From Industrial Insulation to a Rooftop Learning Landscape in the Bronx: The Stevenson Green Roof Project
In the fall of 2005, Research Fellow Joe Hagerman came to Rafael Viñoly Architects with a track record and an idea. An architect with experience in housing and a graduate student in Columbia University’s civil engineering program, Hagerman had won Metropolis magazine’s Next Generation Design Prize in 2005 for “Biopavers,” a manufacturing strategy to incorporate bioremediating plantings within concrete pavers. Now, he wanted to study the performance of green roofs. By learning about how heat is actually transferred through the many layers of a green roof, and by bringing his engineer’s experience with materials, he planned to show how green roofs could be better integrated into the design of building envelopes, enhancing thermal performance, facilitating construction and repair, and bringing down costs.
As Hagerman was beginning his research, Rafael Viñoly Architects was nearing completion of the Howard Hughes Medical Institute’s Janelia Farms Campus near Washington, D.C. With over 200,000 square feet of intensive, monolithic green roof, the building was set to become the second-largest green roof in the United States. Moreover, it included two completely separate green roof systems. Working with architects at the firm as well as project consultants, Hagerman started his research by building a thorough understanding of how the complex structural issues of these massive green roofs had been resolved and how the resulting assemblies performed, especially in terms of water flow and heat transfer. Next, using finite-element heat transfer software developed at Lawrence Berkeley National Laboratory, Hagerman modeled the energy performance of some of the typical monolithic and modular sections used in designing green roofs. He asked how energy performance and water management could be improved, and how both could be better integrated into the design of the building envelope. A key step was the incorporation of an insulation layer within the green roof, but this had to be waterproof and strong enough to support soil, water and the impacts of human feet and gardening equipment. Hagerman settled on Foamglas®, a closed-cell foamed glass industrial insulation product manufactured by Pittsburgh Corning, as the ideal material.
Taking advantage of Foamglas's® properties, Hagerman designed a prototype of a roof assembly whose section is simpler than that of many green roofs and is completely modular, making installation and maintenance relatively inexpensive. Also, by incorporating insulation within the green roof, Hagerman’s system allows architects to meet code requirements while reducing or eliminating additional roof insulation.
Hagerman’s research findings were published by Rafael Viñoly Architects as New Directions in Green Roof Design, covered in articles in Metropolis, Prattfolio, ArchitectsNewspaper.com, and featured at the New York Green Expo in 2008.
The next step was to demonstrate the system’s constructability and thermal performance. Pittsburgh Corning offered to provide the Foamglas® insulation. Tremco, a leading national roofer, offered to help with other materials and installation. But where to build the demonstration roof? A dream began to take shape: put it on a New York City public school. We could equip the roof with flowmeters, thermocouples, and other scientific instruments and send the data in real time to biology and math classrooms. Even better, we could provide a rooftop learning laboratory where students and teachers would be able to observe the complex interactions of plants, sun, and water. We could plant the roof with all-native species so that butterflies and birds would enjoy it as much as children. Finally, the new roof system could lead the way to widespread adoption of green roofs throughout the city, reducing summer heat and electric demand, reducing the runoff that frequently overloads the city’s sewage treatment plants, and improving both air and water quality.
There were challenging problems to solve – problems of weight, building codes, and safety – before we could produce a green roof that was safe to walk on. But the vision was tantalizing. It was not the vision of Joe Hagerman or of Rafael Viñoly Architects alone, but of a multi-disciplinary partnership that came together to envision and implement the project. The Salvadori Center is the city’s leading provider of high school educational materials derived from architecture and engineering. The Stevenson Campus is a collection of seven public schools sharing a single building in the South Bronx neighborhood of Soundview. The Gaia Institute is one of the city’s most innovative environmental organizations. New Visions for Public Schools is a leader in the movement to reform public education by creating small schools. Together with Rafael Viñoly Architects, Pittsburgh Corning, and Tremco, these organizations have conceived and continue to advocate for the Stevenson green roof project.
New York City’s School Construction Authority is another key partner. The SCA has welcomed and supported our interest in the Stevenson Campus. As of now, the agency plans to carry out major repairs to the building’s roof during fiscal year 2009, and we are working to coordinate design details and construction schedules.
When will the Stevenson Green Roof be built?
The answer is: as soon as the necessary funds are raised. Rafael Viñoly Architects and its partners are contributing all design, engineering, scientific, curriculum development, fundraising, and construction management services, as well as some roofing materials and services. The project has also raised over $850,000 in cash, largely thanks to the support of Borough President Adolfo Carrión, Jr., and City Councilmember Annabel Palma. Meanwhile, the consortium is seeking to raise the remaining funds from foundations and private donors. Contributions are being accepted by the Salvadori Center.
The Design
The design for the Stevenson Green Roof is the work of Rafael Viñoly Architects. The structural section follows Hagerman’s design and incorporates a double layer of Foamglas® insulation. The top layer consists of planting trays following a design by Hagerman and the Gaia Institute’s Paul Mankiewicz that is intended to minimize weight and optimize water management. The trays are filled with the Gaia Institute’s light-weight GaiaSoil planting matrix, which supports 50 native plant species according to a planting plan designed by the City of New York’s Greenbelt Native Plant Center. The roof will be equipped with scientific instrumentation designed to measure water retention, thermal performance, and ambient air temperature and quality, following a research design prepared by Columbia University’s Center for Climate Systems Research under the direction of Dr. Stuart Gaffin.
While the design covers the entire 70,000 square foot roof of the Stevenson Campus’s main building, the consortium is currently focusing on completing Phase One, a 20,000 square foot section. This area includes space for three classroom assembly areas as well experimental planting beds for teachers and students.
Links
New Directions in Green Roof Design
The Stevenson Green Roof: A Living Laboratory
Stevenson Green Roof Proposal: Selected Images
Media coverage can be found in the News & Media section
