Kroon Hall Rises

F&ES’ New Ultragreen Home

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.

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Robert Benson Photography

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.

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Robert Benson Photography

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.

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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.