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UNStudio’s Hybrid Approach for Luxembourg’s Kyklos Building

Pioneering hybrid construction for a greener future.

Courtesy of Play-Time Barcelona

UNStudio, in collaboration with HYP Architects, has been selected by Atenor and the Arhs group as the winning team in the competition to design the groundbreaking Kyklos building in Belval, Luxembourg. This initiative is part of the extensive Belval redevelopment project, which has revitalized a former industrial area into a vibrant urban hub comprising a university, a tech center, residential and office spaces, as well as hospitality and retail facilities.


The Kyklos building is poised to be the final piece in the transformation of the Central Square district, embodying a commitment to minimal environmental impact.

Courtesy of Play-Time Barcelona

The project team embarked on this endeavor with a clear objective: to conceptualize a structure that boasts the least possible carbon footprint. This ambition aligns with the broader goals of achieving operational net-zero buildings, in harmony with the Paris Agreement and European taxonomy guidelines. UNStudio is at the forefront of designing structures with significantly reduced embodied carbon, recognizing that the materials used in construction are pivotal to the building’s overall carbon footprint.

UNStudio is developing a robust sustainable design framework, including the innovative ‘Carbon Builder’ tool, which allows for a detailed analysis of embodied carbon in project designs. This tool played a crucial role in the early stages of the Kyklos building’s design, enabling an approximately 80% reduction in carbon footprint compared to conventional office buildings in Luxembourg. By opting for materials like 100% recycled steel and advanced concrete mixtures, the team achieved a superior carbon performance with a hybrid steel-concrete structure.

Courtesy of Play-Time Barcelona

The Kyklos building is an architectural marvel that seamlessly integrates into the urban fabric of Belval. Named after the Greek word for ‘circle,’ it symbolizes the connection between the site’s industrial past and its future as a dynamic urban space. The design reflects a deep respect for the site’s history and aims to complement the existing urban landscape through its innovative form and strategic location.

Courtesy of Play-Time Barcelona

This building is designed to be a pinnacle of sustainability, targeting at least BREEAM Excellent and Well Gold certifications. It showcases that sustainability and architectural innovation can go hand in hand, challenging the preconception that timber is the only path to sustainable construction. The Kyklos building demonstrates the potential of hybrid construction methods to significantly reduce carbon footprints, paving the way for future sustainable architectural endeavors.

Courtesy of Play-Time Barcelona

UNStudio team: Ben van Berkel, Arjan Dingste with Stella Nikolakaki, Bruno Peris Vila and Cristobal Ignacio Burgos Sanhueza, Laura Lopez Iglesias, Regiane Fernandes de Oliveira, Taliia Nurutdinova, Matthias Kooijman.
Local Architect: HYP Architects
Visualisations: Play-Time Barcelona

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