One of the highest-profile double-skin buildings under construction now is Gensler's tapering and twisting Shanghai Tower. At 121 stories and 2,073 feet, it will be the world's second-tallest skyscraper when completed later this year. The building, which includes office space, a hotel, and a conference center, is organized like a tiered wedding cake: nine cylinders with gradually smaller diameters'each between 12- and 15-floors tall'are stacked one on top of the other. Between each zone, triangular two-story mechanical floors serve as platforms for 21 public atria or 'gardens in the sky,' enclosed by the tower's outer and inner curtain walls.

The outer skin, which helps define the skyscraper's serpentine form, consists of laminated glass within aluminum extrusions supported by radial struts and encircling girts. The inner skin's aluminum curtain wall, supported by the office and hotel floors' circular slabs, is made up of insulated glass units (IGUs).