UNStudio calculates lowest carbon footprint for Kyklos Building in Luxembourg

Only timber is not the answer. UNStudio calculates the lowest carbon footprint for the new Kyklos building in Luxembourg and the result is hybrid...

> UNStudio designs the world's highest standing, spokeless Ferris Wheel
> UNStudio wins competition for new mixed-use development in Dseldorf

From the architect: UNStudio, with local partner HYP Architects, were recently announced by the Atenor, Arhs group and Agora Luxembourg as the winners in the competition for the design of the Kyklos building in Belval.

Belval is a redevelopment project that has successfully transformed an old industrial site in Luxembourg into an urban centre that now houses a university and technological centre, residential and office spaces, in addition to hotels and retail. The Kyklos building will be the last building to shape the Central Square district.

From the outset, the design team were determined to propose a building with the smallest possible carbon footprint.

Calculating carbon

As we now have the knowledge and capability to design operational net zero buildings, in order to align our practice with the Paris agreement and European taxonomy, UNStudio is currently focusing on the development of better design for low embedded carbon buildings.

While in recent years the focus when designing new builds has been firmly placed on operational carbon emissions, in fact in the first approximately 40 years, only 10% of a building's carbon footprint is determined by its operational use. 90% is determined by the materials used. So, whilst operational carbon remains an essential concern, for the design of the Kyklos building, great effort was made to consider the entire (whole life) carbon footprint.

Developing the right tools

UNStudio is currently in the process of developing a fully-fledged sustainable design framework that, alongside other applications, enables their designers to have full control of the embodied carbon impact of the designs. As part of this set of tools, the ‘Carbon Builder’ makes it possible for designers to intricately study numerous options to reduce the carbon footprint of their projects.

For the Kyklos building proposal, using the early prototype of the Carbon Builder enabled the team to make the correct decisions early in the concept design process. By assessing the embodied carbon, it was possible to reduce the carbon footprint of the design concept for this building by around 80% compared to a traditional office building in Luxembourg.

Selecting the best materials

The possibility of using steel with 100% recycled content and working with best practice concrete mixtures, improved the carbon performance of the project significantly. Set against the function-use demands, this resulted in the choice of a hybrid steel-concrete structure over other construction methods. It was determined that this hybrid solution offered a better carbon performance in the long run. The early best possible roadmap shows the ultimate possibility of achieving 115kg of CO2 equivalent/m2, compared to 580 kg/m2 for a typical office building in Luxembourg.

The Kyklos building is anticipated to achieve BREEAM Outstanding and WELL Platinum certifications.

Ben van Berkel: “Our new carbon tools have shown us that timber is not always the best option and that highly sustainable buildings do not all have to look the same. We can now demonstrate that interesting geometry and high levels of sustainability are not mutually exclusive.”

Architect: UNStudio
Client: Atenor, Ahrs Group, Agora Luxembourg
Location: Belval, Luxembourg
Building surface: 7,600 m2
GFA: 3,600 m2 below ground
Building site: 1,200 m2
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
Renderings: Play-Time Barcelona