A public library’s green roof helps offset its energy costs and attract community participation.
Since it opened in 2003, the Oaklyn Branch of the Evansville Public Library has helped to increase participation in the library system through its accessibility, location in a rapidly growing suburb, and progressive design. Several design features of the Oaklyn branch are credited with reducing its utility costs and overall environmental footprint, in addition to increasing the library's popularity by a factor of three--as measured by surges in media circulation.
The building's prairie-like green roof is the most visible indicator of the library's commitment to environmentally positive architecture. Designed by landscape architects Storrow Kinsella Associates in collaboration with architect William Brown (of Veazey Parrott Durkin and Shoulders, an Indianapolis firm), the 17,250-square-foot flat roof features native grasses, forbs, and wildflowers associated with the region's mesic meadow prairie habitat. Roofscapes, Inc., a Chicago company, produces and markets the greenroof system used here under the name Type IV: Meadow 1. This greenroof model simulates the deep soil and perched water table common to the mesic meadow. "Perched water table," a term used when an aquifer occurs at elevations higher than the regional water table, offers an oddly apt metaphor for the elevated green roof.
A lightweight steel and concrete roofdeck supports 16 inches of soil while contributing minimal extra weight. The building's creative team designed the structure without roof drains, opting instead for a slightly pitched roof that directs rainfall away from the building for retention in landscaped swales elsewhere on the library grounds. The swales, in turn, contain compartmentalized drainage systems to handle major stormwater flows. While the greenroof is designed to withstand and slow the runoff from heavy storm events, its plants rely for the most part on a responsive irrigation system that dispenses water carefully according to the needs of both plants and soil.
While a planted roof adds weight to the library's framing, the overall effect is of coolness and light thanks to the insulating effects of soil and plants, their mitigation of heat absorption from sunlight, and strategically placed clerestory windows that maximize interior daylighting.
"Green Roof Award Winners Announced." Environmental Design + Construction online (July 1, 2004). Accessed April 10, 2011.
Evansville Vanderburgh Public Library. Accessed April 11, 2011.
"Buildings wear green on top." Electric Consumer (March 2007). Posted on Evansville Vanderburgh Public Library website. Accessed April 11, 2011.
Green Roofs For Healthy Cities. July 21, 2006. Accessed April 11, 2011.
Learn more at: http://www.evpl.org/aboutus/locations/oa/