Promising approaches were identified via participatory stakeholder workshops, that could contribute to establishing circular construction in Berlin. Such approaches include a stronger orientation of the legal framework towards the circular economy, for example through an obligation to selective deconstruction in the Berlin Building Code. On the other hand, there is a need for even stronger public procurement of circular approaches in the building sector by facilitating the consideration of life-cycle costs in procurement practice. With the combination of these approaches, it seems possible to establish Berlin as a Circular City in the building sector in the long term.

This background paper for the research project "Digitalisation – Setting the Course for a Social-Ecological Digital Transformation in Berlin" within the project "Knowledge. Change. Berlin" provides an overview of the sustainability and digitalisation goals of the state of Berlin. First, the paper outlines sustainability goals relevant for the project in the following topic areas: data governance, climate protection, transport and mobility, energy and health.

The project "Data Governance and Regulation for a Sustainable Berlin" examined what forms of data regulation are possible and necessary at city level in Berlin to ensure that data-driven services, products and platforms are developed and used to meet social and environmental sustainability goals.

This paper describes important findings from the project "Data Governance and Regulation for a Sustainable Berlin" and formulates – in addition to the application field-specific papers – overarching recommendations.

This paper examines the concept of an "extended" digital product passport from a socio-ecological perspective using the example of batteries for electric vehicles. It evaluates different approaches to data regulation and formulates policy recommendations for decision makers in Berlin. It is based on preliminary work from the project, in which in particular three ideal types of data regulation and a methodology for their scenario-based evaluation were developed.

This policy brief examines current proposals for the further expansion of photovoltaics. It shows that the two central goals – accelerating the PV expansion and involving residents – are in tension with each other, at least in the short term. Based on the analysis, the following sequence of measures is proposed: First, as an immediate intervention, PV plants that feed all of their electricity generation into the grid should be made economically viable again.

This study examines current proposals for the further expansion of photovoltaics and analyses the solutions used in Spain, the Netherlands and Austria. It shows that the two central goals – accelerating the PV expansion and involving residents – are in tension with each other, at least in the short term.

The city of Berlin has many plans when it comes to climate protection. One major roadblock is the heating transition: To become climate-neutral by 2045 at the latest, around 360,000 residential and non-residential buildings in the capital must be supplied with environmentally friendly space heating and hot water. Furthermore, all new buildings must be planned and constructed in a way that conserves resources. In addition to the organizational and technical challenges involved in achieving a climate-friendly heat supply, a key question is how this can be achieved in a socially just manner that ensures rental prices remain affordable for low-income groups as well. On 2 November 2021, five leading Berlin institutes in sustainability research contributed to the conference "Knowledge. Change. Berlin. 2021" Solution Approaches for Climate-Neutral Housing and Construction and invite stakeholders from the city to the discussion.

In the Ecornet Berlin research partnership, five Berlin institutes of transdisciplinary sustainability research were jointly providing impetus for Berlin's transformation. Their annual conference, "Knowledge. Change. Berlin. 2021" brought current research findings into dialogue with experiences from other cities and the voices of Berlin's practitioners and civil society – for a social and ecological capital.

The more stringent climate targets of the state of Berlin require that both the heat supply is converted to renewable energies in the next few years and that the building envelopes are ambitiously renovated to make them more energy efficient. This poses great challenges for the state and districts as well as the real estate industry. At the same time, due to the tense situation on the Berlin housing market, there is a need for regulations to protect tenants, which is why the number of milieu protection areas in Berlin's districts has risen sharply. In these areas, which already contain a relevant proportion of old buildings which are in need of refurbishment, there are additional obstacles to climate protection measures that are in line with the objectives.

Berlin has set ambitious standards for the prevention of CO2 emissions, with significantly stricter targets in the new Climate Protection Act (EWG Bln). What are the targets and opportunities, and what are still the major challenges and barriers? In order to become climate-neutral, it is imperative that the building sector be given greater consideration. The Climate Protection Act and the Berlin Energy and Climate Protection Program (BEK) 2030 emphasize the exemplary role of the public sector in this area. This means that public buildings such as school buildings are a key factor. In the districts' renovation roadmaps, schools sometimes account for more than 80 percent of the buildings that need to be renovated for energy efficiency in the next few years.

In Berlin, a variety of initiatives show how the economy can be different: with more solidarity, more democracy, more ecological and better for all. We discuss why this is not easy, but can be promising. In the sixth edition of Wandelwecker, our morning impulse for a social and ecological metropolis, we discussed these questions with two experts.

The digital, or perhaps in this case "intelligent" technologies that are to shape all areas of society in the future, especially our cities, need regulation. After all, these kinds of technologies inform, decide and control — but in whose interest and with which objectives in mind? Recently, there has been increasing thought and debate about the possibilities of democratic data governance "from below". Citizens should (also) be able to decide what intelligent, data-driven machines are used for by consciously sharing their data. Can such approaches be a model for the sustainable digitalization of cities and municipalities and provide a counterweight to the data monopolies of large corporations? What could democratic data governance in Berlin look like?

The Berlin Energy and Climate Protection Program 2030 gives solar energy a central role, as it is the most important renewable energy source that can be developed locally. The state government wants to cover 25 percent of Berlin's electricity supply from solar energy as quickly as possible. In the densely populated city, this also requires the roofs of apartment buildings to be used. In the discussion format Wandelwecker on 8 September 2021, Fabian Zuber from the Reiner Lemoine Foundation and Ecologic Institute's Katharina Umpfenbach discussed options transforming the regulation of tenant electricity and local solar power supply. The event was moderated by Valentin Tappeser from IÖW. It became clear that solar expansion can only be achieved at the required speed with a fundamentally new regulatory approach centered around joint self-supply that intelligently links on-site power generation via solar systems with charging of electric vehicles and heat generation.

On 17 June 2021, representatives from Berlin's public administration, business and civil society discussed how to accelerate the expansion of tenant electricity in Berlin in the virtual expert workshop of the StromNachbarn project. Practical experience inputs enriched the discussion.