Steven Holl is probably not the first name that comes to mind when you hear "green architect." His 37-year-old New York–based practice has produced a body of work known for its sculptural composition and poetic subtlety rather than its energy-savings. Yet Steven Holl Architects' (SHA) mixed-use Sliced Porosity Block (or CapitaLand Raffles City Chengdu)—a project that SHA says was "inspired by a poem of the city's greatest ancient poet, Du Fu"—combines eco-friendly technologies and city-friendly site planning to create more than just a pretty place. Its efforts have earned the project LEED for Core & Shell Gold precertification, the first complex in Chengdu to do so.
Location Chengdu, China (Sichuan Basin)
Gross area 3.3 million ft2 (306,580 m2)
Date completed November 2012
Annual purchased energy use (based on simulation) 48 kBtu/ft2 (547 MJ/m2), 16% reduction from base case
Annual carbon footprint (predicted) 23 lbs. CO2/ft2(112 kg CO2/m2)
Program Offices, serviced apartments, retail, a hotel, cafes and restaurants, and public plaza
TEAM & SOURCES
Doors Boon Edam Crystal Toruniket revolving door systems
Glass Chengdu China Southern Glass
Chengdu is a city of 14 million and the capital of the southwestern province of Sichuan. The 3.3-million-square-foot project sits on a site formerly occupied by the Provincial Museum of Sichuan. Its five towers (1 and 2 for offices, 3 and 4 for hotel and apartments, 5 for luxury apartments) ring a three-level outdoor plaza above a 420,000-square-foot underground mall. The complex occupies a prominent corner just over a mile south of Tianfu Square, the heart of the city. Its neighbors are a nondescript mix of concrete buildings common to second-tier Chinese cities like Chengdu: the monolithic Sichuan Gymnasium to the west, low-rise housing to the east, and street-side retail vying for attention along the adjacent road.
The site was chosen in part for its proximity to the city's metro line. The Sichuan Gymnasium subway station had already been planned before the project began, and it opened in 2010. Roberto Bannura, director of SHA Beijing, says that the design team put a great deal of effort into ensuring a direct, physical connection between the subway and the project. Three underground atria, which SHA likens to three gorges mentioned in Du Fu's poem, rise from the metro/shopping levels to entrances on the central plaza. Three corresponding plaza-level ponds, each designed to reflect a period of time, contain skylights that bring water-tempered light into the underground.
Bannura says Sliced Porosity Block's on-site transportation and multiple uses are essential to its sustainability. "In a city that is hyper-urbanized, you try to minimize the way people move to get basic services and entertainment. If you are able to concentrate all those functions in one physical place, you cut down on transportation time." By incorporating living, working, and leisure spaces into one complex, the designers create what Singapore-based developer CapitaLand refers to as "a city within a city." Bannura acknowledges that mixed-use projects are common in China. But, he says, most are offices and retail, so they shut down after ten hours. "When we use the term 'mixed-use,' it's a place you can inhabit twenty-four hours a day."
The various uses are expressed in the five concrete towers of Sliced Porosity Block. The "sliced" in its name refers to multiple cuts that connect the block to its neighborhood. On the ground level these cuts produce five entrances to the plaza. Such "porosity" is atypical in China, where new residential compounds are generally gated on their peripheries. On the upper levels, the slices maximize daylight and ventilation and create thin building widths—towers 1 and 2 are 92 feet wide, while towers 3, 4, and 5 are 69 feet wide—that limit their shadows on neighbors. In fact, the location of the cuts was influenced by a local code designating minimum sunlight exposures for surrounding buildings. "We made a requirement a design tool," says Bannura. "We projected sun exposure from the existing facades to see how that would cut through the property." Every slice is expressed as a glazed wall. Diagonal structural supports—essential in a city near the epicenter of the devastating 2008 Sichuan Earthquake—run behind the glass on these walls and appear on the surface of the concrete facades.
In addition to these site-planning measures, Sliced Porosity Block incorporates material and system choices to add to its greening. As CapitaLand manages its own buildings (a not-so-common practice in China), it benefits directly from its initial investment in low-energy construction. Centralizing the HVAC produced great energy savings compared with the individual air-handling units more common in Chinese construction. The high cost and limited availability of recycled materials in China restricted their use here, although some recycled steel and gypsum board were used. Sourcing local materials cut the project's carbon footprint for transportation and also countered the high tariffs China levies on imported goods.
Isaac Tsang—senior engineer of building sustainability for Arup—notes the influence that Chengdu weather had on choosing systems. Gray skies and abundant rainfall meant that solar technologies were passed over, but rainwater collection from the roofs and the plaza was pursued. The water is used primarily to irrigate ginkgos, Osmanthus, bamboo, and other vegetation in the central plaza and to wash the underground parking area (the complex includes 895 parking spaces).
"The public space is the success of this project," Bannura says. "If you look at all our projects in China, the public component is very important. And I would say without hesitation that it works tremendously well." This space is made possible only by inverting the ubiquitous Chinese skirt building, with its low-rise commercial base beneath a central office or residential tower. The SHA design loses several floors of street-side advertising to gain an active public area, and Bannura credits CapitaLand for being open to this atypical model.
On a recent visit to the site, the central plaza was well occupied by a variety of users: seniors strolling with their grandchildren, monks eating at an outdoor restaurant table, and people observing the Light Pavilion. Seven smaller green spaces along South Renmin Road elicited different activities, including skateboarding. These spaces lacked the line dancers, circuit walkers, and card players that one typically finds in Chinese parks. This may be a product of the newness of the place. Or it may be a matter of design. Sliced Porosity Block's complex formal arrangement of buildings, multilevel plaza, and installations of artistically conceived fountains, landscaping, and pavilions may be more conducive to visual appreciation than to activities. Its sustainable design—including its central Chengdu site, easy transportation access, and multiple uses and attractions—make it a place to visit. Its poetic design makes it a place for contemplation.