Kroon Hall Rises

F&ES’ New Ultragreen Home

“Every building is a compromise,” Steve Kellert said recently in his new office at Kroon. “Translating what you visualize into something real is always a very difficult thing to do.” Yale’s Office of Facilities, known for its cautious, conservative approach to construction, had warned F&ES from the start that it would have to back off from some of its cherished ideas, in the stage of the process euphemistically called “value engineering.” Kellert’s chief regret is the loss of a huge underground concrete labyrinth that would have increased the use of thermal mass for temperature and humidity control. But the 100-year payback period didn’t pass the value engineering test. Likewise, the improved energy performance of triple-glazed windows was too modest to justify the cost.

But many of the other “crazy” ideas the F&ES design team had proposed turned out to make sense. “The first time you hear an idea, you say, ‘I’m not so sure about that,’” said David Spalding, a senior engineer with the Yale Office of Facilities. “The third time, you think, ‘Maybe there’s something to that.’ When we look back at what the school was trying to accomplish, many of the things that were pushing the edge or unusual are no longer unusual and are, in some cases, standard.”

The facilities staff had a powerful motive to overcome its initial resistance. Late in 2005,  with Kroon Hall still in the early planning stage, President Levin announced a commitment to reduce Yale’s carbon footprint 43 percent by 2020, even as the university continued to grow. All new buildings would have to meet the standards for a LEED silver rating, at minimum. Yale had already opened its first LEED building, the Malone Engineering Center, just down Prospect Street. Installation of a single system there, to recover heat from exhaust air, had cost an extra $100,000, but yielded an energy savings worth $50,000 to $75,000 every year, with a corresponding decrease in emissions. People began to ask: “Why didn’t we think of this stuff before?”

Jerry Warren, the construction manager who once banged heads with Kellert, recalled that Levin asked “one very avant garde and interesting question”—not just what a particular building would cost now, but what it would cost if global warming legislation required the university to buy the offsets needed to get that building to carbon neutral. “It was not cheap necessarily,” said Warren, who has since left Yale. Then he added, “The great part about Kroon—everything the team worked on, starting with the vision from F&ES, we got damned close to carbon-neutral.”

Nobody really knows the bottom line yet on Kroon Hall, and they won’t know until the actual performance numbers come in over the next few years. Moreover, it’s not certain that the Office of Facilities, which tends to keep such things close to the vest, will actually go public with performance data, though Spalding ventured a guess that “we will have to.” Construction cost about $576 a square foot—at the high end for a Yale building, partly because the job went out to bid at the height of the market. (The cost of other LEED buildings varies widely, from $200 to $700 a square foot, often depending on factors unrelated to sustainability.) Kroon is also designed to perform far better, with energy consumption projected to be 50 percent below the building code baseline for its size. A 100-kilowatt photovoltaic array on the roof will supply 25 percent of the building’s remaining electrical demand. Kroon will still need to purchase additional electricity from conventional generators, producing an estimated 540 metric tons of carbon dioxide emissions annually. But that is 62 percent less than code, and F&ES will mitigate this carbon output by purchasing renewable energy certificates from green-energy providers.

“The basic design of the building is where you get the biggest bang,” said Spalding, who had the job of calculating costs and paybacks at every step of the way. Thinking carefully ahead of time about the siting, shape, thermal mass and shading for Kroon cost nothing, he said, and dramatically reduced the need for expensive and energy-intensive mechanical systems. Costly sounding green technologies sometimes turned out, on closer scrutiny, to be cheaper than conventional methods. The Menerga air handlers, for instance, cost twice as much as a conventional system. But apart from the projected savings in energy, said Spalding, they also enabled planners to build a smaller basement. He figured the savings at $2 million. For the entire building, Spalding calculated the green premium—that is, the extra cost for sustainability features—at 5.1 percent of the overall $33.5 million construction. The solar photovoltaic array alone accounted for almost half that premium. Not counting that, the building cut projected energy use in half for a green premium of just 2.4 percent.

President Levin praised Kroon Hall as “Yale’s most sustainable building to date” and expressed the hope that “its energy-saving concepts will be emulated widely and inspire others to advance green building even further.” He declined, however, to say whether Yale itself will be among those doing the emulating. That may depend partly on the circumstances of individual site and function. The displacement air system, for instance, wouldn’t be appropriate in a laboratory building. Other urban buildings might not have room for geothermal wells. Other clients might also not be as focused as F&ES on pushing toward carbon neutrality or as strong-willed about facing down impediments. “In the current economic climate,” Spalding said, at one point, “there are all sorts of reasons we wouldn’t build a building like this right now.”

But back at Kroon Hall, the green-building apostles at F&ES were standing by their original audacious agenda. “As more and more companies, and consultants, and construction workers learn about these things, the easier it’s going to be,” said Deputy Dean Alan Brewster, who handled many of the thankless nitty-gritty details of the project. “Right now, we think this is one of the most sustainable buildings in the country. But six months from now, we hope that new buildings will surpass it. It will get less expensive, and the marginal cost for having these green buildings will go down.”

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Top of Page | Spring 2009 | environment:YALE

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Kroon Hall Rises
Robert Benson

The Ordway Learning Center is located on the ground floor, opposite the library, and has ample space for quiet study.

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Kroon Hall Rises
Gregory Nemec

Rainwater captured on the building’s roof and grounds will be cleansed by aquatic plants and used for toilets and irrigation.

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Kroon Hall Rises
Gregory Nemec

Warmed and cooled air both move almost imperceptibly through an air plenum and multiple diffusers in elevated floors so that it envelops people in a room. The air then exits through vents located above office doors. Low-velocity fans in the basement keep the air moving throughout the building.

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Kroon Hall Rises
Gregory Nemec

Four solar panels embedded in the southern facade provide the building with hot water. On days when there isn’t enough sun, fluid in the evacuated tubes runs through externally powered coils that warm incoming city water.

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Kroon Hall Rises
Gregory Nemec

The photovoltaic panels on the roof’s south side turn sunlight into DC electricity (red), which is converted in a transformer box to AC (blue). The AC is used in conjunction with AC power from the Yale grid and then goes to outlets and lighting throughout the building.

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Kroon Hall Rises
Gregory Nemec

In winter, ground-source heat pumps draw 55-degree to 60-degree water from four 1,500-foot-deep wells in Sachem’s Wood. The heat is removed from the groundwater by the heat pumps and is transferred to a separate water loop through the radiators. Then the groundwater is pumped back into the wells and absorbs heat from the Earth, ready to begin the cycle again. In summer, the process is reversed. The heat pumps take the cool from groundwater to cool the air, and then the water is pumped back into the wells.