Cost-benefit analysis for green façades and living wall systems

Vertical greening systems can be used as a mean to improve the environmental conditions of dense urban areas. Several researches have proved the environmental benefits of green envelopes. It is still not clear if vertical greening systems are economically sustainable, differently several Life Cycle Cost Analysis and Cost-Benefit Analysis determined economic costs and benefits of green roofs. This paper presents a Cost-Benefit Analysis of different vertical greening systems - green façades and living wall systems - considering personal and social benefits and costs over their life cycle. Installation, maintenance, and disposal costs of each analysed system are compared with the related private and social benefits (increase of real estate value, savings for heating and air conditioning, cladding longevity, air quality improvement, etc.), determining three indicators: the Net Present Value (NPV), the Internal Rate of Return (IRR) and the Pay Back Period (PBP). The CBA demonstrated that some of the vertical greening systems analysed are economically sustainable. Economic incentives (tax reduction) could reduce personal initial cost allowing a wider diffusion of greening systems to reduce environmental issues in dense urban areas, such as urban heat island phenomenon and air pollution.