Regina Gebauer will not soon forget this day, the first cheers, the many hugs, the way to the stage. In June, her “RoofKit” team from the Karlsruhe Institute of Technology took overall victory in the Solar Decathlon, the university competition for sustainable building in Wuppertal. “It all started for us with a master’s design course in the 2020 summer semester,” she says.
Regina Gebauer is now a research associate at the Sustainable Building Professorship at the Karlsruhe Institute of Technology (KIT). She led the winning team to the final event. On the way there, new members kept joining, others said goodbye. Since 2020, more than 100 students from various faculties of the institute have been working on the project. Around 30 were there at the end in Wuppertal.
In their design, they dealt with adding a storey to a café, the central building blocks: wood and solar energy. The design was so sophisticated that the jury ultimately voted it the overall winner. The team also included students from other areas of the institute, such as economists and civil engineers. The group also received help from outside professionals, including a carpentry and joinery company in the Bregenzerwald. “Their employees first explained each machine to the students, then built parts of the unit together with them,” says Gebauer.
16 university teams from ten countries came to Wuppertal
The Solar Decathlon has been around for a long time. The US Department of Energy first launched the college competition in 2002 to encourage participants to design self-sufficient residential buildings in 2015. Since 2008 there has also been a European version of the Solar Decathlon. In Europe, as in the USA, there is a new call for applications every two years.
Now the competition took place in Germany for the first time. 16 university teams from ten countries came to Wuppertal. For the first time, the task is different. It’s about the energy transition in urban quarters. “In addition to technological and structural innovations, what is needed above all is a social rethink,” says Katharina Simon, Director of Architecture and Urban Innovation for the Solar Decathlon 21/22 at the University of Wuppertal. A consortium led by the university organized the competition, which was funded by the Federal Ministry for Economic Affairs and Energy.
The teams could choose one of three construction tasks that reflect real challenges in the building stock: renovation and expansion of existing buildings, closing vacant lots or the renovation and addition of a storey to a house. Each of these tasks was assigned a specific property in Mirker Quartier, in the middle of the Elberfeld district of Wuppertal, where around 8,600 people live.
The stock is mainly characterized by typical Gründerzeit buildings, mixed with post-war buildings from the 1950s and 1960s. As in many other parts of Germany, the residential buildings are in very different conditions. “In this way, the Mirker Quartier shows the circumstances that make urban transformation difficult and is therefore representative of a large number of urban quarters in Germany and Europe,” says Simon. It offers the perfect basis for developing concrete solutions for the urban planning and socio-economic challenges of the energy transition.
“When the modules were delivered, everything happened very quickly”
Regina Gebauer’s team chose a café that served as a reference object in the competition. “Our design envisages adding a total of three floors to the Gründerzeit building. We are using modular timber construction to make the construction process faster, more efficient and cheaper.” Solar energy should be gained on all possible building surfaces, supplemented by additional solar systems in the backyard, such as a “solar tree”, which can not only generate energy but also provides shade.
In the design of the winning team, a Gründerzeit building is supplemented by three floors. Wood modules should make the construction process faster and cheaper – and solar energy should be gained on roof surfaces.
(Photo: RoofKIT/SDE 21/22)
The two upper floors are intended for living. The team built one of these apartments as a model on the competition site in Wuppertal. “We started late with the construction of the wooden modules, because the scaffolding had to be erected first. Others were surprised that there was almost nothing to see at our place,” Gebauer recalls. “When the modules were then delivered, everything happened very quickly. The timber construction was completed within a few hours.”
The teams did not necessarily have to use one of the objects in Wuppertal as a reference for their designs. The “coLLab” team at the University of Applied Sciences in Stuttgart (HFT) also decided to add another storey, but using the example of a building on their own campus. The members came about as a result of an initiative by students who brought other interested parties and professors on board to apply for the Solar Decathlon. “We opted for a row building from the 1960s,” says Annabell Gronau, team manager and academic staff member at the HFT Stuttgart.
The ulterior motive: There are many of this type of building in Germany and most of them were constructed so stably that they can be increased without structural concerns. “Our design should also work on similar buildings,” says Gronau. That’s why “coLLab” has made sure that the model is adaptable. In addition to flexible floor plans, the team also thought of varying orientations to the sun.
The design is based on a wooden skeleton construction. This three-dimensional grid can be built up in different structures. This makes it possible to place the construction on various existing houses. “In the second step, the residential units themselves are pushed linearly into the wooden lattice,” says Gronau. The grid not only has a supporting function, but also an energetic one. “The spaces in between should be filled according to the climatic conditions of the location and the orientation of the existing building: with collectors for regenerative electricity or heat generation, sun protection, greening or daylight-permeable grilles and openings.” Among other things, the team received first place in the Building Technology & Building Physics category for the design.
“We supported each other and were happy when the others were also successful.”
After the construction phase of two weeks, the teams presented their fully functional one- to two-storey residential buildings. At the disused Mirker train station, where festivals and other major events usually take place, more than 115,000 interested people visited the Solar Campus, the 22,000 square meter competition site, over the twelve event days. “Spending the weeks in Wuppertal together with the other teams was something very special,” says Gronau. “We all had the same goal, were in the same boat, faced the same tasks and challenges.” competitive thinking? On the contrary: “We supported each other and were happy when the others were also successful.” So you have ever borrowed a wheelbarrow and tools or helped with questions.
The modules have now been dismantled again. The Stuttgart model is in the hands of a partner company, but how it will continue is still an open question. The timber construction of the overall winners around Regina Gebauer is now on the campus in Karlsruhe and will be used as a living lab for research at KIT from autumn. In principle, the designs of the teams at the Solar Decathlon were all designed as living labs – i.e. real laboratories.
Means: The constructions are fully functional and can be inhabited. In this way, it can be determined under real conditions whether the interaction of the various elements actually works – in complex everyday life, which cannot be fully calculated in advance when designing. Also from autumn, eight more models can be viewed in Wuppertal as part of the follow-up project “Living Lab NRW”.
The participants also continue after the Solar Decathlon. “We are now looking forward to contacts all over the world,” says Annabell Gronau. A few weeks ago, she says, the team from Taipei came to visit Stuttgart on their trip to Europe.