ASSESSMENT OF THE URBAN HEAT ISLAND (UHI) FOR THE BOROUGH OF SHIPPENSBURG, PENNSYLVANIA. By William C. Pompeii II

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1 ASSESSMENT OF THE URBAN HEAT ISLAND (UHI) FOR THE BOROUGH OF SHIPPENSBURG, PENNSYLVANIA By William C. Pompeii II A Practical Exam Submitted to the Department of Geography and Earth Science and the Graduate Council in partial fulfillment of the requirements for the degree of Master of Science in Geoenvironmental Studies SHIPPENSBURG UNIVERSITY Shippensburg, Pennsylvania February 2010

2 Introduction In recent years the push for more environmentally friendly development and mitigation has became a leading issue for cities across the country. The use of environmentally friendly development and mitigation not only helps the environment, but the people living within it. Leading the push in our region is the Borough of Shippensburg, Pennsylvania. The Borough of Shippensburg is considering implementing green roofs on some of their buildings in the downtown area to become more environmentally friendly and help reduce the Urban Heat Island (UHI). Before investing in such an endeavor, an assessment of the current temperature conditions within the Borough of Shippensburg will need to be analyzed to see if such an investment is worth the benefits in reducing the UHI and helping the environment. This assessment will analysis the data collected for the Borough of Shippensburg s UHI, and discuss the results that will help the Borough of Shippensburg in their decision to incorporate the green roofs in their downtown area. Background information of the Urban Heat Island (UHI) effect, green roofs, and previous studies and findings, as well as costs analysis will be discussed. 1

3 Literature Review Urban Heat Island Before human development began disturbing natural habitats, soils and vegetation constituted part of a balanced ecosystem that managed precipitation and solar energy effectively (Getter and Rowe 2006). The losses of these features have been replaced with impervious areas. In the United States, it is estimated that 10% of residential developments and 71% to 95% of industrial areas and shopping centers are covered with impervious areas. Today, two-thirds of all impervious area is in the form of parking lots, driveways, roads, and highways (Getter and Rowe 2006). These increasing impervious areas consist of cities, towns, and suburbs. It is documented that urbanization can have significant effects on local weather and climate. Of these effects one of the most familiar is the UHI (Streuker 2002). The increase of urbanization has greatly increased over the last century. Though it may seem the study of the UHI is fairly new, it actually was noticed and documented as far back as The UHI is a metropolitan area that is significantly warmer than its rural surroundings (Figure 1). The thermal characteristics of materials used in the city (asphalt, brick, concrete, glass, etc.) differ greatly from those found in the countryside (trees, grass, water bodies, bare soil, etc.). In addition, the canyon structure created by tall buildings enhances warming by the sun (Figure 2). During the day the energy is trapped by multiple reflections and absorption by the buildings (Chapman 2005). This stored energy in urban areas is then reradiated as long-wave radiation less efficiently than in rural areas during the night (Solecki and others 2005) keeping the urban areas 2

4 warmer than the surrounding rural areas, while the buildings play a role in reducing wind speed. The combination of reducing wind speed, and cloud cover aid in the UHI becoming magnified. Heat island magnitudes are largest under calm and clear weather conditions. Increasing winds mix the air and reduce the heat island. Increasing clouds reduce radiative cooling at night and also reduce the heat island (Voogt 2004). Another component that adds to the creation of an UHI is from waste heat. Waste heat is emitted from a range of human activities-automobiles, air conditioning equipment, industrial facilities, and a variety of other sources, including human metabolism (Sailor and Dietsch 2005). Air temperature also is reduced through evapotranspiration. Evapotranspiration occurs when plants secrete, or transpire, water vapor through pores in their leaves. The water draws heat as it evaporates, thus cooling the air surrounding the leaves in the process. Trees can transpire up to 100 gallons of water in a day. In a hot dry climate, this cooling effect equals that of five air conditioners running for 20 hours per day (Gary and Finster 2008). In contrast to the natural landscape cities tend to have little vegetation, and due to large fractional cover of impervious surfaces there also tends to be less surface moisture in urban areas (Sailor and Dietsch 2005). Figure 1. Late afternoon temperature profile over a city. Figure 2. City Canyons. Reflection of solar energy off Source: Environmental Protection Agency, buildings. Source: Chapman

