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Proposal to eliminate voids in NYC buildings will be a ‘challenge,’ experts say

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Elected officials are pushing for shorter mechanical voids while engineers say that’s not feasible

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Advocates are calling on the city to strengthen a zoning amendment that seeks to crack down on excessive mechanical voids often abused to increase a building’s height, but engineers and architects warn that the revision would create “new challenges” for those tasked with efficiently designing buildings.

At a City Planning Commission (CPC) hearing on Wednesday, concerned citizens and builders weighed in on the Department of City Planning’s (DCP) proposed amendment that would make mechanical voids count toward a building’s overall footprint if they rise above 25 feet or are on floors within 75 feet of one another.

Elected officials and community groups have lauded the move as a key first step to curbing unnecessary voids, but argue the amendment must be strengthened to include stricter parameters and additional blocks where supertalls are slated.

“We just need a more comprehensive approach,” Manhattan Borough President Gale Brewer told the commission at Wednesday’s hearing. “The point of closing a loophole is that you do not leave an opening that can be exploited by developers.”

Brewer wants the threshold for voids clustered near each other to increase from 75 to 90 feet and says blocks bounded by West 56th and West 58th streets, and Fifth and Sixth avenues—which are just outside of the district affected by the amendment—must be incorporated. These blocks are home to several proposed or in-progress supertalls. Just two weeks after DCP’s zoning application was submitted, two developers filed demolition plans for their properties—if demolition work is performed before an amendment goes through, those buildings would be grandfathered in.

“This area is facing an imminent threat, and if no action is taken we may see exactly the kind of development that this application intends to prevent,” Brewer continued. City Council member Ben Kallos, who represents the Upper East Side and spoke on behalf of a slew of local elected officials, joined Brewer in calling for the amendment to recognize unenclosed voids—such as Rafael Viñoly Architects’ controversial “condo on stilts”—as mechanical and say they should count toward a building’s overall floor area. Currently, they do not.

Kallos also challenged the commission to shrink mechanical voids even further to 14 feet before they count toward a building’s footprint, but an engineer representing the American Council of Engineering Companies—which represents 300 consulting firms throughout the state—said if voids were mandated at 12 feet or similar heights, “you can’t build that building.”

“Any linking of mechanical space to zoning area creates a pressure on our ability to get mechanical space in a building. That’s our biggest challenge,” said Ed Bosco, a consulting engineer with 30 years of experience, who noted that it costs developers some $500 per foot of mechanical space, but if floor area is attached, it could cost $4,000 per foot.

“Any reduction of mechanical space means we’re selecting equipment for dimensions really not for performance,” Bosco continued. “If we lose that space we are just trying to make things fit.”

While it depends on the building, “there’s almost no reason for a mechanical void more than 35 or 40 feet,” Bosco noted. Mechanical voids that occupy more than 15 precent of a building are generally unnecessary, but if a void is less than eight percent of a structure, that’s usually too little space. Some of the buildings whose voids have provoked ire have voids at 25 percent of a building's floor area.

Several engineers and architects objected to the 25-foot limit, fearing that they’ll be forced to compromise design and efficiency to cram equipment into shortened spaces. Instead, many suggested 35 feet as a more reasonable height. Bart Sullivan, a structural engineer with McNamara Salvia, worries that the amendment’s restrictions are “not based on any apparent engineering logic” and urged the CPC to thoroughly engage with industry experts before moving forward with the proposal.

An architect with Kohn Pedersen Fox, which designed several towers in the Hudson Yard megaproject, also fears the 25 foot restrictions would hamper design and noted that those curtailed spaces could limit the use of future innovations.

“Mechanical spaces should be future-proofed to allow the incorporation of emerging technologies and approaches for mechanical engineering in residential buildings,” Dominic Dunn told commissioners. “It’s prudent to design flexible spaces that will allow for future modifications.”

The CPC will mull the feedback it received during Wednesday’s three hours of testimony in addition to Brewer’s and community board feedback at a future review session.

This will be followed by a not-yet-scheduled vote on the amendment, according to Joe Marvilli, a spokesperson with DCP. If the commission votes to approve or modify the proposal, the plan would finally head to the City Council for a vote.