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Green Roof on Javits Center. Miho Ouyou

Gardens in the Sky

Nature Girl was Inger Yancey’s nickname. Growing up, she and her friends would each point their fingers at different parts of trees, calling them their “offices” under the bright sunlight in California. They climbed all sorts of trees. From one tree to another, they hung a rope to transport a basket of food.

From a young age, she was fascinated by nature and what the environment provided for people.

In 1986, she earned a Bachelor’s degree in Architecture with a minor in History of the Built Environment from the University of California, Berkeley. She then obtained her Master of Architecture from Harvard University’s Graduate School of Design and started a business in Seattle, Staggs Yancey Architects, to design environmentally friendly houses and renovations for apartment buildings.

In the early 2000s, she moved to New York. The East Coast, where “nobody here cared at all about the environment,” gave her culture shock, she said. “You talked to people about it who were renovating apartments or building new buildings, at any scale, and people were like, ‘Why would I do that? It costs too much money.’ I was very frustrated.”

Yancey worked for a friend’s small architectural practice at the time. She thought maybe if she talked to him very nicely, he might want to do something sustainable. But soon she realized the best thing she could do was find materials he thought were beautiful and interesting that were made with recycled content. Clearly, people did not care much about sustainability. This was a problem for Yancey.

One day in 2008, however, she came across news about the newly created green roof tax abatement in New York. Yancey had a dream, she said, where she was flying like a bird and seeing the future of New York City, where all buildings were covered by green roofs.

She wanted to make that future a reality.

“I told a few people, to see if they thought I was crazy, and I decided I didn’t care what they thought and just did it,” she said.

Green roofs are more than just a layer of grass. They are vegetated roofs, made up of multiple layers installed on top of a roof. The layers include a root barrier sheet, protection mat, moisture retention layer, growing medium, and vegetation. Each layer has its purpose, from retaining rainfall to protecting the roof. Green roofs have many environmental benefits, from decreasing air pollution to keeping buildings cool during the summer and warm during the winter with insulation. They even provide a welcoming refuge for birds and butterflies. In a city like New York where so much of the landscape is covered by buildings, green roofs could have a significant impact.

Moreover, green roofs provide benefits in improving the water quality in the city. Over half of the city’s sewer system is what is known as a “combined sewer system,” meaning that sewage from buildings and rainwater from streets and roofs go into the same network of pipes. On rainy days, excessive rainwater can exceed the waste treatment plant capacity; as a result, the mixture of both types of water is discharged into the city’s rivers. Sewage from buildings often includes garbage, which also ends up in the rivers. Around 27 billion gallons of what is known as combined sewage overflow, or CSO, are discharged into New York City waters annually, according to Riverkeeper, an environmental advocacy organization.

Yancey founded her company, Brooklyn Greenroof on April 22, 2008, Earth Day. The first thing she had to do was teach others what a green roof was. Yancey took every opportunity she had to talk about green roofs in her local community. She joined a local garden club and took her message to a private women’s social club to teach about green roofs.

In 2009, Yancey’s outreach paid off and she started to get more orders. But she realized the city bureaucracy could be deadly. Some of her clients were discouraged to apply for the tax abatement because the process was too complicated. So Yancey prepared tax-abatement applications for her clients as a way to tell the government that environmental issues matter.

Her first installation was on a big mansion in Brooklyn Heights facing the southern tip of Manhattan. She was amazed by the view of New York’s financial district. Yancey did her second installation in Brooklyn Heights.

But the pandemic made things hard: so much time and energy were needed just to stay safe. Yancey kept working, though. She believes that green roofs are a way for New York to become a greener city, and for her kids to grow up in a less environmentally damaged world.

In the 1970s, when the oil crisis was at its height, the German government began to explore green roofs for energy conservation. Studies found they were effective at cooling buildings during summer through the process of evapotranspiration, and retaining heat in winter, thus reducing the energy needed for both cooling and heating. Around the same time, a significant amount of technical research on different components of green roofs was being done, including the study of waterproof membranes, drainage, growing media, and vegetation. By 1989, approximately one million square meters of green roofs had been planted in Germany. By 1996, the number had risen to 10 million, according to a 2011 research paper from Southern Illinois University Carbondale. Now, the total estimated amount of green roof area in Germany is around 120 million square meters, according to a case study described in Living Architecture Monitor.

Lawmakers and governmental grants were indispensable for the dramatic growth of green roofs in Germany. For instance, a new building code for installing green roofs on apartments was implemented in the central parts of Berlin in the 1980s, leading to increased green roof coverage in the city. Under Germany’s influence, a new green roof industry was formed in Europe according to the Carbondale study. Green roofs became a common architectural design in countries like France, Austria, Norway, and Switzerland according to a 1999 research paper. However, green roofs are still not a conventional idea in the U.S.

