The Japanese architect duo of Kazuyo Sejima and Ruye Nishizawa has won this year's Pritzker Prize, the world's most important award for architecture. The two partners from the SANAA consultancy –the abbreviation stands for 'Sejima and Nishizawa and Associates'–are well-known for their transparent, elegant, puristic and unpretentious buildings, which often appear to be dematerialised and are reduced to the essentials, but nevertheless possess a fascinating diversity and complexity. Or as the jury put it: The buildings by the architectural consultancy SANAA are at once delicate and strong, precise and flowing, ingenious and elaborated, butnotobtrusive.Apartfromthat, according to the jury, the architects have managed to create a completely independent architectural language.

Sejima (born in 1956) and Nishizawa (born in 1966) are relatively young Pritzker winners; in addition, Sejima is only the second woman to have received this honour, following Zaha Hadid in 2004. Notwithstanding that, both have already realised numerous highly regarded, award-winning buildings, at first predominantly in Japan, but since 2001 also in the USA and in Europe. SANAA came to international attention with the Museum for Contemporary Art in Kanazawa, Ishikawa/Japan, which opened in 2004 and accommodates freely accessible, urban offerings in addition to the exhibition area. The architects distributed the functions over several differently sized structures and placed these in a circular, glazed foyer building. The intermediate spaces form the spatially varied connecting network of paths, squares and inner courtyards. The city seems to continue without interruption on the inside.

Since the opening of the museum, SANAA has been able to realise a large number of additional, very different buildings in Europe and the USA as well: the sculptural fair-faced concrete cube of the Zollverein School of Management and Design in Essen/ Germany, the New Museum of Contemporary Art in New York/USA with its offset cubes stacked on top of each other, the glass pavilion of the Toledo Art Museum in Ohio/USA, which is supported by wavy glass walls, or the Rolex Learning Centre in Lausanne/Switzerland, which opened a few months ago and which sprawls in horizontal undulations across the university campus.

In their buildings, Sejima and Nishizawa always try to dissolve the borders not only between rooms, but also between the inside and outside, or at least to blur them. Transparent and translucent façades in the most diverse implementations envelop their buildings. Whether there are the glass facades of the museum in Kanazawa, the Toledo Museum, the Rolex Learning Centre or even the residential complex in Gifu/Japan, they lift the visual barrier between the surroundings and the inside of the building. At least the thorough-fares, also private corridors, are visible and the outside space seems to flow in or through the buildings in places. Glazed inner courtyards additionally strengthen this impression.

Where glass facades are not possible, the architects cover their buildings with uniform translucent shells that blur the outlines. In the case of the shop building for the Christian Dior fashion label in the Nobel shopping street in Tokyo, they achieve this effect by the use of acrylic panels, which are arranged in a second level behind the glass façade; in the case of the O-Museum Iida, in Nagano/Japan by the use of printed window panes, behind which the closed and open areas show up dimly; and they covered the largely closed body of the New Museum of Contemporary Art in New York /USA with a skin of expanded aluminium metal, which makes the building appear immaterial, depending upon weather and lighting conditions.

In addition, SANAA also remove the borders inside their buildings. They create rooms that merge into one another and sometimes sprawl like landscapes, as in the case of the Rolex Learning Centre. The 20,000 square metre single-storey building, which houses not only the university library, but also a restaurant, exhibition areas and offices, is organised alone by its horizontal undulation. The parallel rising and sinking floor and ceiling levels define the different areas as well as the thorough-fares, with no partitioning walls. This project will be presented in detail in the next issues of opus C.

SANAA's buildings have a deceptively simple appearance, although they are the result of an elaborate and intensive work process. On the basis of the room program and an analysis of the environment, new design possibilities are thought through again and again and examined on the basis of innumerable drawings and models. Ideas are developed, discarded, examined again and refined further until the design is reduced to its essential aspects and aclear form. The possibilities of the computer thereby hardly play a role, as Sejima and Nishizawa prefer the clearness of conventional models.

Where necessary, these are also manufactured on a 1:1 scale. For example, the architects had a 200 square metre sample of the curved glass walls of the Toledo Museum manufactured as a model in order to study their aesthetic characteristics. The result of this dedicated work method is reflected in the realised buildings. The glass panes of the Toledo Museum were finally madeof a glass cleansed of all metals, as a result of which a virtually unclouded view through 19 panes is possible, from one end of the building to the other. The visitors between them can be recognised clearly, but they appear in an irritating way to be floating and distant.

SANAA are tinkerers; their buildings are a skilful combination of structure and organisation, of functioning utensils and precise, beautiful design. Sejima and Nishizawa love the grid, but they love just as much the freedom to break through it; likewise they constantly release themselves from conventional functional patterns and find unusual, new floor plan solutions, as in the Museum of Contemporary Art in Kanazawa and the city theatre 'De Kunstlinie' in Almere in the Netherlands, which offer thoroughfares with multifaceted spatial stopover qualities. In Almere, all of the work rooms were given a window with a view to the outside, despite the extensive building volume. The architects achieved this by the skilful distribution of inner courtyards. SANAA did not stagger the museum in New York backwards, as is usual in Manhattan, but instead built a tower from seven cubes that overhang on all sides. The roof areas created by this are used by SANAA to guide daylight into the exhibition areas via skylights. In the case of the residential complex in Gifu, a project by Sejima, allrooms are placed adjacent to each other in order to accommodate the demanded volume in the leanest possible structures. The private corridors are situated visibly behind the glass facade. The private rooms can be opened up to this transitional area via mobile elements. Even if the constructions are not visible in SANAA's buildings, they nevertheless play a crucial role. Without modern techniques and procedures, including those concerning concrete, the light, transparent buildings with their slim, elegant forms, the large spans and thin roof cross-sections would not be possible to realise; likewise the only building realised so far in Germany, the Zollverein School on the site of the former mine in Essen. The single-layer exterior walls of the 35 by 35 metre concrete cube are only 25 centimetres thick. This was made possible by the use of the warm mine water for the thermo-active building system – the water circulates through the walls in heating pipes. And even with this opaque material, SANAA create a certain transparency and avoid a monotonous hole facade. The architects distributed 134 windows in three different sizes randomly over the exterior walls, so that the internal organisation is not readable and the building looks like an abstract sculpture.

SANAA are currently planning numerous further large-scale projects in Europe. A second project in Germany will come into being on Vitra AG's company site in Weil am Rhein; SANAA are planning an extension to the Institute d ́Art Modern in Valencia/Spain, a dependency of the Louvre in Lens/ France, a multifunctional building for the Serralves Foundation in Porto/Portugal and council housing in Paris/France. In addition to that, a factory is being built for Hyundai in Seoul/Korea.

Following her graduation, Kazuyo Sejima initially worked at Toyo Ito & Associates, before leaving in 1987 to become self-employed with her own consultancy, Kazuyo Sejima & Associates. Only five years later she was named 'young architect of the year' in Japan. Ryue Nishizawa, who is ten years younger, initially worked as an employee at her consultancy. When he likewise wanted to turn self-employed in 1995, this led to the establishment of the joint consultancy SANAA. Both partners still operate their own consultancies on the side, in which they predominantly plan houses in Japan.

The Pritzker Prize, which is worth 100,000 US dollars and is donated by the Hyatt Foundation, has been awarded annually since 1979 to a still living architect for his or her life's work. Last year Peter Zumthor from Switzerland received the award for his likewise very clear, reduced buildings which, however, as opposed to SANAA's dematerialised-looking projects, are strongly characterised by their materiality.

Kerstin Mindermann