The implementation of a climate-neutral building stock is a large-scale task for the whole of society. Increased efforts and investments in energy-efficient building renovation and the use of renewable energies are needed. District-level solutions can address these challenges easier, more efficient and at a lower total cost than optimizing buildings individually. In the urban context, solar energy holds the greatest potential for the use of renewable sources. The existing building envelopes can be activated as a local source of energy, in particular by photovoltaics. 

In cities, the use of this potential turns out particularly difficult. The causes include the building ownership structure and the relatively small number of large roof areas for uncomplicated solar use. In the predominantly multi-storey building stock, the “urban skin” consists to a large extent of facades. Their use for energy production requires a high architectural quality and a careful integration into the built environment. At the same time, various energy-related technical options – apart from photovoltaic modules also solar thermal collectors, bioreactors, decentralized ventilation technology, storage elements, shading solutions or thermally activated building systems – and climate-regulating roof and façade greening compete for the limited space and investment resources.

The research group investigates the extent to which building envelopes in urban areas can be energy activated and which synergies may be exploited on the basis of a trade-off between building culture, energy-efficient renovation and greening. An equally important aspect is the integration into sustainable district energy concepts and into the urban energy system. With the help of large-scale simulations and the superimposition of production and consumption profiles as well as energy management strategies at district level, the research group investigates how these districts can support the local and higher-level grid in the challenges of the energy transition. Flexibility measures considered are, in particular, the operation of electric heat pumps adapted to electricity supply and demand and intelligent charging of electric vehicles. Last but not least, the research aims to quantify and avoid negative effects of a large-scale energy activation of building envelopes on the urban microclimate and outdoor comfort. Thus, the research group combines the areas of climate protection and climate adaptation. In conjunction with a lifecycle-based environmental assessment, recommendations for policy incentives and reduction of legal obstacles can be derived.

Finally, the aim is to identify strategies and options for implementing innovative solutions together with cities and municipalities, as urban development must meet diverse interests and needs of social and economic stakeholders. Several case studies in Bavarian cities serve to test how the potential for energy activation of building envelopes can be realised in a socially, grid and urban climate compatible as well as financially affordable way, for example by involving citizens in urban planning decisions and in the investments and profits of the energy transition.