Commercial Architecture May 2019 - 40

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PROJECT

| windows

The curvilinear design of the JW Marriott Nashville draws inspiration from the nearby Cumberland River, which
weaves around the city, and by the rooftop curves of the adjacent Music City Center.

curtainwall. While curtainwall is typically first thought of for high-rise applications,
window wall offers advantages.
Window wall is often able to meet the requirements of aesthetics, energy, acoustical
performance, flexibility, cost, and speed. Whereas curtainwall is installed in front of
the slab, window wall is a slab-to-slab application. This provides more control over
thermal and acoustical performance, particularly in high-rise applications where energy performance and acoustics are valued. Additionally, a slab-edge cover can often
provide a more modern, clean design, mimicking the look of curtainwall for a reasonable cost.
John McGill, manager of the project center at YKK AP America, recalled the initial
stages of the project, "The overall shape and configuration of the building and the size
and scope of it truly set it apart," he said.
While examining the design for the hotel, engineers identified a total of 25 different angles to create the desired elliptical shape with a continuously changing radius.
The engineers customized one of its window-wall products, the YWW 50 TU thermally broken window-wall system, to fit the job. While the glass itself isn't curved, the
window wall was segmented to create the curve, and a slab-edge cover achieved the
same look and feel as curtainwall.
The YKK AP team achieved the curvilinear design by using three custom mullions
that fit within each of the angles, rather than creating 25 individual mullions for each

angle. The key to integrating a slab-edge cover that continually changed with the
custom mullions was to ensure that they hinged among themselves, creating a fluid
line around the building.
In addition to solving the design challenge of the continuously changing radius,
the YWW 50 TU system also allowed a pre-glazed option, so that all window-wall
panels could be fabricated, assembled, and glazed in the shop, rather than on site. This
solution met a design specification that required as much of the installation to be done
from the inside of the building as possible. Not only did the pre-glazed system speed
up the installation process, it improved the safety of the installation team by not
requiring as much work to be done from the outside of the building.
The pre-glazed window wall ranged from 9 ft. tall on the lower floors to 15 ft. tall
on the upper floors, and took approximately five days to install for each floor. As with
nearly all high-rise developments, an exterior crane helped load the floors.
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Another challenge was meeting energy codes with floor-to-floor and wall-to-wall glass.
With the YWW TU 50 window-wall system, the glass pane is set to the front for thermal performance, which is enhanced by the company's MegaTherm thermal break.
MegaTherm's polyamide material is said to be stronger and have a higher melting
point than PVC or polyurethane. Since its coefficient of thermal expansion is close
to aluminum, the bond between it and the extrusion maintains structural integrity through a wide range of temperature fluctuations. Additionally, it also provides
dual-finish capability and is designed to accommodate 1-in. glazing infill, or 1⁄4-in.
infill using adapters, the manufacturer states.
Spandrel glass and vision glass were used to hide a large portion of the structure's concrete walls that otherwise would have been exposed.

WhiteWalls.com | 800-624-4154

One-inch insulating glass units from Viracon, Owatonna, MN, were constructed with VE 1-2M for use on the podium level of the building. On the tower, a 1-in.

CIRCLE 218

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Commercial Architecture May 2019

Table of Contents for the Digital Edition of Commercial Architecture May 2019