Participation of the coLLab team from HFT Stuttgart in the competition Solar Decathlon Europe 20/21


The thematic framework for the research project was provided by the Solar Decathlon Europe 21/22 competition, for which building prototypes were to be developed that address not only energy excellence but also, for the first time, the urban context. Taking into account sustainability, energy efficiency and responsible resource management, the revitalisation and further development of typical existing quarters through renovation, transformation and re-use as well as the development of solar energy supply concepts beyond the system boundaries of individual buildings were important objectives.

Research Question

  • Redensification in urban space through innovative interventions
  • Development of climate-neutral building concepts over the entire life cycle, including existing buildings
  • Recyclable constructions made of renewable building materials, recycled or recyclable materials and existing components/materials (urban mining)
  • Sustainable mobility
  • Development of sustainable financing concepts
  • Intensification of the dialogue between the actors involved in construction
  • Innovative teaching concepts through interdisciplinary project work


The project is divided into different work packages and is on schedule according to the competitive requirements (deliverables):

  1. project management and controlling
  2. concept drafts and design
  3. detailed planning
  4. implementation planning
  5. construction and test phase of the demonstration unit
  6. competition and operation in Wuppertal
  7. subsequent use

SDE 21/22 – Solar Decathlon Europe 21/22

Solar Decathlon Europe 21/22 ...goes urban!

Urban life in the 21st century is at a turning point. As more and more people are moving into cities, climate problems are becoming more pressing and urban problems must be addressed appropriately. The mission of SDE 21/22 called for urban transformations that took into account social, economic and ecological aspects – focusing on the revitalisation of buildings by adding storeys, extensions and filling gaps. Solutions had to go beyond the mere design of architectural drafts, for instance by developing a strategy for urban mobility. The aim was to create a vision for a modern, livable and environmental friendly city of the future. The Energy Endeavour Foundation and the designated SDE 21/22 Host City Wuppertal were working towards a successful Solar Decathlon Europe 21/22, in which the international university teams from 11 countries competeted against each other. HFT Stuttgart was one of the 3 participating universities in Baden-Württemberg.


Renovation and addition of storey
From the three given urban situations, the Stuttgart team chose the addition of one or more extra storeys to an existing building, including the renovation of the entire building. This is a great opportunity for the proposal of new design ideas and the creation of alternative living spaces, thus sustainably increasing urban density. The addition of storeys is often found in residential and office buildings. In urban areas, warehouses and old factory buildings are also being extended more and more frequently.

The location for this urban challenge was shifted from Wuppertal to the team’s home town Stuttgart. Because of the lack of sufficient airflow in the city center due to the local topography, Stuttgart is urgently called upon to react on the impact of global warming. In addition, the lack of housing and the associated high rents are a major problem for Stuttgart residents.

The existing university building “Bau 5” on the downtown campus is both subject to renovation and platform for the addition of storey. By adding another storey to create student housing, the project aims to transform the campus into a lively urban quarter and neighbourhood and provide new and affordable housing within a comprehensive concept.

Architecture for the community

Until now, the use of Building 5 has been limited to research and teaching. The goal is to design a house full of innovation, a place to exchange and, last but not least, a place for social interaction.

At the moment, the use of Building 5 is limited to teaching and research. In the course of the renovation of the existing building, opportunities for a variety of uses are to be seized. In the future, the building will not only be a place for applied science, but also a house full of innovation, a place to exchange and, last but not least, a place for social interaction. The addition of storey will create new incentives: Living and studying on campus. The vision of long-term use is a functioning community and the emergence of an intercultural village on the roofs of Stuttgart. On the top floor, pensioners, refugees, single parents with children, visiting professors, families and people in need are to be offered a home. Through social mixing, we expect valuable social interactions and a growing house community.


Sustainability in the life cycle

In our planning, we placed great emphasis on energy efficiency. This includes not only the energy expended during the use of the building, but also the energy used during construction and deconstruction.

The energy and façade concept supports the sustainability in the life cycle of the design. The façade cladding is made of recycled wood. In addition, organic PV (OPV) collectors are installed on the façade and roof in a way that provides the most benefit for indoor comfort. The high summer sun is blocked, the low winter sun can come through. A ground-based façade greening system is used in the lower part of the façade. A solar chimney is used to support natural ventilation. An air-to-water heat pump is implemented to extract heat from the preheated air of the solar chimney; in addition, the additional floor is passively adiabatically cooled by a water feature. As the existing building is an office building, there are several server rooms. Liquid server cooling can be used here, and the resulting hot water is used for water heating via a heat exchanger.

Implementation on a grand scale

To ensure that the concept is not only future-proof and innovative, but can also survive on the market, a transferable solution was being sought. Parameterisation and design played an important role here.

The special feature of the design is that the extension not only works on the chosen Building 5, but can also be placed on similar existing structures. The building is a typical 50’s office building and can often be found like this in Germany. To ensure that the concept is not only future-proof and innovative, but can also survive on the market, a transferable solution is being sought. To achieve this, the modules must be flexible in their size. A basic architectural construction was developed based on the existing building. The so-called grid. It is a constructive skeleton, which is adaptable in size depending on the existing building and its load bearing structure. The innovation of the design is to develop a flexible and adaptable system that creates high-quality living space in a minimal area and stands in symbiosis with its surroundings.

This is us – Team coLLab


In the field of architecture, a floor plan concept and construction system were developed that can be transferred to buildings with similar existing structures as the existing one under study. Special attention was paid to modularity and resource-saving construction methods. In the area of building technology, in addition to the analysis of the existing building and an associated renovation concept, an energy concept was developed on the basis of extensive simulations, which combines the existing building and the addition of new storeys in a symbiosis. In particular, the system for a curtain-type energy façade developed in cooperation with company partners stands out here. The system consists of steel frames that are mounted in front of the building's façade. A stainless steel cable net is suspended in these modular frames, which serve as a receptacle for organic photovoltaic cells (OPV) of various sizes. In the area of sustainability, care was taken to use renewable and ecological raw materials for the building materials. The extension is therefore built as a wooden post and beam structure and the insulating material used is a product from our project partner, which consists of sawdust. The façade of the HDU is made of waste wood and care is taken to ensure that the structure and construction can be deconstructed in a pure manner by separating materials and dispensing with adhesives. In addition to a classic life cycle assessment (LCA), the Urban Mining Index (UMI) was also determined for the entire building.  

Project publication

Book with all competition entries
The Bergische Universität Wuppertal makes the book available free of charge on its website in German and English.

Book with all German contributions
This book is provided by the Karlsruhe Institute of Technology (KIT) for free download.

ManagementProf. Dr.-Ing. Cremers
FundingFederal Ministry for Economic Affairs and Climate Action
Project E-Mail
ProgrammeEnergieforschung / Energiewende Bauen



Name & Position E-Mail & Telephone
Architekt, Professor, Dekan+49 711 8926 2591 8/2.01
Akademischer Mitarbeiter+49 711 8926 2828 4/3.26
Akademischer Mitarbeiter