FROM FLAT ROOF TO ROOF GARDEN: COMPARING FIVE DIFFERENT APPROACHES 

ON ROOFTOP DESIGN 

By 

Wing Chi Vincy Tam 

 

 

 

 

 

 

 

 

A THESIS 

Summitted to  

Michigan State University 

in partial fulfillment of the requirements 

for the degree of  

Environmental Design – Master of Arts 

2020

 

 

ABSTRACT 

FROM FLAT ROOF TO ROOF GARDEN: COMPARING FIVE DIFFERENT APPROACHES 

 

ON ROOFTOP DESIGN 

By 

Wing Chi Vincy Tam 

This study addresses categories of design treatments for a rooftop at The Sylvester 

Broome Empower Village, located in Flint, Michigan. Five design treatments: flat roof, self-

design roof, extensive green roof, semi-intensive green roof, and intensive green roof, were 

evaluated by 36 variables chosen by the investigator. The Friedman test was applied to examine 

significant differences between the five treatments (α ≤ 0.05). The Friedman’s multiple 

comparison test revealed the treatment of the flat roof performed the poorest. There was no 

significant difference to demonstrate that the other four design treatments perform better than the 

other, but the treatment of intensive green roof performs better than self-design rooftop. 

Keywords: landscape architecture, green roof, roof garden, flat roof, rooftop design, rooftop, 

self-design rooftop, extensive green roof, semi-intensive green roof, intensive green roof. 

 

 

ACKNOWLEDGEMENTS 

I want to present my most significant appreciation to my major professor, Dr. Jon Burley, 

FASLA, Professor of Michigan State University of School of Planning, Design, and 

Construction. I would not be able to finish this without his support and inspiration.  

I would also like to thank you for my two committee members: Trish Machemer, 

Associate Professor of MSU of School of Planning, Design, and Construction; and Brad Rowe, 

Professor of MSU of School of Horticulture. They provided me with ideas and inspirations.  

I would also like to thank you for The Sylvester Broome Empower Village, located in 

Flint, Michigan, which kindly allowed me to use the rooftop for this research. 

Last but not least, I am thankful to my parents, who are always being my supporting 

backbone throughout my life. They are always there, no matter when and what. College life is 

not easy; I would not succeed through college without them. 

 

 

iii 

TABLE OF CONTENTS 

LIST OF TABLES ........................................................................................................................ v 

LIST OF FIGURES ..................................................................................................................... vi 

CHAPTER ONE: INTRODUCTION AND LITERATURE REVIEW .................................. 1 
1.1 History of Green Roofs ................................................................................................. 4 
1.2 Extensive Green Roofs, Semi-Intensive Green Roofs, and Intensive Green Roofs ..... 5 
1.3 How to build green roofs?............................................................................................. 8 
1.3.1 Components of green roofs ............................................................................ 8 
1.3.2 Green roofs installation ................................................................................ 10 
1.4 Benefits of Green Roofs.............................................................................................. 13 
1.4.1 Green roofs reduce stormwater runoff ......................................................... 13 
1.4.2 Green roofs as tools to alleviate global warming......................................... 17 
1.4.3 Green roofs in noise reduction ..................................................................... 18 
1.4.4 Wildlife habitat and biodiversity enhancement ........................................... 19 
1.4.5 Urban parks benefit in social connection ..................................................... 23 

CHAPTER TWO: METHODOLOGY ..................................................................................... 25 
2.1 Design Scenario Description....................................................................................... 25 
2.1.1 Existing site .................................................................................................. 25 
2.2Study scenario .............................................................................................................. 31 
2.2.1 Conventional rooftop ................................................................................... 31 
2.2.2 Self-design rooftop....................................................................................... 31 
2.2.3 Extensive green roof .................................................................................... 35 
2.2.4 Semi-intensive green roof ............................................................................ 36 
2.2.5 Intensive green roof ..................................................................................... 43 
2.3 Data collection ............................................................................................................ 48 
2.4 Variable Rating Criteria .............................................................................................. 52 

CHAPTER THREE: RESULT .................................................................................................. 59 

