The renowned Swiss architectural firm Herzog & de Meuron has completed Hortus Allschwil, a revolutionary sustainable office building that sets new standards for environmentally conscious architecture. Located in the Switzerland Innovation Park in Allschwil near Basel, this 14,100-square-meter facility represents one of the most sustainable office buildings in the German-speaking world, designed to house approximately 600 workplaces for next-generation technology companies.
The building's design centers around a striking green atrium that serves as the heart of the structure. Built on stilts and appearing to float above the landscape, the four-story timber-frame construction features innovative rammed-earth ceilings and opens to the south through a wide passageway leading to a garden designed by renowned landscape architect Piet Oudolf. The atrium space, adorned with tall shrubs, grasses, flowering perennials, and climbing plants along curved gravel paths, functions as both a recreational area for employees and visitors and an environmental showcase.
Hortus, an acronym standing for House of Research, Technology, Utopia, and Sustainability, embodies radical sustainability principles throughout its construction and operation. The project was commissioned by client Senn with the explicit goal of creating an office building made entirely from renewable and recyclable materials. The design process began with comprehensive scientific analysis of construction materials, evaluating them based on environmental and physical characteristics while prioritizing naturally sourced, renewable options.
The building's most innovative feature is its hybrid floor system, developed in collaboration with ZPF Engineers. Each floor element consists of prefabricated wooden frames made from timber harvested from nearby forests, with compressed clay formed into vaults between the wooden beams. This clay-timber system produces ten times fewer carbon emissions than conventional concrete floors while providing superior fire protection and thermal mass properties. The clay is excavated directly from the construction site and manufactured in a field factory adjacent to the building.
Energy efficiency and carbon reduction remain at the forefront of the building's design philosophy. The compact building form minimizes energy loss, while the absence of a concrete basement allows the structure to essentially float over the landscape. This design creates natural temperature regulation, with cooler air underneath in summer and warmer air in winter, complemented by geothermal energy systems. A photovoltaic surface covering approximately 5,000 square meters on the roof and parapets generates surplus renewable solar energy from day one, ensuring that the embodied energy from construction will be fully amortized within 31 years.
The building's interior spaces promote collaboration and flexibility across four upper floors offering approximately 10,000 square meters of office space. Open floor plans encourage employee engagement and interaction, with various seating arrangements available both indoors and on outdoor verandas. Shared amenities include communal lounges, kitchenettes on each floor, a ground-floor restaurant, gym with café bar, and public seating areas. A rainwater collection system beneath the garden provides water for irrigation and sanitary facilities.
Following strict "cradle-to-cradle" principles, all building components have been catalogued for future reuse. The reduced material palette includes wood, compressed clay, and cellulose, with timber joinery employed throughout to avoid metal connections and facilitate easy dismantling at the end of the building's lifespan. The clay from ceiling modules can be returned directly to the ground, exemplifying the project's commitment to circular construction principles.
According to Jacques Herzog of Herzog & de Meuron, "We need to think anew: sustainability should be at the forefront of everything we produce - indeed, everything we do. This will result in unexpected and surprising architecture with a beauty of its own." Senior Partner Stefan Marbach emphasized that "Hortus stands for maximum ecological sustainability - the claim can hardly be extended any further. The architecture follows the Lego principle: all elements are modular."
The project has catalyzed the formation of an internal Herzog & de Meuron Sustainability Team, with Lead Sustainability expert Alexander Franz noting that "Hortus has shown how radical sustainability in architecture is possible in order to create an attractive place focusing on the well-being of people." The building substantially exceeds guidelines for environmentally sustainable buildings, including SIA 2040 standards, positioning it as a model for future sustainable office construction worldwide.
