Leading by example: circular building in the city of Zurich
With the renovation of the Mööslistrasse kindergarten and the new construction of the Juch-Areal recycling centre, the city of Zurich is gaining important experience to ensure that circular construction can be implemented on a broad scale in the future.
The circular economy is an important lever for achieving the political net-zero targets. Like many other cities around the world, Zurich is also committed to the circular economy: in 2022, a strategy for the circular economy was adopted with “Circular Zurich”. in 2023, Zurich became the first Swiss city to sign the “Circular Cities Declaration”.
The intelligent use of resources is particularly important in construction. With the “Charter for Circular Construction”, politicians and businesses set an example in 2023 and made a joint commitment to conserving primary resources and landfill space and reducing CO2 emissions from their own construction activities.
Initial findings from two pilot projects
But how do the political commitments affect specific construction projects? What challenges does circular construction pose? And how are the planning and construction processes changing? The City of Zurich’s Office for Buildings is gaining answers to these questions through two pilot projects.
The city gained initial experience with the procurement, storage and processing of reused building components during the renovation of the Mööslistrasse 2023 kindergarten (Bischof Föhn Architekten, Zurich). Washbasins and toilets were dismantled, cleaned and refurbished on site. Plant troughs from the balconies were reused as outdoor space boundaries. Where possible, the built-in furniture was sourced from the city’s own stock. Thanks to component screening, steel beams, wooden pergolas, fire doors and kitchen elements from other buildings were identified, dismantled and reinstalled. So-called “component hunters” were deployed for everything that was not found in the city’s used parts warehouse.
The second pilot project, the new “Juch-Areal” recycling centre, is much more comprehensive. The Office for Buildings launched an architectural competition with re-use requirements for the project in 2022. The competition participants were able to use a digital catalogue of components or use other available components from non-urban sources for their designs. The buildings also had to be designed in such a way that they could later be used as a component mine themselves (design for disassembly).
The projects submitted show that it is possible: Yes, it is possible. The jury was particularly impressed by the high quality of the competition entries, which were created despite – or perhaps thanks to – the new specifications. The building material of the winning project by Graber Pulver Architekten AG (Zurich) dismantles the hall of the previous recycling centre and rebuilds it at the new location with only minor adjustments. Disposed books, magazines and clothes are used as insulation material. Sheets of recycled glass and aluminium, old kitchen covers, doors and table tops protect the façade from the weather. Discarded scaffolding is turned into storage shelves.
It is in the nature of things that pilot projects precede a standardised introduction on a broad scale. This is also the case with circular construction. The realisation of the two projects in Zurich shows that many questions still need to be clarified: How can components be catalogued? How can availability be checked? Where will they be stored? Who assumes legal liability?
The planning and construction processes will change as a result of cycle-orientated construction, because the component mines must be known as early as possible, preferably at the beginning of the planning phase. Building Information Modelling (BIM) facilitates the reuse of components, the planning of their dismantlability and the development of future component mines.
Significant savings in indirect greenhouse gas emissions in the pilot projects
The pilot projects show that this approach is worthwhile. According to a subsequent calculation, the consistent reuse of building components saved a good 30% of greenhouse gas emissions during the renovation of the Mööslistrasse kindergarten. Current calculations even predict a 40% saving in greenhouse gas emissions for the Juch-Areal recycling centre compared to a conventional new building.