Improve

What is a green roof, and how do you install one in NYC?

Share this Article

New Yorkers, by nature, are an over-achieving breed—and perpetually short on space. An unadorned blacktop roof, for instance, is a waste of outdoor space, which is why some urban homeowners are not only opting to beautify their fallow rooftops but give a helping hand to the environment, too. At Zeckendorf Towers, for instance, co-op owners decided to replace their aging roof with a green one, which the New York Times writes, can not only increase property values but also provide insulation, lower heating and cooling costs, and offer residents a beautiful retreat.

Green roofs, however, are not a recent innovation in urban architecture. In fact, devoting roof space to gardening and irrigation is an ancient tradition, dating back to the Incas, who carved terraces into mountainsides to water and grow crops.  And enterprising New Yorkers have been making the most of their rooftops since at least the 1920s: Rockefeller Center, for instance, has maintained its own gardens in the sky for decades, which Untapped Cities has photos of here.

So what’s the difference between a green roof and a regular planted roof?

“A green roof is created with the specific objective of having a positive effect on the environment,” says Anna Karp, co-founder of Bolster, a New York City company that has designed a transparent and enjoyable process for area homeowners doing major renovations. “The flora selection, construction materials, the design and engineering are geared towards that purpose, with the added bonus that green roofs, like planted roofs, become lovely outdoor spaces that homeowners can enjoy.”

Karp notes that sometimes, rather “greening” an entire roof, homeowners create green terraces that extend outward, staking out the kind of green space that’s in short supply in NYC, as seen in the Herzon & de Meuron-designed “Jenga” building at 56 Leonard Street, with its strikingly staggered terraces.

The advantages of green roofs

“One major plus of turning your roof green is that it will extend your roof’s life by keeping its membrane—the material that moves water off the roofs of large buildings—protected from the elements,” says Agustin Ayuso, a LEED certified architect with Bolster.

A landscaped roof also serves as a form of insulation.

“On a 90 degree day, a black roof in NYC will register a much higher temperature,” he says. “A green roof reduces the temperature because the plants absorb a lot of the heat from the sun.” The cooling effect of green roofs helps not only the people dwelling underneath one, but also the city at large, where dark roof surfaces can create a “heat island effect” and raise area temperatures by several degrees in the summer.

Finally, a green roof can conserve water—retaining moisture and run-off water--via water recycling systems that safely reuse rainwater that could otherwise flood sewers during storms. This also benefits the city, which is why green roofs are being incentivized through grant programs.

Federal grants can help pay for your green roof

The federal government is encouraging the construction of green roofs through grant programs. NYC owners now have access to two opportunities: One program offers grants for creating green roofs that manage storm water runoff,  while another provides grants for the construction of green roofs that include water reuse systems.

These grants tend to go to roof projects in buildings with 300 to 500 residents, as such properties are where the most significant reductions in water demand are possible, says Sri Rangarajan, Bolster’s advisor on the subject, who helped write a storm water grant program with the Department of Environmental Protection.  Navigating the grant funding process can be tricky, but Bolster can help you get the funding by connecting you to the right team at every stage – from an expert engineer to landscaping professionals. 

Rangarajan says that the process for grant-supported green roof renovations begins with some brainstorming.

“We come up with concepts around what the potential avenues are, and calculate how much storm water is generated within the roof area and what kind of potential uses for it we can explore,” he says. “Then we set up a meeting with the Department of Buildings and the building management. From there, we can go ahead with the engineering design.”

Should the application for a federal grant be approved, Rangarajan explains, “It fully covers the labor and materials, but for the design and engineering drawings to produce them, you’ll need to do some cost sharing.”

On a home renovation scale, however, homeowners can apply to get grant funding for infrastructure, which can cover the cost of planters, plants, irrigation systems, and other materials that are used to create a green roof.  The city also offers a tax abatement program that helps building owners pay for the installation of green roofs.

Karp explains that when a homeowner is approved for a grant, they’re already coming out ahead, as they can get a substantial portion of a larger renovation project financed.

The cost of installing a green roof varies depending on the irrigation systems, planters, and the engineering required. Read about Bolster’s work renovating a Tribeca homeowner’s roof terrace to get a sense of some of the expenses.

“Architectural design services in New York are on average 20 percent of the cost of construction,” says Karp. “In Bolster, those services average 15 percent because of the efficiency we bring to the table with our professionals.” (Click here to read about how Bolster can help you save on architect design fees by streamlining the entire renovation process.)

She adds that architects relish the opportunity to work on a grant-supported roof project because  “many homeowners are doing a bigger renovation, of which one of the components is the roof. The grants can open a door where homeowners can opt to partly finance that aspect of the project, or if they own a brownstone, they can consider doing a roof terrace, whereas in other instances that aspect of the project would have been out of their budget.”

How to plan a green roof renovation

First, make sure you have to go-ahead to re-do the roof, especially if you’re in a co-op or condo with roof access (as opposed to being a building owner). 

“In a co-op or condo, often the roof membrane is owned by the building, and management is responsible for its maintenance,” explains Bolster’s Karp. “They’ll want to make sure they have access to the membrane, because it protects the apartment directly below it. The board may also require you to use only moveable planters in your landscaping, in case they need to fix the membrane.”

This process is not dissimilar to applying for permits for a regular renovation; however, your building may require that you get clearance on the amount and weight of the plants and materials to ensure the roof does not sag over time.

Once you reach the design phase, consider the types of plants your roof requires, from both an aesthetic and an engineering perspective.  

“You may want to choose some edible plants to further capitalize on your patch of green,” says Ayuso, who recommends also that you don’t dismiss smaller, local plants endemic to the region. “They don’t need irrigation and are cheaper, but unfortunately, people don’t always consider them pretty because they’re basically weeds,” he says.

These low-maintenance plants will require less gardening from you, which may also be appealing. Think about how much time you want to spend up on that roof caring for your flora, and whether you’re willing to hire someone to take care of it when you’re not around.

Other considerations during the design phase include:

  • Whether you want the roof to be easily walkable
  • Whether your roof membrane first needs to be replaced—you don’t want to go to the trouble of landscaping a roof whose membrane is nearing the end of its life span.
  • Selecting the right irrigation system—ideally, one that’s practical and easy to use to cut down further on your maintenance time. If you are away on vacation, the plants will still need to be watered—but nowadays, there are smart irrigation systems that can be controlled from afar with apps.
  • The type of construction materials you’d like to use, as well as products for pavers and planters. Weight is a major factor here: Working with a structural engineer will help ensure that your roof is strong enough to hold the amount of soil, plants, and planters you want to use. 

Every year, New Yorkers waste over $700M following the usual renovation process. Bolster is different, using a scientific approach to match you with the highest-quality professionals and financially guarantee your project is delivered beautifully for a fair price - all at no extra cost.

To start your major home renovation project, visit bolster.us 

More from Bolster:

Here's how much it costs to gut renovate a 1,000-square foot 2-bedroom, 2-bathroom Upper West Side co-op

Here's how much it costs to renovate and expand a house in Hudson Valley, N.Y 

Here's how much it costs to renovate a rooftop terrace in New York City

Here's how long it takes to gut renovate a three-bedroom apartment in NYC

Also Around the Web