CHAPTER FOUR: DISCUSSION ............................................................................................ 66 
4.1 Evaluation Between Theory and Reality .................................................................... 66 
4.1.1 Green Roofs as social-inclusive areas.......................................................... 67 
4.1.2 Green Roofs in the Biosphere Concept ........................................................ 68 
4.2 Limitation .................................................................................................................... 69 
4.3 Recommendation ........................................................................................................ 70 
4.4 Conclusion .................................................................................................................. 70 

BIBLIOGRAPHY ....................................................................................................................... 71 

 

 

 

 

iv 

LIST OF TABLES 

Table 1: Differences between Green Roofs’ Categories (Peck, 2008, p.27) .................................. 6 

Table 2: Variables ......................................................................................................................... 50 

Table 3: Variables in rankings ...................................................................................................... 59 

Table 4: Sum in ranking of each scenario ..................................................................................... 62 

Table 5: Design Scenarios Difference .......................................................................................... 64 

 

 

 

 

v 

LIST OF FIGURES 

 

Figure 1: Location of the Sylvester Broome Empower Village in Flint, Michigan. (Copyright © 
2019 Wing Chi Vincy Tam all right reserved used by permission) ............................................. 26 

Figure 2: Aerial view of designated existing design site. (Google, n.d., Retrieved October 15, 
2019, from https://www.google.com/maps/@43.0524912,-83.6954075,17z.) ............................ 27 

Figure 3: Accessibility challenge on accessing to the rooftop. (Copyright © 2019 Wing Chi 
Vincy Tam all right reserved used by permission). ...................................................................... 28 

Figure 4: Accessibility challenge on level two rooftop. (Copyright © 2019 Wing Chi Vincy Tam 
all right reserved used by permission). ......................................................................................... 28 

Figure 5: A latter giving access from level two to level three roofing. (Copyright © 2019 Wing 
Chi Vincy Tam all right reserved used by permission). ............................................................... 29 

Figure 6: No railing on level three rooftop. (Copyright © 2019 Wing Chi Vincy Tam all right 
reserved used by permission). ....................................................................................................... 29 

Figure 7: Accessibility indication on existing rooftop. (Google, n.d., Retrieved October 15, 2019, 
from https://www.google.com/maps/@43.0524912,-83.6954075,17z.) ...................................... 30 

Figure 8: Birdseye view of a conventional rooftop. (Copyright © 2019 Wing Chi Vincy Tam all 
right reserved used by permission). .............................................................................................. 31 

Figure 9: Birdseye view of a self-design rooftop. (Copyright © 2019 Wing Chi Vincy Tam all 
right reserved used by permission). .............................................................................................. 32 

Figure 10: An outdoor teaching area for maximum 20 students. (Copyright © 2019 Wing Chi 
Vincy Tam all right reserved used by permission). ...................................................................... 33 

Figure 11: A corridor connecting active and quite area. (Copyright © 2019 Wing Chi Vincy Tam 
all right reserved used by permission). ......................................................................................... 34 

 

vi 

Figure 12: The active area. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by 
permission). ................................................................................................................................... 34 

Figure 13: Birdseye view of an extensive green roof. (Copyright © 2019 Wing Chi Vincy Tam 
all right reserved used by permission). ......................................................................................... 36 

Figure 14: Birdseye view of a semi-intensive green roof. (Copyright © 2019 Wing Chi Vincy 
Tam all right reserved used by permission). ................................................................................. 37 

Figure 15: A reading area. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by 
permission). ................................................................................................................................... 38 

Figure 16: An interactive children entertaining facility / interactive chess area with seats aside for 
guardians to supervise their children alongside.(Copyright © 2019 Wing Chi Vincy Tam all right 
reserved used by permission). ....................................................................................................... 39 

Figure 17: Perspective overlooking from second level to first level rooftop along the end of a 
ramp. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by permission). ............ 39 

Figure 18: Perspective overlooking from first level to second level rooftop along the end of a 
ramp. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by permission). ............ 40 

Figure 19: A viewing bar with 7 seats. (Copyright © 2019 Wing Chi Vincy Tam all right 
reserved used by permission). ....................................................................................................... 40 

