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The green wall is an engineered technology for stormwater management and climate change mitigation at the urban level. At the building scale, these energy efficiency measures are suitable for improving indoor comfort conditions and for reducing energy needs. Several guidelines are available about vertical greening systems, but these propose design parameters and performance evaluation criteria, often incomparable. In order to facilitate the implementation of proper technical standards, this paper proposes a critical review of more recent scientific investigations. All parameters for the design optimization are discussed as well as the achievable social and private benefits by taking into consideration the type of study (numerical or experimental), the climate conditions, the analysis period, all technical requirements of the green layer as well as of the back wall. The review underlines that a multi-criteria design approach is needed for green vertical systems. Thus, the paper is concluded with a SWOT analysis, evidencing “strengths”, “weaknesses”, “opportunities” and “threats”. The analysis shows that the highlighted benefits will acquire greater relevance considering the increase in global temperatures and the growing need to redevelop densely built urban centers, while some negative aspects may be filled in the future with a deeper preparation of designers and careful choice of materials. The review paper shows, therefore, drivers and barriers occurring designing and implementing green walls.

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The present work concerns the energy retrofit of a public educational building at the University of Molise, located in Termoli, South Italy. The study provides a comparison of the results obtained by different dynamic simulations of passive strategies to improve thermal comfort and energy behavior of the building during the summer regime. Firstly, the building model was calibrated against historical consumption data. Then, a subsequent step involves the technical-economic analysis, by means of building performance simulations, of energy upgrading scenarios, specifically, cool roof and green roof technologies for the horizontal opaque envelope and thermal insulation, vented façade, and phase change materials’ applications for the vertical opaque envelope. Improving the indoor thermal comfort and reducing the thermal energy demand during summertime through innovative solutions will be the primary objective of the present study. The energy efficiency measures are compared from the energy, emissions, costs, and indoor comfort points of view. Phase Change Materials applied to the inner side of the external walls are analyzed in depth and, by varying their melting temperature, optimization of design is performed too. This innovative material, with a melting temperature of 23 °C and a freezing temperature of 21 °C, determines the reduction of summer energy consumption of 11.7% and the increase of summer indoor comfort of 215 h. Even if consolidated, other solutions, like the cool roof, green roof, thermal insulation, and vented façade induce improvements in terms of summer energy saving, and the percentage difference compared to the basic building is less than 2%. For this case study, a Mediterranean building, with construction characteristics typical of the 1990s, traditional passive technologies are not very efficient in improving the energy performance, so the investigation focused on the adoption of innovative solutions such as PCMs, for reducing summer energy demand and improving indoor thermal comfort.

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