"It's incredibly challenging to build 800 unique pieces instead of 800 replicas," says Skanska's Senner.

The wall also incorporated approximately 2,500 vertical solar blades for sun shading, which range from 2 to 18 in. wide. Overall, "It's just a beast of a system," Senner adds.

DEC, working as a subcontractor to Trainor Glass, produced roughly 4,000 pages of fabrication drawings, or about 10 times the usual amount for a conventional wall of the same size, says Arani.

The team had to complete design, fabrication and installation within 13 months. That scared off some subcontractors, many of whom estimated it would take about two years.

To meet the schedule, Skanska, DEC, Trainor and Snøhetta collaborated as if they were working under a design-build contract. "We locked ourselves in a room for two weeks and went through every single drawing," says Snøhetta's Rader.

The group displayed each drawing on interactive whiteboards, altering some designs by drawing on the projected images with their fingers. The "finger paintings" were then incorporated into the sketches.

To keep track of each unit, Skanska and Trainor used electronic identification tags. On this project, the contractors used barcodes to tag units, instead of radio frequency identification tags—a system that Skanska first used on its $1-billion Meadowlands stadium project in New Jersey a few years ago. Otherwise, Senner says, the workflow was the same.

Typically, units were designed to accommodate gravity loads from either the top or bottom. On one stretch of the building, this got mixed up thanks to a miscommunication among DEC, Trainor and Stewart. Some were designed to take loads at the top when actually the opposite was required, and vice versa.

Additional concealed anchors and new framing solved the problem. But a bigger one loomed. To keep to the tight schedule, curtain wall work could not be interrupted to await the fix.

The tags, which incorporated all of the supply-chain information for each unit, allowed Skanska to immediately figure out which units had already been fabricated and were ready to be delivered and installed while the others waited for the fix.

The key to keeping the pace was an out-of-sequence installation, facilitated by the tags. Having that information "really helped us make more quick, intelligent decisions," says Senner.

The instant data also enabled Skanska to better manage adjacent work affected by the curtain wall snafu. And it helped Skanska monitor Trainor's productivity, which, early in the job, was less than half the promised pace.

Tag data also enabled Skanska to identify snags in the fabrication process and eventually to undo glitches through field rather than plant modifications, which were slowing down deliveries.

Staying Productive

Work slowed again when Trainor Glass shut down operations. The company had finished fabricating all the curtain wall units, but Senner says it took Skanska about a month to obtain the wall sections from Trainor's facilities. Once units were in hand, though, Skanska hired a company, formed by some ex-Trainor workers, to erect the units.