Umbauen, Abbauen: Circularity in Swiss construction

Over 10,000 new buildings are constructed every year in Switzerland. However, the construction sector is the leading sector in waste as well as emissions, both nationally and globally. Annually, the sector is responsible for over 80% of all waste and one third of emissions in Switzerland, and 37% of emissions on a global scale. Meanwhile, only 20-30% of elements and materials from torn-down buildings are reused or recycled worldwide, contributing to its massive waste output.

Sustainable construction is on the agenda of several of the United Nations’ Sustainable Development Goals, including SDG 12 which centers on sustainable consumption and production. Like many countries, Switzerland’s progress towards achieving the SDGs is mixed. Particularly challenging is the implementation of a circular economy as the “high demand for materials…exceeds the available volume of recycled materials.” Construction materials are explicitly mentioned in Switzerland’s 2022 report to the United Nations on its SDG progress, where “considerable potential for [construction material] recycling and re-use” is identified.

Though challenges persist, so does progress. According to a 2021 study by the Berner Fachhochschule and ETH Zürich, around 14% of Swiss construction companies implement measures to improve circularity. In June 2023, 12 of the largest public and private building companies in Switzerland signed the Circular Building Charta (CBC). The CBC aims to develop a culture of circularity in the Swiss building sector, by binding its signatories to a commitment to improve the circularity of renovations and new buildings through reducing emissions and use of non-renewable raw materials.

Assessing and fulfilling potential for reuse

One material whose presence in Switzerland cannot be missed is concrete. “Concrete is often pointed to [as a target for reuse] because it is widely used…and accounts for approximately a third of demolition waste,” explains Maléna Bastien-Masse, previously a researcher at the Structural Xploration Lab at EPF Lausanne and now a professor at the Haute école du paysage, d'ingénierie et d'architecture de Genève (HEPIA). In her work, she assesses the reuse potential of structural building elements, with a focus on concrete.

Concrete itself has a large environmental impact. Cement production produces high CO2 emissions - up to 7% of global emissions - which are currently difficult to mitigate because they arise from the chemical reaction involved in cement production. Recycling concrete involves crushing it and using it to replace part of the natural aggregates in new concrete formulations. “Recycled concrete helps a bit by saving natural resources, but unfortunately does not help with the CO2 emissions inherent to cement production,” Bastien-Masse explains.

Reuse on the other hand, consists of deconstructing obsolete concrete structures, extracting large structural elements and making these available for reuse with minimal transformation. This allows to save the embodied CO2 emissions of the elements. Despite its potential, concrete is not frequently reused – underscoring the importance of Bastien-Masse’s work. “Some elements are easier, and more obvious to reuse – windows, doors, tiling and flooring,” she notes. But still not many elements are reused. It hasn’t always been this way. “Reuse used to be normal before industrialization, when materials were expensive and labor was relatively cheap” Bastien-Masse notes. “Reuse stopped being mainstream with industrialization, when machines made the work faster and easier.”

Digital tools to boost reuse

One of the main obstacles in circularity within the construction sector is the sheer logistical challenge of the task – keeping track of materials in buildings, planning demolitions so that reusable materials are saved, storing these until they can be used again, and even identifying reuse opportunities. Thus, reuse often happens locally, due to the relative ease of transporting materials and knowing what is available in the area. Indeed, a 2023 study by researchers at ETH Zürich and EPF Lausanne demonstrated that local reuse efforts have already been underway in Switzerland for over 20 years. Through a workshop held with academic and industry experts, the researchers identified a particular need for digital platforms and tools to facilitate reuse of materials and components, though logistical challenges such as large-scale storage were also noted.

Bastien-Masse was involved in a project to collect building drawings across Switzerland, to “gain better knowledge of buildings and what they are made of,” Bastien-Masse explains. This helps to better evaluate and plan processes like renovations, energy retrofitting, and the reuse of materials and elements. Bastien-Masse and her colleagues collected around 200 drawings, and along with students built parameterized 3D models to digitally map how different materials are built into the structure, and compare buildings with each other. Such mappings allow for an assessment of the reuse potential of different parts of the building. Parallel efforts at ETH Zürich have recently seen the launch of the Innosuisse project ’Swircular’, led by Professor Catherine De Wolf. The project aims to create a digital environment for tracking materials and exchanging information among stakeholders to promote circularity in construction.

“Deconstruction should always be the last resort, when renovation or transformation is not possible anymore” Bastien-Masse asserts. Many factors play into the deconstruction decision, including economic value of elements, logistics, and timing. However, the early assessment of reuse potential is critical, despite its challenges. “Learning what the barriers are and where the levers are is important,” Bastien-Masse notes, so that circularity can rise above its current, slightly “niche” position in the construction sector’s consciousness.

Designing for reuse

Clearly, circularity must be incorporated in the earliest stages of the design process. However, emissions and waste in construction also come from parts of the building process that do not make it to the final product, such as supports and molds for concrete structures. Lotte Scheder-Bieschin, a PhD student with Prof. Philippe Block at ETH Zürich, sees this as a problem worth addressing. “We need to return to key principles that have worked for centuries,” she notes, echoing Bastien-Masse. “We abandoned them during industrialization, when we chose being cheap and fast over saving materials and using smart principles.”

Scheder-Bieschin’s PhD work has focused on a more sustainable way to produce vaulted floors - unexpectedly delicate concrete structures that are considered a more sustainable alternative to flat slabs of reinforced concrete as they use less of the material. To make these curved structures, concrete is usually poured into custom moulds made of plastic foam coated with epoxy resin, which are removed after the concrete has set. These moulds are usually not reused for other projects, ending up as construction waste without ever having been part of a building. “I wanted to find solutions that build on intelligent but simple principles, instead of using more material or using more high-tech fabrication processes,” she explains.

Scheder-Bieschin’s innovative approach, called “Unfold Form”, was inspired by the Japanese art of origami but with curved creases. Thanks to its easy assembly-disassembly process, the formwork can be reused for future projects, reducing a significant amount of waste. “There’s more to a floor than separating two levels,” she says. “Our system reunites principles that sometimes have been separated – geometry, structural engineering, and fabrication, resulting in a new efficiency and aesthetic,” Shredder-Bieschin says. 

Another benefit is the relatively low-tech approach, which she explains is meant to promote adoption on a wide scale. “There is big potential in using new technologies, like digital fabrication, but ETH Zürich is a unique location with means that may not be available elsewhere,” she notes. “My system is independent of high-tech approaches, which increases reach and the potential to have a greater impact throughout the whole world.”

A more circular future for Swiss construction

It is clear that the construction sector, both locally here in Switzerland and globally, cannot proceed ‘business-as-usual’ if we want to be serious about reducing emissions and waste. There are countless ways to approach this multifaceted problem, but fundamentally, it is about using what we already have to make anew.

Scheder-Bieschin identifies the regulations and the change of pace in the industry as key barriers, though shifts are happening. “Change is slower than a snail, but it makes sense,” she says, “as industry can be far from research, with completely different mindsets…and it is complicated to [build in ways that are] not in the [current building] codes.” Education also plays a role – “you need people who are trained to design and build differently” she notes.

Despite industry norms, the pressure to change is growing as research and awareness about the large climate impacts of the construction industry increase. Scheder-Bieschin wishes for “more push from the political side” for adapting regulations and changing the dogma of prioritising low costs over more sustainable approaches. “For me, the first thing is to question every construction and demolition,” Bastien-Masse says – “Could we transform instead of demolish?”. At the end of the day, she notes, “the lowest-emission building is one that is not built, or that has already been built.”

Lead image credit: Sanket Gupta / Unsplash