5 The increase in urban temperatures can affect public health, the environment, and the amount of energy that consumers use in the summertime cooling. Summertime heat islands increase energy demand for air conditioning, raising power plant emission of harmful pollutants. Higher temperatures also accelerate the chemical reaction that produces ground level ozone and smog (EPA 2003). Over the next century, human induced warming is projected to raise global temperatures by an additional 3 to 7 o F (Chicago Climate Task Force 2007) adding to the Global Warming Effect. In response to the increase in temperature, the Environmental Protection Agency (EPA) created the Heat Island Reduction Initiative (HIRI). Through its HIRI, established in 1997, the EPA is working with stakeholders to mitigate the heat island effect by promoting heat island reduction strategies which included planting shade trees, increasing urban vegetation cover, and installing cool roofing and paving materials that were reflective and emissive (Wong 2008). Green roofs are one of the promoting strategies taking hold that helps reduce the UHI effect. Previous Urban Heat Island Studies and Findings A study was conducted by Kent State University in which 31 years of temperature data were studied for Toledo, Ohio. In this study an electronic remote reading thermometer was used with a thermograph that was maintained as a back-up system and was used occasionally when personnel were not available to read thermometers on weekends prior to 1983 (Schmidlin 1989). The study utilized two stations, one downtown and one at a rural site (airport). The study found the average 4

6 annual temperature was 2.0 o C warmer at the urban site than the rural site. The heat island was most intense during the summer months and least evident during winter and spring (Schmidlin 1989). The research also suggested there may be some variance do to the effect of Lake Erie. The lake effect on urban areas will be looked at later in this review. The freeze-free season, when corrected for the local effect of Lake Erie, was approximately 24 days longer at the urban site (Schmidlin 1989). In another study conducted by Singapore to determine the remediation effects of green roofs on the UHI, researchers determined that gardens reduced roof ambient temperature by 4 o C and that heat transfers into the rooms below were lower. The team analyzed climatic data collected from various regions of Singapore and historical climatic data obtained from meteorological services. The researchers found that commercial- and business-district areas were hotter than the green areas by 2 o C (Hein 2002). Green Roof Types Green roofs involve growing plants on rooftops, thus replacing the vegetated footprint that was destroyed when the building was constructed (Getter and Rowe 2006). Greens roofs are classified into two categories, intensive and extensive. Intensive green roofs involve intense maintenance and include shrubs, trees, and deeper planting medium. Extensive green roofs have less maintenance and usually consist of shallower soil media, different plants such as herbs, grasses, mosses, and drought tolerant succulents such as sedum (Getter and Rowe 2007). The creating of green roofs, either intensive or extensive, both have beneficial effects to the environment and the UHI. 5

7 Benefits of Green Roofs Green roofs have multiple benefits such as shadowing the surfaces of a roof. By doing so, they reduce the roof s heat gain by nearly 100 percent. A green roof forms a buffer zone between the roof and the sun s radiation and shades the roof, preventing its surface from heating up and increasing outdoor and indoor air temperatures (U.S. Department of Energy 2004). Green roofs provide many other benefits such as stormwater management, improving roof membrane longevity, summer cooling of interior space, wildlife diversity, air quality, aesthetic, and reduction of the UHI. Studies and models have shown the benefits of green roofs ability to reduce the UHI. A regional simulation model using 50% green-roof coverage distributed evenly throughout Toronto showed temperature reductions as great a 2 o C in some areas (Oberdorfer and others 2007). Also air adjacent to the River Thames in London, U.K., or with urban parks, is on average 0.6 o C cooler than air in neighboring built-up areas (Wilby and Perry 2006). The National Research Council of Canada (NRCC) conducted a field study over a two year period ( ) to evaluate the thermal performances of green roofs. The study found that the daily maximum membrane temperature underneath the green roof was significantly lower than the daily maximum membrane of the reference roof (U.S. Department of Energy 2004). The temperature of the same green roof exceeded 30 o C on only 18 days out of 660-days, whereas the non-green rooftop exceeded 30 o C on 63 days out of the 660-days. Also, the NRCC predicted that if only 6 percent of Toronto s roofs, or 1,600 acres (6.5 square kilometers), were green roofs, summer temperatures could 6

