A review on the mechanisms behind thermal effect of building vertical greenery systems (VGS): methodology, performance and impact factors

Abstract

Vertical greenery systems (VGS) integrate vegetation into the building facades to reduce wall surface temperature, thereby reducing building energy consumption. The mechanisms behind the cooling and energy-saving effects of VGS are mainly related to shading, evapotranspiration (ET), thermal insulation and wind barriers. In this study, we conducted a comprehensive review of the thermal effects of VGS, focusing on these mechanisms. Our review consolidates research methods, performance evaluations, and influencing factors discussed in previous studies. First, we sorted the methods and evaluation indicators used to investigate the thermal effects of the VGS. Field measurements involve on-site and model-buildings investigations, whereas numerical simulations rely on commercial CFD software or self-developed VGS thermal effect models. Second, we explored the performance and influencing factors of each mechanism individually, emphasizing the pivotal role of VGS type, plant and growing substrate characteristics, and meteorological conditions. And shading emerged as a dominant mechanism, contributing approximately twice as much as ET to the overall thermal effect. Finally, we thoroughly analyzed the factors affecting the overall thermal impact of VGS, encompassing meteorological parameters and design considerations. Notably, we identified that certain influencing factors exert diverse effects on each mechanism and the overall thermal effect. In conclusion, our study explored the distinct roles of each mechanism within the overall thermal effect, offering valuable insights to propel the advancement of VGS design.