We will encourage the installation of green roofs through a new incentive program
A green roof partially or completely covers a building roof with plants. It can be a tended roof garden or a more self-maintaining ecology. Similar to swales and tree pits, green roofs can reduce the volume of runoff by absorbing or storing water, and other natural processes, in addition to cooling the air. According to a recent study by Riverkeeper, a 40-square-foot green roof could result in 810 gallons of storm water captured per roof per year. If each installation cost $1,000 then a $100,000 dollar investment could lead to over 81,000 gallons of stormwater captured. (See illustration on facing page: Components of a Typical Greenroof)

The City is developing four residential and two commercial pilots to analyze the potential cumulative benefits of green roofs on the city's combined sewer system. The expected cost for each is $100,000 for design and $1.3 million for construction and equipment.

In order to achieve direct CSO benefits, a large number of green roofs would be required within a concentrated area-an expensive undertaking. Therefore, incentives are necessary to off-set some of these costs.

The City currently provides incentives for the private development of two BMPs through DEP's Comprehensive Water Reuse Program. This program offers buildings that install "blackwater" or "greywater" systems a 25% discount off their water and sewer charges. "Blackwater" systems capture and treat sanitary wastewater and recycle it within the building for non-potable use. "Greywater" systems capture used water from washing machines, dishwashers, and showers and reuse that water for toilets or other non-potable applications.

Starting in 2007, the City will begin providing incentives for green roofs, as well. New York City will support the installation of extensive green roofs by enacting a property tax abatement to off-set 35% of the installation cost of a green roof. The pilot incentive will sunset in five years, when it will be reassessed for extension and inclusion of other technologies.

Progress (as of 4/22/08):
The City is working with members of both the State Assembly and Senate to introduce legislation incentivizing the installation of green roofs in New York City. Once the legislation is introduced the City will encourage the legislature to pass the legislation in a timely fashion with hopes that Governor Patterson will sign it in to law.

Green Roof Tax Abatement Bill, New York State Assembly