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New Roofs Must Now Be Green or Solar or Both

Marianne Schaefer in Green Ideas on November 14, 2019

New York City

Green roofs, solar panels, Climate Mobilization Act, Local Laws, co-ops, condos.

The Javits Center sports a massive green roof.

Nov. 14, 2019

Local Laws 92 and 94, part of the Climate Mobilization Act, go into effect on Nov. 15. They require that all newly constructed buildings and all buildings undergoing a complete roof replacement must have a “sustainable roofing zone” covering the entire roof surface. A “sustainable roofing zone” is defined as a solar photovoltaic electricity-generating system, a green roof system, or a combination of both. Co-op and condo boards that are replacing their roof membrane or patching their roof – by far the most common roof jobs – will be exempt from the laws. 

“Everyone’s hair was on fire when the laws were first announced,” says Christa Waring, a principal at CTA Architects who sits on the Building Code Review Committee, which advises the Department of Buildings (DOB). “But if you have a concrete roof deck, the chance of having to replace it are slim. If you have a wooden roof deck, the laws will apply only if you have to replace all of the plywood sheeting or the supporting joists.” 

Nonetheless, the law is here and it has teeth for those affected by it. And it is generating a mix of enthusiasm and confusion. “I’m very excited about this new, progressive legislation,” says Alan Burchell, principal at Urbanstrong, a green-building consultancy. “In the long run, these sustainable roofing zones will improve the quality of life for everyone in New York. There just remains a bit of work to be done to clarify the path forward.” 

While the requirements for solar panels and the numerous exemptions are spelled out in the new laws – for such things as water towers, mechanical equipment, steep roof pitches, fire department access, and more – there is some confusion as to exactly what constitutes a green roof. 

“The green roof must meet the requirements of the Building Code, Section 1507.16, which sets forth nationally recognized standards for green roofs,” says DOB spokesman Andrew Rudansky “Those standards set requirements for green roof assemblies, such as the type of growth medium, depth, required drainage, and types of plants that are acceptable.” 

But Burchell counters that this section of the Building Code does not provide enough information. “There are many kinds of green roofs,” he says. “So far we don’t know the details about requirements for things like the depth of the growing media, the plant type, or the fill volume of the retention layer.” 

For instance, boards that just want to get the city off their backs might install the cheapest system, called an extensive green roof, which consists of shallow layers of growing medium and a limited variety of small plants that will stay alive without irrigation. Rudansky believes that most green roofs will need irrigation systems. “Irrigation will often be required in the first year of planting to fully establish a green roof,” he says. “And irrigation may be necessary in times of drought to keep the plants alive.” At the highest end of the spectrum is the so-called intensive green roof, which has the deepest growing medium and the widest variety of plants. There are many kinds of green roofs in between those two extremes. 

“When somebody asks us for a green roof, the first thing we ask is what they want to achieve,” says Burchell. “Is their goal insulation and energy conservation? Are they aiming to manage storm-water runoff? Is it important to them to contribute to lower carbon-dioxide levels? How important is a habitat for birds and butterflies? Will they want or need an irrigation system? Maybe they want to incorporate decking, or agriculture? There are so many different options.” 

The DOB promises that clarification is forthcoming. “The department will be providing further details shortly,” says Rudansky, noting that boards that are replacing a roof or building a new structure will need to comply with Local Laws 92 and 94. “The DOB will take enforcement actions,” he adds. “This will include the issuance of violations if we receive complaints regarding maintenance issues with green roofs.”

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