8 potentially be reduced by 1 o C to 2 o C in the urban center (U.S. Department of Energy 2004). Borough of Shippensburg-Study Area Shippensburg is located in south-central Pennsylvania and is surrounded by Southampton Township. Shippensburg lies in the central part of the Cumberland Valley and has an approximate elevation of m above sea level, with a population of about 5,590 people living in an area of 5.2 km 2. Southampton Township has a population of 4,790 people living in an area of km 2. Shippensburg s land use mainly consists of areas of high and low urban density with much smaller amounts of agriculture, forests, and wetlands. Southampton Township is mostly agriculture in the areas adjacent to the downtown Shippensburg area. The average annual daily temperature for Shippensburg, as recorded by the National Weather Service/National Climatic Data Center s Cooperative Observers Network station at Shippensburg University, was 12 o C, with an average low of 6 o C (Doyle and Hawkins 2008). Methods The data used for this assessment were obtained from Dr. Tim Hawkins at Shippensburg University in the Geography and Earth Science Department. Dr. Hawkins has done previous studies concerning the UHI in Shippensburg and in other parts of the country. For this particular case, the data provided consisted of 7

9 temperatures ( o C) taken in an urban and rural setting. The urban setting was located in the Borough of Shippensburg while the rural setting was located north of town in an agricultural area. The urban area consisted of concrete and macadam pavement, brick and stone buildings, and black or dark rooftops, all with little or no vegetation. The agricultural area consisted of typical soil with some type of plant coverage. The overall data file contained 8,762 readings, which were taken every hour on the hour from December 1, 2008 and ending November 30, The results of these 8,762 readings will be presented in a more concise form, which includes hourly averages for the entire year, hourly averages for each season, average UHI temperatures for the entire year, the maximum UHI temperature, and seasonal average temperatures, including nighttime and daytime averages. One of the easiest ways to compare the monitoring results of the urban and rural data is to look at the differences between the urban and rural temperatures on an hourly basis. With 365 days of collected data, the data was simplified to hourly reading averages to create a more concise output. The hourly data for each day was added together and averaged with the same hourly data for all 365 days. The hourly data was then analyzed for the four seasons to see how the hourly average temperatures varied through each season and how they varied through the day and night. The intention of this analysis was to determine which season, including day and night, may have the most effect on temperatures and the UHI. The four seasons consisted of Winter (December, January, and February), Spring (March, April, and May), Summer (June, July, and August), and Fall (September, October, and November). 8

10 Another way the data was analyzed was looking at the average temperature difference between the urban and rural areas for the entire year and finding the average and maximum UHI temperature. The average temperature was also looked at for each season as well. The following section will discuss the results of the above methods in further detail. Analyses of Data and Results The temperatures measured in Figure 3 for the urban and rural areas show that the rural area had lower temperatures. The temperature for both urban and rural areas gradually rose throughout the day starting at approximately 8:00 and increased to the highest average temperature of o C for the urban area and o C for the rural area at approximately 15:00. After 15:00 both urban and rural temperatures decreased due to evening and nighttime cooling. The rural area temperatures decreased at a faster rate than the urban area. The urban area temperatures were warmer until approximately 9:00, when the rural area temperatures became warmer due to early morning warming. The affect of early morning warming continued until 11:00. Though the temperatures for both areas peaked at approximately 15:00, the biggest temperature difference occurred at 21:00 with a difference of 1.20 o C, with the urban area being warmer. The smallest difference occured at 9:00 with a difference of o C with the rural area being warmer due to early morning warming. 9

11 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 Temperature ( o C) Yearly Temperaure Comparison for Urban and Rural Areas Yearly Daily Average Hourly Time (Dec. 1, 2008-Nov. 30, 2009) Urban Temperature ( C) Rural Temperature ( C) Figure 3. Yearly Temperature Comparison for Urban and Rural Areas. Like the yearly temperature comparisons, the daily hourly averages were analyzed again, but this time the data used looked at the different seasons (Figures 4, 5, 6, and 7). In Figure 4, the winter temperatures for both urban and rural comparisons were a little different than the yearly comparisons due the cold temperatures. Though Figure 4 looks different than the other season s figures, it still shows the same results. These results show that the urban area was warmer throughout the entire day in the winter season. The rural area shows a more negative temperature reading which indicates that the urban area was warmer during the same time period. Also, negative readings started at approximately 18:00 and decreased to its lowest temperature average of o C for the urban area and o C for the rural area at approximately 7:00. Starting at 7:00 the temperature rose to the highest positive temperature average of 2.52 o C for the urban area and 2.06 o C for the rural area at approximately 15:00. This is due to the warming of both areas by the sun. Though the temperatures for both areas peaked at approximately 15:00, the biggest temperature difference occurred at 19:00 10

