Washington, D.C., between Rock Creek and Glover Archbold watersheds
Energy-use reductions were achieved with a highly efficient building envelope, lighting controls, and passive strategies to minimize heating and cooling loads. Solar chimneys exhaust hot air during the cooling season without fans, and wind chimes in the towers signal airflow. Recognizing an opportunity to retire inefficient equipment in other buildings, the team designed the middle school’s mechanical system to distribute hot and cold water to much of the campus.
While Sidwell was built under a bid contract, Kieran argues that innovative projects are better procured through a negotiated contract. “You can’t find enough bidders and subs for LEED Platinum buildings that are willing to take all the risks,” he says. With the contractors contributing to the design process, Kieran notes, they understand and buy into the importance of the green components. In this case, even before it won the bid, HITT Contracting was involved at certain points during the design phase to estimate costs and provide input on constructability, which improved the continuity between design and construction. Because the project had to be substantially completed during the school’s 10-week summer break, HITT recommended using prefabricated panels for the exterior walls, according to the company’s director of sustainable construction, Kimberly Pexton, AIA.
While HITT had previously constructed several LEED-certified projects, it entered new territory with several aspects of Sidwell, including photovoltaics and the constructed wetland. In both of these areas, dividing responsibilities among subcontractors was a challenge. If the photovoltaic (PV) provider isn’t a licensed electrician, Pexton asks, “Where does the PV guy leave off and the electrician pick up?” For the wetland, the team thought it had found a subcontractor that could manage both the landscaping and the piping, but “when they got into it, the actual plumbing aspect was more than they could handle,” says Pexton. So HITT turned that part of the work over to its plumber.
After extensive deliberation, the school elected to pursue LEED Platinum certification to serve as a beacon for the community, according to Saxenian. “We had some concern that this would be seen as frivolous, but we felt compelled by our core values and our belief in the importance of stewardship of natural resources,” he says. Although the school will not prescribe a minimum LEED rating for future buildings, Saxenian says they expect their next project, a new lower school on the Bethesda campus, to achieve LEED Gold.
The goal of managing wastewater on-site was accepted early, but the team’s vision of how to do that evolved. “All through preliminary design, we were anticipating putting in a Living Machine,” says Kieran, referring to a proprietary system in which wastewater is treated in a series of tanks, typically housed in a greenhouse. But regenerative-design consultant Bill Reed, AIA, argued that “a Living Machine is just another piece of equipment to fix a problem that we created.” Reed suggested the constructed wetland that became the centerpiece of the courtyard.
Wastewater from the kitchen and bathrooms flows into settling tanks, where solids are collected before the water is released below the surface of the constructed wetland. After about 10 years, the solids will have to be removed to a landfill or composted, according to Reed. Surprisingly, city officials approved this alternative wastewater treatment system quickly. The city’s health department had second thoughts at the last minute but ultimately agreed to let the project go ahead on a pilot basis. “We have a monitoring protocol that we have to follow,” reports Saxenian. At press time, the wetland hadn’t yet become fully operational.
The central wetland became the most prominent element in an integrated water-management system that begins with green roof areas that retain rainwater and also serve as garden space in which students grow vegetables for the cafeteria. With this approach, “the place is the process,” notes landscape architect José Alminana of Andropogon of Philadelphia, and the enormous pedagogical value of the sustainability agenda became a driving force in the design process. In addition to the wetland, the designers introduced more than 80 plant species, all native to the Chesapeake Bay region. The biodiversity suggests that “the landscape becomes a new faculty member,” says Alminana.
The control of water guided other design decisions. For example, the exterior cladding is a rainscreen system that includes a ventilated cavity to resist water intrusion. Interior finishes include cork, linoleum, bamboo, and wood flooring remilled from pilings extracted from Baltimore Harbor. In the landscape, flagstone was reused from sidewalks, and stone for walls came from a dismantled railroad bridge. Crediting the contractor’s initiative in locating and scavenging the stone, Alminana notes, “A project of this ilk tends to attract this kind of thing. It doesn’t happen by chance—the interest is contagious.”
commitment to using this project as a learning opportunity extends far beyond the students. A team from Yale University’s School of Forestry and Environmental Studies is studying the school to determine if the project’s green strategies have a measurable effect on student and faculty performance and health. But it will be harder to measure the long-term benefits of providing students with such a deep connection to natural systems, which is so rare in an urban setting.
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