How Green Roofs Can Improve the Urban Environment In Uptown Waterloo

Transcription

1 How Green Roofs Can Improve the Urban Environment In Uptown Waterloo Photos: Top left-hamilton Apartments, Portland; Middle-Seattle Municipal Courthouse; Right-Hamilton Apartments, Portland; bottom-uptown Waterloo. Top photos by authour, bottom photo from KW Film Society. Nada Sutic April, 2003 Nada Sutic Integrating Natural and Urban Environments (519)

2 Table of Contents Table of Contents... i List of Figures...iii Acknowledgements... iv Executive Summary... v CHAPTER 1 INTRODUCTION STUDY OBJECTIVES RATIONALE METHODOLOGY ORGANIZATION OF STUDY... 5 CHAPTER 2 GREEN ROOFS OVERVIEW WHAT ARE GREEN ROOFS? CONVENTIONAL FLAT ROOFS GREEN ROOF SYSTEMS BUILDING GREEN ROOFS GREEN ROOF INDUSTRY GREEN ROOF BENEFITS THAT IMPROVE THE URBAN ENVIRONMENT Stormwater Management Urban Heat Island Reduction Air Quality Improvements Community Greenspace and Aesthetic Value Urban Agriculture PRIVATE BENEFITS OF GREEN ROOFS Energy Efficiency Roof Durability and Life Extension Private Amenity Space Horticultural Therapy Sound Insulation Food Production SUMMARY OF GREEN ROOF BENEFITS BARRIERS TO GREEN ROOF IMPLEMENTATION IN CANADA MOTIVATIONS AND TRENDS CHAPTER 3 THE CITY OF WATERLOO URBAN STRUCTURE PROJECTED GROWTH WATERLOO S ENVIRONMENTAL STRATEGIC PLAN STUDY AREA ROOFSCAPE CHAPTER 4: GREEN ROOFS IN UPTOWN WATERLOO STORMWATER MANAGEMENT Current Situation i

3 4.1.2 Current Responses Improving Stormwater Management in Uptown Waterloo with Green Roofs Alternatives for Stormwater Management URBAN HEAT ISLAND EFFECT Current Situation Current Responses Potential for Green Roofs to Mitigate Waterloo s Urban Heat Island Alternatives For Reducing the Urban Heat Island AIR QUALITY AND SMOG Current Situation Current Responses Potential for Green Roofs to Improve Waterloo s Air Quality Alternatives for Improving Urban Air Quality and Reducing Smog COMMUNITY GREENSPACE AND AESTHETIC VALUE Current Situation Current Responses Green Roofs Providing Community Greenspace and Improving Aesthetics Alternatives for Providing Community Greenspace and Improving Aesthetics URBAN AGRICULTURE Current Situation Current Responses The Role of Green Roofs in Urban Agriculture in Waterloo Alternatives for Urban Agriculture in Uptown Waterloo ENERGY EFFICIENCY Current Situation Current Responses Green Roof Potential to Improve Energy Efficiency in Waterloo Alternatives for Improving Energy Efficiency SUMMARY OF GREEN ROOF BENEFITS IN UPTOWN WATERLOO CHAPTER 5 OVERALL ANALYSIS GREEN ROOF BENEFITS IN WATERLOO CHALLENGES FACING IMPLEMENTATION OF GREEN ROOFS IMPLICATIONS CHAPTER 6: CONCLUSIONS AND RECOMMENDATIONS REFERENCES ii

4 List of Tables TABLE 2.1: COMPARISON OF EXTENSIVE AND INTENSIVE GREEN ROOF SYSTEMS... 9 TABLE 2.2: SUMMARY OF GREEN ROOF BENEFITS TABLE 4.1 STORMWATER REACHING UPTOWN WATERLOO TABLE 4.2: PRECIPITATION DATA FOR WATERLOO TABLE 4.3 MONITORING RESULTS FOR LAUREL CREEK SITES NEAR UPTOWN WATERLOO, TABLE 4.4 EXTREME DAILY RAINFALL TABLE 4.5: SUMMARY OF STORMWATER BENEFITS EXAMPLES TABLE 4.6: URBAN HEAT ISLAND IN KITCHENER TABLE 4.7: SUMMARY OF URBAN HEAT ISLAND REDUCTION EXAMPLES TABLE 4.8: MOE AIR QUALITY DATA FOR KITCHENER TABLE 4.9 SUMMARY OF AIR QUALITY IMPROVEMENT EXAMPLES List of Figures FIGURE 2.1: SOPRANATURE SYSTEM FIGURE 2.2: GREENTECH ITM SYSTEM FIGURE 2.3: EFFECT OF RAINFALL ON GREEN ROOF PERFORMANCE FIGURE 2.4: SKETCH OF AN URBAN HEAT ISLAND PROFILE FIGURE 2.5: HEAT FLOW WINTER, NO SNOW FIGURE 2.6: HEAT FLOW WINTER, SNOW COVER FIGURE 2.7: HEAT FLOW SUMMER FIGURE 2.8: LINKAGES BETWEEN BENEFITS THAT RELATE TO COOLING FIGURE 3.1: CITY OF WATERLOO (MEIS-IMAGERY, 2000) FIGURE 3.2: STUDY AREA FIGURE 4.1 LAUREL CREEK WATERSHED FIGURE 4.2: COMPONENTS OF A CONCRETE GRID PAVEMENT FIGURE 4.3: UNI ECO-STONE PAVING SYSTEM FIGURE 4.4 POROUS PAVEMENT AT THE ECOTRUST CENTRE IN PORTLAND FIGURE 4.5: TEMPERATURES AT NRC FACILITY iii

5 Acknowledgements This research began as a senior honours thesis for my undergraduate degree in Environmental Studies. Eight months later, it has become so much more! Thank you to everyone who has helped me to gather information and data, and to those who have provided tours, expertise and support. Special thanks to: Dr. Robert Gibson for his guidance throughout the project, the Green Roofs Steering Committee at the City of Waterloo for support, encouragement and an avenue to grow with green roofs, and all of my friends and family who have supported me throughout the year and on this project. iv

6 Executive Summary Green roofs are a tool well suited to densely developed urban environments, where they can add to the amount of vegetation and greenspace. They are an encouraging addition to urban environments where people, goods, and resources are concentrated and have numerous environmental impacts that can affect human health through poor water quality, poor air quality, urban heat islands, noise, the amount of available green space, and other less direct avenues. This study investigates the benefits of green roofs to determine how they can improve the urban environment. The aim is to understand how valuable they may be as a tool for environmental problems in Uptown Waterloo. The benefits of green roofs accrue to both the community and the building owner. The focus of this study is on the public benefits, such as improved stormwater management capabilities, reduced urban heat island effects, improved air quality, more community greenspace, improved aesthetics and local food production. Although energy efficiency gain is chiefly a private benefit, it is considered because of its importance in encouraging green roof implementation. Other private benefits discussed in Chapter 2, include roof durability and life extension, private amenity space, horticultural therapy, sound insulation and food production. Some of the benefits of green roofs can fall into both the public and private categories. Their categorization is dependent on how green roofs are used. Waterloo s Environmental Strategic Plan The City of Waterloo developed an Environmental Strategic Plan and Council adopted it in The plan outlines what Waterloo s current environmental issues are, based on the findings of the Mayor s Environmental Task Force, and results of the Imagine! Waterloo community visioning process (City of Waterloo, 2002, iv). Six key environmental areas of importance were identified, and strategic actions were defined for each of them. The six areas of importance are: 1) planning and growth, 2) water resources, 3) air quality, 4) energy and resources, 5) environmental awareness, and 6) green space (City of Waterloo, 2002, v). Green rooftops fit into the environmental strategic plan in a few areas, most notably under planning and growth, and air quality. v

7 Green Roofs in Uptown Waterloo To determine how valuable green roofs could be in Uptown Waterloo, the urban issues associated with each public benefit (and energy efficiency) were examined within the Waterloo context. Estimates were made regarding the magnitude of the benefits that could be realized in Uptown Waterloo if 25% of the available flat roof space was greened. Findings were as follows. For stormwater management, green roofs can improve Uptown Waterloo by reducing the rate and volume of runoff, delaying runoff and improving water quality. With 25% of the available flat roof space greened, an annual reduction in volume of runoff of about 11,000m 3 or 11 million litres could be expected. A reduction in the urban heat island effect is also expected in Uptown Waterloo if about 26,000m 2 of roofs contain vegetation. The reduction expected is perhaps 1-2 C in the Uptown Waterloo area. Green roofs in Uptown are not expected to alter temperatures outside of the study area. Some improvement in air quality is also expected as well as a reduction in the incidence of smog. This is due to the lower urban heat island effect, and the tendency for deposition of particulate and some pollutants on vegetation. Increasing the amount of vegetation through the addition of 26,000m 2 of green roofs could remove 5200kg of particulate annually. Energy efficiency gains are also expected, but are specific to individual buildings. Green roofs can provide amenity or community space in Uptown Waterloo and provide space for urban agriculture. For example, if an area the size of Waterloo Town Square was devoted to public space, that would be 17,000m 2 of new public space in the Uptown core. Also, if 10% of the area considered in this study was used for urban agriculture, that would be 2600m 2, about half a football field available for food production. Barriers and Challenges to Implementation of Green Roofs Key challenges facing implementation of green roofs include the high capital cost, predominantly old buildings with unknown structural capacity for green roofs, and limited incentives for builders and developers. The key benefits are public benefits but the costs are borne by the builder. Without public incentives or regulatory requirements, it is difficult to encourage green roof development effectively. Another challenge that is not exclusive to Waterloo is the varying and often unknown structural capacity of older buildings. Some may have the structural capacity to vi

8 add a green roof, but verification can be time-consuming and costly, especially if there are no architectural drawings available. Developers, roofers, homeowners, building owners, and policy makers need to be educated about the value of green roofs and their applicability. One of the most effective ways to prove the usefulness of green roofs is to lead by example showcase the benefits and prove that the concept works. Conclusions and Recommendations Key recommendations for the City of Waterloo to promote green roof implementation in the Uptown area are as follows: Partner with the Region of Waterloo and other local municipalities to undertake studies, carry out educational campaigns, and develop incentive programs in the future. Examine potential policy initiatives at both levels of government to determine what would be effective in encouraging green roofs. Develop an educational campaign in Waterloo to educate developers, builders, the public, City staff and councillors about green roofs. Prepare an inventory of the buildings in Uptown Waterloo. The City should perform an initial assessment of publicly and privately owned buildings within Uptown Waterloo to determine which buildings may be suitable for further investigation and green roofs. Prioritize issues related to the benefits of green roofs. These priorities can be used to develop a green roof development strategy for Uptown Waterloo. For example, is the City more concerned with stormwater or greenspace, and how should implementation proceed given the priorities. Involve the community in green roof development plans and decision making. Involvement of community groups, organizations and individuals is important for the success of green roofs. Promote research within the community. Partner with the local universities and colleges to encourage research. Green roofs are an exciting new technology that can be applied in areas such as Uptown Waterloo where there is little available space for other environmental initiatives. Waterloo has an opportunity to be a leader in this field in Canada by partnering with other municipalities, both locally and elsewhere, to demonstrate the viability of green roofs as a tool for improving urban environments. This in turn should attract the support of other levels of government. vii

9 Chapter 1 Introduction Urban environments concentrate people, goods, and resources and as a result have numerous significant environmental impacts. The built urban system consists of the buildings and physical infrastructure that have been constructed to house and service human activities. The built system affects the natural system through removal of species and habitat, excavation and movement of soil, alteration of hydrological systems and temperature regimes, and so on. While these effects are experienced both in the broader environment and within the urban environment, they are concentrated in the urban environment and can damage human health through poor water quality, poor air quality, urban heat islands, noise, the amount of available green space, and other less direct avenues. One particular problem area is that urban environments have an abundance of impervious surfaces, such as parking lots, roads, sidewalks, and rooftops. These intensify problems relating to stormwater management, the urban heat island effect and poor air quality in most urban centres including the City of Waterloo. Reducing the impervious surface area in a densely developed area can help to mitigate these negative effects. This research will study the urban use of green roofs to determine how they can improve the urban environment in order to understand how valuable they may be as a tool for environmental problems in Uptown Waterloo. It will also provide some discussion about other benefits of green roofs and how they can be realized in Uptown Waterloo. 1.1 Study Objectives To determine how green roofs can help deal with the challenges created by an abundance of impervious surfaces in Uptown Waterloo, and to identify lessons applicable beyond the study boundaries, the project will Provide a general overview of benefits associated with green rooftops. Identify the problems green roofs can mitigate, and confirm their existence. For example, identify the air quality problems in Uptown Waterloo, identify current stormwater practices and problems and confirm the existence of the urban heat island effect. Nada Sutic 1

10 Determine the role that green roofs can play in mitigating the identified urban environmental problems in Uptown Waterloo, by: o assessing the benefits to provide estimates of: improvements in stormwater management, reduction in summer temperatures and the urban heat island, particulate removal, any reduction in SO 2, NO x, and smog reduction if 25% of the available flat roof space in Uptown Waterloo was greened. o Identifying the role of green roofs in providing other less widely quantified benefits, such as energy efficiency *, urban agriculture, community gardening, amenity space, community space and aesthetics. Discuss the value of each of the benefits of green roofs in the context of Uptown Waterloo. That is, how valuable these benefits are when the green roof tool is applied in Waterloo. Identify some of the barriers to implementation in Waterloo and identify future research needs. 1.2 Rationale It is important to find out how green roofs can mitigate urban environmental problems to develop an understanding of how valuable they may be in Uptown Waterloo for dealing with those issues. Green roofs offer a range of benefits including stormwater runoff management, air quality improvement, urban heat island reduction, urban agriculture, greenspace, and energy efficiency. The diversity of benefits that green roofs offer increases their potential importance. Determining the value of green roofs is important to provide some direction regarding whether or not green rooftops are an initiative that should be pursued further in Waterloo. The City of Waterloo is currently interested in gaining support for green roofs, and it has funding to perform a feasibility study with the possibility of a pilot project in the future (Moyer, 2002, 7). Before encouraging widespread implementation of green roofs, it is important to have some understanding of the potential value of this tool in its proposed application, and the feasibility study, a pilot project as well as this research can each play a role in determining that value. This study will provide a first look at the * Energy efficiency can be quantified, but because it is very specific to a building, it is difficult to quantify across a wider area, such as Uptown Waterloo. Nada Sutic 2

11 suitability of some green roof benefits in Uptown Waterloo by examining the current problems or challenges, the current responses and then the opportunity for green roofs to be an effective response. Furthermore, in determining the ability of green roofs to mitigate problems in Uptown Waterloo, it requires that these issues be defined first. The City of Waterloo s Environment First policy, requiring all operations are completed with consideration of the natural environment and using sustainable development principles (City of Waterloo, 2002, 1). During the Imagine! Waterloo * visioning process, regard for the environment was ranked at the top of community values, and air quality, water quality and access to natural areas (greenspace) were key quality of life indicators (City of Waterloo, 2002, 1). Hence, examining the effectiveness of green roofs in improving the urban environment is important in understanding how this tool can improve the quality of life in Uptown Waterloo. 1.3 Methodology A combination of research methods has been used to determine the application of green roofs in Uptown Waterloo. First, a literature review provided an overview of green roof benefits in general. The value of these benefits were then examined in the context of Uptown Waterloo by identifying and examining existing problems that green roofs may be able to address, identifying current responses to those problems and then determining the role that green roofs can play and how effective they can be. Literature review and secondary research determined baselines and current responses to the issues that green roofs can address. Based on the literature, some estimates were made to determine the magnitude of the benefits that could be expected in Uptown Waterloo if 25% of the available flat roof space was greened. Essentially, the purpose is to determine the effectiveness of green roofs in mitigating some Uptown issues. One of the most important issues in evaluating the effectiveness of any tool is to determine a baseline for comparison. For each major benefit of green roofs, a comparison was done between the current situation and the potential situation with widespread implementation of green roofs. Baseline information was gathered from a * In the spring of 2000, the City of Waterloo initiated a visioning process, called Imagine! Waterloo. It was a large public consultation that involved individuals, community groups, businesses and considered over 12,000 comments when forming the City s vision for Nada Sutic 3

12 variety of sources, and sources varied depending on the particular issue being examined. For example, information on stormwater management challenges in Uptown Waterloo was from the City of Waterloo, while data on air quality was from the Ontario Ministry of the Environment. Where possible and relevant, quantitative data was gathered, so that green roof potential can be assessed with quantitative estimates. In addition to determining the current situation, current responses in Waterloo are discussed. Responses focus on municipal policies or programs at both levels of government, the Region of Waterloo and the City of Waterloo. It is important to be aware of current and existing initiatives in order to make realistic and relevant conclusions regarding the potential for green roofs to improve upon those situations in Uptown Waterloo. Also, some alternatives to green roofs for addressing the same issues are identified. This document is organized according to the benefits, and the specific methodology and criteria for assessing the green roof potential for each particular benefit will be discussed in that particular section. Any particular limitations will also be discussed there, but general limitations to the study are discussed below. One of the key limitations to being heavily dependent on literature is that sources may be biased. Some sources are definitely biased towards the benefits of green roofs, and are likely to downplay any negative points. Furthermore, in determining current municipal actions about problems affecting Uptown Waterloo, there may be bias in determining which information gets published or put on a website. As such, critical analysis of all literature is important. Another limitation is regarding any quantitative analysis. There are always assumptions associated with quantitative data, and it is important to be aware of their existence when using the data. Also, in using various sets of data to quantify a benefit, it is important to understand that the numbers arrived at will only be an estimate, and will not be absolute. Moreover, an underlying assumption of this study is that research done elsewhere regarding green roof benefits is applicable to Waterloo, because there is no prior research about green roofs in Waterloo. Being critical and using a diversity of sources are important factors in providing a reliable analysis of the potential for green roofs to be a useful tool in Uptown Waterloo. Nada Sutic 4

