Roof and Façade
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A building that could be from another universe

Kunsthaus Graz inspires the imagination. Is it a sea creature? Or a being from another galaxy? The architects christened it the “Friendly Alien.” It is a fitting name: With its biomorphic shape and blue PLEXIGLAS® facade, the Kunsthaus looks like an alien among all the historic buildings that surround it.

Legend has it that, 20 years ago in a hotel room, French architect Colin Fournier picked up a piece of soap. Taking a knife, he began to play around with the soap, repeatedly letting it slip through his wet hands. When he had finished, he had shaped a piece of soap into an organic-looking form – and created the first idea for the building that would open as Kunsthaus Graz in 2003. But there was another challenge: What material should be used for construction?

Inspiration for the facade

The answer came from Thilo Üblagger, engineer and Managing Director of k-tec Thermoforming Solutions in Radstadt, near Salzburg: “When I saw the design for the first time, I knew immediately that it was possible – with PLEXIGLAS®,” says Üblagger. “The material is one of the few that can be shaped in such a radical manner. At the same time, it offers a huge number of variations in terms of optical performance, and is extremely durable.” Üblagger convinced the architects and the decision-makers at the City of Graz of his idea. The huge project could begin.

Challenging production

More than 1,200 individual pieces had to be cut and reshaped to create the impressive, 20 millimeter thick, almost 5,000 square meter envelope of PLEXIGLAS® GS – every one of them in a different way. “We could not just write a milling program and use it to make all the PLEXIGLAS® panels the right size. Every piece had to be produced individually,” remembers Üblagger.

A complex process with a crucial problem: “The process has to be controlled in such a way that each piece is not subject to tension,” says Üblagger. “As soon as it has a strain on it, it is in danger of breaking.” The complex planning and development of the challenging process took a year of preparation.

Striking facade

With its biomorphic shape reminiscent of a shining hovercraft and its blue facade fitted with 16 ‘nozzles,’ the futuristically designed Kunsthaus floats like a friendly alien between the red tiled roofs of the city.

© Adobe Stock / Vladislav Gajic

Detailed work

For the facade, the digital model of the building was used as the basis for milling a unique shape for each panel, serving as a model for the spherical curve of each individual panel. Following thermal reshaping, final drilled holes and milling were added for attaching and marking the individual parts.

© Peter Seelmann, Röhm GmbH

Media facade

900 square meters of the PLEXIGLAS® outer skin is also used as a BIX facade. Behind it are 946 standard 40-watt fluorescent tubes, each 40cm in diameter. Using software, they can be turned on and dimmed individually, flashing up to 20 times per second. The BIX facade is used after dark to display artistic projects. Incidentally, BIX is a new word created from the terms BIG and PIXEL.

© Adobe Stock / jochenL.E.

Durable facade for Kunsthaus Graz

All the hard work paid off: PLEXIGLAS® met the architects’ specific requirements, not only making the biomorphic shape possible, but it is also ideal for the local light situation thanks to its material properties: “PLEXIGLAS® guarantees that direct daylight enters the building through the north-facing ‘nozzles,’ while also being UV-stable and very durable,” explains Üblagger.

While other plastics that are exposed to the elements all year round quickly become unsightly, PLEXIGLAS® retains its optical quality.

Just like on the first day

Barbara Steiner, Director of Kunsthaus Graz, is also certain that PLEXIGLAS® was the right choice: “The building would be nothing without its color – which is still radiant.” There are no visible changes after 15 years. The panels simply have to be cleaned occasionally. That is no surprise to Thilo Üblagger, who used the material’s durability as an argument right from the planning stage. “The Kunsthaus looks just like it did on the very first day. There have been no optical or physical changes of any kind.”

Only the name of the extraordinary facade construction at Kunsthaus Graz is subject to constant change. While some people look at it and see an alien, others compare the Kunsthaus with a sea cucumber, a hippopotamus, a hovercraft or a blue whale. The choice of PLEXIGLAS® as the construction material may have been clear, but the range of fitting names seems endless.

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