Manufactured in Belgium by Saint-Gobain Glass, the strong, resilient, and unusually clear glass used in the Janelia Farm landscape building was fabricated in one large factory run. Because structural glass is rarely called for, Saint-Gobain makes production runs only twice a year. In this case, the request was for a lot of glass.

"As volume of load-bearing structural glass goes, this will be the largest such glass installation in the world, as far as I know," says Charles Blomberg, the architect in building-designer Rafael Viñoly's firm who is responsible for the building's "skin." Blomberg has worked with Viñoly on a number of glass-dense architectural projects around the world.

Manufacturers began adding iron to glass in the 1950s to give windows a green tint (too many people were walking into them) and to make the glass flow better during production. Iron is taken out of the formula for glass that needs to be very clear, such as that used in museums and jewelry display cases—and in the glass used at Janelia Farm. Laminating together multiple panels of low-iron glass creates exceptional strength without a loss of clarity, says Blomberg.

The lamination, solar coating, and other assembly processes required to ready the glass for its particular use in the Janelia Farm landscape building took place at multiple sites in Europe, Canada, and the United States. Nine months of exhaustive performance testing at a site in Pennsylvania assured that the glass is suitable for load-bearing use and that the laminated slabs are able to withstand extremes of factors such as wind, temperature, moisture, air pressure, and impact.

In addition to weight-bearing tests designed to mimic heavy loads from snow and wind, reports Blomberg, there was a series of movement tests, where the mock-up corridor assembly was strongly rocked to simulate severe building movement. Thermal cycling tests evaluated the capacity of the glass to withstand extreme differences between outdoor and indoor temperatures. To test how the glass and joints might stand up to varying wind and air pressures, the mock-up was placed inside a hydrostatic chamber equipped with devices to either push air in or suck it out. "The pressure inward was equivalent to a 110-mph wind," says Blomberg. "And the suction test was actually more onerous than anything the building would experience in real life."

In devising the tests, the team of designers and contractors imagined all manner of worst-case scenarios. One concern was the possibility of a heavy lab cart rolling into the glass. So they created a 100-pound concrete-filled steel cylinder six inches in diameter and hung it from a pendulum. They drew the chunk back as far as possible and let it fly at the glass corridor mock-up. "The force of the blow was somewhere around 400 ft/lbs," says Blomberg, "The whole corridor assembly shook, but the glass wasn't fazed."

To ensure absolute confidence, the team pushed the glass beyond specified requirements in most of their tests. They even broke the glass, to see what the overall impact would be when different layers were broken and under different loads. "We took it to the next level, what is called the Ôfailsafe mode,'" says Chris Fiato of Enclos Corporation, the specialty glass subcontractor working on the project. "We wanted to know if we could ever get a catastrophic or progressive failure. We never did."

—Mary Beth Gardiner

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Reprinted from the HHMI Bulletin,
Winter 2005, pages 30–33.
©2005 Howard Hughes Medical Institute