Figure 20: An Interactive child playing facility. (Copyright © 2019 Wing Chi Vincy Tam all 
right reserved used by permission). .............................................................................................. 41 

Figure 21: A multi-purpose area. (Copyright © 2019 Wing Chi Vincy Tam all right reserved 
used by permission). ..................................................................................................................... 41 

Figure 22: A dry garden. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by 
permission). ................................................................................................................................... 42 

Figure 23: A fire pit with sofas. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used 
by permission). .............................................................................................................................. 42 

 

vii 

Figure 24: Top view of an intensive green roof. (Copyright © 2019 Wing Chi Vincy Tam all 
right reserved used by permission). .............................................................................................. 44 

Figure 25: A butterfly garden. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used 
by permission). .............................................................................................................................. 45 

Figure 26: A secret garden. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by 
permission). ................................................................................................................................... 46 

Figure 27: Ramp with railing alongside. (Copyright © 2019 Wing Chi Vincy Tam all right 
reserved used by permission). ....................................................................................................... 47 

Figure 28: Plaza with a two-level creative seating element which encourage user to interact 
(Copyright © 2019 Wing Chi Vincy Tam all right reserved used by permission). ...................... 47 

Figure 29: Maximize walkable are and visual difference with use of two flooring materials: deck 
and aluminum planting grate. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by 
permission) .................................................................................................................................... 48 

 

viii 

 

CHAPTER ONE: INTRODUCTION AND LITERATURE REVIEW 

Prior studies have shown the benefits of urban green space. One part of a building that is 

scarcely used is the rooftop; however, utilizing the rooftop is often a method of creating an inner-

city alternative social space (Pomeroy, 2012), and tools in response to climate change (Peck, 

2008). This is especially true in developed, highly populated, dense cities. However, this practice 

of building on rooftops in cities like Hong Kong must first receive government authorization.  

First, people are more likely to visit an urban green space than a native green area (Peters, 

Elands, & Buijs, 2010). Secondly, people have a better sense of the neighborhood and better 

relationship with their neighbors if there are green spaces nearby (Kuo, Sullivan, Coley, & 

Brunson, 1998). Research also shows that having more trees and plants in an area is a better 

place-making strategy for social connection purposes than leaving the place abandoned because 

it encourages people to spend times outdoor (Kuo et al., 1998). Moreover, green roofs can boost 

worker creativity and help provide different perspectives for work by breaking the hard edge, 

order, and control of modern cities’ architectures, which people found fatiguing (Loder, 2014). 

Thus, distance to green space is a positive factor for people to observe; but the designer should 

still design urban green space for people who are lacking in mobility (Schipperjin et al., 2010). 

Nevertheless, studies had found that vegetated rooftops are helpful on reducing urban heat island 

effect (Sanchez & Reames, 2019; Sutton, 2015), promote urban ecosystem (Sutton, 2015), 

reduce stormwater runoff (Peck, 2008), and increase water and air quality (Peck, 2008).  

With numerous ecological and social benefits of green roofs and urban green space, 

research on the specific on rooftop design approach is lacking. The proposed study will address 

the different categories (convention rooftop, self-design rooftop, extensive green roof, semi-

 

1 

intensive green roof, and intensive green roof) of rooftop design approaches effects on their 

values to determine if one category of roof top design approach is better than the other.  

Green spaces and green infrastructures play important roles in social activities and 

environment events. Urban cities’ architectures promote orders, hard edges and control, which 

green roofs soften them (Loder, 2014). A green space itself encourage people to be outdoor 

(Perter et al., 2010). While they promote social cohesion, it is also important to look into social 

interaction and place attachment (Peters et al., 2010). Instead of leaving rooftops abandoned, the 

idea of having a social space within a community would make the rooftop accessible to the local 

neighborhood and could become a functional park in densely built areas. This idea provides 

restoration opportunities to the neighborhood and improves residents’ sense of well-being 

(Mesimaki, Hauru, Kotze, & Lehvavirta). Research suggests that green common space is 

beneficial to individuals and the community because it attracts people to be out in a social 

common space and increases opportunities for casual social contact (Kuo et al., 1998). 

