IF THINGS GO ACCORDING TO PLAN, it won't be long before Masdar City in Abu Dhabi is the undisputed pacesetter for sustainable design practices. The desert city—with its highly publicized master plan by Foster + Partners of London—broke ground on Feb. 9. Developed by the Masdar Initiative, a government program for “energy security, climate change and truly sustainable human development,” the project boasts a $22 billion budget and the goal of being zero-carbon, zero-waste, and zero-energy.

Near the city center, the Masdar Initiative plans to build itself a headquarters that will be the world's first large-scale, mixed-use, “positive-energy” building. In other words, the 1.5-million-square-foot complex will aim to produce more energy than it consumes. The schematic design emerged from a two-stage international competition conducted at breakneck speed (about six weeks from start to finish) and won by Adrian Smith + Gordon Gill Architecture (AS+GG)—a Chicago architecture firm launched just 19 months ago by seasoned SOM alumni Smith, Gill, and partner Robert Forest.

The project brief laid out square footage requirements, a mix of office and residential uses, and an ambitious sustainability mandate. Beyond that, the competitors were given a height limitation of eight stories, an outline of infrastructure and mass transit concepts, and a site plan indicating where surrounding open space is planned. Gill maintains that the headquarters will change the way buildings are designed, constructed, and inhabited. “Philosophically,” he says, “we are seeking to absorb the environment and use it to its best advantage.”

wind cones

ELEVEN TOWERING, glass-enclosed wind cones perform many critical functions. At the top, they provide the structural support for the building's curvilinear roof. At the ground plane, they delineate courtyards that serve as entrances, orientation points, and giant intakes to bring ground-source cool air into the building. In between, they siphon warm air up and out of the building and allow diffused daylight from the rooftop into the office floors below.

To aid pedestrian movement, the cones are placed at strategic locations connecting with paths penetrating the site. Some cones serve as entries or gardens on the grand plaza to the west. Others are cut into the building, forming negative space on the east façade. Interior courtyards vary— some are landscaped, some have water features, others have suspended artwork or pedestrian bridges overhead. “We want to make each one memorable, to not be confusing or disorienting as one moves through,” says Gill. The overall layout is regularized to move people efficiently through the building.

While the exact number of cones may vary in the final design, the choice of 11 during the competition phase was based on pragmatic concerns, such as spacing, structure, and projected volume of air movement. The geometry resembles that of a nuclear plant cooling tower, promoting wind movement while preventing sunlight from shining directly on the interior glass surfaces below the narrow neck of the cone. Cones are organized in the core to optimize the penetration of diffused daylight into the office interiors. Workers adjacent to a cone will enjoy views into the courtyard, and operable windows would allow for cross-ventilation.

The design team is exploring the use of operable louvers at the top of the cones to close off the neck during dust storms. Caps on the top of the cones could also help in balancing horizontal air movement through the office space, says Gill, because one cone could be closed off and the next one opened to shift the pattern of air flow. Engineers tested different orientations and forms for the tops of the cones, settling on a chamfered top with the high point facing toward the prevailing wind. This resulted in the most negative pressure at the top of the cone, promoting the greatest draw.

roof and garden

AS+GG COLLABORATED CLOSELY with its consulting engineers from the early stages of the competition. Gill says the fundamental idea of wind cones supporting a broad roof was no more than “a simple little section drawn on a piece of paper about three inches square” before the M/E/P and structural engineers were brought in to react. “With the idea of the cones and the roof, the structural engineers were important,” says Gill. “And that curve in the roof provides structural integrity.”

Gill likens the project to an oasis—a fragile microclimate in which a pool of water provides nourishment to palm trees, which in turn shade the water and keep it from evaporating too quickly. “So you end up with a canopy structure there that's protecting the very source that allows the canopy to exist in the first place,” he muses. “It's totally symbiotic—they coexist in this kind of equilibrium.”

Likewise, Masdar's floating roof literally translates that idea by shading the building and creating a cool environment beneath, reducing the demand for air conditioning. Plans call for the roof to be covered with a 290,000-square-foot photovoltaic array that will harvest the intense solar energy in the Abu Dhabi desert and convert it to power for the building. Beneath the curving roof, which articulates and promotes the pattern of air movement, is a vast garden space—what Gill refers to as “a displaced ground plane.” Residential units with human-scale massing are organized around the perimeter of the garden. Residents will enjoy views of the shaded courtyard or the city, which is limited to a height of six stories (two less than the Masdar headquarters). “It gives one a very unique perspective,” Gill says.

In keeping with its desire to build humane environments, AS+GG has already asked the client to consider the possibility of building the roof and cones first, which would allow the photovoltaics to provide energy for constructing the rest of the building while at the same time shading the construction site so that the workers aren't toiling in the hot sun. The proposal's practicality is still being evaluated.