© acatech

Untapped potential in the existing building stock

The existing building stock offers potential for more affordable housing that has so far been underestimated in this country. Between 2014 and 2023, only around 11 per cent of completed construction projects nationwide involved extensions and conversions to existing housing stock; the majority were therefore new-builds. 1 The fact that the potential of the existing housing stock has not yet been sufficiently utilised is due to economic factors (which apply to both new and existing buildings), such as current financing conditions and steadily rising construction and production costs, as well as to obstacles relating to building and planning regulations.

The options for action compiled in the acatech IMPULS are based on the work of around 40 volunteer working group members from academia, industry and civil society. They highlight how the regulatory framework should be adapted to enable more affordable housing within the existing housing stock in future:

An overview of the topics and options for action:

• Establishing a legally sound municipal right of first refusal:
  clarify the legal basis for its application / enable the right of first refusal in share deals / strengthen local authorities financially (funding schemes, land fund
• Prioritising housing needs under planning law:
  overriding public interest in housing needs in areas with a tight housing market, subject to a time limit
• Inclusion of renovation of existing buildings in the Model Building Code (MBO) and specification in a Model Guideline on Existing Buildings: 
  Reduced need for retrofitting of existing building components when carrying out works on existing buildings through regulations tailored to existing buildings in the MBO and in the Model Guideline on Existing Buildings
• Further development of the framework conditions for simplified construction: 
  to press ahead with amendments to the German Civil Code (BGB) to allow for legally and liability-secure deviations from recognised rules of technology; to enable a practice-oriented distinction between minimum requirements and higher standards; to adapt the Schedule of Fees for Architects’ and Engineers’ Services (HOAI)
• Evidence-based optimisation of construction project management: 
  Initiate the use of data and research as the basis for improved construction project management
• Energy-efficient refurbishment of the existing building stock:
  Promote cost- and energy-efficient refurbishment / carry out refurbishment in stages rather than all at once, and distribute costs fairly
• Further development of funding criteria:
  Future-proof housing support through long-term social commitments, comprehensive land-for-commitment schemes / KfW programmes or tax relief
• Maintaining the VAT rate for construction services
• Developing cross-disciplinary skills for interdisciplinary urban planning: 
  establishing an interdisciplinary qualification framework and teaching and research units

The publication makes it clear that the existing building stock must be given greater legal and political consideration as a distinct area of action. The barriers to conversion, adding storeys, extensions and change of use must be removed so that housing created within the existing building stock can compete on equal terms with new-build housing. Redeveloping existing buildings not only helps to ease the pressure on strained housing markets. The continued use and conversion of existing buildings saves resources, prevents further land sealing, reduces construction waste and preserves architectural heritage. When promoting energy-efficient refurbishments, greater consideration should be given to the ratio of costs to the CO₂ savings achieved. In this way, the existing building stock also offers opportunities for greater sustainability and climate protection.

The publication is available in short and long versions via this link. The authors outline both the obstacles and challenges as well as specific options for action. In the long version, the proposed solutions are supplemented by concrete implementation strategies.

At the same time, the acatech IMPULS “More affordable housing in the existing building stock – options for action for local authorities and municipal organisations” has also been published in both a long and a short version.

¹ Bölting, T./Dylewski, C./Höbel, R.: Wohnungsbau braucht (mehr) Fläche (InWIS Berichte 37), Bochum 2025.