• Construction of a "biodiversity retention green roof" on the Lagerhausstrasse administration building was completed in July.
• 1,200 plants, biodiversity elements such as dead wood, rock piles and duckweed can be found on 500 square meters.
• Cooling and shading effects, climate resilience, rain retention

Extreme weather events such as heatwaves and heavy rainfall are becoming increasingly frequent. Areas with dense development and soil sealing in particular contribute to extreme temperatures in the summer months. The city of Aachen is greening more and more municipal buildings in order to strengthen the green-blue infrastructure and contribute to climate adaptation.

1,200 plants in a 500 square meter rooftop biotope

Last spring, a veritable biotope was created on the roof of the administrative building in Lagerhausstraße with funds from the city of Aachen's integrated climate protection concept. The roof garden, known in technical jargon as a "biodiversity retention green roof", is the first full green roof to be implemented on an existing building. An area of 500 square meters is home to 1,200 plants from 40 different species, including climbing plants, perennials, shrubs, trees, grasses and succulents. In the interests of biodiversity, diverse, insect-friendly and predominantly native plants were chosen, whose different flowering periods promise a biodiverse and attractive design all year round.

Pilot project with potential for expansion

"The greening on Lagerhausstrasse is both our pilot project and a learning field," explains Luisa Strehl, Building Management Officer for the expansion of greenery on municipal buildings. "We now want to closely monitor the development and impact of this area and apply it to subsequent measures. We are planning to expand this project, and this area is just the beginning."

And the roof area on Lagerhausstrasse offers plenty of potential for observation. The location was chosen deliberately: The administration building is located in the city center in the immediate vicinity of Aachen's main train station. Rails and a busy main road run parallel to the building. In addition, a large part of the surrounding public traffic areas, as well as the residential blocks and the property itself, are heavily sealed. The immediate surroundings offer hardly any attractive green spaces for recreation.

Planting on the building roof and façade provides cooling and shading effects and reduces the temperature on hot days. The plants bind CO2 and fine dust particles and produce oxygen, which improves air hygiene.

Expansion of green-blue infrastructure towards climate resilience

At the same time, the green roof is designed as an inner-city stepping stone biotope and the city center gains a new development area for insects, birds, amphibians and small mammals: it offers a diverse range of food thanks to an insect-friendly selection of native and exotic plants. Biodiversity elements such as deadwood, stone mounds and duckweed provide additional habitats.

The greenery also retains rainwater, thereby improving the water supply to the plants and relieving the strain on the sewers during heavy rainfall events by delaying the release of water.

To ensure the long-term functionality and ecological quality of the green roof, a targeted maintenance concept was developed, which also pays particular attention to promoting biodiversity. Targeted maintenance measures are used to regulate highly competitive species in order to preserve other plant species. In addition, the establishment and promotion of insects, birds and other animal species is supported by structural measures.

Networking and further development within the association

Since July 1, 2024, the municipal building management has been a member of the "Bundesverband GebäudeGrün e.V." (BuGG). The BuGG is a professional association and interest group for green buildings (roof, façade and interior greening) for companies, cities, universities, organizations and all interested parties.