12 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 Temperature (oc) with a difference of 0.80 o C. The smallest difference occurred at 10:00 with a difference of 0.20 o C. Both differences indicate that the urban area was warmer. 3 Winter Temperture Comparison for Urban and Rural Areas Winter Daily Average Hourly Time (Dec. 1, 2008-Feb. 28, 2009) Winter Urban Temperature ( C) Winter Rural Temperature ( C) Figure 4. Winter Temperature Comparison for Urban and Rural Areas. Spring showed a more stable trend for temperature flows for the urban and rural areas (Figure 5). In the spring, like the yearly temperature comparison, both temperatures rose starting approximately 7:00 to its highest temperature average of o C for the urban area and o C for the rural area at approximately 17:00. After 17:00 both urban and rural temperatures decreased due to evening and nighttime cooling. Though the temperatures for areas peaked at approximately 17:00, the biggest temperature difference occurred at 23:00 with a difference of 1.36 o C. The smallest difference occurred at 8:00 with a difference of 0.06 o C. Both differences indicate that the urban area was warmer. Unlike the yearly daily average hourly comparisons the urban area stayed warmer through the whole 24-hour period and did not have a period where the rural area was warmer. 11

13 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 Temperature ( o C) 18 Spring Temperature Comparison for Urban and Rural Areas Spring Daily Average Hourly Time (March 1, 2009-May 31, 2009) Spring Urban Temperature ( C) Spring Rural Temperature ( C) Figure 5. Spring Temperature Comparison for Urban and Rural Areas. Summer also showed a more stable trend for the urban and rural temperatures (Figure 6). In the summer, like the yearly temperature comparison, both temperatures rose starting approximately 7:00 to its highest temperature average of o C for the urban area and o C for the rural area at approximately 15:00. After 15:00 both urban and rural temperatures decreased due to evening and nighttime cooling. The rural area temperatures decreased at a faster rate than the urban area. The urban area temperatures were warmer until approximately 8:00, when the rural area temperatures became warmer due to early morning warming. Like the yearly daily average hourly comparisons the rural areas stayed warmer through a particular length of time within the whole 24-hour period. The difference for summer is that the rural area temperatures were warmer than the urban areas for a greater length of time. The affect of early morning and early afternoon warming and urban shading continued until 17:00. Though the temperatures for both areas peaked at approximately 15:00, the biggest temperature difference occurred at 22:00 with a difference of 1.67 o C, with the 12

14 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 Temperature ( o C) urban area being warmer. The smallest difference occurs at 18:00 with a difference of 0.11 o C. Though both differences indicate that that the urban area was warmer, there was a large amount of time that the rural area was warmer as explained previously. 28 Summer Temperature Comparision for Urban and Rural Areas Summer Daily Average Hourly Time (June 1, 2009-August ) Summer Urban Temperature ( C) Summer Rural Temperature ( C) Figure 6. Summer Temperature Comparison for Urban and Rural Areas. The last season analyzed was fall (Figure 7). Fall results replicated the summer trend daily average hourly comparison except for a small period where the rural areas were warmer then the urban areas. In the fall results, the temperatures show the rural area had lower temperatures. The temperature for both urban and rural areas gradually rose throughout the day starting at approximately 8:00 and increased to the highest average temperature of o C for the urban area and o C for the rural areas at approximately 15:00. After 15:00 both urban and rural temperatures decreased due to evening and nighttime cooling. The rural area temperatures decreased at a faster rate than the urban area. The urban area temperatures were warmer until approximately 9:00, when the rural area temperatures became warmer due to early morning warming. The affect of early morning warming continued until 13:00. Though the temperatures 13

