Green Roof Technology

Transcription

1 1 Buec 463 Term Paper Green Roof Technology Leanna Dejneka

2 2 Introduction Green roof technology is based on an old idea which has now become the newest energy conservation idea. Skeptics say that they are just a fad, more hassle in design and maintenance than energy savings; others have embraced the idea and are trying to implement green roof construction in their city buildings. The question worth asking is: When are green roofs an economically feasible construction decision? History The Hanging Gardens of Babylon, of the ancient world, are the first historical models of Green Roofs 1. However, the green roof technology that we are more familiar started in Germany. In the 1900 s green roofs were constructed for use on contemporary residential buildings, for the purpose of fire protection 2. In the 1980 s urban ecology was explored at universities across Germany and the technology was improved to address specification and structure improvements 3. Construction There are two types of green roofs: Intensive and Extensive. Intensive roofs have a landscaped variety of greenery, shrubs, trees and flowers. These roofs often cost more as they take more time and money to maintain. On the other hand, extensive roofs have homogeneous vegetation; they are more standardized and used for industrial projects as they are more cost effective 4. 1 Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 2 Green roofs in temperate climates and in the hot-humid tropics--far beyond the aesthetics, Manfred Kohler, Marco Schmidt, Friedrich Wilhelm Grimme, Michael Laar, et al. Environmental Management and Health. Bradford: 2002.Vol.13, Iss. 4; pg. 382, 10 pgs 3 Green roofs in temperate climates and in the hot-humid tropics--far beyond the aesthetics, Manfred Kohler, Marco Schmidt, Friedrich Wilhelm Grimme, Michael Laar, et al. Environmental Management and Health. Bradford: 2002.Vol.13, Iss. 4; pg. 382, 10 pgs 4 Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug

3 3 Extensive roofs generally have five layers which make up the green roof. First, from the bottom, there is a water proofing membrane, then the root barrier (to prevent root penetration). Third, there is a drainage layer to remove excessive water (to prevent water damage), but it also ensures water retention (important to ensure plants have nutrients during low rain periods and eliminate, or minimize the need for irrigation systems). Fourth, there is a filter fabric layer (to prevent soil from blocking water drainage while maintaining moisture for plant growth), and fifth soil substrate layer to sustain the plant life. The two most common plants are sedum and stone crop. Sedums are the most draught resistant and freeze resistant plants and can grow when no soil is present 5. This is important both in consideration of the climate for growing conditions and for structural concerns of loading the roofs of buildings. Benefits of Green Roofs Moderate temperature fluctuations The main argument in favor of green roofs is its ability to moderate temperatures of buildings. The net effects are that there is a decrease in energy demanded to heat or cool buildings by shading, insulating combined with the cooling effect of evaporating water 6. In 2002 the National Research Counsel of Canada (NRCC) did a study which showed that an extensive green roof would reach a temperature of about 30 C compared to a reference roof that reached over 70 C in the summer. The mean daily temperature fluctuation was 5-7 C on the green roof and C on the reference roof. By moderating temperature fluctuations of the roof there is less expansion and contraction of the roofing materials which would otherwise result in leaks and premature failures with their associated costs. This moderate level of temperature fluctuation can double or triple the life of the roof itself 7. 5 Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 6 Thermal performance of green roofs through field evaluation, NRCC-46412, Liu, K.; Baskaran, B. May 29-30, 2003, Last viewed December 4, Hitting the Roof, American Nursery magazine, July 1, 2001, Dr. David J. Beattie and Dr. Robert Berghage. last viewed December 4, 2004

