Combined strategies for green roof incentive policies in Lisbon: Evaluating the potentiality of concession grants and identifying priority intervention areas

Incentive policies to promote new technologies is a strategy often employed by policymakers and governments. In some cities worldwide, mechanisms to encourage the adoption of Green Roofs (GR) have been implemented over the years. Although GR is not a new technology, the use of incentives, such as subsidies and tax abatements and/or exemptions, is still a recent strategy in many countries. The study covered in this paper proposes to explore the potential of combined incentive mechanisms for green roofs, using direct incentives (financial subsidies) and indirect incentives (tax/fee rebates). The granting incentives were verified by the feasibility assessment from both private (saved money) and public perspectives (reduction in municipal revenue) using scenarios of abatement percentages for fees and taxes and combining direct and indirect incentives. In addition, priority intervention areas for the installation of green roofs were defined based on three parameters: (i) the proportion of existing green spaces, (ii) urban heat islands and (iii) the potential of the building stock for green roof retrofit. The results show that granting a combined solution can be an effective option for facilitating the implementation of green roof projects. Moreover, the study serves as a decision support guide for politicians, urban planners, and public managers to formulate incentive proposals and make well-informed decisions regarding the incentive policies for GR.