Kroon Hall Rises
F&ES’ New Ultragreen Home
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.”
Robert Benson Photography
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.