From vision to action: Boosting building stock decarbonization

• The model optimizes limited budgets in large portfolios of buildings, according to organizations’ strategies priorities. • The model provides a step-by-step renovation passport for large stocks of buildings to meet the requirements of the EPBD. • The model is applied to a portfolio of public buildings. • The model can be easily adapted to other organizations with large portfolios of buildings, regardless of their characteristics and energy markets. The decision to implement retrofitting measures in large portfolios of building stock depends on multiple factors such as the individual building characteristics (including age, existing energy sources and systems), economic considerations, including investment costs and available funds, and the organization’s strategic priorities. This paper develops a novel, low-complexity decision-making model for fund allocation optimization in energy retrofitting across large-scale building portfolios. Using data from readily available energy performance certificates, the model reduces processing time and resource demands and is based not only on the organization’s self-defined priorities, but also on compulsory priorities to ensure compliance with the requirements of the new Energy Performance of Buildings Directive (EPBD). The model was applied to the Universitat Politècnica de Catalunya’s (UPC) portfolio of 50 buildings. It provides a step-by-step retrofitting plan tailored to the priorities set by the university governing board. The results identified photovoltaic panel installation as the most cost-effective strategy for reducing energy bills, which also meets the requirements of the new EPBD. Additionally, phasing out natural gas boilers and replacing them entirely with biomass boilers, with an investment of €2.6 million, would reduce heating energy consumption by 92%. This aligns with EPBD energy efficiency thresholds and facilitates the transition to zero-emission buildings by 2050. The model can be adapted to other (public or private) organizations that manage large portfolios of buildings in any context, with flexibility and scalability.