The architectural office Gautschi Storrer designed the shell for the Masoala Rainforest project at Zurich Zoo, a major project. This large greenhouse imitates the ecosystem of the rainforest of Masoala, a peninsula in northeastern Madagascar, and protects its endangered flora.
Lighting conditions in a greenhouse pose a particular challenge, and the four-ply transparent membrane shell made of ETFE membrane cushions provides the solution. At 94 per cent, the permeability of the ultraviolet radiation spectrum is as high as light transmission, placing it even higher than that of glass or plastic panels. The ETFE membranes offered another advantage in this project: they are very light and very strong. This results in savings both in materials and costs. The double chambers of the air cushions also provide excellent thermal insulation. No expensive cleaning is required and dust and dirt is rinsed off the smooth surfaces when it rains.
The greenhouse is 90 metres wide, 120 metres long and has a surface area of 10,600 m2. Its main supporting frame comprises 10 parallel steel arched girders with a crown height of 23 metres which span the entire width of the hall without any support. The surrounding 14,600 -m2 shell features 54 cushions measuring 4 by 52 metres. One field is formed by two air cushions which run from the eaves to the crown, where they meet. The verge cushions run across the crown from eave to eave and, at over 105 metres, are among the longest in the world. After seven months of preparations, the air-cushion shell was assembled in just 14 weeks, and the entire building completed in six months.
