Cladding

Architects that work for prestigious car makers are inclined to think the building has to emulate the powerful and elegant motors it contains. That was certainly the case for two of last year's Stirling prize nominees: Zaha Hadid's BMW plant in Leipzig, Germany, and Norman Foster's McLaren Technology Centre near Woking in Surrey. And soon we have Snell Associates' arresting office and retail centre for Porsche in Qingdao in the Chinese province of Shandong.

Snell's building is a little more modestly sized than its European cousins, but its cladding system is comparable in spirit. Indeed the practice has created a unique cladding system whose ventilation and glazing can be adjusted depending on the climatic and geographical circumstances.

"One of the key generators was to make a building that would perform in the way this particular car performs. Its reputation is all about performance, speed, economy and efficiency, so we felt we had to integrate that into our design," says Robin Snell, the practice's director.

The Porsche building in China

Snell worked on the cladding design with structural engineer Arup and Italian cladding firm Permasteelisa. Taking into account the specific climatic conditions of Qingdao, what they devised was a cladding system that resembles nothing so much as a giant sheet of bubblewrap.

Despite the cladding's dramatic appearance, the principal requirement is the same as any stick system in Slough: to extract the most value for money from the location. This meant making use of the city's unusually clean air, and coping with the region's hot rainy summers and dry, cold winters.

The team came up with a double-skinned cladding including an opaque interlayer to provide permanent solar shading. During the warm part of the year, air is pulled through the facade using the stack effect. This flow, which is aided by the shape of the bubbles, can also be increased by user-controllable fans. In the winter, the air is trapped in the cladding to form Snell describes as a "thermal jacket".

To protect against solar gain, Snell, Arup and Permasteelisa designed a bespoke shading system that fitted between the two skins.

The proportion of clear glass and opaque glass in the cladding depends on the angle and the intensity of the sun. The southern elevation where the sun is at its highest displays less shading to allow solar heat into the building during the winter whereas the eastern and western sides have a higher density of opaque glass to respond to the lateral angle of sunlight.

Snell’s ambition was to create a high-performance building to emulate the fast cars inside

Finally the cladding had to make the most of the views of the Yellow Sea afforded from the building. This is all the more important as the city will host the water sports element of the Olympics in 2008. The 12-storey building was therefore designed with a facade that allows those outside to admire the cars, and those inside to admire the bay.

Although the building was designed to fulfil the specific requirements of Qingdao, the project team is eager to prove that its innovative cladding is transferable to other areas. The next challenge will be to see how it can be adapted to more polluted environments than Shandong.