Eco-solutions for urban environments regeneration: The economic value of green roofs

Abstract

The installation of green roof systems is being used as a specific action towards a broader objective of increasing the sustainability of the built environment. Yet, their development is still limited by the absence of a full understanding of their economic value. There is an underlying assumption that these solutions can enhance the value of cities, however contrasting results of past studies do not allow to draw specific conclusions about their real economic contribution.This paper intends to improve the decision-making process by providing an adequate methodology to perform cost-benefit analyses of installing green roofs. The proposed economic evaluation balances costs and benefits at three levels of analysis: financial, economic and socio-environmental. The first level compares construction, maintenance and replacement costs of green roofs with private benefits as discount on fire insurance, energy consumption, improvement of photovoltaic performance and urban rooftop farming. The second level also includes the economic gains from increase of property value, aesthetics, recreation and sound insulation. The third level adds social benefits related to storm water management, noise reduction, air pollution removal, mitigation of the urban heat island effect, public health and ecological preservation. The all-inclusive methodology is successfully applied to Lisbon, Portugal. The study confirmed the economic feasibility of green roofs in the long term at a social level but not at a financial level. The estimated net present value of green roofs implementation in Lisbon is about 320 million euros. A sensitivity analysis is also performed to the costs/benefits included. The results show that aesthetics, recreational value and sound insulation have the highest influence on the economic value.