The Effect of vertical greenery systems on building energy performance: overall thermal transfer value-based comparative analysis

Abstract

The construction industry significantly contributes to world energy consumption, representing around 40% of overall energy usage and a considerable portion of greenhouse gas emissions. Tropical cities are exploring sustainable solutions, and passive cooling systems like Vertical Greenery Systems (VGSs) have drawn interest for their potential to enhance energy efficiency. This study examines the influence of VGSs on the energy performance of high-rise buildings in Sri Lanka, utilising the Overall Thermal Transfer Value (OTTV) as the key performance metric. Two high-rise buildings were evaluated: one with a VGS-integrated façade and the other with a standard design without vertical greenery. OTTV were computed using standardised procedures that consider local climate data and envelope features. The OTTV analysis indicates a favourable impact from VGS integrated building, as the average OTTV reduced from 3.681 W/m² in the VGS absence of VGS to 3.527 W/m² with VGS present. The nearly 4.18% reduction appears modest, indicating a considerable improvement in thermal performance. These findings suggest that while VGSs may not drastically reduce OTTV in isolation, they contribute positively to overall energy efficiency strategies in tropical urban settings. The findings offer robust empirical support for the integration of vertical green systems into urban construction plans in tropical environments. This study contributes to the limited body of knowledge on VGS applications in South Asia and advocates for the integration of nature-based solutions in urban building practices. It provides practical insights for architects, policymakers, and green building consultants aiming for energy efficiency and climate resilience in the built environment.