Page B3.2 . 03 February 2010                     
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    Cambridge Public Library

    continued

    "The main facade faces southwest," says Clifford Gayley, a principal at William Rawn Associates. "An ordinary curtain wall simply could not have pulled it off."

    The double-skin system consists of inner and outer glass walls separated by a three-foot- (0.9-meter-) deep multistory flue cavity — a passageway for directing air currents that works like a household chimney. Two types of devices shade the facade: glass "visors" mounted on the exterior, and operable aluminum louvers within the cavity, the latter controlled by a computer.

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    A damper at the bottom of the flue cavity and exhaust vent at the top enable seasonally tailored operation. In winter, the damper and vent are closed to trap air, which then heats up inside the cavity, creating a thermal barrier. The operable louvers are closed to reduce glare from low-angled sunlight.

    In summer, the operable louvers are repositioned to catch high-angled sunlight, heating the cavity while shading the building interior. The warming air rises and leaves the cavity through the open top vent, creating a chimney effect that draws cooler air into the cavity through the open lower damper. The glass visors direct light inward while limiting the direct sunlight hitting the glass.

    In spring and fall, operable windows and modulation of temperature in the cavity allow patrons to enjoy these two favored New England seasons.

    Projected to afford a 50-percent reduction in energy use compared to a conventional curtain wall, the facade also conveys the kind of welcoming transparency sought by the City of Cambridge. "The symbolism of glass as being open and inclusive, almost bringing the adjacent park into the building, was very powerful," Gayley says.

    Other Sustainable Features

    The double-skin facade is only the library's most conspicuous sustainable feature. An open asphalt parking lot was replaced by a garage, built directly under a new children's garden and play area that serves a planted roof, reducing the heat-island effect of the complex. The 33,000-square-foot (3,100-square-meter) intensive green roof includes four inches (ten centimeters) of soil to allow tree planting.

    Finishes low in volatile organic compounds (VOCs) were used in the interior, along with water-conserving toilets and occupancy sensors for lights, and a new 400,000-gallon (1.5 million-liter) system manages stormwater for the neighborhood.

    Quest for a Seamless Solution

    William Rawn Associates and Ann Beha Architects collaborated from the very beginning on where to site the new wing and on overall programmatic configurations.

    "There was a lot of discussion of what went 'here' versus what went 'there,' of old and new," says Pamela Hawkes, a principal at Ann Beha Architects. "There was a real desire to make this a seamless building."

    That seamlessness was achieved by dividing the new wing into four programmatic zones, which Gayley calls "bars," running lengthwise and parallel to the double-skin wall. Bars 1 and 2 contain seating areas and open book stacks. Bar 3, in the center, acts as a Main Street, containing circulation and service desks and connecting the addition to the historic wing, which is largely given over to reading areas and computer spaces. Bar 4 contains such specialized spaces as a silent study room and the Cambridge Historic Collection.

    "I wanted every inch of the library to be usable," says Susan Flannery, public library director for the City of Cambridge, who describes herself as an "opinionated client." Flannery has a particular interest in library architecture, having written an undergraduate thesis on the topic at the University of Pennsylvania. "I did not want part of the building to be 'historic' and not used, like a mausoleum," she says.

    No mausoleum, the interior of the original building has the warm, cozy, quiet ambience that one might associate with a New England Athenaeum. The main reading room has warm oak paneling and exquisite oak ceiling joists, all restored to their original condition. The building's rear apse, formerly used for offices and storage, now accommodates the Young Adults Room and Lounge, somewhat isolated from other spaces.

    The project also included restoration of the original facade of brownstone and granite, including repair of the west facade after removal of a modernist 1967 addition that had obscured and damaged important Romanesque detailing.

    Warm Addition to Cambridge

    The new library is only three blocks from the campus of Harvard University. Despite its proximity to this elite academic neighbor, the library serves an increasingly diverse city of about 100,000 residents. One challenge for both administrators and architects was to reach out to a surrounding residential community known for its fierce resistance to change.

    "We brought the community in at every stage of the project, which lasted more than a decade," reports Flannery.

    On a recent Saturday afternoon in late autumn, the atmosphere around the circulation and information desks was lively and cordial; patrons and employees alike seemed energized by the light-filled space. Toddlers played on the stairway, teenagers flirted in their designated room, and tweedy Harvard professors enjoyed the quiet of the reading room.

    Meanwhile, viewed from the outside, the building seemed to say, "Come in and enjoy."   >>>

    Discuss this article in the Architecture Forum...

    James McCown is a freelance writer based in Somerville, Massachusetts.   More by James McCown

     

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    ArchWeek Image
    SUBSCRIPTION SAMPLE

    While the historic stone building is introspective, the new Cambridge Public Library addition engages its surroundings by way of expansive glass facades.
    Photo: © Robert Benson Extra Large Image

    ArchWeek Image

    The long southern facade features a high-performance double-glazed curtain wall system, with both aluminum and glass shading devices.
    Photo: © Robert Benson Extra Large Image

    ArchWeek Image

    The double-glazed facade stands above a trench with an operable damper, allowing for fresh air intake in the summer to induce cooling through convention.
    Photo: © Robert Benson Extra Large Image

    ArchWeek Image

    Axonometric diagram of facade glazing in summertime "cooling" mode.
    Image: William Rawn Associates Extra Large Image

    ArchWeek Image

    Cambridge Public Library ground-floor plan drawing.
    Image: William Rawn Associates Extra Large Image

    ArchWeek Image

    During construction, a series of manufactured metal frames was fastened to the main structural system to support both layers of the double-skin facade and the shading visors.
    Photo: Courtesy William Rawn Associates Extra Large Image

    ArchWeek Image

    The inner glazing layer was installed first, leaving much of the repetitive frames exposed.
    Photo: Courtesy William Rawn Associates Extra Large Image

    ArchWeek Image

    A horizontal glass visor shades the lower half of each floor's curtain wall.
    Photo: Courtesy William Rawn Associates Extra Large Image

     

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