Sustainability Assessment of Refurbishment vs. New ZEB Construction Systems: A Long-Term LCA Perspective on Durability and Building Lifespan

Two main intervention categories emerge for the renewal of residential building stock: refurbishment and demolition and reconstruction. In the Life Cycle Assessment (LCA) at the building scale, a common practice is to consider default lifespan values, regardless of the durability of the construction system and the average longevity observed within the geographical context. Consequently, this approach involves a significant risk of misinterpretation or partial evaluations of results in long-term assessments deriving from two main factors: (i) the overestimation of environmental impacts associated with heavyweight construction systems, which are characterised by higher embodied energy and carbon, despite their advantages in superior durability and low maintenance compared to lightweight alternatives; (ii) the tendency to overestimate the lifespan of existing buildings after refurbishment, particularly those that have already surpassed 60 years of service life. This paper presents a comparative LCA carried out between refurbishment and demolition and reconstruction of a case study, a 1960s multi-family residential building located in the suburbs of Bologna. In particular, two heavyweight and three lightweight construction systems are evaluated for the new Zero Energy Building (ZEB). The findings highlight a strong dependence between LCA results and building lifespan, significantly influencing the choice when comparing intervention strategies. The results show minor impacts for demolition and reconstruction scenarios compared to refurbishment scenarios after 30 years of analysis and lower impacts of lightweight construction systems in the same period, while in the medium to long term, over 60 years, heavyweight construction systems yield lesser impacts when accounting for their extended lifespan.