What does the future hold for the 21st century city? That was the question which the Hamburg IBA (International Building Exhibition) set out to answer, and it offers some innovative and sustainable exhibits relating to current discussions on urban development. Using over 60 projects as examples, the IBA shows how an ecologically and socially balanced 21st century metropolis can arise. This sets the pattern for sustainable inner city development orientated towards the future.
It is striking how ubiquitous the presence of hot dip galvanized steel is in the numerous IBA structures. It is being discovered, more and more frequently, by architects who see it as a sustainable and timeless, authentic material. Hot dip galvanized steel has been utilised to particular effect in the Energy bunker and Soft House projects.
Energy bunker, Hamburg
The former flak tower has become the sustainability symbol of the Hamburg IBA. The monument, which had scarcely been used since the end of the war, has been renovated and extended to become a renewable energy power station with large-scale heat storage. The bunker gave many people protection in the Second World War but, with its flak towers, also formed part of the German war machine. In 1947, the interior of the building was completely gutted by the British Army. Only the external skeleton, with walls and floors several metres thick, remained almost completely untouched.
The transformation from a wartime bunker into a symbol of a renewable energy supply for Hamburg is the solar envelope, a galvanized steel structure which is visible above the roof and the south facade. The conversion work, with overall planning by Hegger Hegger Schleiff HHS Planer + Architekten AG, Kassel, intelligently combines power generation from the use of solar power, biogas, wood chips and waste heat. The thermal capacity of the collectors is about 750 kW and the output from the photo-voltaic system on the south side is approximately 100 kW at its peak. At the heart of the project is a large heat storage unit. With a capacity of 2 million litres, the large-scale buffer storage unit is the central innovation. It is powered by the heat from a biomethane-fired combined heating and power plant (Blockheizkraftwerk =BHKW), a wood-fired installation, and the solar thermal plant, together with the waste heat from an adjacent industrial plant. The buffer action of the storage unit leads to a big reduction in the generating capacity to be installed, from 11 to 6.5 megawatts, and makes possible the economic utilisation of renewable energy within the heating provision concept.
Looking ahead, the energy bunker is intended to supply a large part of Hamburg’s Reiherstieg area with heat and facilitate renewable energy into the power network. The energy bunker is intended to supply about 22,500 megawatt hours of heat and almost 3,000 megawatt hours of power. That corresponds to the heat requirements of approximately 3,000 households and the energy requirements of approximately 1,000 households. This will bring about a CO² reduction of 95% – ie, approximately 6,600 tonnes of CO² per year. As a local power station, the energy bunker is also an example of a decentralized energy policy. Not only is galvanized steel used to support the external solar power structure, but it has also been utilised for the power station and energy supply apparatus used in the bunker, and for stair elements and handrails. The bunker’s history is documented in an exhibition within the building which is open to the general public. To complete the visitor experience, the “vju” bunker cafe and terrace, located at a height of 30 metres gives a unique view of Hamburg and across to the Port of Hamburg.
Kennedy & Violich Architecture‘s Soft House is one of the so-called Smart Material Houses at the IBA. Thanks to its dynamic textile facade, it uses sunlight in a flexible way and is an example of sustainable construction. Each of the four, three-storey dwellings has its own garden. A suspended, galvanized steel structure is a central design element of the Soft House. It anchors and shapes the textile membrane façade on the south side of the house. Incorporated in the textile membrane facade are photo-voltaic cells which react to sunlight, just as a sunflower turns towards the sun. The membranes tilt towards the solar rays, optimising the sunlight for energy production. The rippling, sail-like facade elements also provide shade in the summer, while during the winter, they minimise energy loss and allow light to penetrate more deeply into the rooms. Flexibility of the system also allows the residents to choose their view. Movable and translucent curtain walls are used internally, making it possible for the residents to structure the generously-sized inner rooms and to vary the layout at any time, aiding regulation of heat and light. The power generated externally through the membrane facade is fed directly to the curtains, so that they provide an additional option for lighting for the inner rooms through built-in LEDs.
Image: Martin Kunze and Bernadette Grimmenstein