13 Also, being aware of the limitations and disadvantages of green roofs is an important factor in determining the role that green roofs can play in improving Uptown Waterloo. The approach of this study is that it examines a particular tool, considers the benefits and uses of the tool, and then considers the problem that those benefits or uses address. Although some might argue that this approach is problematic and even backward, it is simply that the focus of the research is the tool, rather than the specific problems it can address. Instead of being problem-focused research, it focuses on exploring the benefits and issues associated with a tool that is fairly new in the Canadian context, and especially the local Waterloo context. 1.4 Organization of Study The following chapters discuss green roofs in general, provide background about City of Waterloo and then discuss the benefits of green roofs as they apply to the Uptown Waterloo. Chapter 2 explains what green roofs are, how they are constructed and how they differ from conventional roofs. They are described primarily in the context of flat roofs although green roofs can be built on sloping roofs. In Chapter 2, there is also an overview of the state of the green roof industry both in Canada and elsewhere. The core of the chapter is about the benefits of green roofs. There is also discussion of some of the barriers to their implementation in Canada. Background about the City of Waterloo is in Chapter 3, and includes a description of its urban structure and growth potential. The Uptown Waterloo study area and the available flat roof space in it are defined. The core of the study is in Chapter 4. For each major green roof benefit, the problem in Waterloo is defined and described and current responses to those problems are identified. After these two key factors are identified, the potential for green roofs to fit in as part of the overall solution is examined. Conclusions are drawn in each section identifying the potential value of green roofs as a response to the relevant problem. Also, any relevant alternatives or initiatives for dealing with the problem are also discussed briefly. Chapter 4 includes a summary of the benefits of green roofs in Uptown Waterloo. Nada Sutic 5

14 An overall analysis is provided in Chapter 5. Conclusions from each subsection of Chapter 4 will be drawn together to determine the overall potential value of green roofs in Uptown Waterloo. There is also some discussion of spin-off benefits, any negative effects, and opportunities and challenges in Waterloo. In Chapter 6, conclusions are made regarding the effectiveness of green roofs in solving urban environmental problems in Uptown Waterloo. Recommendations are also made regarding future directions for Waterloo and future research needs. Nada Sutic 6

15 Chapter 2 Green Roofs Overview 2.1 What are Green Roofs? Green roofs, also known as eco-roofs, nature roofs, roof greening systems and including roof top gardens, are living, vegetative roofing alternatives (Velazquez, 2002). Green roofs are a way to make use of roof space, which tends to be considered wasted or unusable space. There are several layers of material in a green roof. These other layers on top of a traditional roof actually extend the life of the roof green roofs can last up to twice as long as conventional roofs (Cardinal Group, 2002a). The layers of a typical green roof include: the plants, often specially selected for particular applications, an engineered growing medium, which may not include soil, a landscape or filter cloth to contain the roots and the growing medium, while allowing for water penetration, a specialized drainage layer, sometimes with built-in water reservoirs, the waterproofing / roofing membrane, with an integral root repellent, and the roof structure, with traditional insulation either above or below. (Peck and Kuhn, 2001, 4). Green roofs can be intensive or extensive. An intensive green roof consists of a diversity of plants, including flowering shrubs and trees, and is usually intended for human interaction. As such, it must conform to applicable loading requirements. Intensive roofs are on flat roof surfaces or on a mild slope of up to 3%, and require a soil depth from cm (8-24") (Peck and Kuhn, 2001, 5). Intensive green roofs generally require traditional landscaping maintenance and infrastructure such as water collection cisterns, reservoir boards, irrigation and fertilization (Velazquez, 2002). Essentially, an intensive green roof is an actual rooftop garden, much like a typical garden, except that it happens to be on a roof, and it requires similar regular maintenance and upkeep. Intensive green roofs are more expensive than extensive gardens in both their creation and their maintenance. The growing medium is heavier because of its depth and composition (largely organic and soil based), and this means that the roof must be able to take on the load or be upgraded to bear the load. The saturated weight increase can be between kg/m 2 ( pounds per square foot [lbs/ft 2 ]) (Peck and Kuhn, 2001, 5). The plants are larger and usually more diverse, which makes them more Nada Sutic 7

16 expensive to purchase. Furthermore, intensive green roofs have expensive upkeep because of the regular maintenance requirements. In comparison, extensive green roofs are lightweight, low maintenance and often inaccessible. Velazquez (2002) defines them as 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. Drought-resistant and alpine plants are favoured, because of low maintenance requirements. These types of plants are capable of handling a variety of arduous conditions including hot, dry and windy conditions, and they are good at storing water. Native plants seem to perform better than cultivars (Pearce, 2003). Extensive green roofs can be put onto roofs with slopes of up to 33%, and with little or no additional structural support (Velazquez, 2002). The growing medium of most extensive green roofs is a mineral-based mixture of sand, gravel, crushed brick, leca, peat organic matter and some soil, and varies in depth between five and 15 cm (2-6 ) (Peck and Kuhn, 2001, 4). The added wet weight (i.e. fully saturated) to a roof from an extensive roof usually ranges between 72.6 and kg/m 2 (16-35 lbs/ft 2 ) (Peck and Kuhn, 2001, 4). Maintenance for an extensive roof is limited to watering in the first year, so that plants can become established, and occasional weeding of any invasive species in the following years. Extensive roofs are generally not intended as recreational space or to support people, trees or shrubs. There are also green roofs that are semi-intensive, which usually means that they are accessible, have a slightly heavier growing medium than an extensive roof and use typical extensive vegetation as well as perennials and shrubs. Table 2.1 summarizes the differences between extensive and intensive green roofs by listing their respective advantages and disadvantages. Nada Sutic 8

17 Table 2.1: Comparison of Extensive and Intensive Green Roof Systems Brief Description Extensive Green Roof -thin soil, little or no irrigation, stressful condition for plants Advantages lightweight suitable for large areas suitable for roofs with 0-30 slope low maintenance often no need for irrigation and drainage systems relatively little technical expertise needed often suitable for retrofit projects can leave vegetation to develop spontaneously relatively inexpensive looks more natural easier for planning authority to demand green roofs be a condition for planning approvals Disadvantages more limited choice of plants usually no access for recreation or other uses unattractive to some, especially in winter little or no opportunity for food gain Adapted from Peck et al., 1999, 14. Intensive Green Roof -deep soil, irrigation system, better condition for plants greater diversity of plants and soil good insulation properties can simulate a wildlife garden on the ground can be made very attractive often accessible diverse utilization of roof (ie for recreation, growing food, as open space) food gain urban agriculture greater weight loading on roof need for irrigation and drainage systems, hence, greater need for energy water, materials, etc. higher cost more complex systems and expertise required 2.2 Conventional Flat Roofs All roofs have a waterproof membrane to keep precipitation out of the building. A conventional roof puts the waterproofing membrane at the top of the roof where it is subject to environmental forces such as wind, temperature and ultra-violet radiation (Baskaran and Frégeau, 1996). There are also protected membrane roof systems, or inverted roofs, where the membrane is covered by insulation, protecting it from the elements. When a green roof is installed, it acts as a protective barrier for the waterproof membrane, extending its life. A regular flat roof usually needs to be replaced every years (Peck et al., 1999, 30; Baskaran and Frégeau, 1996). A green roof can at least doube the life of a roof (Peck and Kuhn, 2001, 6). One of the factors affecting the life of a roof is the temperature Nada Sutic 9

18 extremes it is subject to. A conventional roof often has pavers or gravel and tar on top of the membrane to provide some protection. Daytime temperatures on a conventional rooftop can range between -20 in winter and 80 C in summer (Peck et al., 1999, 31). A green roof layer 10cm thick can reduce this range to between 10 and 30 C, resulting in less expansion and contraction stress on the membrane, reducing cracking and aging (Peck et al., 1999, 31). A conventional flat roof with gravel weighs about 12 pounds per square foot and costs about $7-8 USD per square foot ($ CAD/m 2 ) to install, while a green roof costs about $15-20 USD per square foot ($ CAD/m 2 ) because of more materials and labour required (Scholz-Barth, 2001, 96). Note that a gravel roof is heavier than some other types of roofs, such as one with a bituminous membrane, but a gravel roof does provide some shading and protection to the membrane underneath (Köhler et al., 2002, 386). Drainage is an important part of any roofing system. Flat or low-slope roofs usually have drains on the roof surface connected to internal downpipes or leaders, which connect to a storm sewer or drainage ditch (Baker, 1972). The number and size of drains is determined by rainfall information for the geographic area and on drainage information for drains and leaders (Baker, 1972). A flat roof is never actually perfectly flat due to structural deflection, and should slope towards the drains. To minimize damage to the waterproofing membrane, water should not be allowed to pool on the roof. Green roofs help to prevent pooling by reducing the amount of water that reaches the roofing membrane. Conventional roofs, particularly the waterproofing membrane are subject to a variety of environmental factors that reduce their lifespan. A green roofing system can extend the life of the membrane significantly and help to reduce the impact of some environmental factors. 2.3 Green Roof Systems As noted above, a green roofing system includes a vapour control layer, thermal insulation, support panel, waterproof and root repellent membrane, drainage layer, filter membrane, growing medium and vegetation. Three illustrative commercial options are Soprema s Sopranature system, Garland s GreenShield system and GreenTech s ITM system. Note that there are several other companies that produce green roof systems, Nada Sutic 10

19 such as American Hydrotech Inc., American Wick Drain Corporation, the Barrett Company, and Roofscapes Inc. Sopranature is a green roof system manufactured by Soprema, a company that the manufactures SBS modified bitumen waterproofing membranes. The Sopranature system, as shown below, has many layers. From the top down, there is vegetation, growing medium, filter medium, drainage layer, root repellant and waterproof membrane, a base sheet, support and insulation. The key elements are described below. Figure 2.1: Sopranature System (Source: Soprema Canada, 2002.) Sopralene Flam Jardin Cap Sheet: 2-ply system that waterproofs the deck and contains root repelling agents. Drainage Layer: facilitates water flow to roof drains. Depending on roof slope it is made of Sopradrain PSE (expanded polystyrene for slopes of less than 5%), or Sopradrain GEO (drainage geotextile for slopes greater than 5%). Filter: non-woven synthetic geotextile is used to prevent fine particles from clogging drainage. Growing Medium: designed and manufactured to achieve optimum water retention, permeability, density and resistance to erosion. It varies with each project. Nada Sutic 11

20 Vegetation: varies with each project, but is selected because of its ability to adapt to extreme weather conditions. In extensive systems, primarily ground covers are used, and in semi-intensive systems, perennials, shrubs and grass are grown in an irrigated garden. (Soprema Canada, 2002) In addition to the layers, a border is used to protect edge and roof structures. Soprema uses a prefabricated border of concrete, metal or wood to contain the vegetated areas, and uses a 500mm band of gravel or pavers to protect the edge and other roof structures (Soprema Canada, 2002). The Garland GreenShield system consists of the same type of layers as the Sopranature system. GreenShield uses a modified multi-ply bitumen system, StressPly EUV, for waterproofing (Garland Company, 2002). According to Garland, it is the strongest and most durable membrane available, and uses post consumer and post industrial recycled materials (2002). Another option for greening a roof is the GreenTech Integrated Turf Management System (ITM). The ITM system is modular, containing its own drainage, and not needing a filter cloth, root repellant membrane or waterproofing layer, because it is entirely encased in plastic containers. Air pruning substitutes the root repellant membrane (as roots are exposed to air, they become ineffective), and water can be channeled from the modules directly to the roof drains (GreenTech, 2002). Figure 2.2: GreenTech ITM System (Source: GreenTech, 2002.) Nada Sutic 12

21 Equally important as the type of roofing system, is the growing medium used. The growing medium affects the weight of the roofing system, and must be suitable for the type of vegetation grown. The growing medium can be specially selected and mixed for any project. It usually involves a mixture of native soil mixed with organic or mineral additives, such as peat, humus, wood chips, sand, lava, or expanded clay (Velazquez, 2002). This helps to achieve optimum water retention, permeability, density and erosion control necessary to support the green roof vegetation (Velzquez, 2002). The growing medium must provide anchorage for the plants, and provide essential nutrients (nitrogen, phosphorous, magnesium, calcium, oxygen). It is also important that the growing medium retain its volume, and does not become compacted or muddy, because this could lead to acidification of the soil. The composition and depth of the growing medium will vary with every green roof to meet different needs. The types of plants used for green roofs can vary. Generally, plants on an extensive green roof are low and hardy, often being from alpine or prairie environments. Indigenous plants are ideal if they are able to withstand a dry climate and high winds, as would be expected on a rooftop. Sedums, sedges and grasses are commonly used. Because intensive roofing systems have more maintenance associated with them, the variety of plants that can be used is greater and includes growing foods. 2.4 Building Green Roofs In addition to the type of green roof, roofing system and growing medium, plants and irrigation needs, green roof builders must consider the structural capacity of a building. The structural capacity needed ranges between 72.6 and kg/m 2 (16-35 lbs/ft 2 ) for an extensive roof, and between 290 and kg/m2 ( lbs/ft 2 ) for an intensive green roof (Peck and Kuhn, 2001). Roofs can be constructed to be even lighter than 16 lbs/ft 2 have been built, such as the Rouge River Ford Manufacturing Plant in Dearborn Michigan, which is about 12lbs/ ft 2. Capacity calculations consider what the weight would be if the growing medium is completely saturated. A roof in Waterloo also needs to be able to handle a particular snow load, plus any infrastructure related load, such as heating, ventilating, and air conditioning (HVAC) units, and meet the Ontario Building Code. According to the Ontario Building Code, the ground snow load for Nada Sutic 13

22 Waterloo is 1.8 kpa (37.5 lbs/ft 2 ) and the ground rain load is 0.4 kpa (8.3 lbs/ft 2 ) (MMAH, 1998, 2-21). The composite load, which considers 60% of the snow load plus the rain load is 1.48 kpa or approximately 31 lbs/ft 2 (MMAH, 1998, 2-21). However, the specified loading due to snow is calculated with attention to several other factors, including a wind exposure factor, a slope factor and an accumulation factor (MMAH, 1998,4-11). Green roofs can be designed to meet a variety of goals and needs. For example, roofs can be specifically designed to achieve stormwater management goals, energy efficiency goals, food production objectives and greenspace initiatives, among other uses. Determining the type of green roof and the planned use of the roof will help to determine the best roofing system, the type of growing medium, the type of plants, and any irrigation needs. 2.5 Green Roof Industry The green roof industry in North America is at an infancy stage. There are only a handful of manufacturers or importers of roofing systems and growing media. Some American companies have partnered with European companies to bring the technology and experience of the Europeans to the USA (Scholz-Barth, 2001, 84). In Canada, the National Research Council and Environment Canada have units involved in green roof research. There is also a group of private and public actors involved in the green roof industry called Green Roofs for Healthy Cities. The group s mandate is to develop a multi-million dollar market for green roof infrastructure products and services in cities across North America in order to take full advantage of the multiple benefits of these proven technologies (Cardinal Group, 2002c). Germany and Japan have fairly well developed markets for green roof industry, and will be discussed briefly here. Britain, Switzerland, Austria and Scandinavia have also moved forward with green roofs, but Germany remains the leader. The following will provide a brief overview of what green roof developments have taken place in Germany, Japan and North America, and why they have occurred. In 1989, Germany enacted legislation that required all new buildings to have a green roof (Peck et. al., 1999). Federal environmental laws require mitigation or compensation for the destruction of natural open space caused by development Nada Sutic 14

23 (Velazquez, 2002). As a result, Germany s green roof industry is well established, supported and documented. According to Peck et. al. (1999), over 10 million square metres of roofs were greened by Municipalities provide subsidies to developers and building owners to encourage green roofs and offset the costs. Some municipalities reduce property taxes for buildings with green roofs by 50-80% to reflect their savings in construction, maintenance and replacement of stormwater management facilities (Velazquez, 2002). Other indirect subsidies include development ordinances to compensate for lost open space at a green roof to open space ratio of 0.50 or 0.70 (Velazquez, 2002). Some cities also provide direct subsidies to offset capital costs, and these range from $0.51 to $6.20 USD ($ CAD) per square foot (Velazquez, 2002). Government subsidies and initiatives have played a significant role in increasing green roof development in Germany, making it a world leader in the industry. In Japan, the Tokyo Plan 2000, implemented April 1, 2001required that all new buildings in Tokyo greater than 1000 square metres or one-quarter acre must green at least 20% of the roof. Other Japanese cities are planning to develop and implement similar initiatives by Because Tokyo has seen a dramatic increase in urban temperatures over the last four decades, implementation of green roofs has become increasingly important as a way to curb the urban heat island effect (Velazquez, 2002). In North America, there are green roofs in existence, and some policies and incentives are starting to come into place. However, there are currently no such policies or incentives in Canadian cities. In the United States, the American Society for the Testing of Materials established a Green Roof Standards Task Group in 2001 to establish national standards for green roof technologies (Velazquez, 2002). Also, in the USA, under the US Green Building Council, the Leadership in Energy and Environmental Design (LEED ) program now includes green roofs in the rating system used to certify buildings to LEED (Velazquez, 2002). LEED is a voluntary, consensus-based national standard for developing high-performance, sustainable buildings (USGBC, 2002). The LEED program is applied to commercial, institutional, high-rise residential new construction and major renovation projects (Velazquez, 2002). In Portland, Oregon, there are some incentives to build green roofs. All building projects must incorporate some stormwater pollution reduction measures, and green roofs are an acceptable Nada Sutic 15