Shino Tanikawa, executive director of NYC Soil & Water Conservation District, a state agency dedicated to conserving soil, water, and other natural resources in New York City, remembers that in 1998, the city was proposing so-called “civil engineering” solutions to the problem of combined wastewater and rainwater. One idea was to install gigantic tanks around the city. These tanks would store rainwater during storms and drain it into waste treatment plants after the storms had passed. But this turned out to be an unfeasible idea: the tanks needed to be huge and sited in places in the city where space was extremely limited.

The NYC Soil & Water Conservation District instead sought nature-based solutions. Germany by then had demonstrated that green roofs could be an effective adsorbent for rainwater.

The agency began to advocate for green roofs in 2006, and in 2008 helped pass a tax abatement in the state legislature. But advocates soon found that the abatement was not enough. Green roofs did not start popping up on every block in New York City. In New York, according to a 2022 study, only 736 buildings have green roofs, which accounts for less than 0.1% of the buildings in the city. Their work was only beginning.

A 2008 tax abatement provided $4.50 per square foot up to $100,0000 per building or less depending on tax liability. In 2013, the amount and cap were both increased to $5.23 and $200,000 respectively. Priority community districts, meaning those particularly vulnerable to high levels of heat stress and air pollution, are now eligible to receive a $15 tax abatement per square foot from July 19, 2019, to June 30, 2024.

However, it typically costs around $26 per square foot to install an extensive green roof with shallow layers of substrate, and $100 per square foot for intensive green roofs with deeper layers of substrate, according to numbers from SWIM Coalition, made up of organizations dedicated to advocating for clean waterways. In New York City, those prices are significantly higher. It usually costs at least $30 to $50 per square foot to install a green roof in New York, Yancey said. New York’s streets are narrow and a lot of buildings do not have parking lots, Tanikawa said, requiring permits for street closures and cranes to hoist heavy green roof materials, which also makes green roof installations more costly.

“But these are the things a lot of folks outside of the city do not really think about,” Tanikawa said, because everything outside the city is cheaper.

In 2019, the New York City Council passed two laws, Local Law 92 and Local Law 94, to spur further green roof installation. These laws required all new buildings, as well as existing buildings undergoing major roof alterations, to have either a solar panel, a green roof, or both.

At least one firm has seen the effect of these new laws. Dick Bernauer, a partner and sales director of North America at Sempergreen creates pre-vegetated sedum mats for green roofs, says sales have increased by 20% and green roof inquiries have increased by 50%.

One afternoon in June 2018, Yancey received a call from a board member of a residential apartment building in Crown Heights. The board member was asking
about the benefits of green roof installation. As Yancey explained the benefits of soundproofing and creating more energy from the solar panels already installed by lowering the temperature of the roof, she heard the excitement in the caller’s voice.

Yancey biked to the building to assess the multifamily structure. Inside a unit on the top floor, she and a structural engineer visited a bathroom and a bedroom closet. Two holes, approximately 18 inch by 18 inch, had been cut in the ceiling already. Standing on the ladder, Yancey held her phone, and poked her head through the square hole to examine the structural members that supported the roof. She saw three joists on the left and two on the right. She measured the size of the structural members and their spacing. The structural engineer would use the figures to calculate the load the existing roof could bear.

They then walked up to the rooftop.Yancey measured the roof’s dimensions and wrote them down on a sheet of paper. She saw the solar panels and checked the yellow parapet walls that surrounded the roof. They were approximately four feet high. She then pulled out her phone and took some pictures.

On the street, before she left, she took pictures of the white stone building, which showed the rooftop could not be seen from the street.

When Yancey got back to her office, she opened her computer and software to draw the roof digitally.

The measurements were submitted to the Landmark Preservation Commission because this particular building was in a historic district, which places restrictions on renovations and alterations to a building’s exterior.

Yancey says she waited for weeks, in vain, for a reply from the commission.

“You shouldn’t have to go there, but they don’t pick up the phone.” So she went.

One drizzling cold day, Yancey suited up in a raincoat and bike helmet and pedaled across the Brooklyn Bridge to the Landmark Preservation Commission office. She got a little wet, but she didn’t care.

She explained to the staffer that she hadn’t gotten a reply from the commission after weeks of waiting. After some days, Yancey finally received the approval.

She then needed to submit multiple forms to the NYC Department of Building through its digital portal—a PW1, PW2, PW3, PTA3, TR1, and TR 8. She sent them in and once again, silence. So Yancey visited the office a few times.

On one visit, a woman told her that the permit had not been granted yet because Yancey failed to check the “special inspection” box on one form—an odd objection, given that there are no special inspections required for green roofs.

