The Italian influenced Austrian city of Graz contains a vast array of old and modern structures. Its newest, the Kunsthaus, has led to a renaissance of the city and a new lighting master plan by Bartenbach Lichtlabor. Paul James visited Graz to investigate...

With a quarter of million inhabitants, Graz is the second largest city in Austria. The city owes its Italian atmosphere to the many architects who settled here in the sixteenth century from Lombardy. Due to the numerous buildings erected in the Renaissance, the Unesco designated the old city centre as World Cultural Heritage Site in 1999.

Almost 150 years after the Eisernes Haus (The Iron House) caused a sensation in Graz as the first cast iron construction in Central Europe, the floating bubble of the Kunsthaus marked Graz's renaissance in dramatic fashion. Located in the historical city centre on the bank of the Mur and at the corner of Sudtirolerplatz / Lendkai, the museum, conceived by the London architects Peter Cook and Colin Fournier, is a landmark. The biomorphic form, with its bluish cover hovering over the glass-enclosed ground floor like a bubble, acts as an urbanistic and contextual interface between tradition and modernist.

The Graz Kunsthaus is an experimental building, a first step towards an architecture that is playful, fluid and responsive. The insertion of this alien animal in the historical context of Graz creates a new kind of spatial experience in the city, provocative in terms of form, colour and materials, and yet paradoxically respectful of the scale of the urban fabric and well adjusted to activities on the street.

The outer surface of the museum is an 'intelligent skin' displaying text and images as well as changing colour like a chameleon, so that the Kunsthaus could either blend mimetically with its surrounding or take on various guises. This display system was implemented in the form of a programmable matrix of 1000 pixels, using circular fluorescent lighting elements. This solution, BIX, developed by Realities United from Berlin, is deliberately low tech in order to circumvent the issue of technological obsolescence and it is unique in that the display is an integral part of the architecture. There are indeed many examples (Times Square in New York being the archetype) of facades made of large video screens, but the displays are always conventional screens, hung in front of buildings. In this case, the skin itself is the information, so that the whole building can change its external appearance.

Internally, there is an interim solution to the classic controversy between 'black box' and 'goldfish bowl' museums. The Kunsthaus is a hybrid attempting to reconcile these two extremes, offering three distinct lighting conditions: the lower exhibition deck is primarily a black box, although it has a number of window openings (only three as opposed to the nine that were planned, due to budget constraints); the upper deck combines natural light from fifteen north facing 'nozzles' with supplementary artificial light; and the 'needle', a glass box suspended on the upper part of the building envelope, which is totally naturally lit.

Peter Pakesch, the museum director, is convinced, "This building has enormous openness and unconventionality, and this is what generates the tremendous dynamics and suspense."

As for what will be possible in the near future, the ideal solution for the internal lighting of a building of this type would be a continuous luminous surface, with no apparent light fixtures, smoothly varying its intensity to compensate for natural light fluctuations. Zumtobel Staff have already launched an elegant solution using arrays of fluorescent tubes behind opal membranes to achieve large luminous surfaces on the market.

Hannelore Kress-Adams and Gźnter Adams were the Lighting Designers for the interior of the Kunsthaus. Here they describe the lighting distributed from the characteristic 'nozzles' in the roof of the building:

"They were originally conceived as daylight sources. Because of the low incidence of light, they provide only minimal fulfilment of this task, so the staggered concentric circles of light in the conical cavities redefine the daylight concept. The slimline luminaires can be individually dimmed from 1 to 100%, each nozzle can be switched accordingly. Parallel to this, tracks integrated in the ceiling provide for adaptation of spotlights with different light distribution characteristics. The overall concept permits visual variations of the spatial structure, and also a response to secondary, exhibition-specific spatial structures and exhibits through deliberate lighting accents and scenarios.

"The grid-like linear aesthetics from the early days of the opening give the false impression of a rigid pattern, whereas the delicate 36w fluorescent lamps with open light distribution move in every direction of the parallel three-phase tracks and can be fixed on any desired location. Over and above this, spotlights can be added anywhere according to defined requirements. The versatile control and switching options can be freely used for graphic ceiling views from below, or islands of light aligned in wholly individual constellations.

Built and dedicated in 2003 to commemorate the nomination of Graz as the European Cultural Capital, the building of the Kunsthaus marked the initiation of Graz's lighting master plan.

The precise master plan scrupulously defines the technical and design criteria. In cooperation with Bartenbach Lichtlabor, outdoor lighting specialists Hess developed glare-free catenary suspended and wall mount luminaires for this project. Today, they are visible on the museum's facade and in the adjacent streets.

