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While I have never considered myself an environmentalist, my attitudes have been changing as I realize the ease and additional benefits of green building initiatives. Take for instance Green roofs; who would have thought growing grass or other vegetation on a roof would have so many benefits for the environment and the building owner. Green roofs are beneficial because they reduce energy costs, decrease storm water runoff and replace natural habitats that were destroyed by building.

Green Roof Design
Although there are several different types of green roofs, all are composed of mostly hardy, low maintenance succulent plants. In addition to an existing roof, green roof systems require a high quality water-proofing and root repellant system, a drainage system, filter cloth, a light weight growing medium and plants. The weight of a roof with a thin layer of soil and sedums is approximately the same as a roof of clay tiles and the ideal slop is 1:12 and must be less than 7:12 (30 degrees). The following websites provide additional information on green roofs- www.greenroofs.org and www.greenroofs.com

Benefit: Reduced Energy Costs
A benefit of green roofs is that they control building temperature. In the summer they keep the building cooler and in the winter they keep warm air inside. The use of traditional, non-reflective surfaces contributes to a heat island effect as radiation from the sun is absorbed and transferred through convection and conduction back to surrounding areas. As a result of this heat island effect, ambient temperature in urban areas can be artificially elevated by more than 10 degrees F when compared with surrounding suburban and undeveloped areas. Unlike these dark roofs that absorb heat, reflective surfaces such as green roofs help control the building temperature and reduce operating costs by keeping down the cost of heating and cooling your building. The increased insulation factor of the roof helps keep cool air inside during the summer and warm air in during the winter. The decreased energy use helps reduce environmental and economic impacts associated with excessive energy consumption.

Benefit: Decreased Storm Water Runoff
Green roofs reduce the volume of storm water runoff by absorbing the rain and retaining 50-60% of the roof’s total annual runoff volume. The soil on the roof retains 90-100% of the critical 1st hour of heavy rainfall that can overwhelm storm water management systems. In urban & suburban centers, this could aid in alleviating the cost of storm water management and help in flood control. The water that is not retained by the green roof and does runoff is better quality water and is cleaner when entering streams and waterways.

Storm Water Runoff Management Case Study
Ford Motor Company in Dearborn, Michigan, built their Ford Rouge Visitors Center in 2003. The project demonstrated exceptional storm water management practices. During rain and snow, sedum plants on the project’s green roof capture and cleanse runoff before it returns to the natural watershed, this preventing contaminated runoff form harming nearby river and lakes. Storm water runoff that is not soaked-up by the green roof is collected in stone basins under a porous paving parking lot, then filtered through natural wetlands and bios Wales located around the site. The project’s natural storm water management system is much less expansive than installing and operating a traditional storm water treatment plant.

Benefit: Restored Natural Habitats
Rooftop habitats are isolated from other habitats and create wildlife corridors for migrating species. Green roofs can be specifically designed to mimic endangered ecosystems or habitats. These roofs can be designed for minimal maintenance and because they are so protected they make great homes for fragile plants and birds that nest on the ground. Since the soil on green roofs is also less likely to be disturbed, it becomes a safer habitat for insects.

Additional Information on Green Roofs:
Stormwater Best Management Practice Design Guide, EPA/600/R-04/121A, September 2004, Download (PDF)

Maryland Stormwater Design Manual
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