24 measure (Velazquez, 2002). Also, Portland builders can increase their floor area ratio by building a green roof, and they can enjoy reduced stormwater utility fees (Velazquez, 2002). The Cityof Chicago enacted an Energy Conservation Ordinance in June 2002, which requires all new and refurbished roofs to install green roofs or reflective roofing (Velazquez, 2002). Canadian cities are beginning to look into incentive programs, but find it difficult to provide financial incentives at a municipal level. Nonetheless, there are green roofs in several Canadian cities. These include the Toronto City Hall, the Vancouver Public Library, the Eastview Neighbourhood Community Centre in Toronto, Mountain Equipment Co-op in Toronto, the Fairmont Waterfront Hotel in Vancouver, the Royal York Hotel in Toronto, the Environmental Sciences Building at Trent University, the Boyne School for outdoor education near Shelbourne Ontario, the Computer Science Building at York University, the YMCA's Environmental Learning Centre at Paradise Lake in St. Clements, northwest of Waterloo, and Mary s Place (YWCA) in Kitchener. In addition to the actual existence of green roofs and demonstration projects in Canada, there are a variety of research projects exploring urban heat island mitigation ability of green roofs, barriers to green roof implementation, stormwater management implications and the energy efficiency potential of green roofs. These include the works of the Adaptation and Impacts Research Group of Environment Canada, the National Research Council s Institute for Construction, Green Roofs for Healthy Cities, the Toronto and Region Conservation Authority, the Toronto Atmospheric Fund, and a variety of consultants. Although the green roof industry in Canada is relatively small, it is growing. Canadian cities have the opportunity to learn from the works of others and to move forward with that knowledge and apply it locally. 2.6 Green Roof Benefits That Improve the Urban Environment There are numerous benefits associated with the implementation of green roofs. The building owner reaps some benefits, while some are community wide. Communitywide benefits include improved stormwater management, reduction of the urban heat island, Nada Sutic 16

25 air quality improvements, community greenspace and aesthetic value, and food production. Private benefits include: energy efficiency gains, improved roof durability and life span, amenity or recreational space and aesthetic value, horticultural therapy, sound insulation, and food production. There is some overlap between public and private benefits, because some benefits are realized throughout the community and by the building owner. The benefits that improve the urban environment will be discussed in this section, with a section following to describe other benefits. Those that improve the urban environment are the public benefits Stormwater Management Densely developed urban areas generally involve extensive areas of concrete and paved surfaces that do not allow water penetrate to the soil and recharge aquifers. Numerous water quality and quantity problems are caused by the abundance of impervious surfaces in urban areas. During rain events, all the water runs off of these hard, flat surfaces relatively quickly, often overloading a local watercourse. Many urban watercourses end up with a low base flow and high peak flow. Many older downtown areas also have combined sewers, meaning that the storm and sanitary sewers run parallel, and the stormwater overflows into the sanitary if the volume becomes too great. When it rains heavily, the combined flow can overload the local wastewater treatment facility, resulting in diluted raw sewage entering a local water body. Because stormwater systems are engineered to provide quick removal of water from buildings and streets, there is also an increased risk of flooding. A high volume of runoff can also cause erosion at the discharge area of the stormwater. Another stormwater problem is the quality of the water, which is particularly important in areas where the stormwater moves directly to a local Nada Sutic 17

26 watercourse. The runoff from streets and parking lots usually contains some pollutants, such as hydrocarbons, sediment, road salt and litter. This ties to the water quantity problem caused by impervious surfaces, because if the quantity and speed of flow is reduced, it can help to reduce the sediment and litter in the water. Another water quality issue relates to compounds that are already in the rain as it falls, such as nitrogen and phosphorous. In addition, stormwater runs over hot pavement, concrete and roofs, gaining heat, which is ultimately transferred to the water body or water course that it discharges to. Improving stormwater management in urban areas can mitigate some of these impacts. Green roofs can have a big impact on stormwater quantity, because they retain a portion of the precipitation. In fact, they may be the single most effective solution to combat urban runoff from impervious surfaces, (Scholz-Barth, 2001, 84). Information regarding how much rain green roofs can retain varies. Some sources say that the growing medium can retain up to 75% of the stormwater (Scholz-Barth, 2001, 86), while others suggest that between 70 and 100% of water can be retained in summer months and 40 to 50% in winter (Peck et al., 1999, 28). Factors that affect these estimates include substrate and vegetation depth, temperature, wind, sun and the duration of the rain. Green roofs are most useful for smaller rainstorms. For longer rain events, green roofs can still retain a portion of the water, but eventually become saturated, resulting in runoff. A major two-inch rainstorm drops about 1.25 gallons per square foot (59L/m 2 ) and a green roof retains about 0.5 gallons per square foot (24L/m 2 ) (Scholz-Barth, 2001, 86). Figure 2.3 below shows how green roofs affect rain runoff. The light blue dashed line for the case with no green roof, shows that almost 75% of rainfall runs off in a region with about 700mm of annual rainfall. The green lines indicate various depths of green roofs, and show that in the same region, only 20 to 35% of the rainfall would run off from the same area. The data shows runoff from the entire lot or property, not just the rooftop. Nada Sutic 18

27 Figure 2.3: Effect of Rainfall on Green Roof Performance Source: Graham and Hicks, 2002, 21. Green roofs can also play an important role in improving the quality of stormwater runoff. A vegetated roof helps to moderate the temperature of water that runs through it, and removes some pollutants (Peck et al., 1999, 29). The water runoff temperature is moderated because less water runs over hot surfaces such as pavement before entering a watercourse. Heavy metals and nutrients carried in the rain remain in the substrate and can be taken up by the vegetation, reducing non-point source pollution (Peck et al., 1999, 29; Scholz-Barth, 2001, 86). Pollutants from the street such as hydrocarbons, sediment, road salt and litter will also be reduced because of the lower flow and volume. By reducing peak flow volumes, green roofs can reduce the risks of combined sewer overflows, flooding and erosion at stormwater discharge points. The ability of plants and the growing medium to filter and use pollutants improves the quality of water runoff. For example, nitrogen or phosphorous in the rain will be broken down by bacteria as needed and then taken up by the plants (Scholz-Barth, 2001, 86). Although some benefits are observed with even one green roof, the best results are achieved when a number of green roofs are in place within an urban area. For the most part, stormwater Nada Sutic 19

28 management benefits are public benefits. Where stormwater management subsidies and incentives exist for building owners and developers, there are some private benefits as well Urban Heat Island Reduction The urban heat island effect is the temperature difference between a city and the surrounding rural area. It is generally a result of a cluster of hard and dark surfaces in urban areas, which absorb solar radiation and convert it to thermal energy. On a clear summer afternoon, the temperature in a city is usually about 2.5 C warmer than in the surrounding rural area (Rosenfeld et al., 1995, 255), and can be as much as 8 C warmer (Peck et al., 1999, 24). In addition to being hotter during the day, surfaces such as roofs and roads release some of the absorbed radiation at night, making nights warmer in the city as well (Toronto Atmospheric Fund, 2002). The graph below depicts the temperature differences on land. Figure 2.4: Sketch of an Urban Heat Island Profile Source: Heat Island Group, Green roofs mitigate the urban heat island effect by reducing the area of hard, dark surfaces. Dark roofs can have a surface temperature 50 C higher than the ambient temperature, while light-coloured roofs will only have a temperature difference of about 10 C (Akbari et al., 2001, 298) and the surface temperature of a green roof can actually be lower than ambient air (Liu, 2002a, 2). Green roofs intercept the solar radiation that would reach a dark roof surface, and use the solar energy in photosynthesis. For example, of the energy that reaches a tree leaf, 2% is used in photosynthesis, 48% is Nada Sutic 20

29 passed through the leaf and stored in the plant's water system, 30% is transformed into heat (used in transpiration) and 20% is reflected (Peck et al., 1999, 21). Although extensive green roofs do not contain trees, the breakdown of solar radiation is similar. Plants also help to keep the air cool through evapotranspiration; they release water, which draws heat from the surrounding air as it evaporates (Heat Island Group, 1999). Plants use heat energy from their surroundings (approximately 592 kcal per L of water) when evaporating water, and one m 2 (10.76 ft 2 ) of foliage can evaporate over 0.5 litres of water on a hot day (Cardinal Group, 2002d). The key point is that the majority of the solar radiation is absorbed and used, not released into the surrounding environment where it would contribute to increased temperatures. Urban heat island effect reduction offers both public and private benefits. For green roof owners, reducing the urban heat island effect helps to reduce their own electrical costs for summer cooling. It also improves overall public conditions by reducing heat wave discomfort and overall cooling costs Air Quality Improvements In addition to reducing the urban heat island effect, green roofs improve air quality by cutting smog generation and removing particulates and gaseous contaminants. The urban heat island effect and air quality are closely tied because heat makes poor air quality feel worse, intensifying the health effects and actually contributing to smog formation and particulate movement. Smog is a mixture of ground-level ozone and airborne particulates. Ozone is formed when NO x (nitrogen oxide, nitrogen dioxide) and VOCs (volatile organic compounds, such as gasoline fumes or solvents) react in sunlight. Airborne particulates include dust, dirt, pollen, spores, or particles formed through chemical reactions involving NO x, sulphur dioxide, VOCs or ammonia (Environment Canada, 2002a). Many of these secondary particulates are formed as a result of combustion and enter the air from industrial smokestacks or vehicular tailpipes. Smog and fine particulates affect human health by irritating the respiratory system, making it difficult to breathe on smoggy days. By reducing the urban heat island effect, green roofs also reduce smog (Akbari et al., 2001, 301). Because smog is produced in the presence of sunlight and production is Nada Sutic 21

30 accelerated in hot weather, reducing temperatures helps to reduce smog production. Also, cooling urban areas reduces vertical thermal air movements and the associated stirring of particulate matter in the air (Peck et al., 1999, 18). Furthermore, green roofs offer some indirect air quality benefits resulting from the energy efficiency gains they provide (discussed in the section Energy Efficiency). Reducing electrical demand can lead to power plants burning less coal, resulting in fewer NO x,, SO 2 and CO 2 emissions, and this can also help to reduce smog. Green roofs also help to improve air quality because particulate matter gets trapped in the vegetation of green roofs, and is later washed into the growing medium by rain (Peck and Kuhn, 2001, 9). Other pollutants, such as NO x, ozone and particulate matter greater than ten microns in size (PM 10 ) can be removed from ambient air through dry deposition. Some gaseous pollutants are also sequestered in plant leaves (Peck et al., 1999, 19). Direct removal rates of air pollutants are not estimated to be high for green roofs (Bass, 2002, personal communication). However, when these removal rates are considered with reduction of the urban heat island, resulting smog reduction and the indirect removal rates from reduced electrical demands, it is evident that green roofs can play a role in improving urban air quality Community Greenspace and Aesthetic Value In addition to the other benefits that have been discussed thus far, green roofs can also provide a pleasing space for people. This benefit applies especially to intensive roofs, which are designed to include this type of benefit. How the space is used usually depends on the building owners and their intentions. For example, a publicly owned building could house community space, or an area for a community garden. An intensive green roof can also provide some passive recreational space. Extensive green roofs have an aesthetic value for surrounding buildings. For example, the Vancouver Public Library s green roof was designed with the view from surrounding office towers in mind (Peck et al., 1999, 31). Widespread implementation of green rooftops can significantly increase the amount of urban green space and provide more recreational and leisure space for urban residents. Nada Sutic 22

31 2.6.5 Urban Agriculture Rooftops are a reasonable option for urban agriculture projects. There can be community benefits by providing local organic produce to local residents, including lowincome families. Furthermore, growing food locally reduces overall environmental impacts by reducing travel and cooling needs and associated greenhouse gases and other pollutants associated with transportation (Peck et al., 1999, 38). Local food production can also provide employment in growing, processing and distribution (Peck et al., 1999, 38). Green roofs can be used for food production during normal growing seasons, or greenhouses can be constructed on top of roofs. Although greenhouses can offer yearround produce, some of the other benefits of green roofs may not be realized as easily because the vegetation and growing medium covered. Essentially by putting a greenhouse on the roof, it simply adds to the impervious surfaces. Stormwater runoff for example will not directly reach the growing medium. Creating stormwater catchments to capture water for irrigation in the greenhouse can rectify the stormwater issue, but air quality and urban heat island effect benefits may be lost. Putting a greenhouse on a roof results in a trade-off of some year-round food production. 2.7 Private Benefits of Green Roofs The benefits of the green roofs that accrue to the building owner include energy efficiency gains, extended lifespan of the roof membrane, private amenity space, horticultural therapy and food production Energy Efficiency The energy efficiency gains that green roofs provide occur mainly in the summer. This is primarily a private benefit for the building owner. As discussed above, the temperature of the membrane of dark roof surfaces fluctuates greatly with ambient air temperature and levels of solar radiation, while a green roof moderates the temperature changes (Liu, 2002b, 61). Green roofs moderate the transfer of heat and cold into a building, and as such, affect the heating and cooling needs. Nada Sutic 23

32 The most dramatic effects are in reducing summer cooling needs. This has been demonstrated by the National Research Council Field Roofing Facility in Ottawa established in November The Ottawa facility divides the rooftop of a building into two sections: one with a conventional rooftop with a modified bituminous membrane, and the other with an extensive green roof (Liu, 2002b, 41). Both roofs are equipped with instrumentation to monitor temperature profiles and heat flow as well as other characteristics (Liu, 2002b, 41). In the winter, the conventional roof can gain some heat from solar radiation when it is not covered with snow. Both the green roof and the reference roof lose heat through most of the day, but the shaded membrane under the green roof cannot take advantage of any solar radiation (Liu, 2002b, 59). When both roofs were under snow, however, the heat flow across both roofs was essentially the same. Figures 2.5 and 2.6 show the winter heat flux, which is the energy per unit area per unit time. Figure 2.5: Heat Flow Winter, No Snow Source: Liu, 2002b, 59. Nada Sutic 24

33 Figure 2.6: Heat Flow Winter, Snow Cover Source: Liu, 2002b, 60. There is a significant difference between the heat flux for the conventional roof and the flat roof in the summer. Figure 2.7 depicts the difference between the reference roof and the green roof on a summer day. The Ottawa roofs received 1920 MJ of solar radiation for the day (Liu, 2002b, 61). The conventional roof absorbed the heat and transferred it into the building, and the membrane re-radiated it into the local environment during the night and early morning (Liu, 2002b, 61). The green roof moderated the heat flow across the system. The result in terms of energy efficiency is that a green roof keeps a building cooler by not allowing the solar radiation to affect the temperature of the building. The area under the curve in Figure 2.7 is the heat flow (transfer of heat across the building envelope). It clearly demonstrates the benefits of the green roof, which has very little heat gain, while the conventional roof allows significant heat transfer across the building envelope. Figure 2.7: Heat Flow Summer Source: Liu, 2002b, 61. Nada Sutic 25

34 Benefits from increasing building energy efficiency include the benefits associated with a reduction in the electrical demand. These other benefits include reduced electrical bills, reduced potential for brownouts in the summer when demand tends to be high, less burning of fossil fuels, the associated air quality improvements and less use of nuclear power and therefore a reduction in nuclear waste. The reduction of fossil fuel use and nuclear waste are specific though not exclusive to Ontario, where much of the electricity is derived from these two sources. There is also a reduction in the need for hydroelectricity. There are other similar benefits depending on the sources of electrical power. The reduction in burning of fossil fuels is particularly important because it is the most flexible type of electrical production, meaning that if there is a reduction in electrical demand, it is the fossil fuel plants that are slowed down first Roof Durability and Life Extension Green roofs also enhance roof durability. A regular flat roof needs to have the membrane replaced every 10 to 15 years, because of the exposure to temperature fluctuations and ultra-violet radiation (Peck et al., 1999, 30; Baskaran and Frégeau, 1996). Because a green roof is a layer on top of the waterproof membrane, it offers protection. It blocks ultra-violet radiation, which stresses the membrane. Also, as described in the previous section, a green roof helps to regulate rooftop temperatures, thus limiting the temperature extremes to which a membrane is exposed. The result is less expansion and contraction stress on the membrane, reducing cracking and aging (Peck et al., 1999, 31). Extending the life of the roof membrane results in a cost savings and contributes to sustainability by reducing resource use Private Amenity Space Landscaped green rooftops provide private amenity space. For example, the owner of an apartment building or condominium may intend an intensive green roof to be an amenity space for tenants. This provides a financial benefit to the building owner who can charge higher rents because of the amenity. A similar benefit can be realized in hotels that have rooftop gardens, which offer space for visitors and allows higher rates to be charged for garden-view rooms. Homeowners can also take advantage of available Nada Sutic 26

35 roof space. For example, flat garages can be made into green roofs, providing a calming and cool rooftop patio. More greenspace is a good addition to any building or home Horticultural Therapy The beneficial aspects of green roofs in terms of horticultural therapy could be considered a public or private benefit. It can be considered public because more vegetation can improve the psychological well-being of people in general, thus improving the city s society overall. Also, improved psychological health of the community can contribute to more productivity through fewer sick-days. Fewer sick-days could be considered a private benefit because the employer benefits. Furthermore, in the case of rooftop vegetation, there may be restricted access, so not everyone benefits. Essentially, under various circumstances (e.g. publicly owned versus privately owned, various views etc.), horticultural therapy could be considered either public or private. In this study, it is being grouped with private benefits. The belief that views and contact with vegetation improve psychological and therefore physical well-being is not uncommon. In 1984, a Pennsylvania-based study examined the restorative effect of natural views in surgical patients and determined that those with a garden-view recovered more quickly than those with a view of a brick wall (Ulrich, 1984). Furthermore, garden-view patients took less pain medication and had fewer negative evaluation comments from nurses (Ulrich, 1984). In addition, people who live in high-density developments are less likely to get sick if they have a balcony or terrace garden, partly because of the additional oxygen, air filtration and humidity control that plants provide (Johnston and Newton, 1996, 27). The air filtration and air quality benefits that vegetation provides also play a role in improving health. Kaplan and Kaplan also discuss the health benefits associated with vegetation, including that association with nature reduces stress, thus improving health (1989, 173) Sound Insulation Green roofs absorb some of the sound in the urban environment. The soil, the plants and the trapped layer of air between the plants and the building surface insulate for sound, by absorbing, reflecting or deflecting sound waves (North American Wetland Nada Sutic 27

