The PT system was not the only one that called for intense engineering. The unitized curtain wall has 12 systems instead of two or three. These include kinetic blinds, cold-warped glass, operable windows, sloped glass, interior metal light shelves, interior shades with valance boxes and more. The job ranks as the third most complicated building skin "we've ever done," says Jeremy Mucha, vice president of engineering for Benson Industries LLC, Portland, Ore. "That's why we put our A-team on this job."

Of 2,295 curtain-wall units, 880 are unique. For every drawing package, "you can fabricate about three units, which means there is no economy of scale," Mucha adds. The 145,000-sq-ft curtain wall costs $151 per sq ft. Most jobs in San Francisco with two or three wall types cost about $90 per sq ft, says Mucha.

Rossie says the challenge of the SFPUC job isn't in any one individual system; rather, "it is how many new or unique techniques have been combined. The project has touched the boundaries of the amount of sustainability you can apply to a project and still remain commercially viable," Rossie says. "The cost per square foot is significantly higher than any other commercial office building" in the area, he adds.

However, the SFPUC didn't want an ordinary building; it wanted to set an example for sustainable commercial development. "From an asset-preservation standpoint, we get a 100-year building," says DPW's Mebrahtu. "We are very happy with it."