By Allan Wingfield
Nashville’s new Music City Center convention facility features a unique sloped green roof design designed to mimic Tennessee’s rolling hills. There is a 65-ft difference in elevation from the northwest corner of the site to the southeast corner. Many challenges needed to be addressed, including keeping the vegetation evenly watered while diverting excess rainwater to the roof’s drainage and reuse system and a 360,000-gallon rainwater collection tank that allows excess rainwater to be used for flushing the center’s toilets and to irrigate the site’s outdoor landscaping.
Aiding the drainage, as well as the weight issue, was the choice of a particularly lightweight and white geocomposite. The white material is designed to reflect heat to prevent insulation board warping and membrane softening during construction. It provides continuous flow equal to larger drain profiles and protects waterproofing materials during construction.
The geocomposite layer is a 0.5in., thin, lightweight, post-industrial recycled white polypropylene drainage core with a strong, but lightweight, white filter fabric thermally bonded to one side.
Geogrid was installed for slope stabilization over a 2.75in.-thick layer of soil. A second geogrid layer was installed for wind scour prevention. Prevegetated sedum mats were chosen for the vegetative field.