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Did you know about the 'blow through'?


Chicago’s supertall Vista Tower to get empty ‘blow through’ floor, minor height bump

The design of the already under construction skyscraper has reportedly received some revisions



By Jay Koziarz Jul 17, 2017, 12:40pm CDT

https://chicago.curbed.com/2017/7/17/15983912/chicago-construction-supertall-vista-tower-design-update

While the 93-story Vista Tower is now well above ground along the south bank of the Chicago River in Lakeshore East, the design of the upcoming luxury hotel/condo development is still being refined. According to Chicago Architecture Blog, the Magellan-Dalian Wanda Group joint venture will see the residential space on the tower’s 83rd floor replaced with an open-air “blow-through.”

Designed to offer relief from high wind forces, the void will span the widest part of the tower’s highest “frustum” segment. The blog’s author specifically cites language from the Chicago’s Department of Planning and Development, which pointed to occupant comfort as the primary motivation behind the recent change:

Prior to the addition of the blow-through floor, acceleration limits, as defined by the International Organization for Standardization, were predicted to be significantly exceeded, indicating performance that would be unacceptable.

According to a letter from Magnusson Klemencic Structural and Civil Engineers, this would result in building occupants feeling ill and possibly afraid for their safety.

WTF?! Hey honey, the gold fish bowl is sloshing around again.

In other words, the luxury tower would sway uncomfortably without the addition.



These sorts of wind breaks are not uncommon on very tall and very slender skyscrapers. New York’s 432 Park Avenue utilizes five such gaps across its 1,396-foot elevation. With the Manhattan supertall, however, these spaces were always part of the plan so they double as mechanical floors and feature attractive nighttime lighting.

This will not be the case with Vista’s blow-through floor. According to CAB, by law the space cannot be illuminated. The result is likely to appear as a dark horizontal band across the Studio Gang/bKL-designed building’s uppermost extremity.

Other mid-stream changes to the Vista plan include a revised, less complicated exterior glass system that ditches green coloring for more bluish tones. The architectural top of the building has grown by a handful of feet, now appearing to top-out at 1,198 feet. Diagrams also show the tip of Vista’s crown tapering less compared to previous illustrations.