Kopfbau Halle 118 (K.118)

The architectural and structural concept of K.118 is based on the availability of reclaimed materials procured within a maximum radius of 90 kilometers from the construction site. The steel framework for the extension originated from a distribution center in Basel. Because the framework was kept in its original, rectangular geometry for structural reasons, the new addition cantilevers over the conical existing building from the fourth floor upwards. The building envelope utilizes red corrugated aluminum sheets from a former printing plant, along with large, triple-glazed aluminum windows salvaged from a Zurich office building. To address the geometric gaps between the irregular reclaimed windows and the timber structure, the planners used straw bales as a highly adaptable and material-efficient insulation solution.

The re-use principle was applied with equal consistency and versatility to the interior fit-out. Reclaimed solid spruce panels serve as the flooring. The interior walls feature timber constructions made, in part, from used three-layer boards originally utilized in stage design. Doors and built-in furniture were also given a second life. A striking detail involves the former granite façade panels from the same Basel distribution center, which were precisely repurposed as worktops for the kitchens and sanitary facilities. All building services run exposed across the ceiling, ensuring that future maintenance and adaptations can be carried out without interfering with the building's core structure. The reused elements here include radiators and sanitary ceramics, such as porcelain sinks and toilets, which required only cleaning or minor refurbishing.

Heavy, safety-critical components like foundations and seismic bracing, however, had to be newly cast using recycled concrete. The project's ecological footprint is remarkable: during the manufacturing phase, the circular components saved between 85 and 99 percent of greenhouse gas emissions. For the construction of the extension as a whole, this translates to a total saving of 494 tons of CO2 equivalents (around 59 percent) compared to a conventional new build. In the end, total costs were only 2.5 percent higher than the estimated costs for a building made from new materials. The pure material acquisition costs were minimal (between 0 and 3.4 percent); instead, the budget primarily flowed into the labor-intensive dismantling, manual adaptations, and complex planning.

A technical highlight on the roof is the 18.7 kWp photovoltaic system. Although the modules had already been in operation for about 25 years at a different location, they still deliver 90 percent of their original output, efficiently covering the building's daytime electricity demand.

Text: ZAB | Sources: TU Delft, ZHAW Zurich University of Applied Sciences, baubüro in situ AG, Zirkular GmbH, Stiftung Abendrot