The Gewandhaus in Leipzig is partially replacing the gravel areas on its flat roof with green roofing in order to contribute to a more climate-resilient city. A wide range of measures are necessary to keep the plants in good condition. To test these and gain insights into the management of green roofs, the Gewandhaus is working closely with research institutions. These include researchers from HTWK Leipzig, the Leipzig Research and Transfer Center (FTZ), and the Helmholtz Center for Environmental Research (UFZ) in Leipzig. Glass fibers measure temperatures in and on the substrate and can thus indirectly warn of excessive dryness before the plants die.
Advantages of fiber optic measurements on green roofs
In the spring of this year, the researchers were on the roof of the Gewandhaus when the previous gravel surfaces were replaced by a green roof, and at the same time they laid fiber optics in and on the substrate. Under the direction of Dr. Martin Weisbrich from the “Sensors and Monitoring” research group at the Institute for Concrete Construction at HTWK Leipzig, they laid fiber optic measurement technology in several layers and loops on a test field measuring approximately 150 square meters. The green roof was then planted. "The method allows temperatures in the green roof to be recorded continuously and, above all, location-specifically over long periods of time. It provides information about the moisture and condition of the green roof, which would otherwise only be possible through time-consuming inspections by experts," says the civil engineer, who holds a doctorate. In the future, the information from the measurement system will be accessible at any time so that, for example, in the event of drought, the plants can be watered promptly – not according to the watering can principle, but exactly where the substrate is too dry.
"We can supplement the measurements in the green roof substrate with drone-based images taken with a thermal imaging camera, enabling us to derive important correlations between volume and surface temperatures," explains Weisbrich. This correlation has not been possible until now, and most statements about green roofs have been based on infrared images, which can only show the surface. This knowledge is indispensable for assessing the important function of green roofs and ultimately optimizing them for a wide range of possible applications.
Gewandhaus roof as a research laboratory
"The Gewandhaus is an essential part of cultural life in Leipzig. We also want to contribute to making the city a livable place beyond the realm of culture. That is why, with the support of the Office for Environmental Protection of the City of Leipzig, we have created natural green spaces on our flat roof," says Toni Schlesinger, technical director of the Gewandhaus. The Gewandhaus zu Leipzig will therefore continue to allow the green roof to be used for research work in order to gather knowledge about the creation and maintenance of planted roofs in urban areas.
The project was designed and implemented with the support of the “Leipzig Green Roof Think Tank,” in which stakeholders from horticulture, research, and municipal authorities joined forces several years ago on the initiative of the UFZ and the Office for Environmental Protection of the City of Leipzig. "Green roofs are an important component of sustainable cities that can offer livable conditions even under the conditions of climate change. For this reason, we at the UFZ are conducting research on the functions of green roofs, their resilience to temperature and humidity fluctuations, and the reduction of pollutants through planting," explains Dr. Lucie Moeller, environmental biotechnologist at the UFZ.
The participants already have their sights set on the next joint research project: in the ValiGrün project, led by the UFZ, they will investigate microclimatic effects in particular, using the green roof of the Gewandhaus as a research laboratory. Together with HTWK Leipzig, Dresden University of Technology, and the Leibniz Institute for Tropospheric Research (TROPOS) in Leipzig, the UFZ is investigating how well blue-green infrastructures such as green roofs are suited to climate adaptation and how their functions in urban areas can be improved.
Method from building monitoring
The fiber optic measurement method used on the green roof of the Gewandhaus has previously been applied at HTWK Leipzig and UFZ in two other fields: firstly, to monitor buildings and detect cracks or structural problems; and secondly, to measure temperature under the influence of electromagnetic fields, such as in radio wave heating processes. Financial support from the UFZ's transfun® innovation program enabled a joint UFZ/HTWK working group to test whether the measurement technology is also suitable for use in blue-green infrastructure. This is becoming increasingly important as cities adapt to climate change. The first successful representative measurement tasks, for example on a green building facade in Leipzig and on the experimental green roof segment of the UFZ, prompted the UFZ/HTWK team led by Dr. Ulf Roland to transfer their knowledge to blue-green infrastructure.
Knowledge transfer into practical application
Interdisciplinary cooperation is necessary in order to comprehensively answer questions relating to the effect of water retention, the degradation of pollutants, the selection of the substrate used, and the impact on the building climate. Dr. Ulf Roland sees himself as a bridge between research and application. In doing so, he attaches great importance to making the knowledge gained applicable. The Saxony⁵ transfer network plays an important role in this transfer concept, in which HTWK Leipzig has joined forces with four other Saxon universities of applied sciences to bring scientific findings into practical application. In the “Sustainable Construction” subproject, both Roland and the Institute for Concrete Construction are committed to making the construction sector more sustainable.
Dr.-Ing. Martin Weisbrich
HTWK Leipzig, Institut für Betonbau, Forschungsgruppe „Sensorik und Monitoring“
Tel.: +49 341 3076-8823
E-Mail: martin.weisbrich@htwk-leipzig.de
Dr. rer. nat. habil. Ulf Roland
HTWK Leipzig, FTZ, and UFZ
Tel.: +49 341 3076-3224
E-Mail: ulf.roland@htwk-leipzig.de
ulf.roland@ufz.de
Dr.-Ing. habil. Lucie Moeller
Helmholtz-Zentrum für Umweltforschung (UFZ), Dept. Systemische Umweltbiotechnologie
E-Mail: lucie.moeller@ufz.de
Researchers on the roof of the Gewandhaus concert hall in Leipzig installing the sensors
Source: Dr. Ulf Trommler
Copyright: HTWK Leipzig
The sensors measure the temperature in and on the substrate.
Source: Dennis Messerer
Copyright: HTWK Leipzig
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