Benchmarking Embodied Carbon for Retrofits of German Residental Properties

We present a comprehensive benchmark study on embodied carbon emissions associated with (energetic) retrofits during the use phase of multi-family housing in the German residential market, conducted in response to Scope 3 accounting requirements under CSRD/ESRS. The introduction of these reporting obligations has left many companies struggling to meet the new standards, particularly when addressing the Scope 3 emissions within their operations. Despite these requirements, benchmarks to assess the carbon intensity of retrofit actions—whether for investors or construction companies—have been largely absent. This study establishes a benchmark for Scope 3 emissions from retrofits of varying scales. It draws on data from large German housing companies, collectively representing over 1.2 million rental units. The analyzed sample includes approximately 130 datasets of completed maintenance and modernization projects from nine housing companies. The dataset spans a wide range of building types and construction age classes, ensuring the results are representative and applicable to the broader German housing market. Retrofits are categorized into five clusters, ranging from basic maintenance tasks (e.g., refurbishing vacant units) to comprehensive energy-efficiency upgrades (e.g., façade insulation, heating system replacements). Each cluster accounts for the embodied carbon emissions of various products and processes, enabling a detailed assessment of emission contributions and the development of reliable benchmarks. To standardize data collection, a purpose-built recording sheet was developed for documenting measures and materials. Life cycle phases A1 to A3 (“Cradle to Gate”) were analyzed to quantify total upfront carbon emissions, with phases A4 and A5 extrapolated using empirical data from specific measures and products. This research provides actionable insights for housing companies to enhance their Scope 3 carbon accounting. It also supports the development of effective strategies to reduce embodied emissions associated with property modernization projects, offering a critical tool for achieving compliance and driving sustainability in the housing sector.