Example Kö-Bogen II (Düsseldorf): Sustainable urban development in times of climate change

Have you ever been in a city center in the high temperatures of the last few weeks? On these sultry and hot summer days, it often felt extremely uncomfortable in our sealed city centers. The new Green Center in the state capital Düsseldorf has been showing us since 2020 that things can be done differently. For long-time Düsseldorf residents, this is probably old hat. For many who have not yet seen Europe’s largest green facade “Am Köbogen 2”, it is an architectural glimpse into the future and a new inner-city experience.

The numbers alone are more than impressive. Around 30,000 young hornbeams line the sloping walls and the roof to form a hedge measuring 8 kilometers in total, which has a noticeable effect on the microclimate in the city. The planting is the size of 4 football fields. It ensures that the 24,000 m2 of retail space and 5,500 m2 of office space are protected from the heat of our summers. The hedges have the ecological value of 80 fully grown trees and provide clean air and cooling. They guarantee that the facade does not heat up to temperatures of up to 70 degrees Celsius on days of intense sunlight, as is the case with the neighboring glass and concrete buildings. The plants therefore act as a huge heat buffer and largely make energy-intensive cooling systems, which in turn generate heat, superfluous.
The selected native hornbeams are suitable because they are robust and resilient. Each beech leaf removes carbon dioxide from the environment, produces oxygen, binds fine dust and releases the water absorbed through the roots into the environment. This creates a cooling effect in the area.
The whole thing has its price, of course. The building complex, which was financed by an investor project, cost 600 million euros. It was planned by ‘ingenhoven architects’. The ArGe-Carpinus Kö-Bogen II consortium, with the specialist companies Leonhards/Wuppertal and Benning/Havixbeck as a team, was responsible for the realization of the green façade. They also ensure that the hornbeam hedge is supplied with water and nutrients as required all year round by an irrigation system and is cut back 2-3 times a year. The specialist companies relied on expertise from the Beuth University of Applied Sciences in Berlin, which had been developed over several years of research.
Planting a facade shouldn’t be a big problem, one might think. However, maintaining it for decades in a practical and cost-effective way requires a lot of know-how.

What still seems to us today to be a futuristic “urban green miracle” and a “giant energy converter” is in fact contemporary. Because, as we have experienced first hand in recent summers, climate change has long been a reality. The average temperatures this summer are 0.7 degrees above the average of the last few hot summer years. The Köbogen is still a pilot project. In the sealed concrete deserts of our cities, the heat fronts of the heat-radiating facades still dominate over the few green spaces in the inner city that provide shade and cooling. If you want to make inner cities more attractive, the climate aspect must be given greater consideration so that people feel comfortable there – because climate change is today.