In our article on circular building, we explored the concept of the circular economy as applied to construction. In 2021, the Hall 118 head building in Winterthur transformed this paradigm into reality. Get inspired by the story behind the K. 118!
A minimally invasive approach
Picture the former Sulzer model woodworking shop, located at the heart of a storage yard in Winterthur. Add to that a property developer with a vision: the Stiftung Abendrot, a pension fund with a sustainable investment strategy, was pursuing a distinctively material-conscious approach: repairing rather than replacing, and new floors made using secondary raw materials. Together, baubüro in situ and other partners were to turn this vision into reality on 1266 m2.
From raw materials to a concept – planning in reverse
For many years, the Swiss Architect Barbara Buser had accompanied projects in Tanzania and Sudan. In addition to having been a guest professor at ETH Zurich, she was one of four main participants involved in the K. 118 project. The value of materials varies from country to country and from continent to continent. Discarded VW auto parts are, for example, a sought-after commodity in African countries. Considering and valuing construction materials as raw materials is a fundamental principle of circular building.
Making use of secondary raw materials requires reversing the planning process. First, old materials need to be found and cataloged. Only then can the design and assembly process be kicked off. This requires planners to remain flexible in their vision, as the end product’s potential constantly changes with the continual collection of construction materials. The components are then painstakingly measured and categorized. The final design is then created in a process of continuous deliberation.
© Martin Zeller 
© Martin Zeller
Urban mining
The CHF 2,257 construction project was completed in 2021. It comprises four floors, accommodating twelve studios and think tanks, and a tinkerer’s laboratory with workshops on the ground floor and the mezzanine.
The steel structure used in the extension was sourced from the former distribution center of a supermarket chain in Basel. While the planners had envisioned an extension in the original shape, the steel structure had a diagonal section on the southeast façade. Above the fourth floor, the head building projects beyond the building’s footprint, thereby completing the site-internal alignment that is interrupted in the lower floors by the track of an industrial railway line. Why did the architects opt to use the steel structure in its original form?
It’s much more difficult to adapt a building element than an idea.
Marc Angst
“It’s much more difficult to adapt a building element than an idea,” says Marc Angst, who was involved in this extraordinary project, succinctly summarizing a fundamental principle of circular construction. In the same way, the exterior steel stairway from a Zurich office building wound up determining the height of the six floors. Wherever rigid construction elements such as the supporting structure or reused windows are used in such a project, adaptable elements such as straw, which can be integrated with no material loss, become essential. The steel skeleton is lined with untreated straw bales from conventional grain harvests, which, inside the building, also serve as supports for the clay plaster sourced from a nearby quarry.
The characteristic orange façade was produced using corrugated aluminum panels from a printing company in Oberwinterthur. These needed to be mounted individually as scales in three different profiles. Decoupling, layering, and superimposing elements and functions is another fundamental principle of circular building and the flexibility it requires.
Awards and publications
The K. 118 was awarded the “Prix Acier 2021″ and the “Holcim Award for Sustainable Construction – Global & European Gold Winner.” To make the K. 118 more accessible and accompany the process, the construction office “in situ” documented the project in close collaboration with the ZHaW, resulting in the publication: “Bauteile wiederverwenden – Ein Kompendium zum zirkulären Bauen.”
Expomobila has also already carried out projects using circular construction methods. For example, the Netherlands Pavilion at the EXPO 2020 in Dubai was made up of 90% reusable material. With our ISO 20121 certification, we would like to become more and more sustainable. On the way, projects like these serve as inspiration.
Building in circles – a result worth celebrating
Circular building often involves additional work. Cataloging materials, as mentioned above, requires time and personnel. As do the flexibility needed and the material sourcing. So why bother?
The circular construction approach used for the head building in Winterthur saved 60% of greenhouse gas emissions and around 500 tons of raw materials compared to a conventional new building. Thinking in circles protects the environment and offers the possibility to find new creative approaches. Innovations like the “Madaster” help quickly and efficiently categorize materials and build up networks. Experts and flagship projects like this one let us see new perspectives and revolutionize the construction world.
Circular building offers many opportunities. Let’s take advantage of them!
Temporary and sustainable
We proudly bring high-quality projects to life using sustainable, resource-conscious materials and processes. Like the four national pavilions built for the World Expo in Dubai!
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