Kroon Hall Rises
By Richard Conniff
Photos by Robert Benson Photography
Illustrations by Gregory Nemec
A casual visitor to the new home of the Yale School of Forestry & Environmental Studies might not consider it radically different from any other building at Yale. At first glance, Kroon Hall is strikingly simple—a modernist blend of a cathedral nave and a Connecticut barn, just 57 feet wide, with high barrel-vaulted gable ends, set back from Prospect Street and running 218 feet east into the heart of Science Hill.
But from the start, more than a decade ago, proponents of the building set out to achieve an unconventional, even audacious, agenda here, focused on building social capital, breaking with the past and speaking to the future of environmentalism. They wanted a healthy place to study and work, of course, but they also wanted what Stephen Kellert, Tweedy Ordway Professor of Social Ecology, calls “restorative environmental design,” bridging the gap between nature and people even in the middle of the city. That was going to mean demolishing at least one corner of the Science Hill landscape of driveways, dumpsters, parking lots and a power plant and bringing the place back to life as a campus for people. They also wanted the new building to be energy-efficient, and they set out to achieve a platinum rating in the green-building certification program, Leadership in Energy and Environmental Design (LEED). But they aimed to do much better than that. The typical LEED gold or platinum building performs only about 28 percent better than conventional buildings on energy efficiency, according to a 2007 survey. Kroon Hall planners set out to achieve something more like the architectural Holy Grail, a modern building that wasn’t merely efficient, but carbon-neutral. Dean Gus Speth, who together with Kellert was the driving force behind the project, promised a building that would be “a symbol of the school’s ideals and values and a powerful expression in beautiful form of our relationship to the environment.”
It was an agenda that invited close scrutiny and also elicited some anticipatory schadenfreude. In effect, F&ES was pushing the building community, and Yale itself, well beyond their comfort zone, with the help of European thinking from the British firm Hopkins Architects and a shopping list of technologies and construction techniques most American contractors had never heard of, much less attempted. The initial response from some university staff included “barely suppressed ridicule” and “almost outright laughter,” Kellert recalled recently. Discussing the carbon footprint of a building could still seem, as late as 2005, like debating the finer points of theological dogma; it didn’t have much to do with the real world. “They thought we were just out of our minds and had no idea what we were talking about,” said Kellert. Even green-building advocates took a wait-and-see attitude. “Yale is one of the great institutions in the world, and if they make a real commitment to green,” said Richard Cook, of Cook + Fox Architects in New York, “we will all be watching to see what they accomplish.”
Four years ago, standing at 195 Prospect Street, you would’ve seen a one-story-high wall filling most of the space between Sage Hall and Osborn Memorial Laboratories (OML). The wall had barred jailhouse windows. Behind the windows was a gas-fired power plant—whining, humming and emitting carbon exhausts—a bleak symbol of business-as-usual in the fossil fuel economy. Finding your way into Science Hill meant sneaking up a driveway on Prospect Street and through a parking lot on one side of the power plant or walking down to the grand, turreted corner entrance of OML and through an archway—into another service yard.
Yale had come to recognize Science Hill’s shabby character as a neglected outpost of the university, and it had developed a plan to transform it into a place students might actually want to stay for a while, rather than just making quick forays from the main campus. But the parcel between Sage and OML would be a harsh test of just how far the university would go to achieve that goal. The site was an industrial wasteland containing contaminated soil, an underground spiderweb of utility lines and the power plant. It also sloped steeply from front to back and from one side to the other. When the architects first saw it, said Speth, “they gagged.”
Fast forward four years, and the same piece of Prospect Street now feels as if the main Yale campus has opened a scenic beachhead into Science Hill. The resemblance has to do partly with the architects’ choice of the same Ohio sandstone used in many buildings on the main campus. As a result, Kroon Hall’s pale yellow coloring makes a luminous contrast with the gloomy brownstone and maroon brick of other Science Hill buildings. But the resemblance to mainland Yale has even more to do with the way the building connects to its landscape.
Where the power plant used to stand, an elevated piazza now serves as the entrance to Kroon—and also screens it from the noise and traffic of Prospect Street. On the higher ground to the left, at the north side of the building, there is a courtyard and seating area planted with native ferns and bulbs. On the south side, one story down, a sidewalk welcomes people off Prospect Street into a broad, grassy courtyard, with a rain garden at the far end and access to Sachem’s Wood, the green heart of Science Hill, just beyond. For Kellert, who teaches about the restorative power of parks and gardens, having “the Yale courtyard tradition on both sides” is almost as important as the building itself: “People will be teaching out there, dining out there, bonding out there.” For Speth, the transformation of the landscape raised the promise of actually improving on über Yale: “The Cross Campus and the Old Campus are very nice,” he allowed. “But Science Hill is going to be special.”
