The buildings with the poorest energy performance – the so-called Worst Performing Buildings (WPB) – play a key role in the decarbonization of the building sector. Due to the high energy requirements, particularly high energy and CO₂ savings can be achieved through energy modernization measures in these buildings and the conversion to renewable heating systems.

For the targeted development of political instruments to implement the heating transition in the WPB segment, it is necessary to know the specifics of this segment. This applies both to the buildings and, in particular, to the building owners and households in the buildings. After all, the heat transition in the WPB sector can only succeed if the required measures for the buildings can also be financed and implemented by the stakeholders concerned.

In this report the authors examine what data is already available on the WPB and where data gaps still exist. By combining socio-technical data, the WPB segment is examined in terms of technical, energy-related and socio-economic factors. The results make it clear:

• which building types and building age classes fall into the WPB segment,
• show the extent to which refurbishment measures protect against classification as WPBs,
• in which regions WPBs are mainly found in Germany,
• what we know from existing data about the owners and occupants.

The findings are used to identify key conflicting objectives in the field of WPBs and, based on this, to derive policy recommendations for action.