How a “freak out” over Local Law 97 turned into a green overhaul

Perhaps the building’s destiny was always in the name. Built in 1911 on what’s today a leafy stretch of the Upper West Side next to Central Park, the eight-story co-op at 46 West 83rd Street was dubbed the Lathrop, a name which orig­i­nates from an Old Norse term for a lush green rural farm­stead located on a settlement’s frontier. 

It’s unclear who chose the regal-sounding English name for the 60-unit building. But more than a century after its construc­tion, the Lathrop’s co-op board did, indeed, try to remain at the leading edge of ​“going green”. 

Sometime in the early 2010s, the board consid­ered lining the rooftop with rows of energy-harvesting solar panels at the behest of envi­ron­men­talist members who wanted to do their part to fight climate change. But this was before China’s mass produc­tion of photo­voltaics sent the cost plum­meting, and an initial calcu­la­tion of the costs for the Lathrop showed that installing the panels in a way that was compliant with the building’s land­mark status would be expen­sive. Plus, charting out the path to claiming and distrib­uting the bene­fits of nascent state tax incen­tives was compli­cated, so the board aban­doned the idea. 

“We crunched the numbers and we spoke to our accoun­tant, and we said, ​‘It doesn’t work,’” Mindy Stern, the long-time resi­dent who heads the board, said on a recent weekday after­noon. ​“So we said, ​‘Not for us.’”

A few years later, the economics started changing. The passage of Local Law 97 (LL97) meant the Lathrop would be staring down poten­tial fines by 2030 from energy effi­ciency lapses as the statute grad­u­ally took effect. 

Along came the legis­la­tion in April of 2019 and, ​“like everyone else, we freak[ed] out,” Stern said. The board recon­nected with archi­tect Ted Sheridan and McGowan Southworth, the co-founder of DaisyChain Energy, both of whom had engaged in the building’s previous effort to build solar on the roof. This time around, the calculus looked different: lower solar prices, increased state grants for building panels, and the threat of looming fines on the fiscal horizon if they did nothing. 

To offset how much natural gas resi­dents used, the Lathrop needed to use more elec­tricity, but the vast majority of the elec­trons on the New York City grid were now coming from natural gas since the state shut down the Indian Point nuclear station north of the Bronx that once supplied virtu­ally all the clean power in the five boroughs. To guar­antee new power that was both clean and cheap, the building needed solar panels. 

“This time,” said Stern, a lawyer and Bronx native, ​“we could make the numbers work.” 

By the time the project completed earlier this year, the board at 46 West 83rd Street had carried out a first-of-its-kind reno­va­tion that could offer a model for other large, pre-war build­ings looking to comply with a statute the city is fully prepared to enforce, albeit with some poten­tial tweaks. 

It started on the roof

By the time the board called Sheridan again for a consul­ta­tion, the Canadian-born archi­tect noticed a shift. 

“This board was really serious about it,” he said. 

Sheridan, too, had grown more serious about the project. While his firm, Ryall Sheridan Architects, had long special­ized in upmarket green reno­va­tions, Sheridan himself had gained an insider’s appre­ci­a­tion of the new policy condi­tions under which the entire industry was working. During the COVID-19 pandemic, when then-Mayor Bill de Blasio’s admin­is­tra­tion was working out the details on imple­menting LL97, Sheridan joined about 15 other profes­sionals in an advi­sory panel that helped shape the carbon accounting rules the city uses to encourage elec­tri­fi­ca­tion of buildings. 

“The members were incred­ibly varied. There were envi­ron­mental advo­cates, but there were also devel­opers. It wasn’t a one-sided discus­sion,” Sheridan recalled. ​“It was quite effec­tive actually.” 

When the Lathrop board approached him again, Sheridan offered them a list of roughly 20 poten­tial upgrades and reno­va­tions the building could under­take to comply with the law. 

“They picked a few key things from a big menu,” he said. ​“And they actu­ally had the money to do it.” 

The roof was the natural starting point. Aside from first the aborted solar idea, the board had for years enter­tained the idea of greening the sun-soaked roof with some kind of garden or deck, Stern said. Between the cost and the compli­ance issues with the building’s land­mark status, nothing ever came of it. Still, the board resisted selling the roof rights. 

“It turned out to be fortu­itous that we never did [sell],” Stern said. ​“It was just this unused amenity that all of a sudden became avail­able to use.”

