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Skidmore, Owings & Merrill: using laminated glass across three continents

Founded in 1936, Skidmore, Owings & Merrill LLP (SOM) has offices in New York, Washington, Chicago, San Francisco, London and Hong Kong. Senior SOM partners Roger Duffy, Brian Lee and Craig W. Hartman - and the firm's technical director, Keith Boswell - granted LGN interviews on SOM projects across three continents of the world.

Filtered light, acoustic, seismic and security benefits at San Francisco International Airport

Craig Hartman

Ceramic frit is incorporated into the laminated and insulated glass façade to reduce glare and heat gain.

SOM Design Partner Craig Hartman told LGN: "Simplicity, transparency and natural light are three of the defining qualities of the interior space at San Francisco Airport's International Terminal."

The west facade

The terminal's enormous welcoming west façade is all of laminated glass. The facade changes character according to the times of day and year. And each day it has to screen the strong, setting west sun. Hartman explained: "A ceramic frit in a basket-like weave is incorporated into the laminated and insulated glass façade to reduce glare and heat gain."

Yet while being a wonderful conduit and filter for light, the laminated glass in the west façade also plays important acoustic, seismic and security roles in the overall structure of the building.

SOM Technical Director, Keith Boswell said: "For functional reasons, we chose to use laminated glass for the façade. It provides much better acoustics than simple IG units because of the properties of the PVB and reduces jet noise. Safety issues were even more important. We factored in possible heavy seismic loading by designing each glass panel to take part of the movement in a repeating, unitized curtainwall, rather like the scales of a fish. The 'fish scale' structure allows the glass façade to accommodate seismic forces by taking the overall building movement in smaller components; the scales give a margin of flexibility. Even if there is some glass breakage, the glass will stay in the frame instead of showering on people. Blast resistance was another major factor; the Oklahoma City bomb tragedy occurred just as we were completing the drawings."

Boswell continued: "The exterior wall is a custom, unitized curtainwall using the following construction: insulated and laminated glass with a horizontal frit pattern on the no.2 surface, Low-E coating on the no. 3 surface and a vertical frit pattern on the no. 5 surface. The inboard lite is laminated with clear PVB. The letters of the San Francisco International logo, created by SOM's director of graphic design, Lonnie Israel, were created by using a dark grey frit on the no. 2 surface, stopping the frit lines two inches from the letters and using a white frit on the no. 5 surface."

Skylights

Skylights open the airport to the light.

Hartman said: "The silhouette of the airport is wing-like and evocative of flight. The roof form is based on a double cantilevered truss concept. The nature of the skylight responds to the truss design, incorporating very long, thin slivers of laminated glass over the double cantilever trusses and flattened ellipsoid-shaped skylights over the central, bowstring trusses. The large, diameter top tube of the cantilever trusses bounces the light back onto the underside of the roof, admitting a diffused light to the interior. The skylights literally open the airport to the light.

"With such extensive skylighting we had to avoid any possibility of glare. James Carpenter of New York designed an installation of translucent tensile scrims for the broad central skylights that solves this problem. The scrims diffuse the light and register changing shadows cast by the structure on their surface like cinematic screens. A margin of dichroic glass around the edges breaks the direct sunlight into prismatic bands of changing coloured light that project onto the walls, floors and travellers moving through the space. The roof and its skylights create a dynamic space; the patterns of the clouds and the moods of the weather are brought inside, continually transforming the experience of the terminal interior.

"For many people, San Francisco Airport's international terminal is their first experience of the United States. SOM and our joint venture partners have used today's most sophisticated building technologies, particularly laminated glass, to make that experience truly memorable."