Lower temperature heating integration in the residential building stock: A review of decision-making parameters for lower-temperature-ready energy renovations

Lower temperature heating (LTH) involves using the lowest possible supply temperatures to meet residential heating demands, thus supporting the integration of sustainable heating sources and decarbonising the existing residential stock. However, choosing appropriate energy renovation options to prepare existing dwellings for LTH presents decision-making challenges due to the heterogenous dwelling stock with varying building characteristics, numerous renovation options, and various performance indicators for evaluating trade-offs. This study aims to review the scientific literature on integrating LTH into existing dwellings to identify the building characteristics for evaluating the potential of using LTH and the necessity for renovations, presents a systematic method for organising renovation options and summarises key performance indicators. The study employed the SALSA (search, appraisal, synthesis and analysis) framework for systematic review and identified 24 scientific publications. Findings show that dwelling characteristics such as compactness ratio, thermal insulation, thermal bridges, airtightness, ventilation systems, space heating system capacity and supply temperature level are essential for investigating LTH potential and the need for renovations. Most research lacks qualitative renovation criteria and product-level information for selecting renovation options. Key performance indicators related to energy efficiency, thermal comfort and quality-of-services can help indicate the possible solutions, while those related to environmental and economic performance indicate the feasibility of possible solutions. Nevertheless, there is a lack of standard set of criteria for indicating the dwelling's readiness for using LTH. These findings can help address the decision-making challenges of selecting appropriate renovation strategies to enable the use of LTH and contribute to decarbonising the built environment.