MSYInternational visits Build a Green Roof Workshop with GrowNYC, Saturday, September 11, 2010

Green Roof Workshop taught by Marni Majorelle of Alive Structures and facilitated by Tom Twente of GrowNYC with participants. Photo: MSYInternational
A clear and beautiful day, the sun shown brightly upon the sedum reflexum/succulent plants waiting in the wings to land a spot in their new home. In a wooden box on top of a shed in the Greenspace Community Garden, 222 5th Avenue, Park Slope, Brooklyn New York is where students installed a small model of a Green roof. This hands on workshop was led by the founder of Alive Structures Marni Majorelle and Tom Twente of GrowNYC.
What is a Green Roof?
A Green roof is a roof designed with plants/vegetation for the purpose of reducing surface temperatures.

Morgan Mail Processing Facility, New York; Photo Courtesy of EKLA for MSYInternational
Green roofs have many benefits such as providing a buffer between the direct sunlight to the roof’s surface. Energy efficiency, filtration of pollution, storm water management and enhancing the quality of life are some of the reasons why Green roofs are designed and created. The Green roof technology keeps the internal building temperatures balanced and lower in comparison to a roof with no Green vegetation. This results in energy savings. Green roofs last much longer than a non-vegetated one. Heat island effect is a term that refers to a temperature of 10 degrees or more in urban cities which is caused by concrete and asphalt in these urban areas. Ask yourself this if you were on a roof would you be cooler if you were standing in the middle of an asphalt roof or a Green vegetated roof if the temperature outside is 100 degrees. Most likely the Green roof with provide you with a cooling mist. How exactly does this cooling mist happen? Well the plants naturally convert sunlight to chlorophyll which makes it possible for plants to convert carbon dioxide and water that creates the cooling effect. In this workshop Marni discussed two types of Green roofs with the students extensive and intensive:
Extensive Green Roof – Is the common and most affordable of the two. Usually 3 to 5 inches of soil is used. The type of plants used are those that grow low, are resistant to drought and do not require irrigation. Those plants are known as succulents or sedums as mentioned above and also Moss.
Intensive Green Roof – Also know to be more expensive since more structural support is needed and if it’s a public Green roof, safety features would need to be designed within the Green roof space to allow the public access.
Intensive Green roof’s soil is usually 4-24 inches and are planted with various types of plants which will include shrubs and trees. This workshop covered eight components into the Green Roof-shed; vegetation, engineered lightweight soil, irrigation, bio-blanket, drainage mat, root barrier, waterproof membrane and roof deck.
Concrete, flat roofs are structurally the best if you’d like to add a Green roof with a minimum of a 10%-20% slope to promote the best drainage. Plant anchors for plants on a 40% slope to prevent the sliding of the pots.
All participants had the opportunity to have a more personal experience with the creations of mother earth; soil, native plants, and herbs. Added into the mix is engineered lightweight soil consisting of a special blend of organic compost, expanded shale, brick shavings and sand.
[Tip: Compost is organic matter broken down. Consisting of leaves, grass. You can add vegetable and fruit peelings, egg shells and organic scraps from your breakfast, lunch, dinner and snacks. Ground coffee is also added. To make compost, gather organic material into a bin or pile, aerate (create small holes in it to give it air) and add it to your soil.
Note: Expanded shale, is gravel-size rock full of air. It makes the soil easy to work and helps the soil drain better. You only need to add it to garden beds one time;therefore, saving on costs down the road.]