36 Engineering, 1998). The growing medium tends to block lower frequencies, while higher frequencies are blocked by the plants Food Production In addition to the broader urban agriculture benefits discussed in section 2.6.5, green roofs can be used in the private realm to produce food. This benefit can be achieved by the homeowner with a green roof or by larger commercial building owners. The Fairmont Royal York Hotel in Toronto and the Fairmont Waterfront Hotel in Vancouver both use their green roofs for growing herbs and vegetables used in their kitchens. The Fairmont Waterfront kitchen saves an estimated $30,000 annually in food costs (Cardinal Group, 2002a), and has the bonus of truly fresh vegetables and herbs. 2.8 Summary of Green Roof Benefits Many of the benefits described here overlap, either because they stem from the same feature of green roofs or because they address the same issue. The chart below summarizes the benefits, and the following diagram illustrates linkages between benefits associated with cooling. Nada Sutic 28

37 Table 2.2: Summary of Green Roof Benefits Issue(s) Benefit Green Roof Feature Combined sewer overflow Risk of flooding Watercourse erosion Pollutants from street or in rain water (e.g. N or P) Heat pollution High temperatures in cities relative to surroundings Vertical thermal air movements stir up dust and other particulates Particulates Smog (Indirect) SO 2, No x, CO 2, through electrical demand reduction High electrical demand (summer) High costs Potential for brownouts Issues associated with sources of electricity (fossil fuels-air, nuclear-waste) Short life-span of conventional roof membrane Use of resources for replacement, cost Limited urban green space Conventional roofs not aesthetically pleasing Limited local food production Costs of food Noise pollution in urban environments Limited interaction with nature Stormwater Management Urban Heat Island Effect Reduction Air Quality Improvement Water retention Filtration Plant uptake Reduce dark surfaces that absorb solar radiation and reradiate it as heat Shading and surface cooling Evapotranspiration Deposition of particulates onto vegetation See features for urban heat island effect reduction: result includes reduced smog production, stirring of particulates, and electrical demand Absorption and sequestration of pollutants Energy Efficiency Cooling through shading Evapotranspiration, reduction in dark surfaces Roof Durability Shading (reduce UV exposure) Cooling (reduce temperature extremes) Community Greenspace, Private Amenity & Aesthetics Food Production (both public/private) Intensive roofs make use of otherwise unused space Improved aesthetic value Intensive roofs make use of otherwise unused space Sound Insulation Plants and growing medium absorb, reflect or deflect sound waves Horticultural Therapy Increased interaction and visibility of vegetation reduces stress, accelerates healing etc. Nada Sutic 29

38 Figure 2.8: Linkages Between Benefits that Relate to Cooling Urban Heat Island Shading Evapotranspiration Reduce temperature in city (UHI) Reduce vertical thermal air movements Air Quality Reduce dark surfaces Energy Efficiency Reduce electrical demand Reduce particulates and movement Smog reduction Roof Durability Increase lifespan of roof membrane Reduce SO 2, NO x, CO 2 etc. Absorption, sequestration of pollutants Vegetation traps particulates 2.9 Barriers to Green Roof Implementation in Canada There are many benefits associated with green roofs, so why aren t there more of them in Canada? Key reasons are barriers to implementation, especially economic barriers. Cost-based barriers centre on relatively high private capital costs and the lack of green roof incentives in Canada. As well there are technical barriers such as limited or uncertain roof loading capacity, and the lack of knowledge about green roofs, both about their benefits and how to overcome economic barriers. Cost-based barriers include high capital costs, limited data on the cost benefits, uncertainty for insurance companies and potentially lengthy payback periods. Capital Nada Sutic 30

39 costs are high because there are more materials and labour going into a green roof than a conventional one (Scholz-Barth, 2001, 96). There are also challenges in estimating green roof costs because there are many variables affecting cost, such as depth of the growing medium, types of plants, type of roofing system and the ability of an existing structure to support a green roof (Peck et al., 1999, 46). Nonetheless, some experts suggest that a green roof costs between 15 and 20 dollars per square foot (USD) ($ /m 2 CAD) (Scholz-Barth, 2001, 96). The cost of retrofitting buildings with green roofs includes the fees for a structural engineer, which can be high for older buildings without architectural plans (Peck et al., 1999, 46). Structural upgrades can also be very expensive. Moreover, while the capital costs are up-front and private, many of the benefits are long-term and public (Peck et al., 1999, 45). There is also a lack of understanding of direct and long-term benefits, making costs seem even higher than they are (Peck et al., 1999, 46). In some places, energy efficiency benefits have been documented and quantified in dollars, but work is still in early stages for Canadian climates. There is a lack of local success stories in a Canadian context (Peck et al., 1999, 45). Some of key benefits of green roofs are best realized with widespread implementation and in a public context. For a building owner, there may not be direct benefits from better stormwater management or air quality improvement. Insurance companies may be hesitant to insure buildings with green roofs because it is a new field, and there may be concerns about weight, drainage, damage from roots and liability issues for accessible roofs (Peck et al., 1999, 45). To make green roofs more financially attractive and bring about the public benefits, some incentives are needed from the public sector. The well-developed green roof industry in Germany did not develop without incentives. By 1996, over 80 German municipalities had offered some sort of incentive to building owners using a green roof (Velazquez, 2002), and the number may be higher now. In Canada, there are some demonstration projects, but no incentives or by-laws in place to encourage development of green roofs. However, there are some sources for funding for research and implementation. These include the Commercial Building Incentive Program by Natural Resources Canada, which provides a financial incentive for energy efficiency features in renovated buildings or additions, Nada Sutic 31

40 the Industrial Buildings Incentive Program, also by Natural Resources Canada, which provides funding for new energy efficient buildings; the Green Municipal Enabling Fund, managed by the Federation of Canadian Municipalities, which provides grants for feasibility studies; and EcoAction, an Environment Canada program that funds non-profit organizations improving the environment. (Cardinal Group, 2002e). There are no legislative requirements relating to green roofs in Canada (Cardinal Group, 2002e). Some American jurisdictions, however, offer either financial incentives or have some sort of green roof requirement in a by-law. In Seattle, all new municipal buildings must be LEED TM certified and green roofs provide an opportunity to gain as many as five points under this system (Cardinal Group, 2002e). Portland, Oregon, has a density bonus system that allows for building an extra three square feet for every square foot of green roof system (Cardinal Group, 2002e). Portland also has a program that provides discounts to stormwater management charges for actions that reduce runoff (Bureau of Environmental Services, 2002). This program is expected to be fully functioning by Chicago recently passed an Energy Conservation Ordinance, which requires all new and replaced roofs to meet minimum standards of solar reflectance and emissivity using ASTM testing methods (Cardinal Group, 2002e). This requirement can be met by installing a green roof system. These pressure and incentive programs make a big difference in encouraging green roof development. Another key barrier to green roof development in Canada is the lack of awareness about them. Many of the cost issues could be rectified with more knowledge. More policy-makers might be willing to offer incentives if there was more knowledge about the benefits of green roofs, particularly stormwater management and cooling benefits (Peck et al., 42). Another group that needs to be better informed is the roofing industry, and there needs to be more communication and cooperation between disciplines that need to be involved in building green roofs, such as roofers and landscapers (Peck et al., 1999, 42). Finally, better public information would help, so that people in communities can play a role in improving their communities. Improving awareness about green roofs will help to diminish misconceptions about them and the associated technologies and advance their widespread implementation. Nada Sutic 32

41 2.10 Motivations and Trends The key motivations for implementing green rooftops in Canadian communities stem from the benefits they provide, and implementation is very dependent on both political commitment and funding. Benefits related to stormwater management are a key motivator for implementing green roofs in the public sector. Improving stormwater management is important for most local governments because they are responsible for it, and must face the cots of failing to deal with it effectively. For densely developed urban areas, any improvement in stormwater management is a bonus. A second set of motivations for implementing green roofs centre on the energy efficiency benefits that translate directly to cost-savings, for public and private sectors. Other important motivations for private building owners are the amenity space and food production aspects. These also easily translate into revenues because amenity space allows building owners or hotels to charge higher rates, and food production can be a business all its own, or as in the case of some hotels can eliminate another expense. In Canada, the private motivations are not quite enough to make green roofs a viable venture for the majority of building owners. If green roofs become more popular, it may become more common for them to be designed into buildings, making the costs less prohibitive. In the meantime, incentives reflecting desires to gain public benefits will be needed. As discussed previously, Canadian jurisdictions currently offer no incentives to help motivate building owners and developers to implement green roofs, but there are currently no incentives in Canada. The main Canadian efforts focus on demonstration and pilot projects through the development of a network of industry and government professionals and researchers. These projects help to stir up interest in green roofs and are proof that they can be successful. Building green roof demonstration projects requires political will and funding. In Waterloo, both of these factors currently exist. The City of Waterloo has an Environment First Policy, which plays a role in guiding decision making, and it has received a grant for funding a green rooftop feasibility study. Nada Sutic 33

42 Chapter 3 The City of Waterloo 3.1 Urban Structure The City of Waterloo has a population of 102,300. Figure 3.1 shows how built up Waterloo is. The Uptown Waterloo area is small, but quite densely developed, with a lot of commercial land use mixed with residential. Just outside of the Uptown core, there are two universities, more residential and suburban residential land use, and commercial nodes. Trees in these areas tend to be mature. Further west, particularly past the University of Waterloo, and towards Fischer-Hallman Road, there are newer suburban developments where the trees are younger and the infrastructure newer. Similar areas exist to the north and east, near Conestoga Mall. There are still some open and agricultural areas near the eastern and the western borders of the City. The northern areas are mostly developed, either with low density residential or industrial land uses. Towards the southern border, approaching Kitchener, Waterloo is mostly developed. It is important to note here, that although most of Waterloo is developed in an urban or suburban fashion, it does not consist of entirely impervious surfaces. The city contains over 438 hectares (nearly 1100 acres) of small parks (Parks Services, 2002, 4). Furthermore, suburban areas are home to many trees and lawns as well as wide roads and extensive parking lots. Just over 13% of Waterloo consists of wooded areas (Environmental Services, 2002a). Figure 3.1 demonstrates Waterloo s density in the central strip. The western part of the city shows as mostly green and brown, indicating the open space and agricultural land. The northeastern corner of the City, which is home to RIM Park, has a similar look. Most of the city appears somewhat grey, indicating the urban character of Waterloo. Nada Sutic 34

43 Figure 3.1: City of Waterloo (MEIS-imagery, 2000) Waterloo Source: Regional Municipality of Waterloo, Projected Growth The City of Waterloo is expected to grow significantly along with the Region of Waterloo, the 10 th largest community in Canada, in the next two to three decades. Conservative estimates suggest that by 2026, the Region of Waterloo could be home to 596,000 people, a 30 percent increase from the 2001 population of 458,000 (Anonymous, 2002a). The Regional government expects the area s population to reach about 700,000 in the next several decades, a span of about 30 years (Region of Waterloo, 2002, 2) In the City of Waterloo, construction of the Research and Technology Park on the north campus of the University of Waterloo has begun, and the Perimeter Institute for research in physics is being built in Uptown Waterloo (Economic Development and Marketing, 2002). The Centre for International Governance Innovation is also to be built in Uptown Waterloo, where it will provide space for research on international affairs and issues of world peace, as well as a museum (Economic Development and Marketing, 2002). In addition, First Gulf Development Corporation is redeveloping the Waterloo Town Square property. As of January 2003, construction is underway on the southwest corner of King and Erb streets. It is a commercial development, which will be the new Nada Sutic 35

44 home of a bank, children s clothing and furniture store, a fitness centre and a coffee house. First Gulf will be redeveloping the rest of the property in stages, and it will include more commercial developments as well as office space. The new institutes and places of work and learning, are expected to draw many more people into the City of Waterloo, along with increased demand for all types of land uses, and especially high growth in the residential and high technology sectors (City of Waterloo, 2002, 28). The City recognizes the importance of accommodating this growth in a manner that avoids and mitigates any negative environmental effects, servicing inefficiencies and other problems associated with growth. 3.3 Waterloo s Environmental Strategic Plan In addition to and as part of planning for growth, the City of Waterloo developed an Environmental Strategic Plan, which was adopted by Council in Work on Waterloo s Environmental Strategic Plan began in 2001 with an information gathering process. The plan outlines what Waterloo s current environmental issues are, based on the findings of the Mayor s Environmental Task Force, and results of the Imagine! Waterloo community visioning process (City of Waterloo, 2002, iv). Six key environmental areas of importance were identified, and strategic actions were defined for each of them. The six areas of importance are 1) planning and growth, 2) water resources, 3) air quality, 4) energy and resources, 5) environmental awareness, and 6) green space (City of Waterloo, 2002, v). Green rooftops fit into the environmental strategic plan in a few areas, most notably under planning and growth, and air quality. The four strategic actions in planning and growth are 1) enhance existing policy, 2) consider new policy and regulations, 3) establish a development forum, and 4) enhance technical considerations in planning and urban design. Green roofs fall under the last action regarding technical considerations. The Environmental Strategic Plan says that urban design needs to consider opportunities for new environmental technology, and includes green rooftops in the list of examples (City of Waterloo, 2002, 30). Green roof initiatives could also be incorporated under the second strategic action about new policy and regulations. For example, in the future, the City of Waterloo could consider adding a requirement that green roofs be used for all a part of new buildings, or at least be evaluated for use in every new building application. Incentives or subsidy programs that Nada Sutic 36

45 target specific issues such as stormwater management or greenspace could also be the basis of new policies or regulations. Strategic actions considered under air quality include reducing external pollution, such as transboundary pollution, reducing local pollutants, primarily vehicle emissions, identifying sources of air pollution and reducing the urban heat island effect (City of Waterloo, 2002, 39). As noted above, green roofs can play a significant role in reducing the urban heat island effect because they reduce the area that absorbs solar radiation and converts it to heat, and they cool the surrounding air through evapotranspiration. Both actions (considering opportunities for new environmental technology and reducing the urban heat island effect) that directly incorporate green roofs are to be addressed in Phase II of the Environmental Strategic Plan implementation, expected to take place from 2005 to The plan is to be implemented in three phases. The first phase of actions includes actions that can be carried out easily or that amplify existing City initiatives and that promise immediate environmental benefits (City of Waterloo, 2002, 52). Phase III actions may be outside the City s jurisdiction and more complex (City of Waterloo, 2002, 54). Items designated for Phase II may require additional resources to what currently exists and additional lead-time for planning and implementation (City of Waterloo, 2002, 53). Other areas where green roofs could fit into the Environmental Strategic Plan include water resources and energy and resources; the first because of the stormwater management benefits that green roofs provide and the second because of the energy efficiency benefits. Waterloo s Environmental Strategic Plan is a useful document in providing guidance and helping to prioritize action for environmental health and protection in Waterloo in the future. Given the strategies and goals in the Environmental Strategic Plan, green roofs could play an important role. 3.4 Study Area The particular area of Waterloo investigated in this study is Uptown Waterloo. The area is shown is defined in Figure 3.2, and includes the area between approximately two blocks east and west of King Street and two blocks west of King Street from Hickory Street to Allen Street. Key features in this area are Wilfrid Laurier University, the commercial area at King and University, Waterloo Town Square, the Uptown Nada Sutic 37

46 commercial area, Waterloo City Hall, the commercial building at Allen and King and the Brick Brewery. There are numerous flat roofs that could be greened within the study area. Figure 3.2: Study Area Source: Regional Municipality of Waterloo, Nada Sutic 38

47 3.5 Roofscape There is a significant amount of roof space in the Uptown Waterloo area defined in Figure 3.2. The entire Uptown Waterloo area as defined in this study covers an area of approximately 1.27 million square metres. Within this area, there are approximately m 2 of flat roof. Of this area, maybe 80% is available for greening, provided that there is adequate structural support. The other 20% would be required for heating, ventilating, and air conditioning (HVAC) systems, walkways for maintenance access and any other infrastructure. If only 25% of that available space were used for green roof projects, there would be approximately m 2 of green roofs in Uptown Waterloo. For the purpose of any calculations throughout the rest of this study, the number m 2 will be used. In Stuttgart, Germany, approximately 22% of all flat roofs are green, and all new ones are required to be greened (Beattie, 2002). In Tokyo, under the Tokyo Plan 2000, all new commercial buildings over 1000m 2 (0.25 acres) and new public buildings over 250m 2 (0.06 acres) must have green roofs on 20% of their roof, and buildings with over 10,000m 2 (108,000 ft 2 ) of floor area must also include green roofs (Bureau of Environment, Tokyo, 2002 and Velazquez, 2002). In Germany overall, 7% of all new flat roofs are green, and this does not include retrofits or buildings put up a few years ago (Kohler et al. 2002, 384). These numbers suggest that to aim for 25% of available roofspace in just Uptown Waterloo, not the entire City of Waterloo is a reasonable goal. This number was calculated by measuring the flat roofs visible on the 2000 ortho-imagery. Measurements were estimated using the Region of Waterloo Locator website. Measurements included completely flat or nearly flat roofs. Nada Sutic 39

