There are no beakers in these laboratories, no scales, Petri dishes or precision lasers. There aren't even walls. But since the installation of Bucknell University's first green roof in 2010, and the addition of two more since then, close to a dozen students have used the rooftop planters for research that could one day lead to better sustainable building practices around the world.
"It's something we're going to see more and more in the future, especially as LEED (Leadership in Energy and Environmental Design) certification gets bigger," said Meghan Toft, a senior civil and environmental engineering major conducting green roof research. "It's cool to be on the cutting edge of this new technology. When we search for papers to do research on this, there's nothing out there, because nobody has studied it."
Green roofs are rooftop gardens — Bucknell's contain sedum, a hardy succulent that can survive in shallow, dry soil and absorb large volumes of water — that offer a number of environmental benefits. They provide insulation and evaporative cooling that reduce a building's heating and cooling load; they absorb and slow the flow of stormwater runoff, which can mitigate stream bank erosion and flash flooding; they provide wildlife habitats; and in cities they reduce the "heat island" effect, in which sunlight reflected by concrete and roofing materials raises the ambient temperature.
Bucknell's first green roof was installed in a second floor courtyard atop Dana Engineering Building in 2010 under the supervision of Becca Shopiro '12, who proposed the project after seeing a similar roof installed at her high school in Buffalo Grove, Ill. | Read more about the installation.
Since then, the University has added planters to the roofs of the Richard J. Mooney Innovative Design Laboratory and a full-coverage green roof atop Academic West — in both cases integrating the roofs and other sustainable design features into the original building plans.
Professor Kevin Gilmore, civil and environmental engineering, and his students have already quantified many positive impacts of the roofs. They've used thermal imaging to compare the temperature of the Dana green roof with the surrounding rooftop, finding the plant-covered area to be 10 degrees cooler on an average summer day, and they've measured water flowing through the planters on rainy days, discovering that the roof can completely absorb a light rainfall (below 1/3 inches) and significantly slow runoff from a moderate storm (1/3 to 1/2 inches). Now, Gilmore and his students are turning their focus to other impacts, asking how the planters and the plants and fertilizers in them may affect air and water quality.
"We're looking at the benefits of green roofs, but also any disadvantages, and how we can address them," Gilmore said. "Then we can say to people like the U.S. Green Building Council that if someone wants to get credit for a green roof, they have to address these issues. Our hope is that we can influence policy."
Those impacts include runoff of phosphorus and nitrogen from fertilizers, which can degrade water quality, as well as emissions of greenhouse gases from the plants themselves. Toft and Stephanie Houser '16 are measuring both this semester. If green roofs produce significant levels of phosphorous and nitrogen, Gilmore said, the Green Building Council, which issues LEED certifications, might recommend that green roofs be installed in conjunction with rain gardens in order to be maximize credits. The green roof atop Academic West, which received silver LEED certification this year, works in conjunction with such a rain garden.
While they remain a small facet of Bucknell's much broader commitment to sustainability, the University's green roofs are outward examples of that commitment. Dana's green roof abuts third floor offices and classrooms, and Academic West's surrounds an outdoor reception area. Because of that visibility, Dina El-Mogazi, director of the Sustainable Design Program at the Bucknell Center for Sustainability and the Environment, called them SEED (Sustainable Energy and Ecological Design) projects, which remind members of the Bucknell community to incorporate sustainability into future University efforts and their own lives. Houser said that for her, at least, the roofs have had that effect.
"I think it's inspiring," Houser said. "It's nice for students to see people at Bucknell University put effort into green and sustainable practices."
Illustration by Melissa Cuevas ’15