Rainforest House, Hanover
The drops of condensation which obscure the low-lying, tilted dome of the Rainforest House provide just a hint at the ecosystem within. Designed as an extension to Hanover’s Expo 2000 celebrations, the centre, which extends 10 m into the ground, is home to an array of flora and fauna.
The key constraints to consider when designing the roof were those of height and plan. This was an iterative process to ensure the most structurally efficient end product, and although it changed throughout the project, we were careful to keep the height to a minimum to satisfy planners, and the triangular ovoid plan consistent to guarantee a good fit with the concrete substructure below, with all supports pinned to the concrete to avoid the transfer of high moments. The thermal mass potential of the exposed concrete combines with the steady temperatures in the surrounding earth to stabilise internal conditions.
We designed the transparent roof from ETFE panels to ensure excellent visibility and confirmed the light quality using sensors. The choice of ETFE over glass served to minimise maintenance, since microscopically this plastic is smooth and particles cannot be caught on its surface.
At only 4 % the mass of glass panels, restraint of the roof was key to the success of the design. Early sketches included a cable support system, but using Multiframe 3D software, the structure was carefully analysed and this was removed in favour of a supporting arch arrangement to tether the plastic pillows. Three inclined arches are propped against a central node, stiffened with ribs, and spacing between the members was reduced to limit spans.
The internal concept design was similar to that of the Guggenheim Museum, where visitors enter at the base of the building, and walk up a double-helix footpath to the top of the structure. A concrete chimney rises through the middle of the structure, housing a giant services duct.
A tropical forest under a long-span ETFE roof for the Expo 2000
Ray Hole Architects, Bertram Bünemann Partner
£ 12 million