Oaklyn Branch Library
Evansville, IN

Awards

2004 GRHC North American Green Roofs of Excellence Award

Assemblies

Type IV - 14.oo inches of media

A green roof fit into the architect’s concept, to blend the building into the landscape and to demonstrate an ecologically sensitive design appropriate to an educational institution. The site is steeply sloping and the earth-sheltered building is built into the slope. The green roof was designed to support a mesic meadow prairie native plant community that would mirror the landscape design for the remainder of the project. The mesic meadow prairie on the roof blends into the prairie meadow community surrounding the site of the one story building and the integrated landscapes have a high habitat value. In many locations it is difficult to determine where the building ends and the meadow begins.

The assembly is irrigated using the base flood irrigation system which introduces water to the green roof profile at the level of the roots. Since the roof is slopping ‘roof riffles’ contain the water allowing it to be utilized by the vegetated cover. This is an extremely efficient method of irrigating a green roof and closely approximates natural conditions associated with shallow soil over shale bedrock.

The roof deck pitches uniformly at three percent toward one edge of the building. To reduce the potential for long-term service and maintenance costs, the roof deck was installed without roof drains. Runoff discharges from the down gradient side of the roof where it is collected in a vegetated swale. The green roof incorporates an internal drainage network composed of perforated rectangular conduits that intercept percolated water during large rainfall events and discharge it to the storm sewer.

This project is also noteworthy in that it was the first time that Roofmeadow used pneumatic equipment to disperse the green roof media.