Green Roof

 Green roof?  Well, yes – plants growing on top of the building!

 The Green Roof on the boat house is made of sedums, a plant well adapted to extreme temperature and drought. The plants help to clean and treat the water before it even reaches the ground. It even acts as insulation, helping to keep the building cool in the summer and warm in the winter.

 Benefits of Green Roofs

• Stormwater Management: Anne Arundel County is composed of 14% impervious surface, such as parking lots and driveways, which increases the amount of pollutants running into our waterway.  Green roofs naturally filter and retain rainwater as part of a stormwater management system that includes rain barrels, rain gardens, and wetland construction.  North Carolina State University data suggests that green roofs can reduce up to 50% of rainfall runoff annually.

Source: Hunt, William F. “Overview of Innovative Stormwater Treatment Practices: Green Roofs, Permeable Pavement, and Water Harvesting Systems/ Cisterns.” Treating Rooftop Runoff [2006]: 3-14.

• Denitrification: 30% of harmful nitrogen in our environment is present in the air.  This nitrogen in turn falls to earth in the form of acid rain, presenting a huge problem for biodiversity.  In the Chesapeake, eutrophication is a process in which high amounts of nitrogen from rain and runoff have created algal blooms.  When these blooms decay, they create hypoxic (little oxygen) or anoxic (no oxygen) conditions in the Bay, making it difficult for anything to live.  Green roofs catch nutrients such as nitrogen and filter rainwater so it can safely travel into waterways.

Source: United States Environmental Protection Agency

• Aesthetics: The design of our green roof is coordinated so that different varieties of Sedum develop into different colors, displaying the Arlington Echo logo.  They are also an interesting tool in learning about stormwater management.
• Reduced roof temperature: Green roof plants, in the process of photosynthesis, soak up much of the light that would be absorbed into the roof, making the boathouse cooler in the summer.  At the same time, the respiring green roof acts as insulation in the winter, regulating temperature in all seasons.
• Plant Habitat: Although the roof is planted with varieties of Sedum, a plant normally acclimated to desert environments, the roof space provides more area for plants, encouraging a greening of highly populated areas, especially cities.