Enhancing the environmental performance of industrial settlements: An economic evaluation of extensive green roof competitiveness

This paper evaluates the private and social costs and benefits of adopting an extensive green roof as opposed to a cool roof in an existing industrial building in Trieste (North-Eastern Italy). The evaluations from social and private viewpoints both consider costs and benefits of refurbishments, energy consumption, and maintenance. From the social side, the externalities derived from green or cool roofing, such as aesthetic aspects, biodiversity preservation and natural habitat provision, carbon reduction, air quality improvement, and hydrological aspects, are monetized using cost-benefit transfer approaches. The first analysis result is the poor convenience of adopting a green roof compared to a cool one from the private investor's viewpoint. The second finding is the positive net present value of the social cost-benefit analysis for the green roof compared with the cool roof, due to the positive externalities of the former. Monetization of externalities allows calculating the economic incentives needed to promote the spread of green roofing in the Mediterranean area. Consequently, two different types of incentives are proposed: direct contribution for refurbishment intervention and annual reduction of local property tax. A final sensitivity analysis using the Monte Carlo method is performed on intrinsic and random variables, defined by triangular or uniform distributions. The probability evaluation of economic affordability is provided from the private investor's viewpoint, first considering private costs and benefits and, second, introducing the financial incentives for balancing the public benefits provided by an extensive green roof.