4 4 The reduction in temperature also moderates heat flow into the building which in turn decreases the demand for space conditioning. The NRCC study also found the decrease in energy demand to be 75% and that green roofs are more effective in reducing heat gain than heat loss 8. This indicates that there is more energy savings in reduction of cooling unit utilization rather than insulating heat loss. This suggests that green roofs have more economical benefits in warmer climates. In another study the NRCC found that green roof reduced the overall heat entering the building during the day by more than 85% and that leaving the building at night by about 70% 9. This reduction in the use of air conditioning units also leads to a saving in replacing and repairing air conditioning units. In certain circumstances a green roof could eliminate the need for air conditioning in a building 10. Environment Canada found that for a typical one story building a green roof could reduce summer cooling needs by 25% 11. In 2002, Environment Canada did a study in Toronto and estimated a direct energy savings of one million dollars of energy cost per year based on a 3.5 km2 green roof building 12. These savings can be realized in similar projects but results depend on a number of green roof factors: thickness of the green roof, composition and moisture of growing medium, the type of plants used and construction of the roof 13. Heat Island Effect In urban areas, the temperature of the air above cities is warmer than surrounding areas on a summer day because city buildings often absorb the suns rays and do not provide any shading in the area 14. This is a significant difference in temperature that has adverse 8 Engineering performance of rooftop gardens through field evaluation NRCC Liu, K. March 13-18, last viewed December 4, Research quantifies benefits of rooftop gardens, CONSTRUCTION INNOVATION, Volume 7 Number 1, Winter 2002, 10 Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 11 Private Benefits, Copyright 2002, 2003, 2004, last viewed November7, Government of Canada Reveals Major Greenhouse Gas Reductions and Air Quality Benefits from Widespread Use of 'GreenRoofs' October 9, 2002, 13 Hitting the Roof, American Nursery magazine, July 1, 2001, Dr. David J. Beattie and Dr. Robert Berghage. last viewed December 4, Learning About Urban Heat Islands, last modified by Brian Pon on April 27, 2000, Viewed November 1, 2004

5 5 effects by changing weather patterns, causing smog and other pollution problems 15. Using lighter coloured roofing material can help to minimize this effect, but green roofs have even more potential to reduce the heat island effect by absorbing solar radiation then re-radiating it 16. When plants transpire, they cool the atmosphere and decrease surrounding temperatures 17. Lawrence Berkeley Laboratory showed that a 5% increase in green space in a large metropolitan area would reduce the average summertime temperature by 4 deg F, and would reduce smog by 10% 18. The aforementioned Environment Canada study found that the city s average temperatures are 4oC to 10oC higher than surrounding areas. This means that more energy is needed to cool buildings which, as stated above, add to air pollution elements such as smog, sulphur dioxide and other greenhouse gasses. This study showed that if 6% of roofs were green the summer air temperatures in Toronto could be reduced by 1-2oC 19. The same study showed that a 1oC reduction in the urban heat island will result in a 5% decrease in demand for electricity for cooling and refrigeration. Storm water run off City roofs often contribute to the problem of storm water run off. This puts pressure on city sewer and drainage systems. The result can be flooding, sewage back up, and pollution of water supplies that can cost the cities millions of dollars to repair 20. Green roofs can retain about 70% to 90% of the rainfall, which stabilizes water runoff and relieves overloaded drainage systems 21. A 2002 National Research Counsel of Canada (NRCC) project found that the green roof could delay storm water run off and reduce peak run off rate and volume. To quantify this, the study found that the green roof retained 245 mm out of the 450 mm of rain fell during April to September 2002; this is a 15 Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 16 Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 17 Hitting the Roof, American Nursery magazine, July 1, 2001, Dr. David J. Beattie and Dr. Robert Berghage. last viewed December 4, Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 19 Government of Canada Reveals Major Greenhouse Gas Reductions and Air Quality Benefits from Widespread Use of 'GreenRoofs' October 9, 2002, 20 Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 21 Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug

6 6 reduction of 54%. 22 The Ward Catalog Warehouse at Montgomery Park Business Centre in Baltimore has a 30,000 sq ft green roof and it is found to reduce runoff between 50% and 75% 23. This reduction in storm water run off is good for over loaded city sewage systems, but has other spillover effects. Surface water is less polluted; as the rain water runoff is less polluted and removes nutrients from the roofs and there is less sewage over flow. This leads to improved water sources such as city rivers 24. Other Positive Impacts As seen above there are many positive impacts that green roof technology can bring to cities but there are other positive impacts not immediately quantified which continue to add value to green roof projects. The impact of green roofs on the eco system is that it turns an ecologically dead zone in the middle of the city into a home for insects and animals. Also, the green roofs produce a substantial about of oxygen for an urban area. The plants can reduce pollution by collecting dust and other pollutants and reemitting new oxygen 25. The Toronto Environment Canada study found that a 6.5 km2 of green roof could reduce green house gas emissions by about 2.18 MT and remove 300 metric tones of CO2 pollutants from the air 26. The Gap Inc office in San Bruno, California has sq ft of green roof space which in addition to the above benefits provides an acoustic barrier from the San Francisco air port nearby 27. Costs of Green Roofs 22 Engineering performance of rooftop gardens through field evaluation NRCC Liu, K. March 13-18, last viewed December 4, Green roofs for healthy cities "make huge leap forward", Anonymous. BioCycle. Emmaus: Jun 2003.Vol.44, Iss. 6; pg Green roofs in temperate climates and in the hot-humid tropics--far beyond the aesthetics, Manfred Kohler, Marco Schmidt, Friedrich Wilhelm Grimme, Michael Laar, et al. Environmental Management and Health. Bradford: 2002.Vol.13, Iss. 4; pg. 382, 10 pgs 25 Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 26 Government of Canada Reveals Major Greenhouse Gas Reductions and Air Quality Benefits from Widespread Use of 'GreenRoofs' October 9, 2002, 27 Green roofs for healthy cities "make huge leap forward", Anonymous. BioCycle. Emmaus: Jun 2003.Vol.44, Iss. 6; pg. 19

7 7 Traditional flat roofs are less expensive than green roofs, but as mentioned, are constructed of ecologically unfriendly chemicals and materials, such as tar, asphalt, solvents and asbestos. At the end of their life, most of these materials will end up in landfills. As mentioned earlier, green roofs can double or even triple the life span of roofs, and keep harmful materials out of landfills. This fact alone is said to negate the higher initial-cost differential 28. As can be seen by the specifications for the layering and drainage for the green roofs, they are more expensive than conventional roofing. The water proofing and root membrane for example will incur extra initial costs from between 10 to 20% 29. In addition, the structure of the building often requires reinforcement to support the heavy soil 30. This too is more costly. Plant specifications also vary depending on climate and it is recommended to choose draught and freeze resistant plants as well as have a fertile and moisture maintaining growing medium. These plants developed and used in Germany for green roofs are expensive to import and there is usually only a small local niche market that would be able to grow the plants. A network of support industries for the plant and growing material needs to grow in order for the costs to be reduced. The cost of irrigation, fertilization and plant replacement need to be taken into account. Even the most carefully planned green roof will still need to be nurtured as weather conditions fluctuate and change the growing conditions for the plants. For example, in Edmonton in the month of November 2004 there has been little moisture; the city has been seen watering plants around the city. This is costly because irrigation systems, flushed out for the winter, need to be turned back on then re-flushed. A congruent situation would be needed for roof top greenery. First there would be the 28 Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 29 Yaremchuck, Larry of Freeze Maxwell Roofing. Telephone interview regarding green roof technology. November 26, Up on the roof,. Canadian Business. Toronto: Mar 31, 2003.Vol.76, Iss. 6; pg. 13, 1 pgs

8 8 initial costs for irrigation brought up to the roof and second there are unpredictable costs of irrigate in dry conditions 31. Fertilizing costs may also need to be accounted for as weather patterns will affect the growth environment for the plant life. A proportion of the roof top plants will die each year and so the cost of replacing should also be considered in project budgeting and planning. There is a need for industry knowledge about green roof technology in the location of construction to ensure that the roofs are made well in order to reduce maintenance costs that may outweigh the benefits. For example, Germany widely uses green roof technology as it has a support industry that can support well made roofs and can effectively maintain them to make green roofs a feasible business decision. The Canadian Roofing Contractor s Association (CRCA) has found that; The problem is that there is very little reliable data, outside of initial costs, about green roof costs. We are currently gathering information on the direct and indirect costs of roof gardens. Unfortunately, we have such a small population of them we are not yet able to determine annual costs. We do know that it may be significant in the first years until the roof top garden has been established 32. To overcome the costs that may be prohibitive to using green roof technology, the support industries such as roofers, architects and horticultural professionals must be more developed in order to plan and support the new green roof technology. Incentives From reducing energy demand, the use of sewage systems, and improving air quality, green roofs can provide positive benefits to society. Green roofs are a new idea and businesses are cautious to adapting new technologies such as these because they are uncertain about the monetary risks involved. There is an external benefit to society that is not directly realized by a firm or a citizen that considers building or redesigning their 31 Yaremchuck, Larry of Freeze Maxwell Roofing. Telephone interview regarding green roof technology. November 26, Kalinger, Peter, CRCA. RE: Green Roofing to Leanna Dejneka. December 7, 2004