48 Chapter 4: Green Roofs in Uptown Waterloo This chapter examines how green roofs can be used to address six issues and considers the current state of the problem and current responses to it as well as some other alternatives for each issue. The topics looked at are stormwater management, the urban heat island effect, air quality and smog, energy efficiency, green space and aesthetics and urban agriculture. 4.1 Stormwater Management Current Situation A significant portion of Uptown Waterloo consists of hard, impervious surfaces. A short stroll through Uptown would show that the commercial areas are almost entirely pavement, concrete and roofs. Within the study area, water permeates naturally into the soil only from residential lawns, small parks and school properties. As a result of the limited space available for water to move into the soil, Uptown Waterloo has been heavily engineered to facilitate stormwater runoff from streets and parking lots to reduce flooding potential. Laurel Creek is buried underneath Uptown Waterloo and receives all of the stormwater runoff from the study area. The creek goes underground at the eastern end of Silver Lake in Waterloo Park and resurfaces near Waterloo City Hall on Regina Street. It is a concrete channel in that area, but returns to a naturalized state near Weber Street. Runoff from the streets and parking lots of Uptown Waterloo drains directly to the creek. Laurel Creek and its tributaries drain a significant portion of the City of Waterloo before reaching the Uptown core resulting in flooding potential (Siva, 1994, 1). Figure 4.1 shows the Laurel Creek Watershed and the approximate location of the study area. Table 4.1 illustrates the reasons for flooding concerns. There are several tributaries that reach Uptown Waterloo at very close intervals. Nada Sutic 40

49 Figure 4.1 Laurel Creek Watershed Source: Regional Municipality of Waterloo, Table 4.1 Stormwater Reaching Uptown Waterloo Tributary Delay in Reaching Uptown Waterloo (hrs) Upper Laurel Creek above Columbia 12.0 Lake University Lands- Sub-watershed Upper Clair Creek 3.5 South Clair Creek-Sub-watershed Maple Hill Creek-Sub-watershed Uptown Area Up-stream of Silver Lake Sub-watershed 319 Uptown Area Down-stream of Silver 0.50 Lake-Sub-watershed 320 Source: adapted from Siva, 1994, 2. As a result of this information from a 1994 report titled Uptown Stormwater Management Criteria, Waterloo City Council approved recommendations that the quantity control part of stormwater management for any development falling within the Uptown area (sub-watershed 320) limits be exempted (Siva, 1994, 1). The report was approved in January, By exempting Uptown developments from quantity control requirements, the City allowed runoff from Uptown Waterloo to flow immediately to Laurel Creek and leave the Uptown area to reduce the risk of flooding as flows from Nada Sutic 41

50 Maple Hill Creek, South Clair Creek, and the University Lands also drain to Laurel Creek and flow through Uptown at various intervals. Typical quantity control measures focus on reducing the rate of flow of runoff, rather than reducing the overall quantity of the runoff. The report asserted that there should be no stormwater detention in Uptown Waterloo, but efforts should be made to implement infiltration trenches and other best management practices. Council also approved the recommendation that staff continue to investigate the feasibility of changing the characteristics within the upstream tributaries.to reduce the peak flow through the Uptown area (Siva, 1994, 1). Altering detention ponds and flows upstream of Uptown Waterloo in Clair Creek and Maple Hill Creek can help to reduce peak flows through Uptown Waterloo. In addition to local water flows, precipitation data for Waterloo should be considered in order to determine the stormwater situation. For the purpose of this study it is not necessary to detail the precipitation data. Canadian climate normals determined by the Meteorological Service of Canada of Environment Canda show the following precipitation information. Precipitation is highest in the spring and summer. Table 4.2: Precipitation Data for Waterloo Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Rainfall (mm) Snowfall (cm) Precipitation (mm) Source: Adapted from Environment Canada, 2002b. In addition to water quantity issues, there are water quality issues in Uptown Waterloo. Because the Uptown area is densely developed, stormwater runoff is degraded because of pollutants on the ground and the rate of flow of runoff. Waterloo is no exception to common stormwater quality issues. Pollutants such as hydrocarbons, silt, salt, litter, fertilizers, pesticides and fecal matter reside in the streets and on the lawns of Uptown Waterloo. Rain washes these pollutants into local creeks and eventually to Laurel Creek. The Laurel Creek Watershed Monitoring Program (LCWMP) monitors phosphorous levels, water temperature, suspended solids, dissolved oxygen and e.coli Nada Sutic 42

51 levels. Monitoring point 3 is near Weber Street where Laurel Creek becomes naturalized after Uptown Waterloo. At this point, phosphorous levels were high, in a magnitude similar to levels in the rest of the watershed over the period. Water temperature, suspended solids and dissolved oxygen were all within targets for those indicators. However, levels of e.coli in this area exceeded targets and were high above the rest of the watershed. Table 4.3 shows the target for each indicator and the results of monitoring for Sites 3 and 5 in Site 3 is near Weber Street, and Site 5 is near the west side of Waterloo Park at Clair Creek and University Avenue. Data were unavailable for Site 4, which is in Waterloo Park near Silver Lake. Table 4.3 Monitoring Results for Laurel Creek Sites Near Uptown Waterloo, 2001 Indicator Target Site 3 (Weber St) Site 5 (University Ave) Phosphorous Instream maximum 80 ug/l (ug/l) (downstream of Laurel Creek Reservoir) Suspended Solids (mg/l) Water Temperature (ºC) Dissolved Oxygen (mg/l) E. Coli CFU/100 ml Instream maximum of 25mg/L Maximum instream temperature of 26ºC (June1-August1) Maximum instream temperature of 29ºC (Aug.1-Oct.31) (downstream of Laurel Creek Reservoir) Minimum 5 mg/l (downstream of Laurel Creek Reservoir) Class 2 Recreation CFU/100 ml (all monitoring locations)* *Based on U.S. Environmental Protection Agency Criteria, in the absence of equivalent Canadian standards Note: Values are average of summer sampling from May-August, Source: City of Waterloo, 2001, 7 and courtesy of J. Smiderle, Environmental Coordinator City of Waterloo. Sites 3 and 4 are most relevant to Uptown Waterloo, as one is upstream of Silver Lake, and the other is downstream of where Laurel Creek resurfaces (City of Waterloo, 2001, 6). However, data for Site 5 are also useful. According to LCWMP, the stretch of Laurel Creek between where the creek surfaces (near City Hall) and Site 3 has poor water quality (City of Waterloo, 2001, 8). Unlike many old urban areas, Uptown Waterloo does not have combined sewers (Siva, 2003, personal communication). As such, there is no potential for combined sewer Nada Sutic 43

52 overflow as a result of runoff during rain events. The main stormwater issues for Uptown Waterloo remain the water quality in Laurel Creek and flooding potential Current Responses The City of Waterloo conducts a variety of activities to control stormwater runoff and improve the health of watercourses receiving runoff. These initiatives include quality and quantity control measures, such as planting riparian buffers, street sweeping and leaf pick-up (Environmental Services, 2002b). Snow removal in the winter also helps to reduce runoff rates in the spring. The City of Waterloo conducts a monitoring program for Laurel Creek and uses the findings to help guide best management practices to reduce impacts on local watercourses and reduce the chance of flooding. Most stormwater management activities improve both water quantity control and water quality. Naturalizing stream banks and planting riparian buffers involves re-establishing a native plant community around the banks of a watercourse. The buffer improves water quality by reducing the amount of pollutants that can flow into the watercourse. Pesticides and fertilizers, for example, can reach watercourses where lawns are planted right down to the bank. If stream banks are not replanted after construction, there can be high sediment loading and bank erosion. Planting natural vegetation helps to stabilize the bank and reduce pollutant entry. Furthermore, naturalized banks reduce the rate of flow of runoff by capturing some water before it runs to the stream. Although naturalization does not now take place in Uptown Waterloo, it can be performed upstream of Uptown, improving overall water quality in Laurel Creek and reducing flooding potential. The 1993 City of Waterloo Official Plan designated a 15 to 30 metre buffer along all waterways within new subdivisions (Environmental Services, 2002c). This policy has been incorporated into development policies and park maintenance procedures. By December 2000, ha had been designated as creek buffer area. By the year 2000, over 40Km of Waterloo s 91Km total of creek length had been naturalized or rehabilitated to some extent (Environmental Services, 2002c). The City also recognizes the value of its urban forests in intercepting and storing stormwater, reducing flooding potential and erosion (The City of Waterloo, 1998, 5). The Laurel Creek Watershed Study initiated in 1990, recommends Nada Sutic 44

53 strategies to guide development based on sustainability principles and with watercourses in mind (Environmental Services, 2002d). Applicable recommendations went into the City s Official Plan in 1993, and the Laurel Creek Watershed Monitoring Program (LCWMP) was initiated in The LCWMP monitors water quality, hydrology, terrestrial features and aquatic habitat over a long period of time and serves as a baseline for future management decisions surrounding the communities watershed by modeling for long-term trends (Environmental Services, 2002d). The LCWMP includes system monitoring, development monitoring and postdevelopment monitoring. This means monitoring the watershed overall, localized areas during development and after development (City of Waterloo, 2001, 3). The responsibility for monitoring is shared between the City of Waterloo and developers (City of Waterloo, 2001, 4). The City of Waterloo also has wet and dry stormwater management ponds to help control runoff by retaining it for a period of time. Wet ponds are ponds that always have water in them and they also help to improve water quality (City of Waterloo Stormwater Management Team, undated). Dry ponds only have water when they retain it during or after a rain event (City of Waterloo Stormwater Management Team, undated). These stormwater management ponds could prove to be problematic in the future as the threat of West Nile Virus grows, if these ponds provide breeding grounds for mosquitoes. The City of Waterloo has an education program and a variety of information is publicly available regarding what individuals can do to help reduce negative impacts of stormwater. The City s webpage on stormwater management includes Dos and Don ts about common residential activities such as gardening and property maintenance, pet care, car care and household renovations (Environmental Services, 2002b). Clearly, the City of Waterloo uses a variety of methods and conducts several programs to control stormwater runoff so that water quality is not too adversely affected and so that water quantity does not change a great deal. At present, flooding potential seems to be sufficiently minimized, though upstream and headwaters development continues, but the quality of water in Laurel Creek continues to suffer. Currently, the Nada Sutic 45

54 City s initiatives do not include vegetated rooftops. The following section outlines how green roofs can improve stormwater management in Uptown Waterloo Improving Stormwater Management in Uptown Waterloo with Green Roofs How much rainfall Uptown Waterloo receives, and how much rainfall a green roof can retain are key factors in determining how green roofs can improve stormwater management in Uptown Waterloo. Essentially, to determine the effectiveness of green roofs, information about water retention in a green roof needs to be compared to rainfall data for Waterloo. In addition, the filtering characteristics of vegetation need to be examined. Waterloo receives from 52mm to 92mm of rainfall in a month, depending on the time of year, and averages about 900mm annually (see Table 4.2). Table 4.4 shows the extreme daily rainfall experienced over a 30-year period. The highest daily rainfall was 89.8mm on July 15, 1985, while the range of 40-50mm seems to be the common extreme in the spring and fall. Table 4.4 Extreme Daily Rainfall Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Daily Rainfall (mm) Date (yyyy/dd) 1995 / / / / / / / / / / / /29 Source: Environment Canada, 2002b The amount of precipitation that a green roof can retain varies and depends on a variety of factors. These include the depth and the type of the growing medium, the types of plants used, the diversity of the plants and the amount of moisture in the growing medium at the start of the rain event. The following four examples help to define the magnitude of benefits in stormwater management. 1. According to the Green Roofs for Healthy Cities website, green roofs retain 70-80% of the water that falls on them in the summer and 25-40% in the winter (Cardinal Group, 2002d). A grass roof with a growing medium of 4-20cm can hold 10-15cm of water (Cardinal Group, 2002d). Nada Sutic 46

55 2. Monitoring in Portland, Oregon found that over a 27-month period, a green roof retained about 30% of the total volume of rainfall (Liptan, 2002). In summer and fall, retention often ranged between 80 and 100%, but in the winter retention was much lower, below 20% (often below 10%) of volume (Liptan, 2002, 74). Water retention in the spring varied. The data are based on a roof on a residential garage, with several species of sedum and grasses on two to three inches of lightweight soil. 3. The National Research Council s Institute for Research in Construction maintains a green roof site in Ottawa (see Section 2.6.4). The roof contains wildflowers and meadow grass with a lightweight growing medium that is 15 cm deep (Anonymous, 2002b, 7). Monitoring of stormwater runoff found that the green roof delays runoff and reduces the runoff rate and volume (Liu, 2002b, 65). Data from a rain event in October 2001 show that runoff from the green roof was not recorded until 35 minutes after the start of the rain event (Liu, 2002b, 65). Over a 15 hour period, 34mm of rain fell on the roof, which was not dry at the beginning of the event. The runoff rate was reduced from 1.8mm/h to 0.8mm/h, but this reduction was reduced as the growing medium became saturated (Liu, 2002b, 65). The green roof retained at least 8mm of the 34mm of rain that fell, which is about 24% of the total. 4. Another data set by Liu (2002a) from the same Ottawa location found that runoff was delayed by 45 minutes, and at least 2mm of runoff or 45% was retained (Liu, 2002a, 4). Furthermore the runoff rate was reduced by 75% (Liu, 2002a, 4). 5. According to Graham and Hicks (2002, 21) green roofs are most effective in dealing with short rain events, and these types of events occur more frequently. For a long storm in North Surrey, BC, data indicate that an extensive green roof with a 10cm growing medium is little improvement over a conventional roof for reducing the peak runoff rate, but an intensive roof with a 30cm substrate can reduce the peak runoff from 23L/s/ha to about13l/s/ha (Graham and Hicks, 2002, 22). Graham and Hicks data also show that at a growing medium depth of about 8cm, the total volume of runoff from a property (not just the roof) is reduced by about 23% compared to a conventional roof, but there are no significant gains in Nada Sutic 47

56 runoff reduction beyond 8-10cm of growing medium (Graham and Hicks, 2002, 23). In the example, the property has 70% lot coverage, which is mostly roof. The other 30% may include porous media that allow for infiltration to soil. These examples indicate the variability in stormwater management benefits that can be gained from green roofs. Although each example shows quantified benefits, the magnitude of the gains can differ. Table 4.4 summarizes the key benefits shown in each example. Table 4.5: Summary of Stormwater Benefits Examples Source Key Points Green Roofs for Green roofs retain 70-80% of precipitation in summer Healthy Cities Green roofs retain 25-40% of precipitation in winter Website A grass roof with a growing medium of 4-20cm can hold 10- Liptan Portland Example Liu Ottawa Example 1 Liu Ottawa Example 2 Graham and Hicks Vancouver area 15cm of water Sedum, grasses, 2-3 inches of soil (5-8cm) Average over 27 months: 30% water retention Summer, fall % retention Winter under 20%, often under 10% retention Grasses, wildflowers, 15cm growing medium Retained 8 of 34mm of water, about 24% when soil already contained moisture Delayed runoff by 35 minutes Reduced runoff rate from 1.8 to 0.8mm/h (44%); this diminished as soil became saturated Grasses, wildflowers, 15cm growing medium Delayed runoff by 45 minutes, Reduced overall runoff by 2mm, 45% Reduced runoff rate by 75% 23% reduction in total volume of runoff from lot with 8-10cm growing medium on roof In a 5-year storm, 10 cm of growing medium did little to reduce peak runoff rate (North Surrey, BC) 30cm growing medium reduced peak runoff from 23L/ha/s to 13L/ha/s The variation in the findings reported in Table 4.5 demonstrates the difficulty in estimating how valuable green roofs are in terms of stormwater management. Consistent data are difficult to obtain because a multitude of factors affect how much water a green roof can retain and how much it can reduce peak runoff. However, a few things are certain: 1) green roofs delay runoff, 2) green roofs reduce the rate of runoff to some Nada Sutic 48

57 extent, and 3) green roofs reduce the volume of runoff. Factors that affect the ability of green roofs to perform these functions include depth of the growing medium, types of plants used, and the amount of moisture already held by the growing medium. There are some potential problems with applying data from the West Coast to Ontario because Ontario s growing seasons are shorter, the climate is harsher and rainfall patterns are different. Nonetheless, the data are useful because the roofs are similar, and a more conservative estimate may actually be derived from data with wetter climate conditions than may be typically experienced in Waterloo. The Ottawa data are fairly applicable because the climate is similar. When considered together, the examples given above show ranges of rainwater retention ranging from about 24% to 100% in the summer and fall. The numbers vary because of differing soil moisture conditions, various depths in growing medium and different types of plants. Based on the % range for retention, assume that on average about 60% of rainfall in Uptown Waterloo would be retained. Recall that for this study, green roofs are being considered as consisting of about 26,000m 2 of Uptown Waterloo, an area that is about 1.27 million m 2 (see Section 3.5). Randomly selecting a day with rainfall, data from the University of Waterloo s weather station shows that beginning on May 24, 2001, 11.9mm of rain fell between 7:45pm until 1:00am on May 25 (University of Waterloo, 2003). Over an area of 1.27 million m 2, this amounts to a volume of 15,133m 3. If green roofs consist of 26,000m 2 and absorb 60% of the rain that falls on them, then they retain m 3 of the rainfall in Uptown Waterloo. This amounts to 1.2% of the total volume of rainfall in Uptown Waterloo in a 12mm rain event over a 5-hour period. Making a similar calculation for the average annual rainfall (765mm), green roofs would retain approximately 11,294 m 3 of the 971,550 m 3 that would fall on Uptown Waterloo. Although this seems like a small number when compared to the total amount of rainfall, it does add significantly to the other infiltration points within Uptown Waterloo that reduce the total volume of water going into Laurel Creek. The reduction in sediment and nutrient loading cannot be calculated with any confidence based on these data. However, given that the volume, rate of runoff are both reduced, the reduction in sediment and nutrient loading may be higher than the 1.2% reduction in runoff. A reduction of 185m 3 or 185,000 litres in a Nada Sutic 49