15 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 Temperature ( o C) for both areas peaked at approximately 15:00, the biggest temperature difference occurred at 20:00 with a difference of 1.22 o C with the urban area being warmer. The smallest difference occurs at 10:00 with a difference of o C with the rural area being warmer due to early morning warming. The same data used to create the daily hourly averages were analyzed differently to create Figures 8 and 9. Figure 8 shows the entire yearly averages for both the urban and rural areas. The urban area shows an average temperature for the year of o C compared to the rural area temperature of o C. This shows that the yearly average UHI temperature for the Borough of Shippensburg was 0.58 o C indicating it was warmer in the urban area than the rural area outside of the Borough. During the same course of the year, the maximum UHI temperature, or greatest difference in temperature was recorded on February 11, 2009 with a difference of 8.93 o C. The urban temperature was o C and the rural temperature was 7.63 o C at 20: Fall Temperature Comparison for Urban and Rural Areas Fall Daily Average Hourly Time (Sept. 1, 2009-Nov. 30, 2009) Fall Urban Temperature ( C) Fall Rural Temperature ( C) Figure 7. Fall Temperature Comparison for Urban and Rural Areas. 14

16 Temperature oc Yearly Average and Maximum UHI for the Borough of Shippensburg Yearly Urban Average Yearly Rural Average Maximum UHI Temperature ( C) Figure 8. Yearly Average and Maximum UHI for the Borough of Shippensburg. The same data used to analyze the yearly averages were also used to analyze the averages on a seasonal basis. The previous figures looked at the hourly averages for each season. Figure 9 shows the total average for all data within that particular season along with the daytime and nighttime averages for each season. With the data being averaged, all the seasons reflect that the urban area was warmer than the rural area. Also, the daytime and nighttime averages werehigher for urban areas compared to the rural areas except for the summer season. Even in the winter season, the rural temperatures were more negative, this reflects the fact that the urban area was warmer. Like the daytime and nighttime averages for the seasons, Figure 10 also shows day and nighttime averages, but for the whole year. This shows that the urban area is warmer in the urban area compared to the rural area. Also, Figure 10 shows that the UHI effect is more noticeable at night with a difference of 0.90 o C compared to the daytime difference of 0.27 o C. 15

17 Temperature o C Temperature ( o C) Seasonal Average Temperatures and Day and Nighttime Averages Winter Spring Summer Fall Urban Temperature ( C) Rural Temperature ( C) Urban Daytime Temperature ( C) Rural Daytime Temperature ( C) Urban Nighttime Temperature ( C) Rural Nighttime Temperature ( C) Figure 9. Seasonal Average Temperatures and Day and Nighttime Averages Yearly Average Hourly Data for Day and Nighttime Urban Daytime Average ( C) Rural Daytime Average ( C) Urban Nighttime Average ( C) Rural Nighttime Average ( C) Yearly Average Hourly Data Figure 10. Seasonal Average Temperatures and Day and Nighttime Averages. The results from the data gives a good indication of the amount of the UHI effect that occurs within the borough of Shippensburg and its surrounding area. These results also indicate that it is warmer in the urban area throughout the year; no matter if it is winter, spring, summer or fall. 16

18 Discussion of Results The data collected for both the urban and rural areas help in determining the UHI temperatures that currently exist for the Borough of Shippensburg and its close rural area, with results indicating that there is a small UHI effect that exists in the Borough. Figure 3 shows that UHI existed throughout the day and through the night except for a period in the morning where the rural area became warmer. This period occurred between 9:00 and 11:00. This same effect also happened during the summer and fall months (Figure 6 and 7). In the fall months the time period was approximately the same, 9:00 to 13:00. In the summer months the time frame was larger and existed between 8:00 and 17:00. This effect, where a transition from the urban area to rural area becomes warmer is called an urban oasis. Urban oasis occurs when rural temperatures are warmer than the urban temperatures. Urban oases often develop due to enhanced shading in the urban areas during the daytime hours. Also, increased radiation during these morning hours were more likely to heat up the rural area while the urban area remained shaded in the morning (Doyle and Hawkins 2008). Also, another noticeable effect through the yearly hourly and seasonal hourly comparisons was that the UHI effect was most noticeable at night as shown is Figures 9 and 10. This is consistent with Luke Howard s data that indicated that the temperature differences are usually most noticeable in the non-daylight or night-time hours (Chapman 2005). This is due to the thermal characteristics of materials used in the urban areas (asphalt, brick, concrete, glass, etc.) compared to those found in the rural areas (trees, grass, water bodies, bare soil, etc.). In addition, the canyon structure created by tall buildings enhances warming 17