Neighborhood Social Ties are positively affected by the amount of common space vegetation; 

there is a linear correlation for the growth of neighborhood ties near a common space as more 

vegetation takes place (Kuo et al., 1998). Compared to people living near a barren space, people 

living near green infrastructures are more willing to help and support their neighbors and have a 

stronger feeling of belongings (Kuo et al., 1998). These communities also have more social 

activities and visitors (Kuo et al., 1998). Also, as vegetated rooftops are one the best 

management practice for stormwater runoff (Weiler, & Scholz-Barth, 2009). Researchers found 

that its efficiency on lengthen the time of concentration, increase infiltration, resulting in reduce 

workloads for existing sewer systems and decreasing risk of watershed safety by decentralizing 

stormwater, which green roofs keep stormwater on site to reuse and recycle it (Weiler, & Scholz-

 

2 

Barth, 2009). It was determined vegetation roofs, especially extensive green roof, could hold 

reduce around 85% to 90% annual rainfall addressing on one inch falling event (Weiler, & 

Scholz-Barth, 2009). These prior studies support the positive correlation between neighborhood 

connections to green spaces and rooftops; and positive attribute of vegetated roof toward the 

environment, this proposed study focuses specifically on comparing whether if one rooftop 

design approach provide more value exhaustively than others. 

Understanding if one rooftop design approach is better concerning design, maintenance, 

social, and environmental issues, is important for landscape architects, urban planners, 

policymakers, architects, and building owner. It may be possible to convert flat-topped barren 

rooftops into something more beneficial. It is important to understand and compare conventional 

rooftops, self-use rooftops, extensive green roofs, semi-intensive green roofs, and intensive green 

roofs. This research focuses on accessing these different design approaches.  

Rooftops are often referred as the forgotten “fifth façade” that are ugly, barren, where 

people refuse to visit, and dispose elements that are unpleasant to watch, such as heating and 

cooling equipment and telecommunications towers (Peck, 2008). There are approximately 40% 

of impervious paving is composed by rooftops (Shafique, Kim, & Kyung-Ho, 2018). There is an 

opportunity for building owners, developers, urban planners, and governments to develop and 

utilize them in order to create an inner-city, alternative social spaces (Pomeroy, 2012), tools to 

alleviate urban heat island effects (Sanchez & Reames, 2019), and to create and improve urban 

ecosystems (Sutton, 2015).  

The description of the literature is divided into four parts: history of green roof, types of 

green roofs, construction of green roofs, and benefits of green roofs. 

 

3 

1.1 History of Green Roofs 

Green roofs are not new phenomenon. They have been constructed for thousands of years 

to protect people from arduous weather (Peck, 2008). The history of green roofs could be trace 

back to the Neolithic Period, around 600 BC, green roofs were built for royalty, aristocracy, and 

religious purposes, which the first known historical reference of green roof was on a stone 

temple (Peck, 2008; Jim 2017). In 800-1000 AD Viking Age, a new form of green roof – sod 

roofs became widespread throughout Northern Europe, lined the walls and roofs to protect 

housing from extreme weather, including winds, cold, and rain (Peck, 2008). 

Subsequently, the era of modern green roof  started around 1960s Germany, Switzerland, 

Austria, and Norway, since there were growing concerns about rapidly grown cities and towns, 

and intensive urbanization that qualities of livings were degrading and chances of being involve 

in the nature were declining (Peck 2008; Jim 2017). Reinhard Bornkamm, a botanist, who 

conducted research at University of Berlin, helped in developed a green roof system which we 

now known as the extensive green roof system, which is a green roof system with 6 inches or 

less growing media (Peck, 2008), which composed by relatively thin and light growing media 

profile (FLL, 2002). Then, the system had been heavily studied by German institutions and 

found numbers of positive attributes in stormwater management, plant survivability, fire 

retardation, and energy conservation (Peck, 2008). Guideline for the Planning, Execution and 

Upkeep of Green-Roof Sites (FLL), was a non-profit research society aimed at conduct 

researches about green roofs and set standards and guidelines for German landscaping industry 

(Peck, 2008). German then continue to emerge as the world leader on green roofs technologies, 

legislations, and economics incentives (Snodgrass, & Snodgrass, 2006).  