9 9 roof to support green roof technology. This positive externality could serve as a rationale for government to step in and provide incentives to businesses hesitant to use the technology. Steven Peck, Executive Director, Green Roofs for Healthy Cities says research will help us to develop appropriate public incentives to encourage widespread private sector green roof installation and build a green roof industry in Canada." 33 As information about the cost and benefits of green roofs increases, the public will be more able to make informed choices as to whether green roofs are a good choice for their buildings or not and which government incentives are appropriate. Toronto s Deputy Mayor Case Ootes says that, Green roof investment and incentives will generate jobs while reducing air pollution." 34 Jobs will be made by creating a market for green roofs in the design, product, and construction of support industries, and air pollution will be reduced by the green roof converting CO2 into oxygen. Currently there is a construction incentive program under the Leadership in Energy and Environmental Design program (LEED) 35 Sustainable Design category. Credit 7 under this category acknowledges the efforts to reduce heat island effects to control micro climates. Credits are given to buildings that use either green roof technology or an Energy Star roof (which is a white roof reducing the amount of heat absorbed, which similarly to the green roof reduces the heat island effect) 36. When considering these project designs it seems most projects would undertake an Energy Star roof plan in order to receive the credits as there are less maintenance costs. A green roof might be considered when there are other benefits, for example a hospital choosing might choose a green roof for aesthetic purposes, as patients rooms often look out on to adjoining roofs. The University of Alberta is examining the LEED Green Building Rating System for the 33 Government of Canada Reveals Major Greenhouse Gas Reductions and Air Quality Benefits from Widespread Use of 'GreenRoofs' October 9, 2002, 34 Government of Canada Reveals Major Greenhouse Gas Reductions and Air Quality Benefits from Widespread Use of 'GreenRoofs' October 9, 2002, 35 More information about LEED can be found at: 36 Rodrigues, Len Architect AAA, FRAIC, AIA, "LEED" Accredited Professional. Telephone interview regarding LEED program and U of A green roof potential, December 13, 2004

10 10 new Centennial Center for the Interdisciplinary Science building. However, this may or may not result in the implementation of green roofs on this project 37. Canadian Environment Minister, Stephane Dion, is suggesting that all federal building have green roofs and that the Public Works Treasury Board have a green-procurement policy. He is also urging Finance Minister, Ralph Goodale, to budget for tax breaks or hikes to encourage people construct green roofs 38. Tax differentials would be aimed at reducing costs for firms that put the green roof technology into effect for their business. These incentives would help to offset the potentially prohibitive costs of green roofs so as to capture more of the less quantifiable social benefits that the government wishes to have. This tax suggestion hopes to show that the government is leading by example and making changes that will chance public behavior in order to reduce energy use and improving the environment 39. It is commendable that the government is hoping to offer incentives to promote more environmentally friendly activities and reduce energy consumption, but they must also ask; which incentive expense will be the most efficient way of realizing these positive externalities? For example, there may be less greenhouse gas emissions, less gas used and less cost to the government and tax payers if the government offered incentives to the public to purchase hybrid cars or to increase green park area in the city. As mentioned earlier, green roofs started to become commercial in the German market and it has taken a long time to develop; it is not expected that a local developing green roof industry will take off over night. Currently 12 % of flat roofs are green 40 and 7% of newly constructed flat roofs are green, and there are more and more sloped roofs going green as well 41. At this stage of local green roof technology, Germany is able to realize the benefits which over come the costs. In North America, any incentives that are put in 37 Rodrigues, Len, Architect AAA, FRAIC, AIA"LEED" Accredited Professional. RE: U of A green roof to Leanna Dejneka December 13, Edmonton Journal, Monday November 1, 2004, section A1 and A13 39 Edmonton Journal, Monday November 1, 2004, section A1 and A13 40 GREEN ROOFS ATOP CAMPUS AND INDUSTRIAL BUILDINGS, In Business. Emmaus: May/Jun Vol. 26, Iss. 3; pg Green roofs in temperate climates and in the hot-humid tropics--far beyond the aesthetics, Manfred Kohler, Marco Schmidt, Friedrich Wilhelm Grimme, Michael Laar, et al. Environmental Management and Health. Bradford: 2002.Vol.13, Iss. 4; pg. 382, 10 pgs