They ended up using that avail­able space to install an array of 77 solar panels, but ones that looked different than others on rooftops around the city.

On a late morning earlier this year, Sheridan stood atop the roof, squinting as sunlight elbowed through parting clouds, and bounced off the low-slung rows of black glass panels into his eyes. 

The reflec­tive­ness was by design. Crouching down to eye level with the narrow gap between the base of the solar panels and the roof itself, one can see that the Lathrop painted its roof white. 

All of these features — the low-lying solar array, the white roof — were small but crit­ical details of the project. The color not only gives the building a trendy ​“cool roof” that avoids absorbing and radi­ating excess heat like a typical black tar roof, but it also increases the effi­ciency of the panels, Sheridan said. 

The building’s land­mark status and broader aesthetic regu­la­tions in the neigh­bor­hood prevented the Lathrop from elevating its solar panels to an optimal height to convert the most sunlight into elec­tricity. To compen­sate, the white-painted roof reflects more of that light back to the under­side of the panel, giving the photo­voltaics a second oppor­tu­nity to harvest energy from the same beam. 

Those panels now connect to circuitry in the building that carries the power down into the base­ment and to the broader elec­trical grid. The solar panels are not currently powering anything in the building, but rather all the power gener­ated on the roof of the Lathrop is sold back to the grid. 

The board had long wanted to add batteries to the project, allowing the building to store solar power gener­ated during the day and sell it back at night when prices on the grid are higher. But the New York City Fire Department, which has set strin­gent rules on lithium-ion batteries due to the risk of igniting a blaze, took years to approve the proposal. 

The fire­fighters just greenlit the addi­tions this summer. In recent weeks, the board filed an appli­ca­tion for a state grant that would completely pay for the batteries and installations. 

“It would pay for every­thing,” Stern said. ​“If we got that, it’d be unbelievable.” 

Stern, on behalf of the board, declined to comment on how much the building spent on its project, but confirmed that about 60 percent of the costs were covered by a mix of city, state, and federal tax credits

A little power company in the basement

The second big change took place in the bowels of the building. On our tour, Sheridan and I rode down the freight elevator to a neatly kept base­ment hallway leading to a room filled with gauges. This was among the most essen­tial changes. 

Previously, each unit at the Lathrop had its own indi­vidual elec­tricity meter with Con Edison, allowing the power company to collect service fees from each house­hold. Aside from the added expense — to boot, indi­vidual elec­tricity rates are also typi­cally higher than bulk rates — the sepa­rate meters compli­cated the board’s task of fairly distrib­uting the bene­fits of elec­tricity gener­ated from the building’s own solar panels. 

Now, the building is what’s called master metered. A single elec­trical meter measures elec­tricity use for the building, and then the co-op does the billing inter­nally with the help of DaisyChain Energy, Southworth’s group. 

The reno­va­tion didn’t require rewiring anyone’s walls, but the end point of the elec­trical hookups now joined at one master machine in the base­ment with ​“sub” meters for each apart­ment. On each gauge is a sticker for Lathrop Electric — essen­tially the building co-op’s new elec­trical co-op, which buys power from the grid at a bulk rate and offsets the cost with gener­a­tion from its rooftop panels. DaisyChain runs the co-op and struc­tures its bills to make sure each share­holder apart­ment even­tu­ally receives a fair share of the bene­fits. It’s also helping to apply for the state grant for batteries. 

On average, gener­ating solar power is shaving about 20 percent off the building’s total elec­tricity usage, but resi­dents aren’t feeling that just yet.

“Now, because we spent more money than we had planned to, we’re not passing through the savings on the admin­is­tra­tive costs to share­holders at the moment,” Stern said, explaining why the solar array isn’t yet showing up on the bills resi­dents receive from Lathrop Electric. ​“We’re just pock­eting it because we have to build back up our reserve.” 

Still, savings are showing up in other ways. In total, the reno­va­tions avoid about 15 metric tons of carbon dioxide per year, according to a calcu­la­tion by DaisyChain. 

Window shopping

Once the board replen­ishes its savings, Stern would like to see that money spent on knocking off more items on the menu of energy effi­ciency upgrades Sheridan initially offered. 

“We did meters and the solar first, but that list also contains possible window refur­bishing, improved insu­la­tion, working on the boiler, improving the temper­a­ture control system in the building…” Sheridan said, his pupils trained upward as he ran through a mental checklist. 

