Economical sustainability of vertical greeneries in tropical climate

Vertical greening is recognized as a fascinating integration in enhancing urban environmental quality and living standards. A research series was initiated with the aim of implementing a Vertical Greening System (VGS) to achieve the maximum benefit in terms of thermal performance in Tropical Sri Lankan context. However, it is unknown if vertical greeneries are economically sustainable. The current research vacuum should be filled by assessing the economic benefit of various vertical greenery systems. This study assesses the economic value of direct green facade (DGF), indirect green facade (IGF), and living wall system (LWS) by considering installation and maintenance costs and energy-saving benefits during their life cycle, through a cost-benefit analysis (CBA). CBA is computed under three distinct circumstances: worst, middle, and best. Net Present Value (NPV), Internal Rate of Return (IRR), Payback Period (PBP), and Benefit-Cost Ratio (BCR) are the four indicators used to calculate CBA. According to the study, DGF have positive NPVs for all scenarios and have acceptable IRR and BCR values with 6 years payback period. With best and middle scenarios, acceptable NPV, IRR and BCR values with 6-7 year payback period. Over three situations, LWS exhibits negative NPVs and indefinable IRR values. From An economic point of view, DGF and IGF are economically viable and living wall systems are not viable.