 

4 

Green roofs are still an on-going movement. Currently, the potential of retrofitting flat-

topped rooftop has gained public policy support in over 75 jurisdictions resulting in green roof 

explosion in Germany, Austria, Switzerland, and Europe (Peck, 2008). Canada and the United 

have begun to look up to the European model on green roofs, to encourage and reward practice 

green roofs in their lands (Snodgrass, & Snodgrass, 2006). For example, green roofs are installed 

on city halls of Chicago and Toronto (Snodgrass, & Snodgrass, 2006). The U.S. Green Building 

Council had developed Leadership in Energy and Environmental Design (LEED), which is a 

program certification program reward green building practice (Snodgrass, & Snodgrass, 2006). 

Indeed, a higher reward could be obtain if a project included green roof as one of the sustainable 

practice (Snodgrass, & Snodgrass, 2006). This study focusing on compare conventional rooftops 

and other rooftops design approaches to advocate the utilization of rooftops. 

 

1.2 Extensive Green Roofs, Semi-Intensive Green Roofs, and Intensive Green Roofs 

“Green roof” is a term used as an umbrella reference of numerous sustainable systems 

which build over roofs (Weiler, & Scholz-Barth, 2009). According to the Peck (2008) green 

roofs are green space built on roof despite on their elevations. People may also call green roofs in 

eco-roofs, living roofs, planted roofs, and vegetated roofs but they are the same thing (Snodgrass, 

& Mclntyre, 2010; & Mentens, Raes, & Hermy, 2006), or simply open spaces over structures, 

which either serve as roofs or “floor” on the roof (Weiler, &Scholz-Barth, 2009). Depending on 

their substrate depth, planned usage and plant selection (Green Roof Research Program, n.d.; 

Sutton, 2015, p. 6.), modern green roofs could be divided into three major large categories: 

 

5 

“intensive”, “semi-intensive (aka simple intensive)”, and “extensive”. Their differences, as 

describe in Table. 1. 

Table 1: Differences between Green Roofs’ Categories (Peck, 2008, p.27) 

 

Intensive 

Semi-intensive 

Extensive 

Growing Medium Depth 

More than 6” 

25% above or  

6” or less 

below 6” 

Accessibility 

Usually accessible 

Partially accessible 

Often inaccessible 

Fully Saturated Weight 

High 

Varies 

Plant Diversity 

Greatest 

Greater 

Cost 

High 

Varies 

Low 

Low 

Low 

Maintenance 

Varies, is generally 

Varies 

Minimal 

high 

 

Extensive green roofs are usually not accessible for public (Peck, 2008). The main 

characteristics of they are low weight due to swallow, 2-6” growing medium, typically composed 

with mineral-based mixture, including sand, gravel, crushed brick, lightweight expanded slate, 

clay, shale aggregate, volcanic rock, pumice stone, scoria, zeolite, diatomaceous earth, perlite, or 

rock wool (Peck, 2008). Around 12-35 pound per square foot would increase from slat roof to 

fully saturated extensive green roof (Peck, 2008; Pittaluga, Schenone, & Borelli, 2012). Due to 

the sallowness of their growing media, arduous arid microclimates are created on these rooftops 

 

6 

and only hardy and low plants could be successfully grow on extensive green roofs. The 

advantage of this would be low to no maintenance requirement (Peck ,2008, Pittaluga et al., 

2012). On the other hand, low plant diversity would be the downside of extensive green roofs 

(Peck, 2008, p26-27).  

Intensive green roofs are roof gardens. They could also refer as parks on rooftops. 

Intensive green roofs are always accessible to public or certain groups of people such as building 

occupants depending on owners’ wills (Rowe, 2010; & Peck, 2008). Diverse plant varieties 

could be select and plant on intensive green roofs including trees and shrubs, due to support from 

deep growing mediums (FLL, 2008; Peck, 2008; & Pittaluga et al., 2012). Growing medias are 

more than 6” with saturated weight increase by 50-300 pounds per spare foot (Peck, 2008; & 

Pittaluga et al., 2012). However, intensive green roofs require high maintenance especially 

irrigation (Peck, 2008). They also have higher capital costs than extensive green roofs (Peck, 

2008). 

