Zeist: Home to the WWF's innovative new Dutch headquarters

The building, dating from 1954, used to house an agricultural laboratory. RAU Architecture elected to shoehorn a 3-storey organically shaped addition into the middle of the existing building. The addition has upgraded the existing building and brought new life to the previously so stern, impersonal structure. The reconstructed building has had its energy consumption optimised and is now carbon-neutral.

The new central section of the building has opend the facade on the existing building allowing light into the core of the structure. The windows of the facade are triple glazed and with wooden louvers allow for adjustable lighting. The summer sun, therefore, only enters the building indirectly, whereas the lower winter sun is allowed straight in. The facade of the building is covered with tiles made from local alluvial clay. In the shape of the facade there are made space for birds' nests. 'Bat basements' are another feature. Solar arrays on the roof provides both electricity and hot water. Rubble removed during renovation has been reused in the new building. 

 
Inside, the ceilings and walls are covered in mud which, in addition to being 100% biodegradable, absorbs moisture 30 times more efficiently than plaster. This provides a warm atmosphere and makes for optimum regulation of the indoor climate. The indoor climate is further optimised by a combination of natural and mechanical ventilation. Used air from the building is extracted mechanically from the building, making room for fresh air from the outside, which finds its way in through ventilation elements in the facade. Beneath the layer of mud on the walls is a system of capillary tubes which circulate cold or hot water respectively through the building depending on whether it needs to be heated or cooled. The large surface area makes for an extremely stable, homogenous interior temperature. The capillary tubes are connected to the building's heating system which cools or heats the building, using thermal heating in winter and cool air in the summer. There is thus no need for either radiators or air conditioning. If thermal and solar energy cannot provide enough heat, there is a backup installation which runs on carbon neutral linseed oil. 

The new structure links the two original wings of the building and houses all the WWF-specific around a central staircase. The walls of glass and great importance is attached to an open environment. The space around the staircase accommodates a reception hall, call centre, shop, meeting rooms, exhibition area and spaces where staff can meet to talk. Environment friendly materials are also used indoors. The carpets are made from recycled material, the walls are of recycled brick and all the wood is FSC certified. Exactly how environment friendly recycled materials actually are is difficult to ascertain in terms of a carbon account on the basis of current knowledge. However, all materials in the building have been selected with the best intentions as far as the environment is concerned at the given time.