Green Roofs: Looking up for a Solution

CLIMATE CONCERNS NYC 2021 (NYU 1rst Semester Final Project)

All around New York City, gray prevails. Pavements, roads, sidewalks, parking lots—the impermeable surfaces that cover the city are endless. As green is slowly taking over the dense urban landscape, the untapped resource that is the sea of tar and asphalt resting above our heads awaits utilization.

Far from being a simple aesthetic addition to our cities’ landscape, adding greenery up in the sky has become a major driver in the fight to make our urban spaces more sustainable in the face of climate change.

“Green roofs are such a unique and vital technology for establishing sustainability practices,” said Annie Novak, the co-founder and farmer at Eagle Street Rooftop Farm, a green roof in Greenpoint, Brooklyn.

Green roof infrastructures have been around for hundreds of years rising out of mythology as old as the Hanging Gardens of Babylon. But it wasn’t until 50 years ago, starting in Germany, that the green roof as a climate resilient technology started being developed.

Composed from top to bottom of plants, growing medium, a water retention layer, a root barrier coat and a waterproofing basis, this five-layer technology acts like a giant sponge that can soak up water, therefore decreasing the amount of rainwater that reaches the street level and reducing the risk of flooding. Additionally, through evapotranspiration—the evaporation from soil combined with vapor loss from plants—green roofs can lower the temperature of the air, mitigating the urban heat island effect.

The technology reached the United States a couple of decades ago, and though it was adopted slowly at first, it is now gaining momentum as American cities are trying to adapt to the increasing threats coming from extreme weather conditions. Cities like Chicago, Portland, and Denver are leading the way and implementing significant initiatives.

But New York is lagging behind.

Rooftops on the Upper East Side.

In 2016, the first extensive and comprehensive report regrouping data to map out where green roofs were installed in the city was released by the Nature Conservancy. The map was created by putting together publicly available data and remote sensing technologies. It revealed that only 736 out of the 1 million buildings that cover New York had a green roof, representing only 0.1% of all one billion square feet of roofscape.

“The politics and size of New York do kind of make it unique. The megacity is different than Denver or Portland. We are making progress,” said Dustin Partridge, the Senior Ecologist & Green Infrastructure Lead at NYC Audubon.

Since this data was last released, the city has made a greater push to make the roofs greener.

In April 2019, the New York City Council passed the Climate Mobilization Act, with the aim to decrease the city’s carbon emissions by 80% by 2050. The sweeping legislative package was one of the most ambitious building emission set of laws enacted in any large city in the world. Specifically, Local Law 92 and 94 require all new construction to include a green roof, solar, or a combination of both. As such, New York became the biggest city in the United States to require new buildings to include green roofs.

Since the two laws were put in place, there has been no clear indication of how many green roofs have sprouted around the city. As the city released new data for 2020, Mike Treglia, the lead scientist at the Nature Conservancy, is currently working on updating the map. “Everyone is sitting on the edge. We are still in the early stages, but we are definitely seeing more green roofs,” he said.

“The results of this will be really interesting to see how many green roofs were installed between 2016 and 2020 […]. Staten Island as of 2016 only had two green roofs and they were both very small. But I know of at least six new projects that have gone on out there since that,” said Partridge.

Some doubt that the mandate will be enough to create the green roofs needed for New York City.

“Climate change is smacking us right in our face. New York does have this big green law that they passed, but what is happening?” asked Barbara Leatherwood, in charge of communication for Broadway Stages, a studio company whose sustainability efforts led to the creation of three of New York’s iconic green roofs.

The major obstacles to establishing more green roofs are the up-front costs and the lack of understanding of what the financial benefits for the building will be, which the mandate fails to address. Ranging from $15 to $35 per square foot, the installation of a green roof represents a cost that is two to three times higher than the cost of a standard asphalt roof.

Alan Burchell, the principal of Urban Strong, a for-profit company that installs green roofs in New York City, wants to convince people green roofs are a good economic bet. “If in order to defeat climate change we’re relying on people’s charitable nature, we’re screwed. You have to hit them where it counts, you have to prove that battling climate change, ridiculously enough, is going to have an economic return on investment for that individual person,” he said.

The multi-layer technology behind green roofs can drastically reduce the cost of energy by cooling the building during the summer and warming it during the winter. Additionally, the waterproof membrane extends the lifespan of the roof.

Regardless of these benefits, many building owners and developers still see the installation of green roofs as being too expensive. And as such, many have found ways to circumvent the mandate thanks to the many exemptions included in it.

Kingsland Wildflowers – A green roof managed by the Newtown Creek Alliance, sitting atop Broadway Stages’ film studio in Greenpoint, Williamsburg.

Burchell compares green roofs to a “Swiss Army knife” of benefits and tools. These roofs can act as “our therapist, our air conditioner, our air purifier, our farmer, our firefighting Department, our insulators, and so on. No one technology does all of that.”

On top of mitigating the urban heat island effect and managing stormwater, various reports have proven there are many other benefits that can be reaped by the city—the installation of green roofs in a neighborhood can reduce crime rates, reduce the stress hormones of people who can see or access them, and promote biodiversity.

“The cost of that public benefit shouldn’t come from the people that are paying to install the Green Roof, at least not entirely because there is financial benefit to the city of New York,” said Partridge.

Compared to mandates like Local Law 92 and 94 that require individuals to comply with regulations in the face of the threat of fines, incentive programs such as tax abatements can help offset the initial cost of setting up a green roof.

In 2007, the New York City Council created the Green Roof Tax Abatement Program to provide individuals with a reduction of taxes payable to the city—$15 per square feet in priority districts and $5.23 per square foot in others.

Such funds have the potential to entice building owners to build green roofs but for the first nine years after its implementation, the program created only seven green roofs. For Shino Tanikawa, the Executive Director at NYC Soil & Water Conservation District, “the amount is too low, the bureaucracy is on arrest and there is no outreach to private property owners.”

Volunteer working on the maintenance of the Saint Mary’s Recreation Center Green Roof

Different organizations have taken it upon themselves to create programs with complementary goals to raise awareness of these incentives and foster the deployment of green roofs.

“The challenge is to advance the advocacy for green roofs. We need more information and that requires prioritizing green research,” says Timon McPhearson, the director of the Urban Systems Lab.

In 2017, the Green Roof Research Association was created to organize all those working in the field.

“We honestly didn’t know who was doing research, who was working on green roofs in New york. It was maybe like 20 or so researchers and we realized that we weren’t even really speaking the same language,” said Partridge.

Since then, the group has worked on carrying out extensive research to dismantle the misconceptions about the technology, shed light on the available resources and incentives, and help bring green roofs into the mainstream.

Thanks to the combined efforts of policy makers, scientists, researchers and educators, the public perception and the interest in green roofs are growing.

“If the human species gets wiped out from climate change, it’s not going to be one thing that kills us. It’s going to be like death by a thousand paper cuts.” Burchell said.“And similarly, there’s no one silver bullet that helps heal death by a thousand paper cuts. It’s going to be a thousand little small Band-Aids that all together are going to stop the bleeding.”