19 by the sun. This energy is trapped by multiple reflections and absorption by the buildings (Chapman 2005). This stored energy in the urban area is then redirected as long-wave radiation less efficiently than rural areas during the night (Solecki and others 2005) keeping the urban area warmer than the surrounding rural area. These results show how the UHI temperatures increase throughout the day and into the night and slowly deceases after a particular time until the effect begins again. The daily average hourly comparisons for the year and seasons indicate how the UHI effect reacts through the day, night, and throughout the year. Of the seasons, spring time had the most noticeable average UHI (Figure 9). The reason the spring time had the most noticeable UHI effect and also is the only daily average hourly comparison figure, other than winter, not to have an urban oasis effect was due the timing of the year. This is due to the earth rotating around the sun and pivoting on it axis, which creates different seasons. The creation of the seasons creates different solar radiation effects on the earth. These results along with the yearly average UHI temperature of 0.58 o C and maximum UHI temperature of 8.93 o C shows that a small UHI does exist for the Borough of Shippensburg. Though this assessment sets out to address the environmental conditions of the Borough, mainly the UHI and the benefits of green roofs, there are some indirect benefits that green roofs have on lowering the UHI effect. The use of green roofs helps to control indoor temperatures of buildings by acting as additional insulation. The insulation acts as a buffer in the summer and a blanket in the winter. A study of Toronto City Hall indicated that during the summer, heat flow reduction relative to a 18

20 reference roof ranged from 50 to 90% while winter values ranged from 10-40% (STEP 2007). These models show by controlling the indoor temperature flows of buildings, the use of heating and air conditioning machinery is kept to minimum use. The reduction of the use of these machines then leads to the reducing of additional heat released and fuel used. This reduction of energy is then taken away from the urban temperatures which help to create the UHI. Discussion of Costs and Benefits There is no guarantee that green roofs will eliminate the entire UHI effect for the Borough of Shippensburg but many studies on other cities have been conducted to indicate that a reduction can occur. The reduction of the UHI effect as mentioned previously, has multiple benefits, but to obtain these benefits, the initial upfront cost to install and maintain green roofs deters people to make the commit to invest in this green initiative. The biggest cost is upfront, for installation of the green roofs. Green roofs can cost approximately double that of a conventional roof upon installation, not including a structure engineer review of the existing roof and any needed structural support. A conventional roof can run around $9 per square foot and a green roof can run between $12 to $24 per square foot (Banting and others 2005). Some studies indicate that conventional roofs with stone material weigh approximately the same as an extensive green roof with wet soil media. Plus, design standards for particular buildings may 19

21 already meet the structural requirements needed for a green roof. This all will need to be determine by a structure engineer whos rate ranges from $120-$200 and hour. Green roofs have a projected service life of 40 years, while a conventional roof will last 20 years (Banting and others 2005), though some variations have been found. Another cost associated with both conventional and green roofs is long term maintenance costs. Conventional roof maintenance consists of patching damaged areas and replacing the roof after approximately 20 years. Green roof maintenance consists of watering, weeding and occasional replanting until the green roof has been established for one year, then maintenance visits for the weeding of invasive species should be undertaken two to three times a year (Banting and others 2005) until replacement after 40 years. This initial upfront cost deters people in investing in green roofs, but the payback is the longevity of the green roofs compared to conventional roofs. The longevity of green roofs is not the only benefit that can help offset the initial cost of this investing. Other cost savings include indoor heating and cooling costs, cost savings to minimize building large stormwater management facilities, cost savings to minimize stream damage and flooding, and other associated amenities that can be beneficial to the Borough. In relation to the cost savings for heating and cooling reduction, a modeling study was conducted investigating the impact of roof-to-envelope ration on the energy savings provided by a green roof. The potential energy savings associated with roof greening was found to be far greater for single story building than for 2 or 3 story buildings. During a July day in Toronto, a green roof with dimensions of 820 ft by