The Graz City Planning Council contracted Bartenbach Lichtlabor of Aldrans, near Innsbruck in Austria, to draw up a master plan for the illumination of public spaces and streets in 1998/99. The declared objective was to reverse years of uncontrolled lighting and light source installation, step by step, through planned urban development projects while establishing permanent, approved guidelines for public lighting. Included among the new criteria were the reduction of maintenance costs and the improvement in the quality of lighting.

In the first stage, Bartenbach Lichtlabor analysed the existing situation. "We found the same deficiencies that can be found in every city today," recalls Christoph Gapp, project manager at Bartenbach Lichtlabor, citing "inadequate adaptation of illuminance and light distribution to meet the specific requirements of individual applications, as well as inconsistent light colours and annoying glare."

In the next stage, the lighting specialists, together with the architects from the city planning council, defined the hierarchy of the streets and spaces based on use and importance. "With this as the basis, we determined the lighting parameters for each task," explains Gapp. For important spaces and pedestrian zones that are highly frequented in the evening and night hours, we consciously chose luminosity levels that are higher than those that are stipulated by DIN standards. "By varying the brightness of the individual illuminated areas, we created a guidance system that would aid pedestrians' orientation," states Gapp. Pursuant to providing the users of the areas with warm, glare-free lighting and thereby a pleasant atmosphere, the master plan specifies secondary reflector lighting technology with light beam image splitting and metal halide lamps.

In contrast to the commonly used direct lighting systems, secondary reflector luminaires with light beam splitting eliminate virtually all glare. The primary reflector and light source are integrated in the pole, out of sight. They cast their light - without any spill light - onto the secondary reflector above. The secondary reflector is comprised of several hundred facets, which "split" the beam images into numerous smaller light beam images. They distribute the light uniformly to the defined horizontal surface. Each facet disperses its light over the entire illuminated surface.

Due to the minimum luminances of the individual light beam images within the illuminated area, glare is reduced to an absolute minimum for pedestrians and drivers. Moreover, displaced or stray emissions outside the defined illuminated area do not occur. The lesser luminance levels of the surroundings (e.g. illuminated faŤades) stand out, through which perception of the urban environment is noticeably improved at night. In addition, the upward output ratio is held to an absolute minimum (ULOR 1.5%!) by means of a special reflector and a precision mask.

Another objective of the master plan was to meet the various lighting needs with as little model diversity as possible in order to keep the maintenance costs at a minimum. Furthermore, the fixtures should have a reserved character thereby harmoniously blending in with both the old and modern architecture.

Hess was one of the first manufacturers to utilise Bartenbach's patented projector reflector system, implementing it in their Faro pole luminaire. Its trim, gracious design along with the optical system fit into the master plan perfectly. However, wall mounted luminaires and catenary suspended luminaires were required for this sub-project. Thanks to the underlying modular principle, Hess was able to realise the model variations with relatively little effort, thereby meeting the aesthetic criteria, which in the area around the museum were very demanding.

At the Sudtirolerplatz, which is reserved for pedestrians and public transportation, catenary suspended luminaires were specified instead of pole mounted luminaires due to limited space and aesthetic considerations. For the illumination of the Hauptbrucke bridge, this type of luminaire was the right choice, as the suspended cables were already in place.

The merits of the Faro family's characteristic light beam image splitting are evident when employed as catenary suspended fixture. Centred over streets, they illuminate both walkways and streets without a trace of glare. "Their appearance is also becoming," confirms Gapp, referring to the Faro UE luminaires. Shaped like a truncated cone, the primary reflector contrasts with the square shape of the secondary reflector. Attached to the secondary reflector by slender bars, it appears mysteriously suspended under an illuminated roof at night. "The minimalist composition of basic geometric forms gives the luminaire a lightness during the day that is equally surprising," elaborates Gapp.

Where the streets become narrower near the museum, Devio wall mount luminaires, mounted to the faces of the buildings and Kunsthaus museum, provide illumination in the evening. Equipped with twin projectors and 2 HIT 150 W lamps, they bathe the street areas in optimum, warm white light. Thanks to the streamlined styling, the luminaires are hardly noticeable.

"The response to the lighting concept has been very positive," says Gapp. Due to the exceptional light furnished by the new fixtures, the streets have become more vibrant. There are distinctly recognisable brighter and darker zones, whereby the vertical dimensions of the street spaces are discernible. The filigree catenary suspended luminaries create additional space and enable the unobstructed view of the splendid facades and river Mur.

www.graz.at
www.kunsthausgraz.at
www.bartenbach.com
www.zumtobelstaff.com
www.hess-form-licht.com