Intensive and Extensive Green Roofs
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This was our very first project of 6th grade Project Challenge, Turn It Green, where we attempted to convince the school board to allow the installation of a "green roof" on our school. We are waiting for better weather to finish our assessment of realistically applying what we learned. Check back in Spring!!!
1. “Definition:”A green roof consists of vegetation and soil, or a growing medium, planted over a waterproofing membrane. Additional layers, such as a root barrier and drainage/irrigation systems may also be included.//A green roof is a roof of a building that is partially or completely covered with vegetation and soil, or a growing medium, planted over a waterproofing membrane. (www.epa.gov) (www.wikipedia.org)
2. Benefits: Provide amenity space for building users in effect replacing a yard or patio, grows fruits, vegetables, and flowers, reduces heat and cooling, increases roof life span, reduces storm water run off, filters pollutants and Co2 out of the air, filters pollutants and heavy metals out of rainwater, and increases wildlife habitat in built up areas. (www.wikipedia.org) (Also can reduce heat loss and energy consumption in winter conditions)
3. Disadvantages: Some disadvantages of having a green roof are that they have more demanding structural standards, maintenance costs could be higher depending on the roof make or type, place higher demands on the waterproofing system of the structure, both because water is retained on the roof, and due to the possibility of roots penetrating the waterproof membrane, and installing adequate waterproofing system and root barriers can increase the cost of the roof.
4. Major Cities with Green Roofs: Toronto, Chicago, Atlanta, Portland, and New York are some major cities with many green roofs.
5. Mayor Daley's Position on Green Roofs: Mayor Daley supports the idea of green roofs strongly by stating that he believes it could reclaim thousands of acres for the environment, and says they'll help buildings with heating and cooling.
6. Some Buildings in Chicago with Green Roofs: Some buildings in Chicago with green roofs are Chicago's City Hall, Best Buy of 21 North Elston, The Apple Store, Target, McDonald's, Walmart, Menards, Chicago Center for Green Technology, CVS, and Chicago Transit Authority Headquarters are some buildings in Chicago with green roofs.
7. Successful Green Roofs From the Above List: There are four Targets in Chicago that have green roofs. The green roof cools down the building in the summer. It will also reduce pollution and maintenance costs. The green roof is 9,664 square feet and was completed in 4 days. The plants are in rows of the same species, so when they are mature, the roof will look like it is striped.
Also, the City of Chicago Department of Environment (DOE) initiated the City Hall Rooftop Garden Pilot Project as part of the Urban Heat Island Initiative with the United States Environmental Protection Agency. The rooftop garden was designed to test its cooling effects and its ability to sustain a variety of plants in three different depths of growing media. Monitoring of the plants, birds and insects is underway. Results from monitoring the cooling effects during the garden's first summer showed a roof surface temperature reduction of 70 degrees and an air temperature reduction of 15 degrees. Overall, the green roof project of City Hall was a success. (www.asla.org)
8. Schools with Successfully Incorporated Green Roofs: The Calhoun School in New York City, Fieldston Middle School in Manhattan, and Ellington Elementary School in Chicago are some schools with successfully implemented green roofs.
9. Materials: Substrate (enriched soil), filter fabric, drainage, moisture barrier to protect from soaking up excess water, insulation, vegetation that grows well in your region, a drainage system, and a separation layer are the layers of a green roof. (www.epa.gov.)(www.gaf.com).
{An “extensive” roof has a thin layer of soil in which mosses and other shallow-root plants live with little maintenance. “Intensive” roofs have larger vegetation planted in deeper soil. These green roofs sometimes require irrigation systems, since they are more like gardens. (Wikipedia 2006)} (www.lid-stormwater.net)(www.epa.gov.)(www.gaf.com)
10. Process: See diagram on page 3 below. Make careful calculations beforehand of what your soil, plants, chairs and tables, people, etc. will weigh, and check with a constructor to find out that your roof structure can bear the load. Remember to calculate the weight of wet soil, and to add the weight of estimated snow.
Drainage. Make sure that you have adequate drainage from your roof, and that drains can not be clogged by soil.
Your garden will need maintenance. Consider for example if it may need irrigation.
Check the safety fences etc. for people doing maintenance as well as people spending time in your roof garden.
Choose plants that are suitable for the soil type and other conditions on the roof.
The waterproofing membrane should be in good condition. (Today there are several waterproof options from asphalt, to sheeting, to membranes that go on as a liquid.)
Obtain required permits from the Department of Construction and Permits.
Research green roof designers and installation companies.
Pick a type of green roof.
Select plants and irrigation system.
) (www.ehow.com)
11. 4 Site's Average Costs of Installation: 15$ per sq. foot is an average of costs from www.glwi.uwm.edu, www.epa.gov, www.greenroofs.com, and www.lid-stormwater.net.Insert a roof barrier, drainage layer, filter fabric, growing medium, drip irrigation, plants, and a wind blanket.
Some plants that you choose, or that may come as weeds on thicker soil layers, can have aggressive roots that may damage your building. Therefore it is advisable to add a root barrier, for example a rubber mat with heat-sealed edges, to protect the underlying structures. (www.greenroof.se/)(www.glwi.uwm.edu
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Intensive and Extensive Green Roofs
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-Intensive green roofs are mostly for viewing, and usually we can't have students visiting the top of a building.
-Much Cheaper
-Less maintenance required
-Less materials to install
-Requires less structural support