Paving the way towards circularity in the building sector. Empa’s Sprint Unit as a beacon of swift and circular construction

In order to achieve the CO₂ targets stipulated within the Paris Agreement, future buildings must be constructed in such a way, that their emission profile will be close to zero. In order to achieve this, a radical shift towards a circular construction manner which encompasses topics like material reuse (i.e. design for multiple lifecycles), design-for-disassembly (allowing for maximum recovery of materials and minimization of construction waste) must be promoted against todays, conventional construction practices. Furthermore, the current Covid-19 pandemic has shown that buildings must be constructed in a more flexible manner, in order to be adaptable to changing needs as quickly as possible – including new types of needs. A transition to such a circular construction practice requires also new approaches for Life Cycle Assessment (LCA), taking into account issues such as the circularity or multiple life cycle of materials. Conventional LCA methods fail to deliver trustworthy results as they are designed to assess products and buildings that have only a single life cycle. In this context, a newly constructed unit, set to be the embodiment of the circular construction principle that incorporates all the above-mentioned concepts in the form of a cluster of flexible office spaces, has been integrated into the research building NEST (Next Evolution in Sustainable Building Technologies) – a platform located at the Empa campus in Dübendorf (Switzerland), where novel building technologies can be tested and validated under realistic conditions. Its name: Sprint. In this paper, the environmental performance of Sprint is assessed through LCA, using three different approaches – the EN15804 method, the Product Environmental Footprint method and the Linear Degressive approach – with the latter two approaches considering the circularity of materials, while each one having an own, distinctive allocation rule for the split of the impacts between the current, the previous and the subsequent lifecycles.