58 12mm rain event is likely to be important in reducing overflow potential, sediment loading and transport of pollutants among other issues. Furthermore, flow rates will be reduced, limiting erosion of the creek bed. Green roofs also delay runoff, which may actually be problematic in Uptown Waterloo, because of flooding potential. Recall that current stormwater management practice in Uptown Waterloo is not to delay runoff. Given that green roofs are being considered as only 2% of the total land area in Uptown Waterloo and can actually retain a significant amount of stormwater, this may be negligible. This issue requires further investigation. Roof greening has also been shown to improve the quality of runoff. Research plots in Berlin, Germany showed retention of about 95% of lead, 90% of cadmium, 80% of nitrates and 70% of phosphates over a 36 month period (Köhler et al., 2002, 398). In particular phosphate retention improved over time as plants became established, rising from 26% in the first year to 80% in the fourth year (Köhler et al., 2002, 398) Alternatives for Stormwater Management The stormwater management problems in urban areas like Uptown Waterloo are not caused solely by rooftops, but are a result of numerous impervious surfaces. Therefore, there are a number of other ways to deal with the impervious surfaces. These include the use of turfstone and other permeable paving options, porous pavement and even tree planting. Turfstone is a type of interlocking paver, which allows some vegetation to grow, allows rain to permeate the soil and is suitable for heavy truck traffic to drive over. A turfstone surface can provide a grass surface which is capable of surviving vehicular traffic, and is commonly used for parking areas, multi-use open areas, driveways, airfield runway and taxiway shoulders, highway shoulders, medians, trailer parks, boat launching ramps, emergency access roads and fire lanes, and for stream bank and lake side erosion protection (Metromont Materials, undated). Turfstone pavers are usually made of concrete and are able to withstand high levels of stress and pressure. Figure 4.2 shows the typical configuration and components of turfstone, including the compacted aggregate under bedding sand and the pavers on top. Nada Sutic 50

59 Figure 4.2: Components of a Concrete Grid Pavement Source: Metromont Materials, undated. Turfstone systems are not suitable for all applications. For example, in areas where people walk with heeled shoes regularly, the porous nature of turfstone may be problematic. Another permeable paving option is the Uni Eco-Stone or similar paving systems. These pavers leave gaps in between the pavers to allow for water infiltration, as shown in Figure 4.3. Most interlocking bricks, such as cobblestone, are useful in allowing for water infiltration and even those that are tightly placed together are superior to regular pavement in this respect. Figure 4.3: Uni Eco-Stone Paving System Source: Interlock Paving Systems, Inc., Nada Sutic 51

60 Another way to allow for water infiltration is to use porous paving materials. Porous pavement consists of an open-graded asphalt concrete on top of an open-graded aggregate base on a draining soil (Thelen and Howe, 1978, 3). Basically, porous pavement is similar to regular asphalt, but uses mostly coarse materials and particulate matter in both the asphalt and the base. Figure 4.4 Porous Pavement at the Ecotrust Centre in Portland Photo by authour. There are no fine particles or dust in the aggregate mix for porous pavement (Robinette, 1993, 146). This allows for water to move through the material to the soil underneath. The potential trade-off is that although runoff is reduced, contaminants normally in road runoff may infiltrate the soil and potentially the groundwater. Advantages of porous pavements include 1) no the need for curbs, gutters, catch basins et cetera; 2) puddles do not form, improving safety; 3) skid resistant; 4) traffic markings are clearly visible on a rainy night; 5) aerobic bacteria can live in the soil underneath, breaking down some organic pollutants; and 6) storm runoff is filtered through the soil (Thelen and Howe, 1978, 17-18). There are also disadvantages and limitations associated with porous pavement. These include: 1) the potential for loss of porosity due to sediment remaining on the pavement and being ground in by traffic; 2) the potential for soil to be dropped off dump trucks and plugging pores; and 3) stress arising from many vehicles braking at the same spot reduces porosity (Thelen and Howe, 1978, 15-16). Nada Sutic 52

61 There is also potential for road pollutants to leach into soil, although bacteria can break down some of those pollutants. These particular disadvantages indicate that porous pavements would not be suitable for all applications, but are useful for others. It is important to note that freezing, thawing and snow and ice conditions have not caused problems with porous paving (Robinette, 1993, 146). Other alternatives for stormwater management are disconnecting downspouts, using swales near parking lots, constructed wetlands and rain barrels. Tree planting and increasing the overall amount of vegetation are also very helpful. Trees can reduce and retard stormwater runoff because tree canopies detain and evaporate some rainfall, reducing peak and total runoff (Childs, 1999, 119, 188). Unfortunately, some of these options may not be suitable for Uptown Waterloo because of limited space. This is precisely why green roofs are considered in densely developed and populated urban areas; there is no available room for tree planting or gardening. Stormwater management in urban areas is a complex issue with many different options for controlling runoff. As has been demonstrated above, green roofs in Uptown Waterloo could improve stormwater management significantly, by reducing the volume of runoff by about 1.2% of total rainfall. Green roofs will also reduce the rate of flow to some extent and delay runoff, though figures for these benefits have not been calculated. Studies in Berlin also demonstrated how green roofs directly improve water quality, and there has been discussion of how green roofs can indirectly improve water quality. Although demonstration of these benefits has been largely qualitative, it shows that green roofs can play a valuable role as a tool for stormwater management. Further research is needed in order to quantify these benefits reliably. 4.2 Urban Heat Island Effect Current Situation Given that most cities with a population of over 50,000 are subject to the urban heat island effect, it can safely be assumed that Waterloo is as well, particularly because of its proximity to two other sizeable cities (Peck, personal communication, 2002). It is difficult to determine the actual extent of the urban heat island effect in Uptown Waterloo because there are no comparable data for the Uptown area specifically and a local rural Nada Sutic 53

62 area. However, examining data from the 1970s, a local climatologist determined that Kitchener averaged nearly 1 C warmer than the local airport (Sanderson, 1996, 88). The study considered maximum and minimum temperatures in both January and July to compare heat retained in urban areas in both winter and summer. Findings are shown in Table 4.6. Given that the urban size and population of Kitchener and Waterloo have grown since the 1970s, it is likely that the urban heat island effect is more pronounced now than it was 30 years ago. Table 4.6: Urban Heat Island in Kitchener Average ( C) Difference ( C) Jan Max Kitchener ( ) Airport -3.3 Min Kitchener Airport July Max Kitchener ( ) Airport 25.8 Min Kitchener Airport 13.1 Adapted from Sanderson, 1996, Gomez et al. (1998, 356) report on how the maximum heat island effect for a city can be calculated as a function of the population. The equation is as follows: MHI=2.01 log P 4.06 C, where P is population. The maximum heat island is the maximum difference in temperature between the urban area and surrounding rural area. For Waterloo, based on a population of 103,000, the maximum heat island is 6.02 C. there is also a speed limit beyond which the heat island is no longer produced, and for Waterloo, this limit would be 5.44m/s or about 20km/h. Waterloo is in a unique situation given its proximity to Kitchener and Cambridge. If the population of all three cities were to be taken together, the maximum heat island would be higher, at about 7.1 C, and the limiting wind speed would be 7.4m/s or 26km/h. It is important to note that this calculation is not suggesting that Uptown Waterloo is commonly about 6 C warmer than a local rural area, but that based on its size, it could be that much warmer. Also, the actual equations do not seem to consider the density of an urban area. However, the equation is based on measured data about the heat island effect, suggesting that density may be accounted for in the original data. Nada Sutic 54

63 4.2.2 Current Responses The urban heat island effect has not been well documented in Waterloo, so although there are not policies specifically directed towards the urban heat island effect, there are policies that acknowledge the heating effect of pavement and buildings. The City of Waterloo s urban forestry policy for example, states that the City recognizes the multitude of benefits that arise from an urban forest (City of Waterloo, 1998, 5). One of these benefits is that trees moderate the heating effect of pavement and buildings and provide shade and shelter, thereby reducing energy consumption and heating and cooling costs (City of Waterloo, 1998, 5). In addition, part of the urban forest policy is to maintain and expand the urban forest through proactive planning (City of Waterloo, 1998, 6). The City of Waterloo has over 26,000 trees and plants over 1400 each year (Environmental Services, 2002e). In addition, one of the air quality objectives in the Environmental Strategic Plan is to reduce the urban heat island effect (City of Waterloo, 2002, 37). Strategies to accomplish this include planting shade trees, installing reflective materials on roofs and pavements and the installation of rooftop gardens (City of Waterloo, 2002, 40) Potential for Green Roofs to Mitigate Waterloo s Urban Heat Island Green roofs help to reduce the urban heat island effect. Numerous models can be used to estimate the urban heat island effect reduction potential of green roofs, but actual data are scarce. These studies are difficult to conduct because reduction of the urban heat island effect is realized when numerous green roofs are in place, so it cannot be measured from just one roof. Moreover, in areas where there are numerous green roofs, baselines may not have been established prior to their installation (e.g. in Germany); and there are several other variables affecting the urban heat island effect, making it difficult to measure the causal relationship between green roof implementation and urban heat island effect reduction. Nonetheless, some studies model the urban heat island effect and the moderation that vegetation can provide. 1. A study by Gomez et al. considered the impacts of vegetation in Valencia, Spain. They found that there was a heat difference of over 5 C between the city centre and the outskirts (Gomez et al., 1998, 357). On average however, the difference Nada Sutic 55

64 in temperatures between the city and the outskirts is 1.3 C in the winter, and nearly the same in the summer (Gomez et al., 1998, 357). Gomez et al. observed that in green areas (not necessarily roofs) the temperature was about 2.5 C below the city s maximum temperature (1998, 360). This could be extrapolated to green areas on rooftops, where the cooling effects would be similar, though perhaps less pronounced. Based on this information, it is not possible to determine what the reduction of the actual urban heat island would be, only the differences between greened urban areas and other urban environments. 2. In another study modeling Toronto, it was found that if green roofs were 1% of the total land area in Toronto or 6% of total roof area, the reduction in the UHI would be 1-2 C (NRC/EC, 2002). The green roof area was 6.5 million square metres of roof (NRC/EC, 2002). The examples show that vegetation, in particular green roofs can play a role in reducing temperatures in urban settings. The reports from each study do not detail the assumptions and variables in the articles or summaries, but they certainly differ. Types of plants used may vary and there may be climatic variables built into the models in different ways, affecting the outcome. Table 4.7 summarizes the examples given above. Table 4.7: Summary of Urban Heat Island Reduction Examples Source Key Points Gomez et al. Valencia, Spain Green areas about 2.5 C cooler than city s maximum temperature Unable to determine actual urban heat island effect reduction NRC/EC Toronto 1% of total land area with green roof coverage 1-2 C reduction in urban heat island effect Given that the NRC/EC modelling study found that with 1% coverage of total land area, green roofs could be expected to reduce the urban heat island effect by 1-2 C, similar results might be expected in Waterloo. The area being considered in this study is 2% of the land area of Uptown Waterloo, but only about 0.05% of the City s total land area. With Waterloo being a smaller and less densely developed city than Toronto, it could be expected the urban heat island effect is less severe, so it is feasible that a smaller proportion of green roofs would have a greater effect in Waterloo. It is difficult to compare 0.05% coverage to 1% coverage in cities as different as Waterloo and Toronto to provide an estimate of the overall urban heat island effect reduction. However, with Nada Sutic 56

65 green roofs as 2% of the land area in Uptown Waterloo, it is expected that they would produce a notable reduction of at least 1-2 C in local temperatures, though the reduction is unlikely to be noticeable elsewhere Alternatives For Reducing the Urban Heat Island Vegetation helps to reduce the urban heat island effect in general, whether on a roof or not. Increasing the size of the urban forest and planting vegetation wherever possible would help to reduce the urban heat island effect. Using light coloured roofing materials is also helpful in reducing the urban heat island effect. In another study * the value of using light coloured roofing materials with an albedo ** of 0.6 instead of green roofs, found reduction in the urban heat island effect similar to the reduction found from green roofs (Bass et al, 2002, 9). Light-coloured pavements, such as light-coloured slurry seals or a top-coat with light-coloured aggregate also help to reduce heating (Childs, 1999, 197). Reducing the urban heat island effect in Waterloo through initiatives in Uptown Waterloo is certainly possible, though difficult to measure. However, based on the examples given above, temperatures in Uptown Waterloo might be reduced by 1-2 C if 26,000 square metres of green roof were added to the Uptown area. 4.3 Air Quality and Smog Current Situation The Waterloo area has been documented as having poor air quality. In a 2000 article in Canadian Geographic, Kitchener was dubbed the fifth smoggiest place in Canada (Vincent and Fick, 2000, 33). While the title was given to Kitchener, the results for Waterloo would be similar. Monitoring data from Ontario s Ministry of the Environment (MoE) show that this area exceeded limits for ozone and particulate matter often over a five-year period including The Waterloo Region is in an area subject to transboundary pollution because of continental wind patterns. Winds transport air masses and contaminants from areas to the southwest, including the Ohio Valley, which is home to many heavy industries and coal- * This study is not included in the list of examples because its key author suggested that the second study (NRC-Toronto) is more accurate. ** Albedo is the fraction of light that is reflected by a body or surface, such as the ground or a roof. Nada Sutic 57

66 fired power plants (Vincent and Fick, 2000, 33). Some sources suggest that up to 50% of the air pollution in the Waterloo Region is from transboundary sources (Vincent and Fick, 2000, 33; MoE, 2002). The MoE monitors air quality in Ontario for sulphur dioxide, nitrogen dioxide, ozone, fine particulate matter, carbon monoxide and total reduced sulphur compounds. The closest station to Waterloo is in Kitchener at Homewood Ave. Table 4.8 displays data collected from that station. Table 4.8: MoE Air Quality Data for Kitchener SO 2 (ppb) O 3 (ppb) NO 2 (ppb) PM 2.5 (µg/m 3 ) Criteria # Times Criteria 1h 24h 1Y 1H 1h 24h 24H Exceeded N/a N/a Source: MoE, According to the MoE data in Table 4.8, the K-W area suffers most from high ozone levels and particulate matter. At both tiers of local government, there are policies and plans regarding air quality Current Responses Within the Waterloo area, there are a number of responses related to air quality, including plans, policies and air quality inventories and monitoring, which may lead to broader action. The City of Waterloo has an air quality page on its website, with information for citizens about what they can do to reduce their impacts on air quality. The City s urban forest policy is also important to air quality, because trees moderate the heating effect of pavement and buildings and provide shade (City of Waterloo, 1998, 5). Particulate matter can deposit on tree leaves and trees absorb some pollutants while producing oxygen (City of Waterloo, 1998, 5). The City of Waterloo has adopted the principles of the Regional Clean Air Plan (described below), which includes an anti-idling campaign, use of ethanol enhanced fuel and low-sulphur fuels, and implementation of a smog alert protocol to guide municipal operations during smog alert days (City of Waterloo, 1998, Nada Sutic 58

67 48). Furthermore, the City participates in the annual Commuter Challenge and the Repair Our Air Fleet Challenge (City of Waterloo, 1998, 13). Through these initiatives, the City of Waterloo is attempting to lead by example in taking action to reduce its impact on local air quality. Air quality is also discussed in the City of Waterloo s Environmental Strategic Plan. Strategies to address air quality issues include reducing external pollution emissions, reducing local pollution emissions, reducing the urban heat island effect and identifying sources of air pollution (City of Waterloo, 2002, 37). In the City of Waterloo s Environmental Strategic Plan, increasing vegetative cover and capacity to absorb carbon dioxide and other pollutants are part of the initiative to reduce local pollution emissions (City of Waterloo, 2002, 41). Waterloo Region s Clean Air Plan includes a number of short-term and long-term initiatives aimed at reducing local air pollution, beginning at the municipal level. In 1998, each of the townships and cities within the Region of Waterloo agreed to implement the plans and activities in the Clean Air Plan (Regional Municipality of Waterloo, 2002b). Short-term strategies include a number of ideas aimed at vehicles, such as the Green Fleet policy, which ensures vehicles are maintained properly and the use of less polluting fuels, compliance with Ontario s Drive-Clean program, refueling vehicles after sundown and before sunrise in the summer to reduce volatile organic compound emissions, and a no-idling protocol (Regional Municipality of Waterloo, 2002b). Other short-term strategies are directed towards encouraging use of public transit and alternative modes of transportation, increasing naturalized areas and the development of the smog alert program and protocol (Regional Municipality of Waterloo, 2002b). Long-term strategies of the Clean Air Plan include initiatives to promote public transit and make it more accessible for residents, education campaigns about smog, encouragement of participation in clean air initiatives and the development of an audit plan for tracking activities in order to achieve clean air initiatives (Regional Municipality of Waterloo, 2002b). As part of the Clean Air Plan, the Region of Waterloo conducted an air emissions inventory to identify current sources and volume of air pollution emitted by Regional activities (Region of Waterloo Public Health, 2002, 7). Emissions were calculated for Nada Sutic 59

68 five criteria air contaminants (NOx, SOx, CO, VOCs and PM10) associated with Regional operations (Region of Waterloo Public Health, 2002, 7). In addition the emission reductions predicted suggested measures were calculated, and the measures were ranked according to their feasibility, cost-effectiveness and impact on reducing air emissions (Region of Waterloo Public Health, 2002, 7). The Citizens Advisory Committee on Air Quality (CACAQ) (Waterloo Region) is a community group that includes representatives and volunteers from other local organizations, the community and staff from local municipal governments. The group s mission is to work with the community to improve air quality and reduce air pollution impacts on human health and the environment (CACAQ, 2003). The group has local projects and attempts to raise awareness about air quality and pollution issues and also has subcommittees on Policy Development, Public Education, and Green Transportation (CACAQ, 2003). CACAQ and the Public Health Department of the Region of Waterloo work closely together, while the group is primarily citizen driven. These responses to air quality issues at the municipal level are useful and each action is valuable. Nonetheless, air quality is an ongoing problem and more measures are need to improve it Potential for Green Roofs to Improve Waterloo s Air Quality There is a mix of local and transboundary sources of contaminants in Waterloo. The local sources can be addressed at the source locally, but distant sources cannot be addressed by Waterloo in a way that reduces emissions at the source. While, source reduction is ideal, it can take a long time to reduce emissions at the source, so methods that help to reduce pollutants in the air now are needed. Vegetated rooftops are one way to combat urban air pollutants, including ozone and particulate matter. There are limited data on how green roofs specifically improve air quality. Numerous studies suggest that vegetation in general helps to improve air, and some of these can be extrapolated to green roofs. Others may be more specific to the urban forest and not viable for extrapolation, such as those that refer to the cooling effects of trees. 1. A study in Frankfurt, Germany demonstrated that a treed street had about 3000 dirt particles per litre of air, while a street without trees had 10,000 to 20,000 particles per litre (Minke and Witter, 1982, 11). When Peck et al. extrapolated Nada Sutic 60

