For a long time, the scientific and political consensus was that the goals of the heating transition in the building sector could only be achieved through a combination of a change in generation and ambitious efficiency measures on the building envelope and systems technology to reduce energy demand. Currently, at least some players seem to question this consensus. They question the relevance and/or economic feasibility of measures to comprehensively reduce energy consumption.

However, there are a number of aspects that the current debate does not take into account at all or only insufficiently, but which can be of decisive importance for the (re)assessment of the significance of efficiency measures in residential buildings for the heating transition. The aim of this report is to make a contribution to the discussion based on scientific findings and thus provide orientation knowledge for the debate.

Against this background, the report examines the significance of efficiency measures with regard to three central questions. The first part examines which macroeconomic and (energy) systemic effects are associated with lower or higher building efficiency in the building stock as a whole and what can be deduced from this in terms of the importance of efficiency for the success of the heating transition. The second part of the report takes a closer look at the role of business-as-usual costs in energy-efficient refurbishment. These costs are of great importance for a correct assessment of the additional costs of energy renovation activities beyond pure maintenance measures, both at the building level and with a view to the most cost-efficient path to climate neutrality in the building sector for society as a whole. The third part focuses on the micro level – i.e. the building level. Here, the scientists examine whether, and under what conditions, efficiency measures can bring benefits for the two important groups of owner-occupiers and tenants, even under the current framework conditions.