Framework for a Performance-Based Green Roof Incentive in New York City

Cities around the world have implemented incentive programs or adopted legislation to support the construction of green roofs. To date, most incentive programs offer a one-time grant, rebate, or tax break for green roofs, with a requirement to cover a minimum area or percentage of the rooftop area. Generally, the incentive amount is a flat rate per unit area of green roof, independent of design features. This study addresses the need to develop a framework for a performance-based incentive to maximize cost effectiveness. This framework was developed in three steps: (1) evaluate stormwater retention benefits of green roofs in New York City, (2) generate cost-benefit curves and (3) use these findings to develop a framework for a cost-effective incentive program. This framework lead to the implementation of a tiered incentive schedule, based on green roof depth and area, that accounts for both performance and economies of scale.