Continuing our coverage of the 2014 AIA COTE Top Ten green projects, this article is part of a series of 10 pieces that examine a specific, defining design challenge or innovation of each of this year's winners.
The competition brief for the John and Frances Angelos Law Center at the University of Baltimore said nothing about a 20,000-square-foot atrium rising 12 stories through the full height of the building. Yet this tall, narrow atrium, which opened in 2013, is a signature element of the winning design by Behnisch Architekten with Ayers Saint Gross (ASG). The architects successfully pitched the atrium’s ability to improve the interior environment through daylighting and ventilation, and to serve as a “social engine” facilitating communication among students and faculty, says Robert Matthew Noblett, AIA, a partner in the firm. One of the five jury members who selected the Behnisch and ASG plan in 2008, James Polshek, FAIA, referred to the naturally lit, shaft-like space as a “green stalk.” The botanical metaphor was apt, and the name stuck.
The atrium regulates fresh air and light throughout the 192,000-square-foot building. The natural ventilation system, activated during mild weather, creates a pressure differential between the atrium and the surrounding spaces, and the passive thermal chimney or buoyancy effect of the atrium is augmented by the slow spinning of the smoke exhaust fans in the roof, pulling air up and out of the building. Indicators prompt occupants in the surrounding offices, classrooms, and library to open their windows, resulting in a gentle cross-breeze. During hot or cold weather, with windows closed, a mechanical system delivers conditioned air to the cellular spaces—and that air percolates into the atrium. The ventilation air does not bear the primary responsibility for heating and cooling, which is handled by radiant tubing embedded in the building’s 11-inch-deep slabs.
But if all of these spaces are sharing air, how do they maintain acoustical and fire separation? The project required a special wall detail that is rare in the U.S., but not uncommon in Europe, Noblett says. A slot in the drywall admits air into a concealed box containing a labyrinth of acoustic insulation. The air, pulled by the pressure differential, escapes into the atrium from a slot on the opposite side of the wall.
Behnisch custom-fabricated its own version of the device using ordinary sheet metal and acoustic insulation components. A similar device is used where transparent glass partitions separate the atrium from faculty offices. Louvered grilles in the ceiling allow air to pass from one side of the glass to the other, but fire dampers automatically close the louvers when a spike in heat is detected.
The interior glazing allows natural light from the atrium’s curtainwall—itself shaded by external louvers—to penetrate deeper into the building. Transparency between private offices and public areas allowed for a comprehensive daylighting strategy with lower electricity consumption, Noblett says. It also put the activity of the building on display, creating visual connections that animate the atrium and its cascading platforms and stairs.
Note: This article has been updated since first publication to include Ayers Saint Gross was a partner architect on the project.