Hopkins Architects’ elegant Kroon Hall houses Yale University’s brightest ecological thinkers in suitably green surroundings. Hattie Hartman assesses the AJ100 Building of the Year. Photography by Morley von Sternberg
Any architect who builds at Yale University is in good company. Its campus in New Haven, Connecticut, is a who’s who of modern masters: two art galleries by Louis Kahn, an ice hockey rink and student residence halls by Eero Saarinen, and Paul Rudolph’s Art and Architecture Building. Hopkins Architects beat two other shortlisted European practices - German firm Behnisch Architekten and English practice Short and Associates Architects - to win the commission for Kroon Hall, a new building for Yale’s School of Forestry and Environmental Studies, previously scattered over eight different buildings. The £23.2 million building, which completed last year, is certified LEED Platinum.
Hopkins faced a triple challenge: the creation of a new home for the school’s 50-odd staff, which would foster a sense of community among independently minded professors; the design of an explicitly sustainable building to demonstrate the university’s commitment to low-carbon design; and the transformation of a brownfield site containing two car parks and a decommissioned power plant into an attractive entrance to a quadrangle of science buildings at the northern end of the university campus.
Hopkins chose to play it straight, respond-ing to the orthogonal site plan of neighbouring neo-gothic buildings with simplicity of form, matching eave heights and contextual materials. The 66.5 x 16.5m building - kept narrow for cross-ventilation - is clad in Ohio sandstone and nestles its northern flank into the sloping site, creating courtyards on either side. The symmetrical section of this highperformance building surprises, and only the extensive photovoltaic (PV) array on the massive arched roof hints that more is going on behind this understated exterior.
A piano nobile tucked up under the glulam roof structure is the building’s tour de force. ‘Seeking natural light and views, we took every element of the brief that we could find and stacked them on top,’ says Mike Taylor, senior partner at Hopkins. That included an auditorium, two seminar rooms, an informal study zone with a café and an environment centre that hosts both university and external events. Panelled in exquisitely detailed red oak, largely from Yale’s own nearby forests, the space exudes warmth and feels equally comfortable when occupied by a large conference or a handful of students on a study break. Dappled light filters through the rooflight PVs and the fixed timber louvres on the two end facades, animating the space. The delight in craftsmanship recalls naval architecture, or inverted timber church roofs built by sailing communities.
A piano nobile tucked up under the glulam roof structure is the building’s tour de force
Kroon Hall does not flaunt its LEED Platinum credentials. In an unusual teaming, Atelier Ten worked as sustainability consultant alongside Arup services engineers. Operational energy loads have been reduced to a minimum through passive design. Atelier Ten’s Paul Stoller cites the building’s high-performance envelope as its most noteworthy feature. Deeply recessed windows are punched into the long north and south facades, while the building’s glazed short ends are protected by fixed timber louvres, controlling east and west solar gain. The building’s average glazing ratio is an astonishingly low 31 per cent.
Mechanical ventilation, essential for New Haven’s hot humid summers and cold winters, switches off automatically during the spring and autumn ‘shoulder’ seasons, and red and green lights signal when windows may be manually opened. Acoustic transoms over the doors allow cross-ventilation without sacrificing privacy. A service zone for Kroon Hall and three neighbouring buildings is tucked under a green roof in a corner of the site.
Kroon Hall’s entire heating and cooling load is supplied by ground-source heat pumps connected to four 450m-deep boreholes, while the PV array carries roughly 25 per cent of electrical loads. To meet accepted LEED protocol, Yale has purchased carbon credits to offset the remaining loads.
The building incorporates numerous other features common to green buildings, such as raised floors, heat recovery and low-energy lighting. Over 2,400 sensors measure temperature and CO2 levels; a concrete structure, rare in New England, is exposed internally on lower floors for thermal mass; and toilets flush with rainwater. The university is monitoring Kroon’s performance but has not yet released figures. Performance data is critical to understanding this building, and hopefully it will be forthcoming.
Kroon Hall deals masterfully with its context and creates a sense of place for a school that previously had none, fostering interaction between students and faculty members as diverse as environmental lawyers and biometeorologists. Its most memorable space is the timber-lined top floor, with its nave-like ceiling, filtered natural light and long views. Clearer external expression of this lofty internal space might have added subtle visual interest to the building’s exterior and
softened its monolithic roof form.
The building’s quality and durability - it boasts a 100-year life span - contribute to its long-term sustainability and form part of a university-wide strategy. To date, Atelier Ten has worked on about 35 buildings across the campus to slash their energy consumption and help the university meet greenhouse gas-reduction targets established in 2005. Commissioning a building of Kroon Hall’s calibre as the centrepiece of that strategy is an excellent start for Yale - one that other institutions might emulate.
For more on Kroon Hall’s environmental strategy and green specification visit ajfootprint.com
Start on site March 2007
Contract duration 22 months
Gross internal floor area 6,208m2
Form of contract Guaranteed maximum price
Total cost £23.2 million
Client Yale University
Architect Hopkins Architects
Structural and services engineer Arup
Sustainability consultant Atelier Ten
Quantity surveyor Turner Construction
Planning supervisor Centerbrook Architects
Main contractor Turner Construction
Selected subcontractors and suppliers OLIN (landscape), Nitsch Engineering (civil engineer)
Annual CO2 emissions 113kg/m2