Multicriteria Evaluation of the Technical Capacity of the Green Walls of the Existing Building: Application to the Campus of the University of Palermo

Urban areas are increasingly exposed to climate-related pressures, including rising temperatures, air pollution, and the intensification of urban heat island effects, which undermine environmental quality, public health, and resilience. Nature-Based Solutions (NBS) are recognised as effective strategies to address these challenges, but implementation on existing buildings is often limited by regula- tory uncertainties and the lack of operational tools for early-stage decisions. Green walls offer significant potential in dense contexts where horizontal green space is scarce, yet their feasibility depends on structural, geometric, regulatory, and infras- tructural constraints. This chapter introduces an indicator-based multicriteria frame- work for the preliminary assessment of green wall feasibility on existing buildings. Seventeen technical and contextual indicators—covering constructive and struc- tural characteristics, regulatory conditions, geometric and operational aspects, and enabling infrastructures—are normalised and aggregated into a composite feasibility index, supporting transparent comparison between buildings and the identification of priority candidates for vertical greening. The methodology is applied to the Univer- sity of Palermo campus, characterised by diverse building typologies, façade tech- nologies, orientations, and accessibility conditions. The resulting feasibility profiles highlight that suitability for green walls emerges from the combined behaviour of multiple prerequisites rather than a single dominant factor. The framework does not prescribe specific technologies but provides a flexible technical layer that can be integrated into different decision-making schemes and adapted to other urban contexts, offering a scalable tool to support the integration of green walls as NBS within broader climate adaptation and sustainable campus development strategies.