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Our project got an objection due to sustainable roofing system laws. We have a high-slope roof, so we’ll need to put in solar panels. How should we account for this new element and answer?

First, a brief rundown: As of November 15, 2019, Local Law 92 and Local Law 94 of 2019 require new buildings and certain alterations (generally those that involve replacing most or all of the roof deck) to include some kind of sustainable roofing zone in their plans.

This can mean a solar photovoltaic (PV) electricity generating system (like solar panels), a green roof system (with vegetation, soil and drainage systems), or some combination of the two. (Please refer to our previous article on the sustainable roofing laws for more details.)

First, you will need to calculate the pitch and size of the roof. This will determine many elements of the design of your sustainable roofing system, including whether you actually need one – according to Buildings Bulletin 2019-10, roofs with a slope greater than 17 percent are at such an angle that a solar PV system cannot meet the minimum 4kW solar energy capacity, and thus are exempt from the requirement.

To make these calculations, you’ll need the assistance of a qualified professional, such as a mechanical engineer or qualified contractor. They can take a look at the area and plans in question, and do a structural analysis of the building as a whole, to properly determine what will (or won’t) work with your set-up.

This is especially important because any green roof system adds weight to your existing building’s structure that, if improperly installed, can cause a major hazard.

If your project does in fact qualify for a sustainable roofing zone, new roof elements created in compliance with LL92 and 94 must be illustrated on roof plans and submitted to the DOB, with sections showing the pitch of the new roof and showing the solar PV panels in compliance.

If your professional finds that your roof cannot support a sustainable roofing zone, they will submit supporting documents, including calculations and a shading report, as proof that your roof qualifies for exemption.

Again, please note: Any supporting documents, whether to prove compliance or the need for an exemption, must be calculated by a qualified professional.

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