Ben van Berkel of UNStudio didn't have to look far for inspiration when the city of Chicago commissioned his firm to design one of two pavilions (Zaha Hadid Architects has designed the other one) in honor of the 100-year anniversary of Daniel Burnham's famous Chicago plan: It was all right there before him in brown ink on sepia-toned paper. Burnham's map opened up the teeming city of 1909 by slashing its orthogonal grid with avenues that ran diagonally out from the center of town. Berkel's pavilion has a square floor and ceiling, which is scooped in parts to form a supporting structure. These drooping elements open up vistas of the city and allow for a roofed structure without walls that invites the public to step aboard.

Continuing these civic-minded gestures, lighting designer Tracy Dear of DEAR Productions and artist Daniel Sauter were asked to devise an interactive lighting scheme that would engage visitors. “The question was how to get the light in without creating a lot of light pollution in the surrounding foliage,” explains Dear, referring to the nearby trees of the installation's Millennium Park location. “The solution is what I call a ‘light sandwich,' which goes between the roof and the floor of the pavilion.”

The designers embedded 42 LED uplights into the structure's floor, each containing 36 1W color-changing LEDs. While Dear wanted to custom place the luminaires to best obtain an even distribution of light, UNStudio had another idea. The firm insisted on a rigid six-by-seven grid to further reference Burnham's plan. In answer to this demand, the lighting team varied the beam spreads: They removed the lenses on the fixtures in the center to achieve the widest beam-angle distribution possible, and narrowed those on the perimeter to 30 degrees. Frosted glass rings, set in the floor plane and 3 inches above each recessed light source, diffuse the beams to avoid creating hot spots on the pavilion's white-painted surfaces.

The entire system is wired serially, both for power and data, which proved a boon when integrating it into the congested steel and plywood framework of the pavilion floor. Each luminaire is outfitted with a motion detector, and sets off a scroll of color throughout the pavilion when activated. The color-changing evolves slowly so as not to become muddy and confused. The color palette was derived from Burnham's plan, which is based on the tones of a century ago: muted green and blue, burgundy, and orange. The LEDs provided enough range to match these hues fairly well, and the fact that they generate substantially less heat than conventional light sources put to rest concerns that hot lamps might burn visitors. “We had to use all LEDs,” said Dear. “Their energy efficiency and color rendering properties can't be beat. They're the only source that makes sense at this point. Burnham would have encouraged that.”

Project Burnham Pavilion, Chicago
Design Team UNStudio, Amsterdam (design architect); Garofalo Architects, Chicago (architect of record); Third Coast Construction, Chicago (fabricator); Rockey Structures, Chicago (structural engineer); DEAR Productions, Chicago (lighting design); Daniel Sauter, Chicago (interactive lighting concept)
Photographer Ben Dickmann. Images courtesy Iluminarc
Project Size 6,400 square feet
Manufacturer Iluminarc