CPC passes mechanical voids proposal

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Critics pan “stunningly weakened” zoning text amendment, which now heads to City Council for review


  • A rendering illustrating the proposal to tighten restrictions on mechanical void space. Image: Department of City Planning

  • The Department of Buildings has approved revised plans for Extell Development’s in-progress 775-foot tower at 36 West 66th St., which includes over 170 feet of mechanical space in its middle section. Rendering: Snøhetta.

“I am deeply disappointed that ... the City Planning Commission would disregard the community, evidence from their own experts at the Department of City Planning, and vote in favor of taller buildings for billionaires.” Council Member Ben Kallos

The City Planning Commission voted April 10 to advance a long-awaited proposal that would place new limits on the use of mechanical voids, tightening a loophole that developers have exploited with increasing frequency in recent years to inflate building heights through the use of largely empty spaces.

But the proposed text amendment approved by the CPC is more permissive than an earlier version of the policy put forth by Department of City Planning staff. It was met with a tepid response from many zoning reformers who have spent years advocating for stronger mechanical void restrictions.

Current city zoning law exempts spaces designated for mechanical use from the floor area calculations that in many districts effectively govern a building’s maximum permissible height. These mechanical spaces are not currently subject to height restrictions. As a result, some developers have utilized large, tall spaces in towers’ middle sections — which nominally hold mechanical equipment but are often mostly empty — to boost the sightlines and values of residential units on the floors above. In some extreme cases, the city has approved buildings with mechanical voids exceeding 100 feet in height.

The text amendment approved by the CPC would discourage excessive void spaces by limiting the floor area exemption to mechanical spaces 30 feet tall or shorter; voids exceeding this height would count toward a project’s buildable floor area. The DCP’s earlier proposal had suggested a height limit of 25 feet for exempted mechanical spaces.

Under the proposal, buildings would be permitted to claim the exemption for multiple void spaces, provided that each void space is separated by at least 75 feet in vertical distance.

The commission increased the height threshold in response to feedback from construction industry experts, who had testified that taller spaces would allow for greater flexibility to house new equipment that meets energy efficiency and resiliency standards.

“This [change] is based on the testimony of the various engineers, and our desire to assure that new, more energy efficient mechanical equipment not be constrained by zoning,” CPC Chair Marisa Lago said. “Further, the analysis that was done by the department shows that the excessive mechanical voids that we believe violate the intent of our current zoning aren’t spaces that are a foot or two above the norm, but rather are patently unreasonably tall spaces.”

“Developers Write the Rules”

Many Manhattan community boards and land use advocacy groups had pushed for the CPC to strengthen the original proposal, arguing in favor of shorter height limits for exempted mechanical spaces with larger intervals between voids.

Critics also point to several other perceived shortcomings with the proposal, which would apply strictly to enclosed spaces (meaning voids classified as outdoor space would be unaffected) and only targets certain residential zoning districts, primarily in Manhattan. The Department of City Planning plans to expand the scope of the proposal through a second zoning text amendment later this year.

Assembly Member Linda Rosenthal, state Senator Robert Jackson and seven prominent land use nonprofits issued a joint statement criticizing the “stunningly weakened” proposal as “a prime example of what happens when City Hall shirks its responsibility and developers write the rules.”

“Buildings simply do not need 30 feet of space, every 75 feet, to house mechanical equipment,” the statement read, continuing, “This is space that could be used for affordable housing, to maintain access to light and to open air, but will now be empty so that luxury developers can continue their assault on our skies to reap sky-high profits.”

Rosenthal and Jackson have introduced state legislation that would place stricter limits on voids, as well as discourage excessive floor-to-floor heights on non-mechanical floors by mandating that floor area calculations correspond to ceiling height.

The CPC’s proposal now heads to the City Council, which has 50 days to review and modify the text amendment before sending its decision to the mayor for final approval.

Council Member Ben Kallos, a longtime supporter of efforts to close the voids loophole, vowed to push for the Council to reverse the height limit increase.

“I am deeply disappointed that after every Community Board and nearly a dozen elected officials in Manhattan spoke out for fewer and shorter mechanical voids, that the City Planning Commission would disregard the community, evidence from their own experts at the Department of City Planning, and vote in favor of taller buildings for billionaires,” Kallos said in a statement. “The City Council must overturn what the City Planning Commission has proposed by reducing the heights of mechanical voids.”

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