Carbon payback time for residential building replacements in Zurich under the stock-level consequential replacement LCA

This study proposes a stock-level method combining Consequential Replacement LCA (CRLCA) and range-bound analysis to assess the carbon payback time (CPBT) of large-scale construction strategies. Extending CRLCA beyond individual cases enhances representativeness and policy relevance. Leveraging stable stock-level population dynamics, the study introduces a per capita metric alongside the conventional per area approach, highlighting the individual dimension of carbon impact. Against the backdrop of Switzerland's inward development policy, the study examines 335 residential building replacement (BR) projects in Zurich (2001-2019), compared with two assumed refurbishment-based alternatives. Results show a CPBT of approximately 16 years per area and 21 years per capita for BR under the most optimistic carbon assumptions. Even in this best-case scenario, BR fails to achieve payback for post-2019 decisions, as decarbonization reduces new buildings' operational advantage. This pattern holds for public buildings, where BR performs even worse. Per capita metrics yield more conservative outcomes than per area metrics under identical conditions, underscoring the importance of metric choice and its role in linking individual accountability to more inclusive, citizen-informed policymaking. Thus, this study supports prioritizing refurbishment over replacement as a climate-conscious urban renewal strategy and stresses that construction strategies are time-sensitive to decarbonization and must be reassessed as conditions evolve.