The city of Aachen is pursuing a greening campaign for municipal buildings in order to strengthen the green infrastructure and contribute to climate adaptation through green façades and roofs. A feasibility study is used to identify suitable façades in existing buildings, while sustainable solutions for integrating green façades are developed and promoted in new construction and renovation projects.
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Strategy
Expansion of green infrastructure
Alongside tree planting, green roofs and unsealing, green façades are an important element in the expansion of green infrastructure in the Aachen urban area. For this reason, the building management department has received the political mandate to carry out a greening campaign for green roofs and façades on existing municipal buildings.
Facility management strategy
To achieve this ambitious goal, ideas and strategies have been developed, the content and processing status of which are presented below.
Building management has two main fields of action for establishing green façades:
- in the portfolio,
- for new builds, conversions and extensions (NUE) as well as refurbishment projects. In addition to the conceptual approach, building management is currently taking concrete action with the first initial projects.
Façade greening offers many benefits for the common good, but also brings challenges and development needs that must be taken into account.
Potential effect no. 1: Cooling
In addition to the benefits in terms of Co2 absorption, oxygen production, noise reduction, thermal insulation properties and increased biodiversity, we are targeting one effect in particular: cooling.
The evaporation capacity of the plant parts results in an increase in humidity, which people perceive as cooling. There is also an actual reduction in air temperature as the greenery shades the façade surfaces behind it, preventing them from heating up and reflecting heat back into the urban space.
Advantages of façade greening compared to other types of greening
Façade greening has a "close-to-human" effect during periods of heat, unlike roof greening. Façade greening has the further advantage that it requires less rootable space than, for example, an urban tree and can therefore be more easily integrated into densely built-up urban spaces without restricting the equally important ventilation of the urban space.
While roof surfaces and urban open spaces are often in competition with other uses, façade surfaces are available without competition in an unbelievably large amount of existing space. It therefore makes sense to exploit the potential of façade greening and use it to increase the general biomass in the urban space.
Procedure in existing buildings
Based on the political decision of 15.02.2023, the entire municipal building stock is to be examined for green facades. With the help of a feasibility study designed as part of a master's thesis (Strehl, 2023), the overall potential of the municipal building stock is to be demonstrated.
Simple ground-based forms of greening are taken into consideration, as well as facades with the highest possible impact potential in order to introduce the biomass obtained into the urban space as cheaply, effectively and in large quantities as possible.
The amount of work involved in investigating almost 700 properties with around 2,700 façades is a major challenge. For this reason, the criteria of the feasibility study were designed in such a way that green façades can be efficiently identified with minimal effort.
The financing of the study is currently being clarified and may be covered by state or federal funding programs. As a result, the feasibility study will not only identify and prioritize suitable façades for greening, but will also be used as a basis for the planning of specific façade greening measures.
Procedure for new construction/conversion and extension projects and for renovation projects
In contrast to green roofs, the implementation of green façades is not mandatory for NUE* and renovation projects*. At the same time, our new buildings and extensions in particular are planned and implemented according to high sustainability standards. Some projects currently being planned therefore already include green façades.
Future potential for envelope renovations
Energy-efficient envelope renovations, which will take place in large numbers over the next few years in the course of achieving climate neutrality, also offer particular potential for façade greening. One challenge here will be to use green façade construction methods alongside conventional, already established façade construction methods.
Establishment and type of construction
In order to establish green façades in regular construction activity, feasible and economical types of façade greening must be identified and established. Furthermore, existing hurdles, such as the maintenance debate on building greenery, must be overcome.
Guideline in Spe
The creation of a guideline based on the Bochum model should also help to establish green façades in NUE/refurbishment projects(Bochum guideline). In this guideline, the building management would like to use different quality levels to define in a binding manner in which projects green façades should be taken into account and at what coverage levels and application targets. The guidelines are currently being prepared and coordinated.
Entry projects
In the status report on façade greening from November 2024, you can get an overview of the façade greening projects currently being implemented or planned.
Challenges and areas of development
Maintenance plays an important role in ensuring that green façades are implemented and recognized. Building management and municipal operations are in close contact to establish regular care and maintenance of building greenery to ensure long-term quality assurance.
Interdisciplinary expertise
As façade greening represents a new interdisciplinary area of expertise, it is particularly important to train and develop our own employees. The specially created position "Climate Adaptation Buildings - Green Roofs and Façades" in the Sustainable Building Unit E26/02 provides support in this regard.
Partnerships
The integration of voluntary efforts in the construction and maintenance of green façades is conceivable alongside the efforts of building management. We offer suitable facades to strong partners who want to establish and maintain green facades on municipal facades on their own responsibility. Valid specialist planning, greening strategies, maintenance concepts and the assumption of responsibility for traffic safety during construction and operation are of paramount importance to us.