Life Cycle Assessment of Green Wall Systems in the Built Environment: A Systematic Review of System Boundaries, Inventories, Methodological Gaps, and Design Implications

Green walls, as part of nature-based solutions, have been implemented in urban environments, enhancing energy efficiency, thermal regulation, biodiversity, environmental quality, and human well-being. Despite these benefits, green walls’ environmental performance across their life cycle is reported inconsistently in the literature, limiting robust comparisons and evidence-based decision-making in the built environment. This review synthesizes current knowledge on the environmental performance of green walls, living wall systems, and active living walls, including systems that improve indoor air quality and enable water reuse. A systematic literature review was conducted following PRISMA guidelines using the databases ScienceDirect, Scopus, and Google Scholar. The results show that methodology gaps in life cycle assessment (LCA) studies of living wall systems restrict their applicability for evidence-based design and specification. Future research should integrate embodied and operational impacts in scenario-based and sensitivity analyses considering plant selection, irrigation strategies, maintenance regimes, replacement rates and service-life assumptions. More focus should be given to tropical cities to understand the impact of climate, water demand, vegetation performance. and maintenance intensity. These improvements would lead to more comparable, context-sensitive, and design-oriented LCA evidence for sustainable building applications.