Green roof media not only has to both retain and drain water, it also has to keep these properties for a very long time.
To support plant growth, the product must also have the proper nutrients, pH, and salinity levels.
Material is often placed using pneumatic blower trucks.
Combining lightweight aggregates with varying amounts of organic matter creates a lightweight planting media for intensive and/or extensive rooftop gardens.
These designer soils can be created or altered to meet design specifications or address precise project requirements. Designer soils are often required for rooftop gardens, raised planters, containers and urban tree plantings.
Natural sand and soil are heavy. Because of their weight, structural modifications are often required to incorporate a green roof into a project’s design. Native soils have silts and clays that may clog the filter materials or drainage layer and reduce effectiveness.
The physical properties of natural volcanic aggregates vary widely with source and location. Organic materials may degrade and compact over time, and require additions to or replacement of planting media. Some horticultural products used in greenhouses and container planting, such as vermiculite and perlite, are extremely light in weight and do not offer adequate anchorage and support for larger plants. In exterior applications vermiculite and perlite often float to the top of the planting media where they can be carried away by wind or water.
Expanded lightweight aggregates are an all-natural, eco-friendly, non-degradable soil enhancer. This material has a higher absorption rate than competitive products and helps neutralize acid rain runoff and maintain pH levels in the growing medium.
SELECTED CASE STUDIES
CONVENTION CENTER GREEN ROOF AIDS IN STORMWATER MANAGEMENT
There’s a meadow five stories above the busy city streets of Nashville complete with green grass and rolling hills. This green space in the sky is actually the roof of a new convention center in the Music City.
The downtown development is part of the city’s green infrastructure program created to manage Nashville’s urban storm water challenges. The building boasts a 175,000 square foot green roof containing rooflite®, a certified green roof media manufactured by Skyland USA.
Ordinarily, rains pouring over the massive 1.2 million square foot building would drain into the city’s storm water system. But rather than tax the already strained system, some of which dates back to the 1880’s, most of the storm water landing on the new Music City Center will be retained by its specially designed roof.
“Storm water management is a huge problem and that’s why there’s a push for more green roofs,” says Skyland USA’s Managing Director Joe DiNorscia. “They allow 60 to 80% of rainwater to stay on a roof to be absorbed by the plants or evaporated. What’s left comes down slower and that gives the sewer system a chance to better handle the runoff,” he says.