6th International Holcim Awards for Sustainable Construction

The project describes a building extension in which the added floors are designed to utilize the demolition waste from other construction sites. An industrial building in Winterthur, Switzerland will be repurposed to create a series of 12 units/studios. The design process starts with the collection and classification of building elements sourced from dismantling and demolition operations, and the identification of their potential for recycling. An external steel staircase, aluminium windows, metal corrugated sheets, roof insulation and photovoltaic modules are all salvaged from previous construction and given a second life. Steel beams are reused for the new structure, old façade stone cladding is redeployed as floor tiles.

Wherever it was not possible to reuse old building elements, the architects opted for natural materials including wood for structural components, straw for the wall insulation, and clay for the interior plaster. The recycling operation and adoption of low-impact materials reduces the embedded carbon footprint by about 60% compared to traditional buildings. Constructed so as to be easily disassembled in the future, the proposed design allows for further recycling in the future. To maximize energy autonomy, the project considers the integration of solar systems on the roof to meet operational energy requirements.

The jury highly commended this project for the disruptive construction methodology it proposes to achieve carbon neutral buildings and enable circular economy models in the field of design and construction. Energy savings here are achieved on three levels: demolition is minimized in favor of adding new elements to refurbish an existing fabric; construction material mainly consist of reused components; when new materials are needed, the project opts for low carbon or carbon negative ones. In contexts like Switzerland where demolition is still a rather frequent practice that precedes new construction, this project shows how much potential exists – and is lost – in buildings that are torn down, to the point that dismantled elements are reused as brand-new components for new construction. The ability of the building to be easily assembled and disassembled to allow for future modifications and reuse was also highly commended by the jury and recognized as a quality towards which the building industry should increasingly aim.