‘Aqua’ changes Chicago skyline
Chicago’s high-rise skyline is forever changed. Under construction for four years, the 82-story, 1.9 million-square-foot Aqua building in Chicago’s downtown area is now one of the city’s most prominent jewels.
The Aqua — built by developer James Loewenberg of the Magellan Development Group, with design by Jeanne Gang, FAIA, of Studio Gang — is now a 28-acre Lakeshore East complex on the old Illinois Central Railroad yards along Lake Michigan. At its center, the Aqua Tower surges high above the surrounding area.
Gang’s alluring design includes a residential tower, which rises from a mixed-use podium at its base. All told the entire project, from land to furnishings, required an investment of $4 billion.
The design team devised ways to make Aqua energy efficient through sustainable strategies that enabled the developer to apply for LEED Silver status. Loewenberg admits that green wasn’t the first thing on his mind at the beginning of the process, but, because of Chicago’s strong environmental laws, he soon thought, “We could make this building green. We were already heading in that direction, and I wasn’t even aware of it.”
Gang, who has incorporated energy-saving features into a number of her previous projects, was delighted.
Concrete and glass
In a city known for its rectilinear skyscrapers, Gang introduced dramatic curves by wrapping the tower with sinuous concrete balconies. The building’s plan reserves floors four to 18 for The Radisson Blu Aqua Hotel, which opened in late 2011, with 334 rooms and suites. Floors 19 to 52 will have 474 rental apartments. The remaining upper floors provide space for 264 high-end condos, with penthouses on floors 80 and 81.
Gang designed the balconies for sun-shading, making them deeper on the south than on the north. As many balconies as possible were placed next to living rooms, thus forming visual extensions of the living spaces.
While the concrete decks cut solar load on the glass facades, the architects left certain glazed areas exposed — organically shaped expanses of wall they call “pools” — for interiors where balconies aren’t needed but direct sunlight is welcome. To reduce solar load on the exposed glass, Studio Gang conducted sun pattern studies that in turn led to its specifying six different types of glazing. In addition to low-E coatings, the firm selected reflective glass for the exposed parts of the east and south facades.
Studio Gang acknowledges that the concrete balconies, which are extensions of the floor slabs, shed Btu in the winter, much like fins on an air cooled engine. The idea of adding thermal breaks between the indoor and outdoor portions of the slabs was considered, but it proved too difficult. In terms of overall energy use, the heat loss in the winter is more than offset by summer savings from shade provided by the balconies and the use of reflective glass in the “pool” areas.
Inside the dwelling units, the architects selected materials and equipment with sustainable features, such as bamboo for the floors. Low-flow plumbing fixtures were selected to cut down on water use, and Energy Star-rated appliances were installed.
Mechanical bliss
Heat for the 870-foot tall building comes from four, 12,800 mbh gas-fired boilers that feed a 10-inch riser. Two 1,030 gpm pumps are used to circulate the water, while another pump is on standby. The boilers are also used to fire indirect water heaters to supply nearly the entire building with domestic hot water. The upper condominium floors have individual gas-fired water heaters.
“That 10-inch main supplies three risers for the whole building,” said Dan Krebsbach, VP of Advance Mechanical, which is based in Arlington Heights and kept between 30 and 40 union workers on the Aqua job for nearly four years. Engineers at Advance designed the mechanical system.
“The biggest challenge we had to overcome was the height of the building,” said Krebsbach. “It necessitated breaking the hydronic systems apart vertically to keep the hydrostatic pressure within reasonable limits.” The tower was broken into three sections, with the use of two large plate-and-frame heat exchangers and powerful base-mounted pumps.
Hot water is delivered to 1,600 International Environmental Corporation (IEC) fan coil units, most of which are either 300 (9,000 Btu) or 600 CFM (1,800 Btu) units. The concealed vertical stack units cut installation time and material costs. “The units are generally located one on top of the other, making hot water, chilled water and condensate drain line installations very simple and cost effective,” said Ron Porter, senior product manager at IEC. The risers, which were installed at IEC’s Oklahoma City manufacturing facility, essentially became extensions of the cooling and heating water mains.
“Each fan coil unit has separate heating and cooling coils with water valves that respond to the local room thermostat,” said Porter. “With this system, individual apartments or hotel rooms can enjoy heating or cooling as desired, creating an optimum luxury environment.” The four pipe, stacked fan-coil units are often situated against an exterior wall, where maximum heat gain and loss is noticed.
On the lower level of the skyscraper, two 1,200-ton heat exchangers tap Thermal Chicago’s underground chilled water lines. In operation since 1995, Thermal Chicago Corporation is the world's largest interconnected district cooling system, serving about 100 buildings in the downtown Chicago area, for a contracted capacity of 100,000 tons. The Aqua building fulfills its name; it calls for 12-inch water mains to cool the entire structure.
Lush greenery
At the base of the tower, a three-story podium contains the hotel and apartment lobbies. Most notable is the 80,000-square-foot garden on the podium roof. The garden includes an outdoor swimming pool and a running track, while the tower rises from the center, high above the greenery.
On this park-like roof, meandering paths weave between low evergreens and deciduous plantings. A continuous drainage layer allows water to flow under soil, gravel, and concrete walls to drains and pipes. The roof’s vegetation is not only aesthetic but also combats the heat-island effect during the hot summer months by lowering ambient temperatures around the building.
The Aqua is also host to Chicago’s first electric-vehicle charging station open to the public, in the tower’s underground parking garage. The station can accommodate 24 electric and hybrid vehicles. Other sustainable features include rainwater harvesting systems and energy-efficient lighting.
For those with a soft spot for wild animals, the tower has a design concept unlike any other skyscraper in the city. The balconies, railing and etched glass minimize bird casualties by making the building easily seen, minimizing aerial impacts.
All this comes at a price, however. The tower’s condominium models include a 1,251 square-foot, two-bedroom, two-bath plan with a southeast view on the 58th floor priced at $755,000. A two-bedroom, 2.5-bath with den design with 1,577 square feet of living space on the 71st floor with a south view, costs $759,000.
On Magellan Development Group’s Aqua Tower sales website, high-speed zoned elevators are listed as a selling feature. So are breathtaking views from all apartments, floor to ceiling windows, hardwood floors and granite countertops. Among the selection of top-tier appliances and creature comforts, the list includes “year-round, individually-controlled heating and air condition.” It omits, however, “courtesy of Advance Mechanical and IEC.”