Special inspections are usually done when deep foundation work is involved and there is the potential for cave-ins that might swallow surrounding buildings, or when welding is involved, Yancey said. But green roofs are so simple, nothing like that, she said. Not a single nail is hammered into anything because you don’t want to disturb the building or do anything to create leaks.

Yancey told this to the staffer, who she overheard explaining the matter to her manager. Later that day, Yancey got the permit.

The installation started on a cold and windy day last November. Yancey and around four other people gathered at the building. Because the building did not have an elevator, they carried some of the layers of green roofs themselves up flights of stairs. The growth medium and vegetation tiles were lifted by a crane.

The first layer was the root barrier sheet; it is a black plastic-like sheet that prevents plants from penetrating the roof membrane. It took three people to carry each roll of the root barrier to the rooftop. The team crouched down and unrolled each roll. They continued until the whole rooftop was covered. Each sheet overlapped the other by about three feet. Holes were cut out for the rubber pavers that surrounded the legs of the solar panels.

The next layer was the protection mat, a felt material that acts like a cushion and protects the roof from anything sharp or dropped objects. The team rolled out the mat on the rooftop overlapping by six inches to cover the green roof section. Then came the moisture retention layer in stacks. It is a hard, 3D, egg-crate-shaped plastic sheet, with the egg cups facing up and down. The sheet came in at about one meter by two meters. The team carried the stacked sheets.

“They are quite heavy,” Yancey said.

The moisture retention layer has multiple purposes. First, it retains water inside the cup facing upward. When it is full, the extra water drains through the holes at the top of the egg crate. This holds water for the roots of the plants and also prevents pooling.

“Imagine a frame holding a picture,” Yancey said. For the green roof, you need edges that hold the growth medium and all other materials together, she said. Aluminum was placed to hold everything together. Next, they laid down a filter fabric that allows water, but nothing else, to pass through.

The Green Roof Installation. Inger Yancey

The last two layers, growth medium and vegetation tiles, came on the last day of the installation, lifted from the street by a crane. Each layer required seven crane loads. The installers watered their creation. It was done.

The obstacles to green roof installation in a place like New York City are significant. It is expensive. It is laborious. Many streets are quite narrow, meaning it’s hard to get construction equipment onto them. Some buildings are so tall that cranes can’t reach the rooftop, making it extremely difficult to make modifications. On top of that is the fact that many parts of the city are historically landmarked, meaning that there are various rules and restrictions on what can be done to buildings.

Rafael Espinal, the former representative of the 37th District of the New York City Council, who sponsored Local Law 92 and Law 94, is hopeful that New York will become like Germany someday, but believes it will take decades. The laws need to become more robust and the incentives more generous. Espinal’s original proposal for Local Laws 92 and 94 was to mandate that all buildings, regardless of age, have solar panels and green roofs installed—but this was deemed too burdensome. Nonetheless, he thinks that such a law has a high potential to eventually pass.

At some level, Espinal’s laws put the two environmental solutions—green roofs and solar panels—in competition. But according to Meagan Kestler, marketing coordinator at Chatfield Farms Green Roofing, there are limitations to solar panels, as they usually weigh more than extensive green roofs and some roofs cannot bear the weight. Some experts in the field are advocating installing both green roofs and solar panels, as green roofs can lower the temperature of the roof and help solar panels generate electricity more efficiently.

Green roofs are mandated to eliminate of stormwater from entering the sewer system. The laws are impactful, but people could ask for the thinnest, lightest, and cheapest green roofs to fulfill the bare minimum requirements, Bernauer said. If people could add more layers to their green roofs, they could be even more effective at storm management, handling long, heavy storms as well. He actually advocates purple roofs, which have an additional layer called the detention layer that slows down the outflow of water.

Experts in the field believe that a higher tax abatement, direct subsidies, lower costs of installation, and more education are essential for wide adoption, in New York City and elsewhere in the US.

It took Germany 50 years, Kestler said, but it’s only been 10 to 15 years or so in large cities in the U.S. to see a push for green roofs.

The roof of Inger Yancey’s home is covered with all sorts of green roof materials, from filter fabrics to growth mediums as a way to test if they withstand the strong, direct sunlight. For 14 years, they have been going strong, Yancey said. They clearly passed the test.

Despite being an architect for decades, Yancey’s passion for sustainability has not faded; she is still hoping to see all rooftops in New York City covered by green roofs one day, the dream she had 15 years ago.

Now, she is discussing with an organization that builds free and secure modular bike parking shelters called pods with green roofs on top of them. The company is aiming to build a network of pods across the city. The organization is discussing with Yancey a potential collaboration.

“We live on a beautiful planet, and it’s starting to slip away already,” she said. “As a nature girl, it is important to care for this earth we are on.” We only have Earth, Yancey said. There is no Planet B. This is our Planet A, “and I’m working to make sure it doesn’t die.”