This Holcim Awards winner shows how to turn design processes upside-down in favour of circular construction. Architects baubüro in situ and partners salvaged most of the components in this high-quality building conversion from demolition sites.

Winterthur was once one of Switzerland’s bustling industrial hubs. The city’s factories were converted into cinemas, high-end loft apartments and offices after the manufacturing sector declined. This building conversion constructed in a storage yard that was abandoned since the 1980s is next to the main train station.

Investor-driven sustainability

The Abendrot Foundation pension fund acquired the site in 2009. Its sustainability-driven investments favour real estate that is built and managed with as few pollutants and least environmental impact possible. With the aim to preserve all buildings on the site, Swiss architectural firm baubüro in situ and their partners have adapted the old building fabric rather than demolish and start again.

Starting with salvaged materials

Building K.118 was one of the last sub-projects on the site. The project team established the ambitious vision to use only materials salvaged from demolished buildings in the conversion and extension. This reverses conventional planning. Instead of creating a design and then specifying materials to build it, they created a materials catalogue and then the design takes form as it makes use of the available building components.

The architects had to evaluate the condition of materials, their sustainability and embodied energy – and unlike new products, data was not readily available. The Abendrot Foundation fully supported the architects’ vision, but also required the recycled building not to exceed the cost of a new building.

Reducing carbon emissions

Designing a building from recycled components needs a great deal of labour, which is very costly in Switzerland. But, with full commitment to the process, the team achieved a 60% carbon emission reduction (around 500 tons) – and all within budget, and on schedule.

Read the full interview:

“Next again and again” in Sixth Holcim Awards