University of Baltimore
To win the commission for the recently completed John and Frances Angelos Law Center at the University of Baltimore, Behnisch Architekten, Boston'in partnership with architect of record Ayers Saint Gross'gave daylight a starring role. The design employs building skins of varying porosity and massing to represent the programs housed within the 190,000-square-foot, 12-story structure: punched windows within rainscreen cladding demarcate classrooms and offices; a fritted library volume reaches the staggered mass's full height; and all other rooms surround an extensively glazed atrium through which they visually communicate.
Daylight guided the design from inception. 'Building dimensions, setbacks, and transparency of materials were key to achieving the highest possible daylight factor,' says Behnisch partner Matt Noblett of using sunlight to maximize occupant well-being and minimize electricity consumption. Responding to sun angles, Behnisch placed the atrium glazing on a north'south axis, with fixed louvers on the south elevation to minimize heat gain.
Yet even this careful approach to daylighting has its pitfalls, notes Scott Guenther, senior designer at the Washington, D.C.'based MCLA, the project's architectural lighting design firm. Because one's eye assimilates the highest intensity in a field of vision, he says, 'areas deep inside the building had to have higher illumination levels to compensate for the perimeter.' To this end, the MCLA team paid particular attention to spaces near the core on the first seven floors, which receive lower levels of illumination from a modest atrium skylight, despite the extensive glazed walls.
MCLA's solution is based on LEDs. The client was attracted to the light source for its energy efficiency and long life, and because it offered the least visual and thermal disruption to exposed radiant slabs. Combining daylight and LEDs yields an installed Lighting Power Density (LPD) of .76 watts per square foot, about 25 percent better than code, helping Angelos beat ASHRAE Standard 90.1-2007 by 43 percent.
To account for rapidly changing LED technology, the lighting designers wrote performance-based specifications for a custom disc-shaped luminaire to be mounted on ceilings throughout the building. The 1,640-lumen fixture, with a color temperature of 3,000 kelvin, is equivalent in intensity and warmth to a 100-watt incandescent A lamp. From an oblique perspective, the luminaire's acrylic plate emits an even glow; viewed from underneath, the diodes are visible. This honest technological expression embodies Behnisch's philosophy, but it also implies a new LED-centered design vocabulary, says Maureen Moran, MCLA principal.
For the atrium, MCLA created chandeliers of cascading 12-by-18-inch panels made of the same acrylic used for the disc-shaped luminaires. These are suspended on steel cables, with the lowermost parallel to the floor and four others canting at alternating angles, drawing the visitor's eye upward. LEDs within each of the panel's aluminum spines radiate light. 'The chandeliers are about scale,' says Guenther. 'The illuminated surfaces make you perceive the space as having more light.'
MCLA programmed daily themes for the atrium, from dawn to midnight. Photo sensors override the system according to actual conditions, dimming luminaires within 25 feet of the perimeter. 'It's in that zone where you get the most benefit in terms of energy savings,' Guenther says.
Indeed, controls were integral to the LEDs' performance. In addition to photo sensors, the building has 319 wall-mounted passive-infrared occupancy sensors, all wireless, that permit programming and overrides from central or tablet computers. As in the atrium, MCLA created scenes for classrooms. These include dimming for videos, which also prompts motorized interior shades to block the punched windows; the shades otherwise operate independently, according to rooftop solar-radiation readings, and the photo sensor'controlled classroom lights respond in turn.
Lighting Designer: MCLA Architectural Lighting Design
Engineers: Cagley & Associates (structural); Mueller Associates (m/e/p); RK&K (civil)
Client: University of Baltimore
Size: 190,000 (gross) square feet
Cost: $114 million
Completion date: April 2013
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