surface of the dome consists of scale-like, lapped elements of 24 mm laminated safety glass in aluminium frames, with additional horizontal glazing. Photovoltaic panels on the roof of the building with a peak capacity of 40 kW provide energy for the ventilating plant and the operation of the sunscreening to the dome.
The consistent, restrained internal detailing affords numerous glimpses into the debating chamber, thereby supporting the concept of openness and transparency and the aim of integrating the public into the legislative functions of a parliament. The two-layer glazing with elliptical aluminium sections and movable sunscreening in the intermediate space allows most rooms to be ventilated naturally.