Prof. Dr. Stephen Wittkopf, how do you find a flat that is built according to the principles of the circular economy? That would be very difficult at the moment. In Switzerland, there are only a few residential buildings that have been built according to the principles of the circular economy, in Winterthur for example. In industry and office buildings, people are already a bit further ahead.
The idea of reuse is very plausible. Why is it only being implemented hesitantly? Because not everything that is built today is suitable for reuse. In many buildings there are so-called composite materials. This means that different materials such as concrete, wood or steel have been glued together. You can’t just separate them. This creates an enormous amount of construction waste. Of all the material that is imported into Switzerland, i.e. clothes, computers, food and other commodities, by far the largest part is destined for the construction sector. That is, for roads, bridges and buildings. All of this is enormously weight-intensive. The construction sector therefore clearly has the greatest potential for saving material and energy through reuse.
Is the circular economy only about reusing, or also about rebuilding or continuing to build? The concept of the circular economy can indeed be defined so broadly that it includes all reuse. The question of how to preserve and repurpose existing buildings is the first level of the circular economy. The second level is the reuse of building components and the third level is about recycling and reprocessing materials.
How would new buildings have to be designed so that the components can be reused decades later? The materials must be separable and the components repairable. This means that the purest possible materials are central, which are not glued together but provide stability with plugs and screws. Repairability is important for the longevity of the individual components. It must not be the case that you have to throw away an entire window just because the window handle no longer works. And last but not least, meticulous documentation is important so that it can be traced later which materials are where. At the moment, this is not yet sufficiently recorded.
Components are continuously being developed; my grandmother had front windows that could be removed, today there is triple glazing. Is it realistic to reuse them in 50 years? Many products are so good today that a noticeable improvement can only be achieved with much greater effort. And you don’t have to reuse components one to one. In the case of windows, there is a good example from the canton of Zurich: older, double-glazed windows were supplemented with a third glazing; as a result, the improved windows could be reused in a new building.
That sounds as if the reuse of materials completely changes the work for architects. Yes, it requires a radical change. Architects’ work no longer starts on a greenfield site. They have to incorporate existing materials and the availability of products into their concept. But this paradigm shift does not have to become a design or economic obstacle; it can lead to a new language of form.
So the client must also be on board. Exactly, they play at least as important a role. The client can shape the brief differently, and specify, for example, that only second-hand materials are to be sought and that planning is to be based on this. It will certainly be a complex puzzle – but other industries also work with complex and flexible supply chains. The construction industry is lagging behind.
What is the situation in terms of profitability? Can the circular economy in construction be profitable? It can, but not without effort and not overnight. It needs new business models, but also financial support, because it is currently a niche market. However, I am firmly convinced that this will change.
And what might the new business models look like? Maybe one day we will rent recyclable materials – windows, doors, wood or concrete – instead of buying them. Or we design a new building from the outset as a material store for later buildings. This results in a completely new basis for calculation, because the material costs do not have to be amortised in their entirety. The materials could be traded on material exchanges – by the way, this is already done in other countries like Denmark. Maybe even new professions will emerge, such as component hunters.
That sounds exciting. So it changes the whole concept of new buildings? Definitely. If the future of a building is taken into account, it will be built in such a way that it can be converted with as little effort as possible. Society is changing, and with it the needs for living space. A neighbourhood that was once designed for families may no longer fit the needs of the now older generation decades later. If the family flats can be converted into smaller ones with relatively little effort, money, materials and energy can be saved.
In which areas of the construction industry would you describe Switzerland as progressive? Switzerland is already quite advanced in the reuse of concrete. Today, natural stone or gravel is replaced by processed construction waste that would otherwise end up in landfill. In addition to reuse, this has the advantage of saving landfill fees. In large new construction projects, building concepts are also becoming more and more flexible. In general, I observe a growing interest in circular economy among building owners. In Switzerland, the canton of Zurich has a pioneering role. And we, as a university, are of course researching the topic and have the task of sensitising a young generation to the issue by giving high priority to used materials in our training and further education courses.
