Integrating operational and embodied CO2 emissions: a comprehensive life cycle approach to buildings’ system-installations retrofitting with a new indicator

In the context of increasing energy efficiency requirements and climate neutrality goals for the building sector, evaluating comprehensive retrofit strategies for existing public buildings has become a key research and policy priority. This study presents a comprehensive life-cycle assessment (LCA) of energy retrofit strategy for a 40-year-old public kindergarten in Poland. The analysis evaluates twelve cumulative retrofit scenarios encompassing both building envelope enhancements and technical system upgrades. Envelope improvements include stepwise insulation of the entrance canopy, external walls, flat roof, basement walls, and replacement of windows and doors. Technical system interventions span the retrofitting of domestic hot water (DHW) and central heating (CH) systems, replacement of the heat source with an air-source heat pump (ASHP), and integration of rooftop photovoltaic (PV) panels and battery energy storage. Each scenario’s impact on energy demand and CO2 emissions was quantified over a 30-year service life using averaged local climate data. Results demonstrate that envelope retrofits can achieve up to 60% reduction in final energy demand, while technical upgrades, particularly the transition to a high-efficiency ASHP and renewable electricity integration, can yield over 90% total energy savings. A novel indicator was introduced to assess CO2 reduction efficiency per unit of energy saved. While the LCA followed standard methodologies by focusing on product and operational stages, the study acknowledges limitations related to the exclusion of demolition and waste phases, which may underestimate total environmental impacts. Thus, there is a need for future studies in this area.