Modeling of the German residential building stock as a basis for the simulation of the energetic and economic transformation process

Limited economic feasibility due to high investment costs and relatively small energy cost savings is seen as a major reason for low refurbishment rates of the building stock in many countries. Improving economic feasibility can therefore be essential to grow refurbishment rates. Carbon tax or funding grants are possible ways to achieve this. Furthermore, the cost-effectiveness of energy-efficient modernization depends on the necessity for refurbishment. If refurbishment measures are necessary, additional energy-efficient modernization can be carried out at comparatively low cost. Accordingly, modernizations are strongly dependent on the refurbishment cycle of the building. In order to achieve the intended climate targets for the building sector, it is therefore necessary to use refurbishment options for energy-efficient modernization as well. In addition, it must be taken into account that the younger the building is, the lower the potential for energy savings and thus the economic sense due to lower energy cost savings. The most challenging modernizations are all yet to come. As the refurbishment cycle is essential, the question arises as to how high the theoretical refurbishment rate is, how high it is effectively, and how high it must be to achieve the climate targets for the residential building stock. This paper aims to model the basis for the target-oriented transformation of the residential building stock, so that scenarios in line with climate goals for the residential building stock can be simulated depending on the necessary economic incentives. Using current statistics and the past development of the German residential building stock, central parameters like living space, new construction, deconstruction and the modernization rate are modeled endogenously. The modernization rate represents a full modernization and thus allows an easy connection of the model with energetic parameters for building classes defined in the European web database TABULA. The results are of relevance for modelling the building stock and deriving suitable modernization measures also in other countries.