Without missing a beat, Stern jumped in to add to the list converting more resi­dents to induc­tion stoves: ​“Bringing elec­trical risers up so that we can convert more people from gas to electric.” 

She sighed. ​“That was back when we were feeling opti­mistic — for the building and the country — about the cost asso­ci­ated with all of this,” she said, refer­ring to the period before President Donald Trump returned to office and elim­i­nated many federal poli­cies to support clean energy. 

Political realities

The Lathrop, like many build­ings plan­ning to make decar­boniza­tion upgrades, are staying attuned to changing polit­ical winds at all levels of govern­ment. Here in the city, the current mayoral admin­is­tra­tion has not yet formal­ized any changes to the imple­men­ta­tion of LL97, but the lived reality of imple­men­ta­tion has not been as straight­for­ward as intended when the law was first passed in 2019. For one thing, the companion climate law at the state level was recently changed by state legis­la­tors to ease some of the dead­lines, which experts say will affect LL97. 

And there’s still the possi­bility for local changes. During a mayoral candi­date forum ahead of the June 2025 primary that vaulted Zohran Mamdani to victory, then-candi­date Mamdani said he supported LL97, but also crit­i­cized the diffi­culty of imple­men­ta­tion for condo and co-op owners in partic­ular, saying ​“what I’ve heard from so many is that it’s easier to pay the fine than to get into compliance.”

At that time, Mamdani suggested he supported reforms to make compli­ance the easier choice. But while the city has revamped its tools to help build­ings navi­gate compli­ance, this admin­is­tra­tion is still main­taining the existing rules final­ized in December 2024 under former Mayor Eric Adams, and published its latest list of covered build­ings in March. 

At the federal level, mean­while, the Trump admin­is­tra­tion has gutted incen­tives for funding home upgrades to make struc­tures more energy effi­cient, and in partic­ular the 30 percent tax credit for resi­den­tial solar. 

Still, the Lathrop board is glad it acted early and in fact may be a canary in the coal mine as more build­ings take on retrofit projects to be able to stay in compli­ance with ever-tight­ening emis­sions limits. 

“A lot of these co-op build­ings have boards with, like, eight people, some­times 10. In this building, about half the board were inter­ested in energy effi­ciency for philo­soph­ical reasons, just wanting to try to do their part for green­house gas reduc­tions,” Sheridan recalled of his early conver­sa­tions with the Lathrop board. 

“Two of them were keen because they wanted to avoid fines from Local Law 97, and they wanted an A rating to stick on the door. They didn’t want an embar­rassing B, C, or D on display for everyone to see.” 

Today the building boasts a B grade for its energy effi­ciency rating. In response to emailed ques­tions, the board said the rating is ​“on the cusp of an A” and suspected it would ​“hit A this year,” noting that a high B is still ​“very good for a pre-war apart­ment building.” Without any further changes, Sheridan said the building would be LL97 compliant through 2035. 

Ultimately, Stern said, the prag­ma­tism of the latter messaging won the day. 

“We didn’t get into those philo­soph­ical discus­sions with the share­holders. What we focused on was, if we do nothing, we’re going to be fined, so we have to do some­thing,” she said. ​“It’s going to be more cost-effec­tive in the long run to do this, and it has the added benefit of doing the right thing for the universe.” 

Therein lies what Stern called the ​“conun­drum” under­pin­ning New York’s efforts to decar­bonize its build­ings, the largest source of green­house gas pollu­tion. Unlike power plants or cars on the road, which fall more directly under City Hall’s authority, the work of decar­bonizing resi­den­tial build­ings is a shared responsibility. 

“On the one hand, it’s very impor­tant to reduce the carbon foot­print,” she said. ​“On the other hand, it has become so expen­sive to live in New York and main­tain prop­erty here that those two things are really in major conflict with one another.” 

Local Law 97 works, Stern said, because ​“it’s going to affect us in the pock­et­books.” But the reno­va­tions also only made finan­cial sense because the project managed to wrap up before Trump’s tax law changes took effect and phased out key credits for solar installations. 

“We certainly are relieved that we did it when we did it before the federal tax credits went away,” she said, then shrugged her shoul­ders. ​“But whether it is cost effec­tive for build­ings now has to be care­fully evaluated.”