When Hopkins Architects was interviewed about designing the new building for Yale’s School of Forestry & Environmental Studies, project director Mike Taylor and Sir Michael Hopkins took the opportunity to look at the university’s plans room. Their aim was to see the drawings for such important Yale buildings as Louis Kahn’s art gallery, but while there they made a discovery that had a vital effect on their design.
“We saw that Yale had its own forests in New England,” Taylor explained. ‘We thought then that it could be a masonry building with a timber lining – and that it could use their own timber.” The result is a building where much of the internal excitement comes from the use of American red oak, on stairs and walls, drawing you up to the most dramatic space on the top floor, and imparting a warmth to the building that might otherwise have been lacking.
Yale had specified that the building, known as Kroon Hall, was to score LEED platinum, the highest category in US eco-building and to go further, to be carbon neutral.
Hopkins’ design has features that are common in the UK, but unusual in the more extreme climate of New Haven, Connecticut, with its humid summers and cold winters. Its approach combines orientation, high thermal mass and good insulation to minimise energy use. There is as much natural light as possible, and an exposed southern façade to allow solar gain in winter, but with shading, made from Douglas fir, to keep out the summer sun. Having kept the energy requirement as low as possible, the building has windows that can open in spring and autumn (red and green indicators show when it is appropriate to do so). The rest of the time the building uses displacement ventilation with heat recovery.
Heating and cooling come from heat exchange with 500m-deep geothermal wells and there are photovoltaic panels on the roof.
If all this sounds complex, the building itself is surprisingly simple: a single, barrel-vaulted structure, two storeys high on one side, three on the other to accommodate a change in level on the site and provide access beneath for service vehicles.
It is initially surprising that the most public spaces are on the top floor, with relatively routine cellular offices below. At the top are an environment centre, classrooms and gathering spaces including a canteen. This was a deliberate attempt to create a new heart for the school, to complement the informal gatherings that can happen outside.
The centrally placed red oak-lined staircase draws people up to this space, its warm patina contrasting enticingly with the cooler exposed concrete finishes. Red oak is used for all the internal timber, with the exception of the Douglas fir glulam beams, and about half of it is from the FSC-certified Tourney forest in north-east Connecticut, the largest of the seven forests donated to Yale in the 20th century.
Previously Hopkins had used only white oak, which it featured in Portcullis House and Haberdashers’ Hall in London. “We were a bit guarded,” said Taylor. “Red is more characterful than white oak and we were concerned that it could look like exaggerated variation.”
When working with timber, Hopkins’ normal habit is to create panels and hang them directly, but at Yale it went with a more American process of using ‘V-line’ boarding – roughly equivalent to tongue and groove, and a cheaper solution in the US.
Hopkins selected the timber, which was all kiln-dried, before specialist contractor Legere Group started installing the boards. Any material with extreme variation, or too many knots, was rejected. The contractor then installed them, deliberately randomly to retain some natural variation. On the upper floor there are three rows of vertical planking at the ends, and an alternation between horizontal and vertical planking on the main entrance walls, with the horizontal element acting almost like a portico.
The stairs also have red oak treads, with non-slip strips set into them, contrasting with the concrete risers and an informal space at the end of the top floor has red oak flooring, including removeable panels so services can be accessed. The overall ambience is a little like a modern, and determinedly non-exclusive, gentlemen’s club. The use of red oak for low-level tables and other furniture adds to the harmonious impression.
After the panelling, the most obvious use of red oak is on the ceiling panels of the vault running the length of the building. Made by Rulon Company, these are of solid formaldehyde-free MDF and contain apertures for lighting and sprinklers. They include an acoustic backing and are finished in red oak veneer and solid red oak edging.
Initially Taylor was concerned about the contrast between the red oak panelling and Douglas fir glulam, but the effect is harmonious. Externally, Kroon Hall is clad in pale yellow Briar Hill Stone, used widely across the campus.
What is most striking about the building is that almost every design decision was informed by an environmental agenda, yet it is a strong, rational piece of architecture that doesn’t proclaim its environmental credentials.
The architect describes it as “a modernist blend of cathedral nave and Connecticut barn”. It is orientated east to west, with the long northern side set into the hillside, and a much more open southern side giving onto a garden.
The concrete structure, exposed internally to provide thermal mass, has 50% of the cement replaced by blast-furnace slag, while low-velocity fans in the basement circulate the air in the displacement system. The hall also includes a rainwater harvesting system. Collected from the roof, the water is filtered by aquatic plants before it goes to underground storage tanks and is used for flushing toilets. The system saves around 500,000 gallons a year.
Even the lift is green, a counterweighted, roped, pit-less hydraulic model, which uses less energy.
On completion of the building in April 2009, Yale president Richard Levin praised it as “Yale’s most sustainable building to date”. And for the students and faculty, what could be better than to be reminded of the subject of their study every time they look at those red oak walls?
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The exterior of Kroon Hall |
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The red oak stairway |