Though it hardly seems like architecture at all, the south courtyard was the elegant stroke of design that made the entire Kroon building project work, on at least three counts. It isn’t a conventional courtyard but a raised platform, with a green roof of engineered soil just one foot deep. Beneath it lies a service node where all trash, recycling and delivery traffic for the southwest corner of Science Hill now get handled underground, out of sight. University staff initially resisted the full scope of the service node idea, said Speth. They wanted to keep an above-ground driveway running from Prospect Street along the north side of Kroon to supply Kline Biology Tower. “We really blew a gasket about that. It would’ve been a mess, just as it was before.” Instead, a single driveway off Sachem Street now brings all vehicle traffic into the service node, with deliveries continuing through an underground tunnel to Kline. “I think they knew we were right, but they didn’t want to pay the price.”
The courtyard was also essential on aesthetic grounds. At the beginning of the project, the dark, Gothic mass of OML loomed four stories high at the lower end of the site. Raising the ground level one story reduced the two wings of OML to a more manageable scale, according to Mark Simon, whose Connecticut firm, Centerbrook Architects and Planners, worked with the British design team as on-site architects. It also brightened both buildings by bouncing light off a higher surface. Olin Studio, the landscape design firm, came up with the idea of tapering the courtyard down at the lower edges, so people on the bottom floor of OML now look out on a slope planted with oaks and sweet gum trees. The tapering also lent itself to a stairway in one corner, leading from OML’s grand archway into the courtyard. So for the first time in almost a century, this entrance to Science Hill now opens onto someplace people actually want to go.
That kind of coordinated thinking also figured in the courtyard’s third role as a stormwater-harvesting area. LEED requires new buildings to reduce stormwater runoff by 25 percent below pre-construction levels. So both north and south courtyards, as well as the roof of the building itself, now drain into underground holding tanks. The floating rafts of iris, wild rice and cattails in the south courtyard’s rain garden are meant to look nice, of course. But they also help purify rainwater by removing 80 percent of suspended solids—another LEED requirement. After further treatment, water from the north courtyard gets used to flush toilets and water from the south courtyard for irrigation, avoiding the need for about 500,000 gallons of city water a year.
“It’s the combined power of multiple systems that makes this building much more sustainable,” said Cricket Brien, a design associate with Olin. “If you took one piece of it out, a lot of the other pieces would suffer. Yale was really committed to this idea of integrated planning and design so that systems, buildings and sites work together.”
Integrated thinking, with architects, engineers, landscape designers, contractors, facilities staff and faculty all listening to one another from the start, was also critical to the design of the building itself, and nothing about it felt like business as usual. Yale had recently brought in a hard-nosed corporate construction manager named Jerry Warren, and on a European tour to choose an architect, he and Kellert soon banged heads. “He would bully me and I would just go back at him,” Kellert recalled. “We argued about energy efficiency and sustainability and whether these newfangled approaches worked or not. He said, ‘I’m an engineer. I’ve worked with buildings for 30 years. Don’t tell me how to do my job.’” But Kellert added, “He turned around. This thing wouldn’t have happened without Jerry Warren.”
The project also faced resistance from university energy staff over the plan to shut down and remove the Pierson-Sage Power Plant (PSPP), which they considered essential as a backup facility to meet peak energy demand. F&ES had agreed to accept the building site only after the administration promised to get rid of what Speth referred to as “the monstrosity.” But it kept reappearing in the plans, year after year, and research into strategies for replacing it never seemed to go anywhere. Speth persisted, bluntly arguing that having “this outmoded, unsightly, polluting, 19th-century facility in the heart of Yale’s new green building … would make a mockery of what we are trying to do.” Finally, tired of “squabbling with officialdom,” he delivered an ultimatum: “I decided that it was either me or the power plant—one of us was not going to remain at Yale.” Yale President Richard Levin, who had been going through his own awakening on the issue of global warming, soon called to thank Speth for forcing the issue. It dawned on university energy staff that they could get rid of PSPP and save money in the process.
Despite such rough patches, the collaborative process was by all accounts more often positive than not. “This wasn’t a frustrating project,” said Shanta Tucker, who worked on Kroon for the environmental engineering firm Atelier Ten. The drive to be carbon-neutral made Yale open to unfamiliar technologies and systems with higher up-front costs, if the long-term benefits made sense. Budget wasn’t the only bottom line. The design and construction team coalesced around the green mandate and, early on, they made a leap of faith and agreed to give up their traditional reliance on big, rolled-up blueprints. Paperless communication via the internet avoided an estimated $100,000 to $250,000 in costs for printing and shipping documents overnight around the world. With consultants spread out from Los Angeles to Abu Dhabi, it also saved time.