69 these figures and applied them to a 2000 m 2 roof with unmowed grass, they found that the roof could remove 4000 kg of dirt particles (1999, 19). However, it was acknowledged that this estimate was high, because lower portions of the grass might not be in direct contact with air. To make the estimate more conservative, the authours considered only one-tenth of the particles that trees could remove. They found that a grass roof would remove about 0.2 kg of particulate per square metre of roof over a year (Minke and Witter, 1982, 11). Recall that the MoE standard for particulate is 30µg/m 3 (see Table 4.8). Each square metre of green roof remove 0.2kg of particulate annually or 200,000,000µg/m 2, which works out to approximately 550,000µg/m 2 daily. 2. Green roofs also have value in the exchange of oxygen and carbon dioxide. In green roof applications, one m 2 of mowed lawn 3-5 cm high has a leaf surface area of 6-10 m 2, while one m 2 of uncut meadow has a leaf surface area of up to 225 m 2 (Peck et al., 1999, 25). Based on this information, one might assume that 1 m 2 of uncut grass roof, could have a leaf surface area of 100 m 2, 1.5 m 2 would meet the yearly requirement of oxygen for one human (Peck et al., 1999, 25). 3. A study modeling Toronto (mentioned in the Urban Heat Island Section above) suggests that with green roofs covering 1% of Toronto s total land area, an area of 6.5 million m 2, would result in a direct 30 tonne reduction in air pollutants including carbon monoxide, sulphur dioxide and particulate matter 10 microns in size (NRC/EC, 2002). In addition, the study estimates that there would be a 5-10% reduction in the incidence of smog formation, and a reduction in greenhouse gas emissions of 2.18 mega tonnes annually directly from energy conservation and indirectly from a reduction in the urban heat island (NRC/EC, 2002). Nada Sutic 61

70 Table 4.9 Summary of Air Quality Improvement Examples Source Key Points Minke and Witter/Peck et al. Frankfurt street trees Dirt particles removed by street trees extrapolated to grass roofs. When considered at 1/10 as effective, grass roofs still remove 0.2kg/m 2 annually Peck et al. general 1.5 m 2 of grass roof could provide the annual oxygen requirement for one person NRC/EC Toronto 1% of Toronto s land area covered in green roofs: o could remove 30 tonnes of pollutants o reduce incidence of smog formation by 5-10% o reduce greenhouse gas emissions by 2.18 Mt In Chapter 3, Waterloo s potential roof area available for green roof applications was determined to be 26,000 m 2. At a removal rate of 0.2kg/m 2, 26,000 m 2 could remove 5200 kg of particulate matter, a rather significant amount. On an annual basis, this works out to 100kg per week, or over 14kg daily, and considering the MoE standard for fine particulate matter is 30µg/m 3, making 14kg per day quite valuable. In addition, 26,000m 2 could provide oxygen for over 17,000 people. The actual removal of pollutants from 26,000m 2 would be limited, estimated at about 0.12 tonnes. The reduction in smog formation would probably be less than 5-10%, given that 26,000 m 2 is only 0.05% of Waterloo s land area, compared to the study that considered 1% of Toronto s land area. Based on the numbers in the NRC/EC study above, the greenhouse gas reduction might be approximately Mega tonnes or 8.72 kilo tonnes. Note that these numbers are merely an estimate extrapolated from the data given above to provide an estimate of the magnitude of benefits that can be expected. The first two examples apply to grass roofs, while the third applies to a mix including urban agriculture and intensive green roofs. If the mix of types of roofs were changed, the numbers applied to the benefits might change as well. It is also important to keep in mind the close ties between reduction of the urban heat island, reduction of smog production, improvement in air quality, and energy efficiency gains. Nada Sutic 62

71 4.3.4 Alternatives for Improving Urban Air Quality and Reducing Smog Initiatives that can be implemented to reduce urban air quality problems include tree planting, changing modes of transportation and land use planning steps to cut vehicle use. Some of these initiatives can be very complex and will only be discussed briefly here. Tree planting and increasing space for vegetation, which, as has been described above, can remove particulate and pollutants. In addition, vegetation has cooling effects, which help to reduce the urban heat island effect and reduces the incidence of smog. A behavioural change that can be made to improve air quality is changing one s mode of transportation. This means switching from a single-occupancy vehicle to cycling, walking, in-line skating and public transit, among other alternatives. The transportation sector is a significant contributor to poor air quality, so using transportation modes that have zero emissions or are more efficient (that move more people with less energy) is helpful in reducing emissions and improving air quality. Land use planning changes that would improve air quality are tied directly to transportation. Land use planning that encourages people to live near their place of employment would be helpful to reduce the need for commuting. In addition, land use and transportation planning could be used to make driving less appealing for the individual, thus improving the feasibility of public transit and other modes of transport. 4.4 Community Greenspace and Aesthetic Value Current Situation One of the findings of the Imagine! Waterloo visioning process was that citizens wanted to have more greenspace. Greenspace in the city can also be a public space, where the community can gather and interact, but there is little public space in Uptown Waterloo. Waterloo Park is nearby and provides some public space, but it is not right in the Uptown core. A public urban space in Uptown Waterloo could provide a venue for citizen expression and simply as a common gathering space where people can get away from the constant bombardment of corporate influences. Even as private space, green roofs provide residents, homeowners or commercial employers with the benefit of additional outdoor space. This is particularly beneficial in Nada Sutic 63

72 areas like Uptown Waterloo where the only expanse of green space is Waterloo Park. In residential areas in and around Uptown Waterloo, most homes have some yard space, but many are small. Apartment dwellers may have a balcony, but a rooftop garden space would surely be an appreciated bonus. The aesthetic value of green rooftops may not be as valuable in Waterloo as in other cities. There are not many tall buildings as most of the Uptown core is at about the same height. However, with expected growth and redevelopment, this may change. In addition, even at similar heights, some buildings do have views of other s roofs and vegetation is more appealing than the bland grey or black of conventional roofs Current Responses The need for public space and improving the bird-eye view aesthetics are not pressing issues in Waterloo. As such, there are no particular responses directed towards these issues. However, the City of Waterloo is attentive to street aesthetics, so perhaps rooftop aesthetics are not too far off Green Roofs Providing Community Greenspace and Improving Aesthetics The provision of green roofs in both private and public venues in Uptown Waterloo would improve aesthetics and provide more outdoor space for Uptown residents and others. There are issues associated with providing public space that would need to be addressed, such as safety, accessibility and the potential for vandalism. These considerations could drive up the costs of the roof. However, the need remains for public space, and the fact is that there is little room at ground level for any sort of public square, so the roof may be the only option for Uptown Waterloo. Private green roofs would also be useful in providing an outdoor space for some Uptown residents. Both publicly owned and privately owned green roofs could be used for community gardens as well. Public roofs could be used by anyone in the larger Waterloo community, while private roofs might be restricted to a particular building or community. Both would provide opportunities to strengthen community ties, whether used as a community garden or simply as an available green space. Nada Sutic 64

73 If an area 80% of the size of Waterloo Town Square were converted to an intensive green roof, it would provide 17,000 m 2 of new green space in the heart of Waterloo. Given that Waterloo Town Square may be redeveloped in the future, a green roof could be easily built into the design of the new development. The development is not a public one, but there may be potential to make it somewhat public through some sort of partnership. Improving aesthetics in Uptown Waterloo would take a step towards a more prestigious and welcoming city. With expected growth and development in the next few decades, improving the appearance of Waterloo is a positive move Alternatives for Providing Community Greenspace and Improving Aesthetics Alternatives to rooftop gardens for providing a community or private amenity space generally require space at grade. However, Uptown Waterloo does not have much available space at grade. Waterloo Town Square could and may include this type of space when redeveloped. However, it will be a private redevelopment, and may not be a place where anyone can relax on a break without having to purchase something or be subject to corporate influences. As mentioned above, some sort of partnership could make it a more public space. To improve the aesthetic value of Uptown Waterloo, there is not much that compares to green roofs in improving the view of rooftops, although additional vegetation at grade can improve any view. 4.5 Urban Agriculture Current Situation The food system today is a global one, where the average distance food travels from field to table is about 1500 miles or about 2400 km (Roberts, 2001, 11). While food travels from faraway places like California or Chile to reach local grocery stores, Southern Ontario has some of the most fertile land in Canada, where climate and nutrient quality can support the variety of foods needed for local food security. Local farmers markets provide local foods, but not exclusively, as imports appear there too. A trip to the local grocery store in Waterloo reveals that much of the produce is from the United Nada Sutic 65

74 States, often from California, and increasingly it comes from as far away as Chile. Food is a basic need that can be provided locally, but instead is trucked hundreds or thousands of kilometres burning fossil fuels, spewing particulates and greenhouse gases along the way. A study by Pirog et al. compared the conventional food system with a hypothetical regional food system in Iowa to determine the differences in distance traveled, fuel use and greenhouse gas emissions. The findings of the study concluded that if 10% of the produce consumed in Iowa were grown and transported in a regional or local food system, fuel savings would range from 280 to 346 thousand gallons of fuel, and CO2 reductions from 6.7 to 7.9 million pounds, depending on the system and type of truck (Pirog et al., 2001, 2). These are the types of costs that are externalized and commonly ignored in the conventional food system. The study is based on the situation in Iowa but the qualitative findings are applicable beyond that boundary. The conventional food system has been created over decades and continues to be exacerbated by policies on farming and trade agreements. Canadian policy has encouraged agricultural exports in the last 15 years, and exports doubled in the period from 1989 to 1996 (Qualman and Wiebe, 2002, 4). However, as exports rose, so did imports, and net exports today are not much higher than in the 1980s (Qualman and Wiebe, 2002, 6). What s more, it is difficult for small farmers to survive in food production because of rising costs and lower profit margins. Regulations are expensive to meet and directed towards larger operators. Governments have overlapping mandates and responses to requests for help are usually negative and answer only what the small farmer can not do, instead of what he or she can do (Verhagen and Knight, 1995, 35). Furthermore, financing is difficult to obtain for the small farmer as banks do not have a strong tradition of lending for small farm business, but are more comfortable with the larger farm operations (Verhagen and Knight, 1995, 35). Ultimately, the result is that it is increasingly difficult for small farmers to succeed, thus limiting the availability of locally grown food, because larger producers are more export-oriented Current Responses FoodLink Waterloo Region is a local non-profit organization dedicated to strengthening the local food system (Community Health Department, 2002, 1). The Nada Sutic 66

75 organization attempts to ensure that no one in Waterloo is without food and that all citizens have access to nutritious food through encouraging local consumers to support local food producers (Community Health Department, 2002, 1). The Region of Waterloo s Community Health Department has played a role in supporting the development of FoodLink by providing technical, administrative and consulting support and well as sponsoring interviews and public forums (Community Health Department, 2002, 2). FoodLink has a Buy Local Working Group, which is identifying strategies to link local consumers to local farmers. One strategy is the publication of a map of the Region that identifies where consumers can purchase food at farm gates (Community Health Department, 2002, 2). FoodLink also tries to work to influence public policy at the City and Regional levels to promote better food security and the local food economy. Aside from FoodLink and the Region of Waterloo s Public Health Department s involvement with FoodLink, there appears to be little action taken towards promoting a local food economy. Furthermore, FoodLink does not focus specifically on urban agriculture, although it is something the organization considers. The existence of FoodLink and the involvement of the Community Health Department indicate that there is some movement to link local governments and planning with food security The Role of Green Roofs in Urban Agriculture in Waterloo Green roofs can play a small role in improving local food security by providing space in urban areas where produce and herbs can be grown. Instead of traveling about 2000 km to reach consumers, food may only have to travel the distance from roof to kitchen. When green roofs are used for urban agriculture, the magnitude of some of the other benefits may decrease somewhat. Because space must be left in order to tend to the garden, there is less vegetative cover and growing medium cover. Roofs devoted to agriculture need to have more structural support than an extensive green roof, but not quite as much as an intensive roof. Also, some safety measures may need to be taken because there will be people working on the roof. Clearly, with the amount of work and material that goes into a creating a rooftop vegetable or herb garden, the cost of agriculture in the city will be higher than Nada Sutic 67

76 conventional agriculture. However, given that roofs are otherwise unused space, the capital investment can pay itself off because the space is being used to provide food for the urban population. The food may go to the building owner, be sold at markets or be donated to local food bank programs. The payoff does not have to be monetary, but there are certainly benefits from agriculture. In Waterloo, green roofs can help to reduce the distance between field and table by providing an urban space for farming. This study has suggested that approximately 26,000 m 2 of flat roof space could easily be available for greening in Uptown Waterloo. If only 10% of that were devoted to urban agriculture, that would be an area of 2600 m 2 producing food for people who live in Waterloo. That s nearly 30,000 square feet, about two-thirds of an acre or a little less than half the area of a Canadian football field. This could help to provide fresh vegetables and produce to low-income citizens and would help to empower citizens of Waterloo while they support local economies. Agriculture needs space, which is one thing that urban areas like Uptown Waterloo lack. There is little available space where plants can grow, but roofs can provide the needed room for urban agriculture Alternatives for Urban Agriculture in Uptown Waterloo Essentially, urban agriculture comes down to making space available for agriculture in the city. In the area of Uptown Waterloo, agricultural plots could be put into Waterloo Park or around the Waterloo Memorial Recreation Complex. FoodLink Waterloo Region is already looking into alternatives to urban agriculture to improve local food security and develop a linked regional food system. Urban agriculture could form a part of this system and contribute to food security and ensuring that all of Waterloo s citizens have nutritious food to eat. 4.6 Energy Efficiency Although the focus of this chapter is on benefits that can improve the urban environment of Uptown Waterloo, energy efficiency, a private benefit, is included for three reasons. The first reason is that in the Imagine! Waterloo visioning process, energy and resources was identified as important to the people of Waterloo. The second reason is that there is an abundance of literature available on this benefit, making it fairly easy to Nada Sutic 68

77 demonstrate the benefit. The third reason is that it is one of the more important aspects of green roofs that is expected to play a significant role in advancing the implementation of green roofs in Canada, and likely in Waterloo Current Situation Efficiencies gained through green roof applications are in heating and cooling of buildings, and Waterloo buildings are expected to have an energy profile typical of Canadian buildings. Based on data for Ontario from 1998, 1999 and 2000, about 10% of the energy used in commercial buildings goes towards space cooling, and between 42 and 50% goes towards space heating (OEE, 2003). In the residential sector, similar data show that about 2% of energy use is for space cooling, while 56 to 60% is for space heating (OEE, 2003). As prices for energy rise in Ontario, any cost-effective gains that can be made are beneficial. Consider that for every degree Fahrenheit in heat, an additional 5-10% of cooling energy is needed (Peck et al., 1999, 20). Consequently, any cooling that can be achieved is valuable. Furthermore, improving energy efficiency contributes to improved air quality because of Ontario s mix of electricity sources. Coal fired power plants account for approximately 25% of electricity in Ontario, and as energy demand decreases, coal-fired production is the first to slow down Current Responses The City of Waterloo and the Region of Waterloo both have some energy efficiency initiatives. However, efforts to educate the citizenry about the importance of energy efficiency seem limited. Neither level of government seems to stress the importance of conserving energy and energy efficiency. However, energy is not a service that is provided by either level of government. Most local utility companies do make information available regarding energy conservation and encourage energy efficiency. Both levels of government sponsor REEP, the Residential Energy Efficiency Project, which conducts home energy evaluations for residents in the Region. The goal is to encourage energy efficiency by helping people find cost-effective solutions to improving efficiency and lowering their bills. Nada Sutic 69

78 The City of Waterloo acknowledges energy and resources as an important issue in the Environmental Strategic Plan. The strategic actions involved include reducing energy use, supporting alternative energy sources, supporting alternative transportation and supporting continuous improvement of environmental standards (City of Waterloo, 2002, 42). Reducing energy use is a strategic action to be taken in Phase II of implementation of the plan, between 2005 and 2008 (City of Waterloo, 2002, 54). The City is already supporting alternative energy sources by having solar panels installed at City Hall (Burtt, 2003). Taking action on building energy efficiency is an individual responsibility as much as a government responsibility. As such, there is little to be seen from a local government level in terms of action. The Government of Ontario also plays a role in encouraging and promoting energy efficiency, but with the current price cap on electricity prices, energy efficiency is actually discouraged. Ultimately, it comes back to the building owner or homeowner to be concerned about energy efficiency Green Roof Potential to Improve Energy Efficiency in Waterloo Several studies have demonstrated the ability of green roofs to improve energy efficiency. The challenge in applying data to other situations is that key factors tend to be specific to each building. Energy efficiency in buildings is affected by the level of insulation used, the type of HVAC system, the effects of solar radiation, the size of the building, and the climate among other factors. The insulation value of a green roof is in the plants and the growing medium and is also dependent on the type of roof. Extensive roofs are thought to be better insulators than intensive ones, likely because of the greater coverage they achieve. Mixed grasses perform better than limited-species grasses, which are still better than a layer of lowgrowing sedums (Liesecke et al., 1989, 16). Minke and Witter demonstrated that an 8 (20cm) layer of substrate plus an 8-16 (20-40cm) layer of thick grass has an insulation value of about R20 (RSI 0.14) (1989, 34). This is a fairly thick growing medium, with plants that have been established over a period of a few years. This seems a good deal more than could be expected in Waterloo within the near future, because a green roof of that size would take years to establish and due to the depth of growing medium is likely to be costly. However a roof that is about Nada Sutic 70

