Yale Opens Ultra-Green Kroon Hall

Yale University has completed construction of a new ultra-green building—designed to use 50 percent less energy than a comparably sized modern building—for its School of Forestry & Environmental Studies (F&ES). Kroon Hall achieves its remarkable energy savings from a host of design elements and technical strategies molded to fit the building’s New England weather and climate.

“Yale’s most sustainable building to date reflects the School’s mission and the intellectual passion of its faculty and students,” said Yale President Richard C. Levin. “It is an extraordinary design, and we hope its energy-saving concepts will be emulated widely and inspire others to advance green building even further.”

Designed by Hopkins Architects of Great Britain in partnership with Connecticut-based Centerbrook Architects and Planners, the new $33.5 million home for F&ES is expected to achieve a platinum rating in the green-building certification program, Leadership in Energy and Environmental Design (LEED).

“More than a decade ago, the School of Forestry and Environmental Studies set out to achieve an unconventional—even audacious—agenda, focused on building social capital, breaking with the past, and speaking to the future of environmentalism,” said F&ES Dean Gus Speth. “We wanted a healthy place to study and work, but also wanted to bridge the gap between nature and people even in the middle of the city. We have achieved that with this very special place. Our thanks go to Deputy Dean Alan Brewster and Professor Stephen Kellert. Their inspired leadership and hard work made possible a new home for the School that expresses in physical form our best traditions, values and aspirations.”

The building, located in the area of the University known as “Science Hill,” is named for the family of benefactor and Yale College alumnus Richard Kroon. Providing 56,467 square feet of space, it is 57 feet wide and 218 feet long. With its high barrel-vaulted gable ends, simple lines, and curved rooftop, Kroon is a modernist blend of cathedral nave and Connecticut barn.

“Kroon Hall is on course to be among the greenest buildings in the United States,” said Hopkins Director Michael Taylor. “True sustainability, however, is about more than improved quantitative performance. We have striven to create a piece of contemporary architecture that belongs in the context of the historic Yale campus. We think it will encourage interaction among its occupants and stand up to several generations of intense use. Using natural materials, such as Briar Hill Stone and red oak from the University’s own sustainably harvested forests, we have tried to create a building that is warm in character, a place where the school will instantly feel at home. Seeing how the faculty, staff, and students have immediately adopted the building is very satisfying.”

The building’s tall, thin shape and east-west orientation provide most of the heating and cooling. The lowest floor is set into a hillside, with only its south side exposed, providing thermal insulation, minimizing northern exposure, and increasing the amount of natural light that enters the building from adjacent courtyards. The long south facade maximizes solar gain during the winter, and Douglas fir louvers covering glass facades on the east and west ends keep out unwanted heat and glare. The building’s shape, combined with the glass facades, enables daylight to provide much of the interior’s illumination. Light and occupancy sensors dim artificial lighting when it is not needed.

Half of Kroon Hall’s red oak paneling—15,000 board feet—came from the 7,840-acre Yale-Myers Forest in northern Connecticut, which is managed by the School and certified by the Forest Stewardship Council and the Sustainable Forestry Initiative. Kroon’s pale yellow exterior, composed of sandstone from Ohio, echoes other Yale buildings.

A 100-kilowatt rooftop array of photovoltaic panels will provide about 25 percent of the electricity for the building. Four 1,500-foot-deep wells use the relatively constant 55-degree temperature of underground water to heat and cool the building, replacing the need for conventional boilers and air conditioning in the all-electric building. Four solar panels embedded in the southern facade provide the building with hot water. Renewable Energy Certificates will be purchased to provide the additional electricity needed for the building, reducing to zero the greenhouse gas emissions from Kroon Hall’s operation. The estimate of Kroon Hall’s energy use compared to a typical modern building is based on standards set by the American Association of Heating, Refrigerating and Air-Conditioning Engineers.

Exposed concrete walls and ceilings provide thermal stability by retaining heat in winter and cooling in summer. Fifty percent of the concrete mix is blast slag, a postindustrial recycled material. Instead of air being forced through overhead ducts, an energy-saving displacement ventilation system moves warm and cool air through an air plenum and multiple diffusers in elevated floors. Low-velocity fans in the basement keep the air circulating throughout the building.

In winter, the ventilation system also transfers the heat from exhaust to incoming fresh air. In summer, the system uses the exhaust air to cool the incoming air. In mild weather, Kroon’s occupants assist in the ventilation by opening windows in response to an electronic, color-coded prompt system.

A rainwater-harvesting system channels water from the roof and grounds to a garden in the south courtyard, where aquatic plants filter out sediment and contaminants. The grey water, held in underground storage tanks, is then pumped back into Kroon for flushing toilets and is used for irrigation. The system is expected to save 500,000 gallons of potable city water annually and to reduce the burden on city sewers by lessening the amount of storm runoff. A single driveway brings all vehicle traffic into a service node beneath the south courtyard, centralizing all pickups for trash and recycling and deliveries for the southwest corner of Science Hill.

The building’s north and south courtyards add greatly to Kroon Hall’s attractive environment for work and study. Centerbrook architect Mark Simon said the courtyards are almost as important as the building itself in creating a community from disparate buildings on Science Hill. “The courtyards are quintessentially Yale,” said Simon. “We wanted to create great outdoor spaces where people want to go. For the first time in a century, people passing through the arch at Osborn Memorial Laboratories have a destination.” The south courtyard is a raised platform, with a green roof of soil one-foot deep. Olin Partnership of Philadelphia landscaped the courtyards with 25 varieties of native plantings.

President Levin directed in 2005 that Yale reduce its greenhouse gas emissions from its facilities by 43 percent within 15 years. The University is making progress toward its goal through green construction such as Kroon Hall, campus-wide conservation measures, and renewable energy projects.

The Yale School of Forestry & Environmental Studies is a professional and graduate school that offers master’s degrees in environmental management, environmental science, forestry, and forest science, as well as a doctoral program, and serves as a locus for research on local, regional, and global environmental issues. The school, established in 1901, provides a broad-gauged educational experience that equips its graduates to assume influential roles in government, business, nongovernmental organizations, public and international affairs, journalism, research, and education.