As in the courtyard, the collaboration often focused on getting each part of the building itself to serve multiple functions. Much as in a medieval cathedral, structural elements would have to do most of the heating and cooling, according to Hopkins architect Michael Taylor. Thus energy considerations dictated the east-west orientation, exposing the long south facade to maximum solar gain. Stone walls and lots of exposed concrete were essential for thermal mass to retain heat in winter and retain cooling in summer. Energy considerations also determined the building’s tall, thin shape: a narrower profile, combined with glass facades on the east and west ends, meant that daylight could provide much of the illumination. Light and occupancy sensors now dim artificial lighting when it isn’t needed, and Douglas fir louvers on either end of the building keep out unwanted heat and glare.
Ventilation is also largely a function of architecture. In a conventional building, energy-intensive mechanical systems blast air through overhead ductwork. Those systems also require chillers and cooling towers to refrigerate the air in summer down to 55 degrees, so it mixes to a comfortable temperature at head height. Kroon uses a displacement system instead, and the air never has to vary much on either side of 70 degrees. Warmed and cooled air both move almost imperceptibly through an air plenum and multiple diffusers in the elevated floor. (The plenum also doubles as a chase for electrical and other utilities.) Low-velocity fans in the basement keep the air moving, but it’s not like the conventional practice of “energizing air through fans,” said Taylor. “We’re letting it find its own way, so it envelops people in the room.” In mild weather, the building’s occupants become part of the ventilation machinery by opening windows in response to a red light/green light alert system in the hallways.
The high barrel-vaulted ceiling on the third floor draws air naturally upward, via a “stack effect,” through the long open staircase in the middle of the building. Then the air travels back down via passageways in two stairway towers on the north side of the building. In the basement, banks of big orange air handlers from the German manufacturer Menerga use heat exchangers to pull the warmth out of the exhaust air in winter, shifting it over to the incoming stream of fresh air, so what gets vented is just stale air, not BTUs. In summer, water sprayed into the exhaust air causes evaporative cooling—like a dog panting—and drops the temperature by 10 degrees or more. Then heat exchangers pull this “coolth,” as Taylor calls it, out of the exhaust and into the incoming fresh air. The exhaust system also runs throughout the night in summer to purge heat from the building and store the cool of night in the building’s exposed concrete surfaces.
The challenge for Hopkins Architects was to make these energy requirements work socially and aesthetically, too. One of the design stipulations, for instance, was to create a collegial gathering place for the F&ES community, which had long been scattered among nine different buildings on campus. The lower floors had to be “quite tightly planned” for office space, according to Taylor, especially after budget and other considerations scaled back the overall square footage by about 15 percent to 58,200 gross square feet. But the high ceiling and bright light on the top floor made it the logical place for seating and dining areas, classrooms and an auditorium. “It’s slightly unusual to have the piano nobile effectively in the attic,” Taylor acknowledged. But it works. Almost from the moment a visitor enters the building at ground level, the long open stairway carries the eye up. People move naturally toward the big window high up on the eastern end of the building, with its view into Sachem’s Wood.
The architects also clearly gave thought to making Kroon work not just in its own right, but also as a building at Yale. In the past, for instance, the rolling whaleback roofline of architect Eero Saarinen’s David S. Ingalls Rink, just across the street, was an isolate on Science Hill. Now it’s got company in the rounded line of the standing seam metal roof on Kroon Hall. Kroon’s use of exposed concrete surfaces also consciously echoes architect Louis Kahn’s two masterworks on the main campus, the Yale Art Gallery and the Yale Center for British Art. (Both Hopkins and Centerbrook Architects count themselves among Kahn’s many disciples.) To soften the concrete and remind people that this is, after all, a school about forestry and the environment, the architects also employed red oak paneling from the Yale-Myers Forest, managed by F&ES and visited by all incoming students as part of their basic training.
On the other hand, translating European ideas into an American context also proved challenging. A basic strategy for Hopkins was to avoid the wasteful use of materials by making structural elements double as finished surfaces, often through the use of precast concrete parts for a smoother, more precise look. But American suppliers were only prepared to do rough precast work for parking lots or for buildings where the concrete would get wrapped in layers of other material. Contractors were also reluctant to try self-leveling concrete, which delivers a better finish but requires meticulous formwork. “If I called today, they could do it,” said Chris Meyer, the project manager for Turner Construction Company. “Two years ago, it was a different story.” The job also required construction workers to learn a different mindset. “They had to be very conscious of every little detail, making sure that nails that fell out of the pouch didn’t rust on the floor. Putting in rebar and pouring concrete were like installing finished millwork.”
