Zhong Xiao Pavilion
Treehouse In A Concrete Jungle: Architect Sergio Palleroni and Taipei students break through asphalt to create a garden and green office space.
As director of the basic initiative at the school of Architecture at the University of Texas, Austin, for the last 20 years, Sergio Palleroni has helped his students build housing, clinics, and schools in underserved communities throughout the world, including rural United States, Mexico, Africa, and India. In each of over 50 projects, a collaboration with local people has been key to designing sustainably.
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When the National Taipei University of Technology (NTUT) invited Palleroni to lead a local project with its students, instead of introducing new concepts to them, he found his methods had to be modified to adapt to an already strong local effort toward making Taiwan an ecological world leader. The project’s outcome, which he dubs “Sustainable Taiwan,” includes a campus garden designed and built by an interdisciplinary team of architecture, planning, and engineering students; a “green” pavilion designed by students and built with assistance from the local construction industry; and a breakthrough in relations between NTUT and its surrounding community.
To begin, Palleroni’s Taiwanese students researched and wrote initial position papers, figuring out their own sustainability priorities. The papers acknowledged their island’s high-tech accomplishments—Taiwan is a world leader in the production of solar panels, and the country has made great progress in dramatically increasing its recycling rate and reducing its carbon footprint. But the students’ main interests concerned grassroots issues, as expressed by “the grandmothers,” vocal groups of Taiwanese women concerned about the environment that future generations will inherit. That these activists came from every social stratum, but worked together and spoke as one voice, was key to their persuasiveness, according to Palleroni.
Ready to listen to such groups was Professor Jen-Hui Tsai, his colleagues, and students at NTUT. They realized the university could not remain isolated from political and social issues and were eager to forge civic connections. NTUT is unique among Taipei’s universities in that it lies at the heart of this densely populated (nearly 2.7 million) city, surrounded by high-rise commercial and residential towers. The entrance to the urban campus had been a gap in a 4,000-foot-long wall along the formidable eight-lane Zhong Xiao East Road. Buses stopping along this boulevard would drop off riders into a hellish thermal sink: the expanse of asphalt amplified the steamy tropical climate.
The first student project knocked down 1,000 feet of this wall for an urban garden and bioswale—a relatively cool, inviting respite for pedestrians—that the university now shares with the community. The bioswale is a planted absorption trench engineered to promote water movement. Small rocks and low-head dams along the trench churn the water and introduce oxygen, which helps feed the microorganisms that break down organic solids. The stream flows to a campus lagoon, where it is pumped back to the top of the bioswale and recirculated. Solar collectors that double as window shades on university buildings power the pumps. Native plants and trees recall the city’s former life as an estuary, and the garden does double duty by educating passersby about the cycles of nature. The grandmothers helped with the planting, further strengthening community relations and adding to the symbolic value of the garden.
The students decided the architectural component of their project, the so-called Lotus Pavilion, should serve the community as a resource for information about sustainability, offering design services and a demonstration of how an ecological building looks and feels. One unexpected outcome—in a construction culture with no modern precedent—was the education of local architects and builders who were eager to help. So, unlike Palleroni’s previous student projects, the pavilion was a collaboration with professionals. Because Taipei rests on soft estuary soil and is subject to both 150-mph typhoon winds and earthquakes measuring up to magnitude 8.0 on the Richter scale, the structural demands were considerable. Engineers specified deep pylons and a hefty structural steel base for the lightweight pavilion. Even with that substantial foundation work, construction was completed in three months.
The 3,000-square-foot pavilion is basically one large room, with an open loft over the southern portion. In form and materials, it is a showcase for passive cooling and low-energy lighting. Above the steel stilts, the lightweight metal-stud structure rises 32 feet above ground to catch any available breezes. Palleroni describes it as a “treehouse in the woods of the bioswale.” The students shaped the building in section to maximize natural ventilation and daylight. There is no air-conditioning, and the team has found electric lights to be unnecessary during the day. To induce natural ventilation, the north wall has twice as much area in operable windows as the south wall; the space is much higher on the north end, creating an internal thermal-chimney effect, further encouraging ventilation. Ceiling fans and low-velocity bathroom fans at the north transom windows aid in exhausting hot air. Despite the local extremes in heat and humidity, postoccupancy studies show the induced air movement is sufficient to lower the effective temperature to within the human comfort zone. Solar panels on the sloped portion of the roof satisfy all the space’s electricity needs, and plantings on the flat portion further insulate the interior space from the brutal sun.
The pavilion’s wall construction also contributes to the cooling strategy. The materials are low in mass to prevent heat buildup. Rigid insulation on the interior surface of the metal studs creates a thermal break. An exterior rain screen of timber bamboo was installed on vertical metal studs 2 inches away from the insulation’s reflective surface. This air gap has vents at the top and bottom to induce continuous venting, allowing the skin to breathe and preventing sun-heated air from penetrating into the occupied space. The horizontal strips of bamboo are separated by 3/8-inch gaps that are slanted to prevent water from dripping back into the wall cavity.
In addition to designing and constructing the bioswale and the pavilion, the enthusiastic students also retrofitted a few of the existing buildings along the bioswale. They designed and installed window-shading devices that support solar panels. They also noticed that vines would naturally climb exterior building walls in this verdant climate, damaging the architectural surfaces; rather than fight the trend, they exploited and encouraged the phenomenon by suspending a mesh 6 inches from the facades to hold the plants. They planted green roofs on existing buildings and channeled the runoff to irrigate the wall climbers. The vegetated walls and roofs have multiple benefits: The greenery protects the surfaces from direct solar radiation, the evaporative skin further helps cool the interiors, and less rainwater ends up as runoff, a severe problem in the rainy season in a city of impervious surfaces. Together, the students and grandmothers have gathered inspiration from their successes and begun tearing up the campus’s other asphalt surfaces to plant rice paddies.
Professor Tsai has invited Palleroni to return to tackle the opposite end of campus. It seems a river once flowed where there is now a curving road through a pleasant residential neighborhood. The plan is to re-create the river. If it’s anything like this first project, the riverbed plan will likely spill over to become another community event with unexpected results.
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