79 half the size of the one in the example is reasonable to expect, and as such about half of the insulation value. Added insulation of about R10 is certainly notable, given that attic insulation should be about R40. Section on energy efficiency discusses some of the findings at the National Research Council s facility in Ottawa, which compares a green roof with a conventional roof. Data from that facility indicate that indoor temperatures remain lower with a green roof, thus reducing energy demands for cooling. Figure 4.5 demonstrates the differences in temperature between the conventional and green roofs. The red line shows indoor temperature, which rises more significantly without a green roof. The blue line, which is the most pronounced difference shows the temperature of the roof membrane, which is underneath the green roof system on the vegetated roof. Note that the graph is representative of data from 2001, when the roof was still fairly new. Plants will become more well-established over time providing even better insulation values. Figure 4.5: Temperatures at NRC Facility Source: Liu, 2002b, 55. Another study suggests that indoor temperatures under a green roof, without cooling were 3-4ºC lower than hot outdoor temperatures between 25-30ºC (Liesecke, 1989, 18). This is similar to the temperatures shown in Figure 4.5. There are also some energy efficiency benefits to green roofs in the winter. Essentially, the green roof provides another layer of insulation, but does not allow a building roof to take advantage of solar radiation. This was also discussed in Chapter 2. Nada Sutic 71

80 Overall green roofs are useful in improving energy efficiency by preventing solar radiation contact with the roof and thus reducing heat transfer across the building envelope. As shown above, green roofs could potentially increase insulation values in Waterloo by a factor of about R10, and can moderate indoor temperatures in the summer time Alternatives for Improving Energy Efficiency There are numerous ways to improve energy efficiency, including methods that have similar effects as green roofs in providing protection from solar radiation and wind. Passive solar landscape design can achieve energy efficiency benefits in ways similar to green roofs. For example, planting shade trees on the south and west sides of a building provides shade in the summer, and allows solar radiation to warm the building in the winter. In addition, vertical gardens or vines on a building can help to shade and protect from wind. Protecting a house from wind can cut heating demand by 25% (Peck et al., 1999, 20). Planting conifers on the north side of a home also helps to protect from wind. Other ways to improve the energy efficiency of a building are improving insulation levels and sealing air leaks. In fact, these two actions are probably the most cost-effective way to improve efficiency and see a relatively quick payback on the capital costs of improvement. Green roofs are one of many ways to improve the energy efficiency of buildings. However, while other initiatives have benefits only in energy efficiency, green roofs have many other benefits too. 4.7 Summary of Green Roof Benefits in Uptown Waterloo For stormwater management, green roofs can improve Uptown Waterloo by reducing the rate and volume of runoff, delaying runoff and improving water quality. With 25% of the available flat roof space greened, an annual reduction in volume of runoff of about 11,000m 3 could be expected. A reduction in the urban heat island effect is also expected in Uptown Waterloo if about 26,000m 2 of roofs contain vegetation. The reduction expected is perhaps 1-2 C in Nada Sutic 72

81 only in the Uptown Waterloo area. Green roofs in Uptown are not expected to alter temperatures noticeably outside of the study area. Some improvement in air quality is also expected as well as a reduction in the incidence of smog. This is partially due to reducing the urban heat island effect, and because of the tendency for deposition of particulate and some pollutants on vegetation. Increasing the amount of vegetation through the addition of 26,000m 2 of green roofs could remove 5200kg of particulate. Energy efficiency gains are likely, but are specific to individual buildings. In addition, green roofs can provide amenity or community space in Uptown Waterloo and provide space for urban agriculture. For example, if an area the size of Waterloo Town Square was devoted to public greenspace, 17,000m 2 of new public space would become available in the Uptown core. Also, if 10% of the area considered in this study was used for urban agriculture, that would be 2600m 2 available for food production. This would be brand new space available without having to convert existing land uses. This chapter has discussed some of the key benefits of green roofs, and how they could be applied and/or realized in Uptown Waterloo. Some estimates have been made to demonstrate the magnitude of the benefits, but little attempt has been made to convert these benefits into cost-related benefits. There are also numerous other benefits and spinoff benefits that have not been discussed here, such as job creation within the roofing industry, landscaping industry, and food industry. These are all issues for further research. Nada Sutic 73

82 Chapter 5 Overall Analysis Many green roofs benefits accrue to the public rather than the building owner. Stormwater management and air quality improvements, urban heat island and smog reduction, and increased community space and aesthetic value are all public benefits. Energy efficiency gains, extended roof life, sound insulation and private amenity space are chiefly private benefits, while urban agriculture and horticultural therapy can be either public or private benefits. The benefits listed here are all direct benefits and have been discussed primarily in that context, but there are also indirect benefits such as job creation in the building and roofing industries, and those related to agriculture. There have been numerous challenges in specifying and quantifying some of these benefits in this study. Using other literature to gauge the magnitude of benefits proved to be somewhat problematic because many factors affect these benefits, such as the size of the roof, depth of the growing medium, types of plants, how well-established the plants are, local climate variables and building-specific variables. Furthermore, some of the reported literature findings involved the use of models or estimates, each with its own, often unknown assumptions. Another challenge in this study has been the attempt to average over a fairly large area using data that are not specific to Uptown Waterloo. All of these challenges reduce the reliability of the quantitative findings to some extent, but the qualitative findings remain valuable. Accurate quantitative findings are beyond the scope of this research, as the study is too broad to quantify the benefits with any certainty. Nonetheless, the study serves the purpose of identifying the magnitude of benefits that could be expected and has identified and defined some of the issues that green roofs can solve in Uptown Waterloo. 5.1 Green Roof Benefits in Waterloo Several green roof benefits would be significant in Uptown Waterloo. The public benefits are especially important in improving the overall urban environment. The community benefits researched and studied within this study are stormwater management, urban heat island effect reduction, air quality improvements, community greenspace and aesthetic value, and urban agriculture. For each pertinent issue, the current situation in Uptown Waterloo was described along with a description of current Nada Sutic 74

83 municipal responses to those issues. Following those descriptions, there was discussion of how green roofs can improve on those issues and some other options for dealing with them. Overall, it was found that green roofs could offer much benefit to Uptown Waterloo. With widespread implementation of green roofs in Uptown Waterloo, there could be reductions in the amount of stormwater runoff to Laurel Creek and some improvement in water quality as well. The urban heat island effect could be reduced in Uptown Waterloo, reducing the incidence of smog. Air quality could be improved by having more vegetation to remove particulate matter and act as an air filter. There could be an increase in community greenspace in Uptown Waterloo as well as an improvement in aesthetics. In addition, green roofs could provide space for urban agriculture in the dense urban core of Waterloo. Section 4.7 provides a summary of each of these benefits, and they are all discussed within Chapter 4. Some of the private benefits are also important in the public realm. For example, energy efficiency is a private benefit, but by reducing energy consumption everyone benefits through reduced burning of fossil fuels, and extending the life of the roof membrane contributes to sustainability. One green rooftop alone would provide little public gain. However, through implementation numerous green roofs in Uptown Waterloo, the core of Waterloo could achieve all of the benefits of green roofs. 5.2 Challenges Facing Implementation of Green Roofs Key challenges facing implementation of green roof initiatives include the high capital cost, the numbers of predominantly old buildings with unknown structural capacity for green roofs, and limited incentives for builders and developers. The capital costs of a green roof are approximately double the costs of a conventional roof. This cost is recovered eventually through the doubling of the life of the roof, but there is a limited understanding and continued skepticism about this fact. Furthermore, the main benefits are public benefits but the costs are borne by the builder or building owner. In Waterloo and elsewhere, there are no public incentives encouraging use of this technology, even though many of the benefits of green roofs are public benefits. The main private benefits are gains in roof life, energy efficiency and amenity space or food Nada Sutic 75

84 production, depending on what the roof is designed for. Although there is some cost recovery with each of those benefits, it is fairly slow when compared to the capital costs, resulting in a lengthy payback period. Without public incentives or regulatory requirements such as those in Portland and Chicago, it will be difficult to encourage green roof development effectively. Recall that Portland offers a density bonus for developments with green roofs, and Chicago has an energy conservation ordinance. There are a few options for funding in Canada that my fund a green roof, evaluated on a case-by-case basis. These funding opportunities exist are with the national Office of Energy Efficiency s Commercial Building Incentive Program and Industrial Building Incentive Program, the Green Municipal Enabling Fund through the Federation of Canadian Municipalities, and the Environment Canada program EcoAction. These programs are described in Section 2.9. Unfortunately, these funds are limited, and it is unlikely that all projects that would receive funding. These types of programs are not enough to encourage widespread of implementation of green roofs in Canada s cities. An additional problem for Uptown Waterloo, like many other urban core areas, is that most of the buildings are old. Within the study area, there are a number of buildings estimated to be from the 1920s and 1930s and clusters from the 1960s and 1970s, with other buildings in between. Some older buildings may have the structural capacity to add a green roof, but verification of this is time-consuming and costly if no architectural drawings are available. Many buildings may simply not have the capacity to support the additional weight of a green roof. However, there are also new opportunities in Waterloo including current developments at Waterloo Town Square and Wilfrid Laurier University. Some of these opportunities have already been missed as new buildings have been completed within the last year, and construction has already begun for others. However, developments that have not yet started represent opportunities for green roofs. Even for the buildings that have been built already, there may be some potential for retrofitting them. A significant challenge for green roof implementation is limited understanding of many of the benefits associated with green roofs. Developers, roofers, homeowners, building owners, and policy makers need to be educated about the value of green roofs Nada Sutic 76

85 and their applicability. One of the most effective ways to prove the usefulness of green roofs is to lead by example showcase the benefits and prove that it works. 5.3 Implications The City of Waterloo is on the right track with green roofs. A feasibility study has been initiated in the spring of 2003, with the hope to create a demonstration green roof on a municipal building. A demonstration plot would be used to showcase some of the benefits of green roofs and help to educate the residential and commercial community about green roofs. There are benefits to being an early adopter of green roofs, such as encouraging more green roofs both locally and in other municipalities. By setting an example and showing that green roofs can work, the City of Waterloo has an opportunity to inspire others to invest in them too. Work on green roofs may also inspire similar positive environmental thinking elsewhere. Furthermore, there is potential for job creation. Because green roofs are fairly new, only a handful of consultants and roofing companies perform this work. However, if as a result of the City of Waterloo s leadership, more interest develops, new firms may be attracted to this area or existing firms may be inspired to take on this type of work. Many new doors can open up with an interest in green roofs. There are also implications for the Region of Waterloo to get involved with green roofs. The City of Waterloo may be a leader in the Region, but greater benefits can be achieved with Region-wide initiatives and cooperation. The Region of Waterloo is currently planning for significant growth in the next two to three decades. Planning for this growth is likely to include intensification of the core, resulting in an increased need for greenspace, and presenting an excellent opportunity to reap the benefits of green roofs. Furthermore, the Region of Waterloo can play a role in addressing the need for incentive programs, by forming partnerships on green roof initiatives with the cities and townships of Waterloo Region. Also, by developing a common priorities and common ideas about green roofs, the Region and its cities and townships can be more effective in trying to reach the federal and provincial governments. Although green roofs do well as a municipal initiative, municipalities are continually strapped for funding, while federal and provincial government budgets grow with the economy. As such, they should be Nada Sutic 77

86 called upon to help provide funding for green roof related projects and research. In addition, the City of Waterloo could develop relationships with other Ontario and Canadian municipalities to build the case for green roofs and encourage their development. There have been challenges in performing this study, and there will be challenges in implementing green roofs. It is nonetheless clear that green roofs are an exciting new technology that can be applied in areas such as Uptown Waterloo where there is little available space for other environmental initiatives. Waterloo has an opportunity to be a leader in this field in Canada by partnering with other municipalities, both locally and elsewhere, to demonstrate the viability of green roofs as a tool for improving urban environments and attract the support of other levels of government. Nada Sutic 78

87 Chapter 6: Conclusions and Recommendations This study has made some estimates regarding the magnitude of potential green roof benefits. While quantitative estimates were not always feasible, case and qualitative evidence of the benefits of green roofs suggests that green roofs could provide Uptown Waterloo with a number of excellent benefits and could be a viable tool for improving the urban environment in Waterloo. Improvements in stormwater management include reducing the volume and rate of runoff and improvements in water quality. Runoff could potentially be reduced by 11,000m 3 annually if approximately 26,000m 3 green roofs were intercepting rain in Uptown Waterloo. From the same area of green roofs, a 1-2 C reduction in the urban heat island might effect might be expected in Uptown Waterloo. There would also be some improvement in air quality as vegetation filters particulate matter and other pollutants from the air. Energy efficiency gains are expected, but are specific to individual buildings. Green roofs could provide new public space, amenity space or agricultural space in the heart of the city. The most important outcomes of this study have been to provide a comprehensive overview of the potential for green roofs and to demonstrate the complexity of some of the issues, revealing the need for further research. Inevitably, some technical, social and political challenges confront widespread implementation of green roofs. The technical challenges, such as determining if a building can sustain a green roof are relatively easy to overcome. The social and political challenges lie in educating builders, developers, the public and policy makers about the benefits of green roofs, and in providing appropriate incentives. A conventional and reasonable way to demonstrate the benefits of green roofs is through proven research and examples. In general, people need to see that this technology works. The green roof industry and individuals who would like to advance the industry need to compile more case studies in various climates to clearly demonstrate that this technology works. However, in any new venture there will always be some risk and people are needed to take on those risks in the beginning so that they may collect the benefits later. The existing green roof industry needs to continue to find organizations, institutions or individuals who are willing to build green roofs and willing to showcase Nada Sutic 79

88 the benefits. Furthermore, policy makers need to be lobbied and informed about the potential for green roofs to improve the environments of dense urban areas and to reduce other costs. For example, green roofs can improve air quality and stormwater management. Therefore, fewer people will need medical attention because of respiratory problems and less of the budget needs to be spent on stormwater management infrastructure. Policy makers need to be aware of the potential for preventative methods that green roofs offer and dollar savings through spin-off benefits. Those spin-off benefits, such as reduced health care and stormwater management costs, should be the drivers for incentive programs. Responsible levels of government should be directing funding into green roofs through incentive programs in order to achieve those public benefits. Ultimately, those public benefits will likely save money for governments and taxpayers in the future. These technical, social and political challenges to green roof implementation can be overcome in Canadian cities. The City of Waterloo is in the process of joining the ranks of Canadian municipal leaders in Canada in the green roof industry by performing a feasibility study to determine the feasibility of green roofs in Waterloo. Furthermore, the City is already encouraging research, such as this study and others, indicating the growth of green roofs is budding in Waterloo. Green roofs can clearly improve the urban environment, and should be encouraged in Waterloo. Key recommendations to promote green roof implementation in Uptown Waterloo are as follows: Partner with the Region of Waterloo and other local municipalities to undertake studies, educational campaigns and develop incentive programs in the future. Examine potential policy initiatives at both levels of government to determine what would be effective in encouraging green roofs. Develop an educational campaign in Waterloo to educate developers, builders, the public and City staff and councilors about green roofs. Prepare an inventory the buildings in Uptown Waterloo. The City should take on the role performing an initial assessment of publicly and privately owned buildings within Uptown Waterloo to determine which buildings may be suitable for further investigation and green roofs. Prioritize issues related to the benefits of green roofs. Determine what is more important urban agriculture or stormwater management and urban heat Nada Sutic 80

89 island reduction. These priorities can be used to adjust the focus of a green roof development strategy for Uptown Waterloo. Involve the community in green roof development plans and decision-making. Involvement of community groups, organizations and individuals is important for the success of green roofs. Promote research within the community. Partner with the local universities and colleges to encourage research. Some research ideas are as follows: Set up a research roof in Uptown Waterloo. This roof should be instrumented to measure the volume and rate stormwater runoff, delay and water quality, and energy efficiency. In addition, this roof could be used to determine the air quality benefits of green roofs. Develop a decision-making guide for some of the pertinent issues to determine the best tool or combination of tools to combat the particular issue. For example, what are the tools that can impact air quality issues, and what makes one tool better than another in some situations. Determine the effects on Laurel Creek if there were widespread implementation of green roofs. Examine and quantify runoff volume, runoff rate, runoff delay and associated water quality issues. Model the urban heat island in Kitchener-Waterloo and determine how green roofs can mitigate the effect. Examine which types of green roofs are best in achieving the greatest energy efficiency gains. Calculate representative expectations for energy efficiency in Waterloo for particular building type. Given that green roofs last at least twice as long as conventional roofs, define a methodology for determining when the green roof needs replacement. Define when to replace the roofing membrane under your green roof, and calculate the costs. Determine what could be expected of rooftop urban agriculture in Uptown Waterloo. Calculate how many of the low-income families in Waterloo could be provided for through urban agriculture projects. Develop a plan for a food system that includes rooftop urban agriculture in Waterloo. Define the demand for public space in Uptown Waterloo. Survey Waterloo citizens to determine what they expect in public space, and if green roofs can meet that expectation. Nada Sutic 81

90 Green roofs are an excellent tool that could improve the urban environment in the City of Waterloo. This study has shown that green roofs could be very useful in Uptown Waterloo, and these findings are applicable outside of Waterloo as well. Current literature and experience indicate that green roofs could offer many of the same benefits to any urban environment. They are an excellent way to increase the amount of greenspace in an urban area, and bring with them all of the benefits associated with greenspace: cooling, stormwater management, air quality benefits and even food production. The City of Waterloo needs to form partnerships locally to promote green roof implementation, and direct an education campaign to inform citizens of the benefits of this tool. In addition, the City should inventory buildings in Uptown Waterloo to provide an initial assessment of the feasibility of green roofs, and the City needs to prioritize urban issues. The City of Waterloo should continue to promote research and involve the community in green roof initiatives. Nada Sutic 82

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