Green Roofs - Living Architecture Monitor - Summer 2020 - 28

RESEARCH

IDENTIFYING OPPORTUNITIES TO
INCREASE GREEN ROOFS IN NYC
(WHERE THEY ARE MOST NEEDED)
MICHAEL L. TREGLIA AND ALAINA VAN SLOOTEN, THE NATURE CONSERVANCY, NEW YORK STATE CITIES PROGRAM

The Nature Conservancy and partners estimate that as of 2016 only about 736 of more
than one million buildings in New York City (NYC) had green roofs, based on the first
analysis of their distribution.

he Nature Conservancy and partners estimate that as of 2016
only about 736 of more than one million buildings in New
York City (NYC) had green roofs, based on the first analysis
of their distribution. Though not all buildings are suitable for
green roofs, significant untapped potential remains. Furthermore,
green roofs are not equitably distributed across the city - some
areas with limited greenspace, higher exposure to the urban heat
island effect, air pollution and stormwater challenges that do not
have many green roofs can potentially benefit the most from local
expansion of green roofs.
Recently, several new policies have been developed to increase
the number and area of green roofs across NYC. Generally, these
policies do not explicitly prioritize green roofs in areas of higher
opportunity or need. To generate dialogue, The Nature Conservancy, with support from the mapping company, Azavea, and their
Summer of Maps Fellowship Program, examined how green roofs
could be prioritized across NYC, based on various types of need
and at multiple spatial scales. This work can inform the development of relevant policies and programs.
POLICY BACKGROUND
The new policies and programs designed to help increase green
roofs across NYC include mandates, tax incentives, and grants.
For example, Local Laws 92 and 94 of 2019 require green roofs,
solar, or a combination of the two on nearly all newly constructed
buildings, building expansions, and full roof replacements.
Though there are multiple incentive programs for solar panels,
there are only two for green roofs. The NYC Department of
Environmental Protection has a Green Infrastructure Grant

LIVING ARCHITECTURE MONITOR / SUMMER 2020 / 28

Program, providing financial support for construction of green
roofs above a certain size. There is also a tax abatement which was
renewed and amended in 2019 for property owners who install
green roofs on their buildings.
A key amendment to the tax abatement was an attempt to
help address inequity in green roof distribution by providing a
higher abatement rate ($15/sf ) in "priority Community Districts," with a lower rate offered in non-priority areas ($5.23/sf).
According to the legislation, priority areas would be determined
based on "potential to minimize net stormwater runoff and increase green space." These criteria are a great start, but they are
not comprehensive. Green roofs indeed can help manage stormwater - greatly needed in cities like New York where outdated
Combined Sewer Overflow (CSO) systems discharge raw sewage
directly into local waterways when overwhelmed by rainfall.
Green roofs also function as wildlife habitat, and sometimes as
places of respite, recreation, and education for local residents.
However, they provide other benefits that address critical urban
environmental issues that can also be considered in spatial
prioritization, including mitigating urban heat and absorbing air
pollution.
DATA AND METHODOLOGY
We explored four factors in potential prioritization of green roofs,
based on relevance to NYC and data availability. We considered
greenspace and need to manage stormwater, in part because these
were specified in the tax abatement. For greenspace need, we calculated the percentage of land that was not covered in vegetation,
based on recent land cover data for NYC (Figure 1 Map b). For
LIVINGARCHITECTUREMONITOR.COM

http://www.LIVINGARCHITECTUREMONITOR.COM

Green Roofs - Living Architecture Monitor - Summer 2020

Table of Contents for the Digital Edition of Green Roofs - Living Architecture Monitor - Summer 2020