11 11 place now will not change behavior overnight; green roofs and the surrounding industries will take time to develop. The Business of Green Roofs Ford Case In 2000 Ford Motor Co. was advised by a soil scientist at Michigan State University to install a 10.6 acre green roof 42. This green roof is supported by a modified bitumen roof 43 and the plant used is sedum, developed by a German company which is specialized in green roofs. The sedum was grown like sod and transferred to the roof when the structure was ready 44. Ford says that this green roof can absorb 4 million gallons of water per year 45. Thus, green roof technology has reduced storm water runoff (into the nearby Rouge River) and eliminated the need and the cost of storm water drainage systems 46. The green roof also lessens the impact of UV deterioration and freeze-thaw cycles; 47 this is expected to contribute to increasing the lifespan of the roof. The roof is expected to last 20 to 40 years 48. In this time, the green roof will save the company money by conserving energy by reducing heat gain 49. In the winter Ford has found its long term energy savings to be about 25% due to the green roof s insulation 50. These savings however, are offset by maintenance costs that are about one hundred thousand dollars per year 51. In addition to the use of green roof technology, Ford has extensive environmentally friendly features on their building such as ivy covered walls and a porous surface used for 42 GREEN ROOFS ATOP CAMPUS AND INDUSTRIAL BUILDINGS, In Business. Emmaus: May/Jun Vol. 26, Iss. 3; pg Ford's new Rouge plant gets "living roof", Building Design & Construction. Chicago: Jul 2003.Vol.44, Iss. 7; pg Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 45 Ford's new Rouge plant gets "living roof", Building Design & Construction. Chicago: Jul 2003.Vol.44, Iss. 7; pg Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 47 Ford's new Rouge plant gets "living roof", Building Design & Construction. Chicago: Jul 2003.Vol.44, Iss. 7; pg Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 49 Ford's new Rouge plant gets "living roof", Building Design & Construction. Chicago: Jul 2003.Vol.44, Iss. 7; pg Up on the roof,. Canadian Business. Toronto: Mar 31, 2003.Vol.76, Iss. 6; pg. 13, 1 pgs 51 Yaremchuck, Larry of Freeze Maxwell Roofing. Telephone interview regarding green roof technology. November 26, 2004

12 12 parking lots. Tim O'Brien, director, Ford Environmental Quality Office says that this unconventional system is estimated to save $US 35 million 52. Ford starts its company tours at a tower which looks across the green roof 53. This business decision of choosing green roof technology is congruent with Ford s Public Policy 54, and their focus on sustainable economic development and protection of health and the environment. They are not only concerned with technology improvements of their vehicles but their business operations as well. Conclusion The benefits of green roof technology are far reaching. Some benefits are easer to realize such as reduction in energy used for air conditioning units. However, some benefits which are even relatively easy quantify, such as a reduction of CO2 in the air and cleaner runoff water, are not taken into account by the businesses and builders considering green roof technology. The costs of green roofs are also uncertain, and in developing green roof industries these costs could be prohibitive especially if the benefits to society cannot be realized in planning for the use of green roof technology. This is where the government must play a role in deciding if the combined social benefits associated with an increase in green roof technology should be encouraged. These benefits must be contrasted with other technologies that can attain similar benefits. The Canadian government has suggested using tax incentives to help cover the costs of the green roofs. This will have a positive role in encouraging development of the supporting industries and reduce the currently higher start up and maintenance costs. Once a local industry is more developed, green roof technology will be better able to be self sustaining and businesses can choose this technology even without government support. 52 Green roofs offer environmentally friendly alternative, Michael D Perry. Plant Engineering. Barrington: Aug 53 Ford's new Rouge plant gets "living roof", Building Design & Construction. Chicago: Jul 2003.Vol.44, Iss. 7; pg Ford Motor Company Health and Environmental 2004 Ford Motor company. Last viewed Nov. 3,