Dynamic life cycle assessment of staged energy retrofits: evaluating time-variant carbon emissions in decarbonising pathways – a use case in Ireland

Buildings account for almost 40% of global greenhouse gas emissions, making the assessment of their full carbon impact critical. Life Cycle Assessment (LCA) provides a means of evaluating both embodied carbon, from materials and processes, and operational carbon arising during a building’s use. However, standard Static LCA (SLCA) methods assume unchanging emissions over time, limiting validity in the context of grid and product decarbonisation. This study presents a Dynamic Life Cycle Assessment (DLCA) framework that incorporates time-varying emissions factors, applied to a case study of staged energy retrofits in a public building in Ireland. Several retrofit scenarios are modelled, with varying timelines and specifications, under both business-as-usual and accelerated grid and product decarbonisation trajectories. The results show that SLCA consistently misrepresents cumulative emissions, particularly where retrofit is delayed, while DLCA highlights the significant climate benefits of earlier intervention. The analysis also finds that the emissions-reducing potential of rooftop photovoltaics diminishes as the grid decarbonises. Compared against prospective industry benchmarks, only early, deep retrofits consistently meet future emissions targets. The findings reinforce the importance of incorporating temporal dynamics into carbon assessments, particularly under the 2024 recast of the Energy Performance of Buildings Directive (EPBD), which supports staged retrofit pathways. This work, by demonstrating a practical DLCA approach and highlighting its implications for policy and planning, makes clear time-variant emissions treatment is essential for evaluating retrofit programmes and achieving long-term climate goals.