New York City’s Sustainable Roof Initiative

The Challenge

Effective November 15, 2019, Local Laws 92 and 94 of 2019 require existing buildings undergoing major roof renovations and new buildings create a sustainable roofing zone. The zone must consist of a solar photovoltaic system, a green roof system, or a combination of the two.  One hundred percent of the roof area must comply with this requirement, unless specifically exempted in Buildings Bulletin 2019-010.  Exemptions include roof areas occupied by rooftop structures (water towers, mechanical equipment, antennas, etc.), and NYC Fire Code access areas.  The NYC Department of Buildings has created a brief compliance path to determine when sustainable roofing zones are required.  See Figure 1 below.

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The Solution

If a sustainable roofing zone is required, the next step is to determine what type will work best for your building.  Solar panel and green roof systems can add significant weight to a building’s roof.

Solar panel systems typically weigh 3 to 8 pounds per square foot.  Green roofs are a heavier system, typically weighing 13 to 35 pounds per square foot.  While a new building can be designed for this additional weight, existing buildings must be carefully evaluated.  A structural engineer should be consulted to review the building structure to determine what additional capacity, if any, the building may have.  Buildings that cannot support the added weight of a sustainable roofing zone may be exempt from adding a sustainable roofing zone.

For a solar panel system, there are two common ways to secure the panels to the roof.  Most solar panel systems installed on flat roofs rely on ballasted mounting systems.  Ballasted systems use ballast blocks to hold the solar panels in place without penetrating the roof.  This allows for a relatively simple and quick installation that does not impact the roof membrane.  Fixed mounting systems are more commonly used on sloped roofs.  Fixed systems rely on clamps or clips that penetrate through the roof membrane and attach to the roof structure (joists, beams, etc.).

We have been working with building owners and contractors designing solar panel projects for over 10 years.  As a full service engineering firm, we can follow your solar panel project from concept through construction. Our structural department can inspect the building and perform an evaluation to determine the allowable system weight.  Our MEP department can prepare the solar system design.  As a NYC registered special inspection agency, we can perform the inspections during the solar panel system installation.

Please contact HBE for assistance with your solar panel systems.

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