At the push of a button, San Francisco City Hall has a lighting scene ready for any occasion…starting with its centennialBy Paul Tarricone
The deadlines are hard and fixed for a centennial celebration—“101st anniversary” just doesn’t have the same ring to it—so there would be nowhere for city officials and their local design team to hide if San Francisco City Hall wasn’t ready for the party in its honor. The city, quite literally, was watching. Ultimately, the thousands gathered in Civic Center Plaza in June 2015 went home happy, as color-changing LED lighting and a 3D projection show helped mark City Hall’s 100-year milestone.
And what a party it was. As dancers rappelled from the building, a multimedia presentation played across the building’s façade. The show began with a stunning re-creation of City Hall’s collapse during the 1906 San Francisco Earthquake, followed by a timeline illustrating the city’s history since the new City Hall emerged from the rubble in 1915 (would you believe Martin Luther King Jr. and Jefferson Airplane in the same video sequence?).
Nearly two years in the making, the multimedia extravaganza was produced by Obscura Digital. The second and more permanent piece of the centennial celebration—new LED lighting—was the work of Arup, which earned a 2017 IES Illumination Award of Merit for an upgrade that accentuates the upper dome and columns. Obscura and Arup collaborated on the timeline theme and pitched it to the city, explains Toby Lewis, senior lighting consultant at Arup. The objective was to sync the lighting scenes to each video snippet (e.g., the Pride Celebration, the baseball Giants coming to the city) for maximum aesthetic effect.
Once the plan was greenlighted, Arup had only eight months to complete the design and ensure delivery of bespoke fixtures from Color Kinetics. “It was the bare minimum amount of time needed to execute a project like this well, particularly with a custom modification to a fixture,” notes Lewis. “The standard Color Kinetics’s Reach luminaire has two large LED boards using the same chips. In our case we needed the flexibility of having great white color with color-changing capabilities,” meaning one board was to produce 2700K-4000K light (to approximate the previous 3000K metal halide) and the second board would produce the RGB illumination. Four fixture types in two form factors were specified. To keep the chip sourcing as coordinated as possible, one manufacturer was selected. To meet the deadline for the centennial event, the fixture order was issued before construction documents were completed.
TRANSITION TO LED
Illuminating San Francisco City Hall in RGB light for celebrations or civic functions was standard operating procedure even prior to the upgrade. Work crews, however, had been expending roughly 6,000 hours in labor per year to manually install and remove theatrical gels to each of the 220 metal halide fixtures. The annual cost to do this roughly every other week was $8,000.
Aside from the labor savings, slashing energy use was the second impetus of the upgrade. With the new LED floodlights, the building will either be bathed in white light or colored light. Lewis points out the fixtures are never on at 100% output, and no more than 50% of the LED chips at each mounting location are ever on in any one scene. The result is an estimated 50% reduction in daily energy use from the 31,600-W connected load of the metal halide system to 14,120 watts using LED luminaires. Adding to the energy savings is the expected lifespan of the LED fixtures. The metal halide luminaires had a rated lifetime of 4,000 hours, at approximately eight hours of use per day. The LED fixtures’ lifetime is projected at 50,000 hours. As a result, the LED system is expected to yield an 80% reduction in total exterior lighting cost over the life of the project.
The luminaires are mounted in four areas on City Hall in a tiered “layer-cake” formation, as Lewis describes it. In ascending order, they’re positioned on the second-story balconies; the roof (where projectors are aimed at the dome); the colonnade (below the dome) and at the lantern (or crown) level above the dome.
https://youtu.be/h5xOwvJdbJc
While the city wanted there to be a “reveal” during the centennial event, on-site mock-ups were necessary in advance of the unveiling. “Ultimately, we couldn’t prevent passersby from seeing the mock-ups, but they were fairly limited—only two balconies at a time,” says Lewis.
White light is the default color on City Hall, supplemented by color-changing schemes for holidays and other civic celebrations. Lewis notes that there was trepidation about “having a lot of flashy, fast-moving color chases. The building is closer to the ground than other landmark buildings—the Empire State Building, for example—so there was more concern about the effect on drivers.”
Naturally, there were no motorists near City Hall on the night of the centennial, and Arup staff had a particularly good view of the festivities. Says Lewis, “We took a team and had dinner on the plaza.”
THE DESIGNER
Toby Lewis, LC, Member IES (2017), is a senior lighting consultant at Arup, San Francisco. In 2018, she was named to Lighting magazine’s “40 Under 40” list of designers.