Impact of bundling and sequencing of measures in retrofit roadmaps with hybrid heat pump systems – A case study for a municipal non-residential building in Germany

Achieving climate neutrality in the building sector necessitates a well-balanced mix, entailing measures that reduce the space heating demand and measures to decarbonize the heat supply system. In non-residential buildings, the space heating demand can be reduced through both renovation measures targeting the building envelope and heat recovery from the ventilation system. In order to avoid CO 2 emissions, the implementation of the entire set of retrofit measures should be aimed at, but is often not practically feasible due to financial and other constraints. This issue may be addressed with a hybrid heat pump system, wherein the existing, fossil-fueled boiler continues to be operated to cover the residual thermal load until other retrofit measures have reduced the space heating demand to a level that it can only be covered by the heat pump. The proposed approach combines a techno-economic assessment of retrofit measures with a detailed simulation of the hybrid heat pump system across different stages of implemented retrofit measures. The process of bundling and sequencing gives rise to a multitude of combinatorial permutations of possible retrofit roadmaps. To apply the methodology to a real building as a case study, realistic requirements and constraints are transferred into filters to obtain a manageable number of possible roadmaps as a basis for exemplary roadmaps as scenarios. Hence, this approach is suitable for a techno-economic assessment of adequate measure bundles that ensure the transformation to carbon-neutral buildings despite limited resources.