USGlass -2009 August

Volume 44, Issue 8 - August 2009

Architects' Guide to Glass

All the Right Pieces
Customized Systems Play Key Role in Atlanta Mixed-Use Development
by Ellen Rogers

Imagine spending hours upon hours putting together a puzzle only to find that one little piece is missing—a critical component that would bring the whole thing together. Bringing all of the pieces and parts in place to form Atlanta’s 12th and Midtown development was a lot like putting a puzzle together—if one component had been missing the project may not have been completed as it stands today. All of the building materials had to work together, as did everyone on the design and construction teams—each played a unique role, and when they all came together it resulted in the successful completion of the project.

“A remarkable puzzle was put together with all these pieces and parts … that made the economics work, the aesthetics work, and it structurally worked,” says Rob Rule, a partner with Atlanta architectural firm Rule Joy Trammell + Rubio (RJT+R).

Design Vision
Situated along the city’s “Midtown Mile,” 12th and Midtown is a 2.5-million-square-foot, mixed-used development that includes office towers, hotels, condominiums, retail and restaurants. Consisting of several components, the tower known as 1010 Midtown (1010) stands 35-stories tall and includes more than 400 condos and 50,000 square feet of retail and dining space. A second tower, located at 1075 Peachtree Street (1075), consists of 725,000 square feet of office space, 60,000 square feet of retail space, a 400-room hotel and 100 residences. The use of customized glazing systems was key to creating distinctive architectural details in both towers.

“1010 has a very distinctive sculptural glass design, including a [curved wall] facing Peachtree Street,” says Rule. “We decided early on that 1010 should be an all-glass structure and its design strength would come from its 3-dimensioanality that resulted from the balconies and the floor-to-ceiling glass. When we started looking at different glass types we decided to relate it to a project that we had done previously with Daniels Corp. [project developers] called Plaza Midtown. That glass had nice coloration, good light transmittance, was not too reflective, not too clear and using it again would start to establish a [brand identity] for the developer.”

Like 1010, 1075 also has a strong sculptural form.

“It has a pleated trough that comes out of the building and we knew it, too, would have to be distinctive,” says Rule. “We debated whether it should be more of a stone or pre-cast building, but in the end we decided to go with glass, though it does have stone within the spandrel.” While both 1010 and 1075 include glass supplied by Viracon, Rule says for 1075 they decided to use the company’s VRE 137 instead of the VRE6-54 used on 1010. “We liked the blue-gray color as it was a slight contrast to the blue-green used on 1010,” says Rule. “It had good visible transmittance from the interior and was very clear looking out; it’s not reflective, but had a comfortable amount of tint to it that was very natural so you could still see in. It also had a good solar heat gain coefficient.”

Custom Made
In addition to the glass, the window wall and curtainwall systems were also important elements and required upfront design approval meetings.

“We sat down with the architect early on to get system approval and then we did shop drawings based on that profile approval,” says Frank McCoy, vice president of Glass Systems, contract glazier for the project. “On 1010 there is about 220,000 square feet of custom window wall and on 1075 there is 185,000 square feet of custom window wall. On 1010 we have about 11,000 lites of glass; on 1075 we have 8,000 lites of glass. On a condo you have a custom sliding glass door and on 1075 there are about 150 of these custom sliding glass doors; 1010 has about 400.”

McCoy adds “Sliding glass doors drive these projects. The lead-time on them is long—they have to be ordered before we order the window wall and we do a separate shop drawing on the sliding glass doors themselves,” says McCoy. “That’s why we don’t use standard curtainwall; it does not work with sliding glass doors.”

YKK AP supplied the metal systems. And while the systems were not 100-percent brand new, they were customized for this project.

“Both 1010 and 1075 utilized systems that our company has used on other condo, mixed-used type projects,” says John McGill, regional business manager, project business group, for YKK AP. “Where we had the most involvement was in how we customized [the materials] for these projects and how we incorporated multiple systems into the same project and could still achieve the desired look.” For instance, two different window wall systems were used—a 5-inch and a 6-inch depth system. “Those varied mainly due to structural requirements as there were different parts of the building where the floors would be larger in height so those areas needed a stronger system,” says McGill.

In addition to the window wall, several floors incorporate curtainwall. This meant a smooth transition between the curtainwall on one floor and window wall on the next would be necessary. To do so, a slab edge cover concept was used.

“A lot of custom detailing went into that because while we are using the two systems from floor to floor, these were not straight lines,” says Luther Hudson, president of Glass Systems. “There are radii involved and multiple odd-degreed corners that we had to turn and shape.”

McCoy says curtainwall had to be used on some of the 1010 floors because the window wall would not meet load requirements. There are a lot of shear walls on 1075, which are poured-in-place concrete walls that are structurally sound and required spandrel glass.

McGill says incorporating different systems into the project and customizing them to the specific needs without the expense of designing something totally custom was significant.

“I think if you’re starting from scratch and you’re doing something totally new, there are a lot of upfront expenses and lot more testing that must be done,” says McGill.

Unique Features
One of the most unique characteristics of 1010 is a serpentine glass wall that follows the curve of Peachtree Street. The segmented wall goes from concave to convex and does not have any 90-degree angles.

“It’s a fairly tight curve so we wanted to have a module in the vertical mullion system that would allow for straight pieces of glass,” says Rule. “While you can bend glass to create curves … we knew we needed to go in there with a design that would use straight glass. This required us to carefully balance the spacing of the mullions with straight segments of glass to create a building that feels like it has a smooth curve over the convex and concave portions without looking segmented.”

McGill agrees that the spacing of the mullions was an important consideration.

All for One
With so many unique considerations, open communication and synergistic working relationships between all the groups involved was key. In this case, RJT+R, Glass Systems and YKK AP had all worked together on previous projects so everyone already knew what to expect from each other from the start.

“This project had the exact same requirements in terms of systems and profiles as what we did on the Plaza Midtown project,” says Hudson. “So we had a natural tie-in with the architect, YKK, the contractor and the owner.”

Having everyone based in Atlanta was also a plus.

“Being able to work closely with the architect and contract glazier was important,” McGill says. “A team approach makes the chances of success that much greater.” AG

Ellen Rogers is the editor of the Architects’ Guide to Glass and Metal.