There are a few systems around that can provide a thermal break for a concrete cantilevered balcony, mostly from Europe, but they are expensive, a couple of hundred bucks a foot. One can see from the construction photos that they are probably not being used here.
As an architect, I love the look of this building. As a TreeHugger, I wonder how in this day and age we can still be permitting continuous floor to ceiling glass walls and eighty stories of radiator fin balconies in a "green" but cold city like Chicago.
How will they heat this thing twenty years from now? ::Daily Dose of Architecture