The concrete was also a challenge in global-warming terms. Because of the energy-intensive manufacturing process, the 10,400 tons of concrete in Kroon Hall and the adjacent service node would normally have translated into 10,400 tons of carbon dioxide emissions. The design team knew that they could avoid roughly 40 percent of those emissions and get a stronger concrete by substituting blast furnace slag, a waste product, for some of the Portland cement in the mix. But they were shocked when the forms came off and the concrete was a dark, mottled blue. F&ES had declared its intent to make this project an educational experience, and it was. Everybody waited nervously until the concrete cured to the consistent color they’d expected.
The site itself also delivered complications and surprises. For the foundation hole, the builders had to use hydraulic hammers and excavators to remove the underlying sandstone. Blasting would have saved about a month on the construction schedule—but might have disturbed the mating of mice in nearby laboratory experiments. Utility lines turned up everywhere and, at one point, 2,700 Science Hill phone and data lines hung from the tooth of an excavator bucket; miraculously, they did not break. Contractors had to bridge excavations with steel beams and use belts to suspend working steam lines in mid-air. It looked at times like an M.C. Escher drawing or a scene from Lord of the Rings. A hole 40 feet below the old power plant, where steamfitters had to work in a tunnel crammed with heating pipes, got dubbed the “Pit of Despair.”
Because all available space was under construction, equipment and supply deliveries had to be tightly scheduled, with big tri-axle trucks lumbering into the site along a treacherous track named “the Ho Chi Minh Trail.” Waste material had to be hauled away and spread out in a parking lot for sorting. That cost an extra 30 percent, according to Meyer, but vouchers showed that 97 percent of waste was eventually recycled.
Throughout the construction process, the shell of the old power plant stubbornly survived, as both an aid and an obstacle to the new project. The fire marshal had ruled that OML needed a fire exit on its north end, right into what was scheduled to be a deep excavation. The design team finally hit on the idea of keeping the power plant roof intact as a sort of stepping stone and building a bridge across to it from the OML fire exit, with a stair from the power plant roof down to the street. But keeping the power plant structure intact also complicated everybody’s life. It meant that the piazza, which now forms such a stately entrance to Kroon Hall, had to be built in the tight space beneath the roof, with the concrete forms supported by a forest of posts carefully positioned amid the steam lines underneath. Finally, near the end of the job, the last remnants of Speth’s “dire PSPP” went away. Only a roomful of pipes and power lines now lies beneath the piazza.
The worst moment in the construction of Kroon came in March 2008, when a contractor went for a permit to drill three geothermal wells on the north side of the building. The wells were to be the building’s main source of heating and cooling, with Yale’s conventional utility lines hooked into the building only as backup. Occupancy was just nine months away. The city had earlier granted permission for the contractor to drill a test well 1,500 feet deep on the site. But now officials said the wells needed to be 75 feet from septic and other utility lines, just like drinking water wells. The ensuing legal battle lasted into November.
Yale had already gone to unusual lengths not just in commissioning a geo-thermal system for such a large building, but also in revising its plan to reduce the likely environmental impact, according to Kathleen Dorsey, an engineer with the design firm Haley & Aldrich. Geothermal systems work by drawing water up from underground, where the temperature remains constant year-round at about 58 degrees. Ground source heat exchangers pull the thermal energy out of the water and into the building. In the initial design, water running through the system would have been bled out as wastewater, a standard practice, but hardly sustainable. Most people “just assume the groundwater is going to be there,” said Dorsey. Yale sent the plan back for revision, resulting in a system that would return the water to the same wells from which it had come.
All it needed was the wells. But now it had to abandon the test well and decide whether to try four new well sites in Sachem’s Wood at an extra cost of $500,000. Alternatively, F&ES could simply rely on the university’s existing utility system and resign itself to depending largely on fossil fuels. “Any other client would’ve said, ‘Just hook it up to the house system,’” said Ted Tolis of Centerbrook Architects. “It was up to the dean to say, ‘This building has to operate on its own, whatever it takes.’” Centerbrook’s Mark Simon added: “Even when Rick Levin says from the top, ‘I want this to be a super-sustainable building,’ you still need very strong people to make that happen, because all kinds of impediments get in the way.” Speth went to Levin and the Yale Corporation and won approval to spend the extra $500,000.
“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.”