22 ft was found to bring about energy savings of 73%, 29%, and 18%, for 1, 2, and 3 story air conditioned buildings, respectively (STEP 2007). In another study, energy costs were estimated using the energy model based on the Power DOE program, yielding annual energy savings of between 5,000 and 29,000 kwh. An extensive green roof under these conditions would result in cost savings of $4, each year, and these energy cost savings could significantly decrease costs of installing both extensive and intensive green roofs (Banting 2005). Another cost benefit to installing green roofs is the use of green roofs for stormwater management control. A study conducted in Vancouver, BC showed that a suitably designed green roof has great potential benefits in terms of protecting stream health and reducing flood risk to urban areas. The modeling results for a 50-year watershed retrofit scenario also showed that green roof retrofits on existing buildings could help restore watershed health overtime by filtering contaminants out of the rainwater (Banting 2005). Others studies showed that typical green roofs, depending on substrate depth, could retain 60 to 100% of the stormwater (Banting 2005). The financial benefits of green roofs on stormwater management can include the following: 1. The reduction of infrastructure that is required for typical stormwater management can be reduced. 2. The reduction of flood and erosion damage by green roofs ability to control water flow release. 3. The reduction of artificial heating of rainwater (from conventional roofs) can help preserve fisheries and other aquatic life. 4. The reduction of pollutions before the water enters the stream and underground aquifers. 5. The reduction of the overall negative effects on streams that lead to the Chesapeake Bay. 21

23 While the above are feasible financial benefits for the Borough, other possible benefits include aesthetics, property value, possible roof usage for actual gardens, and tourism are other possible financial benefits. Since the Borough has a wide range of building types, including stores, restaurants, and residents, incorporating green roofs could be beneficial for both the general public and tourism. A company in downtown Toronto installed a green roof and currently receives 3000 visitors to view their green roof each year. Visitors to view green roofs can create revenue for the Borough. This revenue increase would come from local stores and restaurants. The restaurants themselves can benefit no just from the visitors but from the green roofs themselves. For example, the Fairmont Waterfront Hotel in Vancouver has a green roof on which herbs, flowers and vegetables, are grown. They estimate this saves the hotel approximately $30,000 per year in food expenditures (STEP 2007). The initial upfront cost for green roofs maybe larger than conventional roofs, but over time the additional benefits associated with green roofs will out weight the continued use of conventional roofs. The benefits from reduction of the UHI to aesthetics; all will have some type of financial benefit for the Borough of Shippensburg. Conclusion This assessment set out to find the current environmental conditions for the Borough of Shippensburg particularly the UHI as well as the financial investment involved. The assessment of Shippensburg shows that there was a small UHI effect that 22

24 occurred throughout the year, particularly in the spring time. The ability to understand the amount of the UHI effect that currently exists in the Borough and how green roofs can reduce this amount helps to give the Borough of Shippensburg a better understanding of the investment they want to make. By installing green roofs in the borough, the reduction of the UHI can possibly be met. The green roofs will not just help reduce the UHI, it will also have multiple other benefits for the citizens of the borough with the positive effects on streams and aquatic life, open space withon an urban area, possible tourism, and the ability to use the roofs as gardens. 23

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26 STEP An Economic Analysis of Green Roofs: Evaluating the costs and savings to building owners in Toronto and surrounding regions. [cited 2010 Feb 14] Available from: Streutker DR A remote sensing study of the urban heat island of Houston, Texas. International Journal of Remote Sensing 23, U.S. Department of Energy (US). Green Roofs [Internet]. Federal Technology Alert. Federal Energy Management Program (FEMP); 2004 [cited 2008 Sept 29]. Pub. No. BK ; DOE/EE Available from: United States Environmental Protection Agency, Cooling Summertime Temperatures: Strategies to Urban Heat Islands. Publication Number: 430-F Voogt J Urban Heat Islands: Hotter Cities. American Institute of Biological Sciences. Wilby RL, Perry GLW Climate change, biodeiversity and the urban environment: a critical review based on London, UK. Progress in Physical Geography 30(1): Wong, E. The U.S. Environmental Protection Agency s Heat Island Reduction Initiative (HIRI): Status and Future Directions [cited 2008 Sept 29] Available from: 25