Green Roofs

1. Green Roofs Andrew McKowen amckowen@spsu.edu

2. History • “Green Roof Technology started in Babylon in the 7th century B.C. Back then it was known as the Hanging Gardens of Babylon, a majestic structure built by King Nebuchadnezzar II for his wife, Amyitis.” 1 • “The first known historical references to manmade gardens above grade were the ziggurats (stone pyramidal stepped towers) of ancient Mesopotamia, built from the fourth millennium until around 600 B.C.” In France, gardens planted in the 13th Century thrive atop a Benedictine abbey.” 2 • “The original inspiration for contemporary green roofs came from rugged Iceland, where sod roofs and walls have been used for hundreds of years. The sod roofs soon became popular throughout Scandinavia.” 3 • “Switzerland has one of Europe’s oldest green roofs, created in 1914 at the Moos lake water-treatment plant, Wallishofen, Zurich. Its filter-tanks have 30,000 square meters (320,000 sq ft) of flat concrete roofs. To keep the interior cool and prevent bacterial growth in the filtration beds, a drainage layer of gravel and a 15 cm (6 in) layer of soil was spread over the roofs, which had been waterproofed with asphalt.” 4

3. History • Five roof gardens were installed atop the seventh floor of the Rockefeller Center in New York City, New York, between 1933 and 1936. Designed to be ‘viewscapes’ for the enjoyment of skyscraper tenants (at higher rents, of course), these gardens continue enhancing the view in New York City. 3

4. History • “[In 1961] ReinhardBornkamm, a researcher at • Berlin’s Free University, publishes his work on green roofs.” His works are the foundation of all modern green roof technology. 4 • Until 1970 green roofs were mainly a luxury item for homes. • “[in 1975] the Landscape Research, Development & Construction Society, which has established widely followed green-roof standards, is founded.” 4

5. Extensive Green Roofs • “Extensive green roofs are lightweight veneer systems of thin layers of drought tolerant self-seeding vegetated roof covers using colorful sedums, grasses, mosses and meadow flowers requiring little or no irrigation, fertilization or maintenance after establishment.” 3 • “Typically, only maintenance personnel have access to this type of roof.” 2 • “Generally, extensive green roofs can be constructed on roofs with slopes up to 33%, and can be retrofitted onto existing structures with little, or most often, no additional structural support.  The average weight of a fully saturated minimum extensive green roof is 17 pounds per square foot, which is comparable to the weight of gravel ballast placed on many conventional roofs.  These roofs are not intended for recreation, or to accommodate the weights of people, larger shrubs nor trees. Extensive green roofs are less costly due to single or double layer construction.” 3 • This website has more information on this topic. • http://www.wbdg.org/resources/greenroofs.php

6. Extensive Green Roofs Gap Headquarters in San Burno, CA. 69,000 sq ft.

7. Intensive Green Roofs • “Intensive green roofs are more elaborately designed roof landscapes, such as roof gardens and above/underground parking garage roofs, that are intended for human interaction and will need to be engineered to conform to the load requirements.” 3 • “Different growth media types and depths allow for a larger selection of plants, including flowering shrubs and trees. Typical soil depths start at 6 - 8 inches and can reach 15 feet or more - the limiting factors here are the roof loads and perhaps the client's budget.  Pathways, terraces, water fountains, ponds, and other architectural features result in beautiful and dramatic spaces. Depending on the plant selection, additional water collection cisterns, reservoir boards, irrigation, fertilization and/or maintenance may be necessary, just as it would be for a traditional garden.” 3

8. Intensive Green Roofs Atlanta City Hall. 2000 sq ft vegetation & 1000 sq ft pavers Left: Roof Garden in Manhattan

9. Ecological Benefits • “Perhaps greatest ecological function a green roof can provide is its storm water management capacity.” 5 • ”According to civil engineer Charlie Miller, Principal, of Roofscapes, Inc., “Vegetated roof covers may offer the only practical ‘at-source’ technique for controlling runoff in areas that already are highly urbanized.”5 • “Depending on rain intensity and green roof soil depths, runoff can be absorbed between 15 to 90 %, thereby considerably reducing runoff and potential pollutants from traditional impervious roofing surfaces.” 5 • “Green roofs reduce the volume of storm water flowing into streams and drainage channels, resulting in the control of sediment transport and overall soil erosion.” 5 • “Green roofs can reduce ambient air temperatures and increase humidity levels in the surrounding areas.” 5

10. Economic Benefits • “The initial extra short-term capital costs of green roof construction can be offset through long-term energy and maintenance savings.  The economic benefits represent real reasons for local municipalities, developers and private residence owners to consider opting for a green roof although first costs may be higher.” 6 • “According to Oak Ridge National Laboratory (ORNL), most roofing systems fail from leaks, and the average roof needs to be replaced four times.  In addition to replacement cost savings and construction waste reduction, ORNL estimates that if low-slope roofing systems could be kept dry, more than three-fourths of a quadrillion BTUs of energy could be saved each year in the United States.” 6 • “Depending on local ordinances, green roofs may be installed in lieu of conventional storm water practices. They can significantly reduce the size, or even completely eliminate, the necessity for unsightly, space-wasting, and expensive detention ponds or underground galleries.” 6

11. Economic Benefits • “The life of the underlying roof waterproofing membranes can be extended by using green roofs to shield the roof from the effects of ultraviolet radiation, temperature extremes and mechanical damage.” 6 • “Overall building energy costs can be reduced due to the green roofs’ natural thermal insulation properties – vegetated roofs reduce building heat-gain, so  structures are cooler in summer and warmer in winter.” 6

12. Other Benefits • “Green roofs reduce sound reflection by up to 3 dB and improve sound insulation by up to 8 dB. This is important for people who live near airports, noisy discotheques, or industrial parks. Additionally, electromagnetic waves from transmitting stations can be effectively shielded by the vegetation layer.” 7 • Green roofs can offer natural habitat for animals and plants. • “Green roofs are visually enhancing the quality of life in the cities.”8 • Green roofs reduce the level of dust particles in the air. “One square meter of Green Roof can filter approximately 0.2 kg aerosol dust and smog particles per year.” 8

13. Other Benefits • “Converting or designing normally unused roof areas into green roofs, simply makes sense. Increase your property value by reclaiming the fifth elevation of a building and make it an amenity to be used by the buildings occupants.” 9 • “More and more municipalities and other government agencies are providing incentives that can help off-set the cost of a green roof.” 9

14. Links • 1http://www.ifenergy.com/50226711/the_history_of_green_roof_technology.php • 2http://www.proenviroconstruction.com/pdf/GreenRoof.pdfGreat source for information • 3http://www.greenroofs.com/Greenroofs101/history.htm • 4http://www.greenecoservices.com/history-of-green-roofs/ • 5http://www.greenroofs.com/Greenroofs101/ecological.htm

15. Links • 6http://www.greenroofs.com/Greenroofs101/economic.htm • 7http://www.igra-world.com/benefits/private_benefits.php • 8http://www.igra-world.com/benefits/public_benefits.php • 9http://www.hydrotechusa.com/benefits.htm