Europe’s largest hemp building takes on climate change
A newly opened apartment building in Switzerland, completed in 2024, uses hempcrete for its walls and cuts CO₂ construction emissions by 50%.
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At first glance, the four-storey block near the Swiss–Austrian border looks like any other new development. But behind its facade stands Europe’s largest building made from hemp, a pioneering project in sustainable construction.
An alternative to carbon-intensive concrete
The project, called Openly Valley Widnau, is remarkable because it manages to do almost entirely without carbon-heavy concrete. Inside, the walls and intermediate floors are built from clay plastered with lime. The exterior walls are made of a timber frame structure filled with hemp and lime, also known as hempcrete, and enclosed with hemp bricks. This hempcrete was developed by the Swiss construction company Openly.
50% CO₂ savings in construction
Building with hempcrete costs about 20% more than conventional concrete. However, the environmental benefits are significant. Hempcrete acts as a carbon sink, absorbing CO₂ from the atmosphere and storing it. Thanks to this property, the greenhouse gases emitted during construction were effectively offset and the project became virtually CO₂-neutral. According to Openly, around 900 tonnes of CO₂ were saved compared with a conventional build. That represents a 50% reduction and marks a major milestone, especially considering that roughly one third of Switzerland’s total climate emissions come from the building sector.
Inspiration for other property developers
The project has drawn considerable attention from across the real estate sector. Openly has set itself the mission of sharing the insights from this pilot scheme with other architects and builders. To support this, the company has launched a knowledge database and an academy, and also hosts monthly guided tours of the building.
More projects are already in the pipeline. According to their website, around 300 additional units are being planned with property developers and construction partners. An almost identical apartment block is also under way right next to Europe’s largest hemp building. While the existing building contains 19 flats, the new development will have 11 with a focus on reducing construction costs even further.