Colour moves: Slowly, a major hospital in Furstenfeld, Austria is being transformed with additions that are both lively and very responsive to patient demand.

The regional hospital of Furstenfeld belongs to the ambitious wave of care provision of the beginning of the twentieth century which included the Graz Regional Hospital and, like that larger example, it was fulfilled architecturally with a symmetrical-fronted Wagnerschule pavilion. As often happens with hospitals, it was extended piecemeal over the years without much thought of the larger picture, and even the central entrance hall got an insensitive 1950s conversion. The whole thing had become untidy and inefficient, so the intention of the 1998 competition was to devise a plan in three stages to extend and rebuild, recovering the dignity of the listed historic parts while reconverting interiors and providing a series of extensions. Illmaier won with a scheme that attempts to complement the old building with new parts in a distinctive new vocabulary that nonetheless echoes something of the scale and rhythm of the original 1910 building. Since the hospital had to continue in operation during rebuilding, the p hasing of the building process was taxing.

Illmaier decided to retain the two-storey Classical frontage of the existing building, restoring it faithfully and reconstructing the entrance hall. He built new behind. As in Giselbrecht's hospital, he decided to use the old rooms as wards and offices, building an entirely new highly-serviced block for the clinics and operating theatres. In the final plan, this block is linked back to the main building by two passages, left for patients and right for doctors. Between them will be a small open court, outdoor extension to the cafeteria which will sit at the heart of the reorganized complex. There will also be a small circular chapel, centrally positioned. Ambulances will arrive at the emergency unit at the back: operating theatres will be on two levels to the right, while clinics for day patients will be to the left. The whole building will be raised half a storey above the ground to comply with existing levels.

But all this is yet to come: so far only a couple of new pieces have been built, the most substantial being the new wing of patient rooms to the rear and the left. Planning is relatively straightforward, but the architectural vocabulary is unexpected. The multicoloured glass facade was inspired by a painting by Paul Klee, and the two sides are more different than they seem to be at first glance. The east is largely opaque, with a few windows added to illuminate passage and staircase.

On the west side are patient rooms on two levels, and the facade is much more complex. Not only do windows open: there are also vertically sliding panels of grey translucent glass to cut down light. These are driven by electric motors and controllable by the patients. So, many different options between open and closed are possible, and the facades are lively and mobile. Projecting horizontal sunscreens for both room levels extend the layering. On the front corner of the building, Illmaier has added a different kind of glass structure for the common rooms: translucent above and below and a slot of transparency for the view. Illmaier likes to articulate elements like the lift and side stair in a clear and simple way, and these set the pattern for the vocabulary of the later additions. The lift shows its white steel frame within the bolted-on glass cladding, and the side stair has a tubular steel structure supporting it at a single point. Also admirably delicate is the canopy slung over the stair on stainless-s teel rods.

This is not the first 'old and new' project undertaken by Illmaier: he made a bold and uncompromising reinterpretation of a school building of similar period a few years ago, and made it clear there too that there would be no aping of the old building's style. His use of lightweight structures and glass is a reminder of how much building technology has changed during the past century, and while it is worth preserving the old building historically and ecologically, it makes little sense to limit the new one for the sake of consistency. When the whole complex is complete, it will have been reinterpreted functionally and made much more efficient but it will have two visible layers set in contrast.

I spent a delightful day last Easter with the architect, an engaging fellow and one of the rising stars of the Graz scene. Three months later I received the news that he had gone on holiday in Greece, saw somebody in difficulty swimming off a treacherous part of the coast, and in his generous and impetuous way had rushed in to save them. Within minutes he had also disappeared and was drowned. His sister, an architect too, has taken over the practice.