Karin Hoffmann

Back during my doctorate at TU Berlin, I was tackling the question of how to calculate the effects of green buildings on the urban water/energy balance. To make our cities more climate-friendly in the future, resource-saving measures need to be implemented in a targeted way. When it comes to green building, however, there is a lack of knowledge both regarding the parameters (in terms of plants and substrates) that can be used to optimise the systems for each specific site, and there is also a lack of calculation tools for integrating optimised systems into the plans.

One of the working groups playing an important role in this area at global level is the LaSIE at the University of La Rochelle in France, in particular the “Sustainable Buildings and Cities: Energy and Environmental Quality" working group. Thanks to the KSB Foundation Scholarship and the DAAD-Stiftung, I have been given the opportunity to build on our respective research findings and further develop common approaches during a six-month stay at the University of La Rochelle.

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Fassade greening in La Rochelle

The first goal of my research visit was to define green building systematically based on its plant and substrate parameters. In addition to my own preliminary studies and data from the literature, I was able to access data from the LaSIE, which has been operating an outdoor measuring station in La Rochelle for many years.

Alongside this, I familiarised myself with the VegBat numerical model which describes the transport of heat and water to green buildings and which was developed at LaSIE. For my subsequent sensitivity study, I further developed the model in such a way that the building is now also included directly in the model. This means that analyses can be carried out more efficiently without linking it to a complex building energy model.

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Technoforum La Rochelle

Thanks to the close cooperation with my colleagues at LaSIE, I was able to complete my sensitivity study of plant and substrate parameters in green buildings and the resulting potential for cooling. In addition, we carried out a parameter study in which we were able to compare the cooling effect on the interior and exterior of extensive green roof systems using the model.

At the end of my visit, I presented the results at the international UPWARD (Urban Physics for Wellbeing and Resilience in Dynamic Climates) conference. In addition, we outlined the results in a scientific article that is currently in the peer review process.

At LaSIE, about 70 people are permanently employed in teaching and research on the topics of sustainability and protection of materials under environmental stress, quality of living and habitat environments as well as eco-processes for product quality and energy recovery from bio-resources. About the same number of PhD students are also employed at LaSIE. Both French and international colleagues work at the institute.

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Cornerstone of the university

My way of working at the institute was very much in line with my experiences from other research projects. What was new to me was working in a group where there is not one professor at the head of a group of post-docs and PhD students, but several professors working together in a working group.

In my day-to-day work, there was a weekly meeting with the two colleagues with whom I had initiated the project application. Alongside my own research project, I also received a range of insights into work at the institute, such as participation in a laboratory tour, lectures by PhD students; seminars and a heat action day initiated by my colleagues, to which other key players from planning and city administration were invited.

As well as the weekly meetings, I came into contact with the extended working group every day over lunch or coffee. These were sometimes five, and sometimes ten people working in other areas in the field of "sustainable buildings and cities". Our working and everyday language was French, which was a particular challenge but also enriching for me. Even though I have a good level of French, the use of specialist vocabulary and French in the professional context was new to me. I will definitely keep in touch with some of the contacts I made, especially with my two closest colleagues. We have already discussed options for further cooperation.

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La Rochelle City Hall

In addition to my work at the institute, my research stay allowed me to get to know the city of La Rochelle. La Rochelle has a long and eventful history, as the city dates back to the 10th century. This place is dominated by the Atlantic, it gained its great wealth through maritime trade, was once the capital of the Huguenots and played a key role in the colonial history of France as part of what was known as the Atlantic Triangle Trade. The cityscape is characterised by the old port, the Gothic town hall, which is considered one of the most beautiful and longest-standing in France, numerous cultural offerings and lively economic activity in commercial and leisure shipping.

As the housing market in La Rochelle is rather challenging, I tried to find a small holiday apartment for the first month. After an initial chat, the landlady of a suitable holiday apartment surprisingly offered me a temporary lease for the duration of my stay. I first contacted a local tenant advisory service, which is offered free of charge at the municipal level in France. Once I had had the contract offer checked over by a rental property lawyer from the counselling centre, I agreed.

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The old harbour

Fortunately, my accommodation was very central and I was easily able to reach the university as well as numerous restaurants and the central market on foot, by bike or by electric water taxi. During my stay, I enjoyed many French dishes (especially the wonderful pâtisserie) and local specialities. I was also surprised by the abundance of cultural events in the city. My personal highlights were a street theatre festival with amazing performances as well as the performances by local "fanfares"; brass bands that got bystanders dancing.

I often took trips by bike to the outskirts of La Rochelle. I saw countless bunkers from the Second World War. Some of these are grown over, some have fallen off the washed-out, steep wall onto the beach, and some have been used as viewing plat-forms. These bunker facilities are part of the former "Atlantic Wall" which was built under forced labour by Nazi Germany to ward off possible attacks by the Allies.

La Rochelle itself was occupied by German troops during the Second World War. In today's fishing and commercial port area, a gigantic submarine bunker testifies to the strategic importance of La Rochelle to the former German occupiers. As a result, La Rochelle and the region were one of the last French territories to be liberated.

During my stay there, La Rochelle celebrated the 80th anniversary of the end of the Second World War. Memorial ceremonies were held in the city, which were also attended by the mayor of the twin city of Lübeck. Coming face to face with this part of Franco-German history moved me. At the end of the day, my stay in La Rochelle was really a testimony to the joint efforts for reconciliation and friendship. I am very grateful that the KSB Foundation and the DAAD-Stiftung promote exchanges and international cooperation, which contribute to living together in a caring and peaceful way.

As well as my scientific work, my personal perspectives were greatly enriched by my stay at LaSIE in La Rochelle. I have been encouraged to continue my involvement in Franco-German networking in the future, and I am looking forward to the upcoming opportunities to collaborate with my highly-valued French colleagues on further research projects. I am very grateful to the KSB Foundation and the DAAD-Stiftung for having made this stay in La Rochelle possible.