 

Semi-intensive green roofs are combinations of extensive green roofs and intensive green 

roofs that they have characteristics of both (Peck, 2008; Pittaluga et al., 2012). They are always 

accessible (Peck, 2008). Their growing medias are 25% below or above 6” and saturated load 

vary (Peck, 2008). 

Due to variations in construction depth, greening selections are different. According to 

FLL, there are three types of greening: intensive greening, simple intensive greening, and 

extensive greening (FLL, 2002). Intensive greening includes shrubs, coppices, grass, and trees. 

Intensive greening needs regular maintenance, especially irrigation and fertility. Simple intensive 

greening involves usage of grass, shrubs, and coppices. It is less costly than an intensive 

 

7 

greening site. Extensive greening uses greening that require minimum maintenance or 

propagation. Plants that are enclosed and flat such as mosses, succulents, herbaceous, and 

grasses are typical extensive greening. (FLL, 2002, p.12)  

 

1.3 How to build green roofs? 

Similar to other built structures, the strengths green roofs are highly variable depending 

on their foundations. Reliable structural system foundations required calculation of loading, 

waterproofing, draining, etc. (Osmundson, 1999, p153) There are three rules of thumbs on 

designing, building, and maintaining green roofs: (1) stay within structural loading limit, (2) 

prevent leaking, and (3) keep plants alive (Sutton, 2015, p.7). Indeed, there are three methods of 

green roofs installation: (1) conventional roofing system, (2) pre-vegetated mats, and (3) 

modules (Rowe, 2018). 

 

1.3.1 Components of green roofs 

The roof flat, which design is usually determined by architects and structural engineers, is 

base of green roof structure. It could be made with different materials, but roof flat made with 

site cast and precast concrete are the most prevalent due to its needs to provide ultimate support 

to elements that would establish on top if it (Osmundson, 1999, p.154). A layer of waterproof 

membrane is immediate above the roof flat to prevent roof leakage (Weiler, & Schoz-Barth, 

2009). There are three major recognized waterproofing for low-slope roofing, which are: 

 

8 

1.  Layout membrane, which is consider as the most reliable and susceptible from leaking. 

Its life expectancy is often from 15 to 20 years. It is assembling in-place by pouring 

molten bitumen mixed with fibrous materials, such as fiber glass or polyester. However, 

it is not as commonly used as simple-ply membrane because it requires more labor and 

maintain. 

2.  Simple-ply membrane, which apply a layer of large thermoplastic sheet. Its life 

expectancy is often from 10 to 15 years. Since its nature of low cost, easy to apply, and 

required less labor, it is being widely employ since late 1970s. However, if is less 

susceptible for leaking, cracking, and seam failure due to its flexibility. 

3.  Fluid-applied membrane, which often used in complex shape roofing. (Weiler, & Schoz-

Barth, 2009, p. 134-141) 

After that, a protection board will be place directly on top of the waterproofing layer. Protection 

boards are typically 1/8 to ¼ inches pressure-laminated fiberglass or mineral-reinforced asphaltic 

core (Weiler, & Schoz-Barth, 2009, p148). Then 2 inches thick, rigid polystyrene foam board 

would place on top of the protection board as an insulation layer to prevent heat transfer. Finally, 

a 2½ to 4 inches thick concrete flat would be place as the finished surface. (Osmundson, 1999, 

p.154) On top of this finished surface, a root repellent layer or component, a drainage layer, a 

landscape or filter cloth, an engineered growing medium, then plants would be install from 

below to the top as listed (Peck, 2008, p.27).  

 

 

9 

1.3.2 Green roofs installation 

As mentioned, there are three green roof installation methods: conventional roofing 

systems, pre-vegetated mats, and modules (Rowe, 2018). Choosing the best-fitted installation 

method will depends on the complexity of green roof design, budget, availability of resources 

and expertise, and how much maintenance and responsibility the owner is willing to take to the 

roof (Snodgrass, & Snodgrass, 2006).  

 

a.  Conventional 

The convention roofing system includes seeds, cuttings, plugs, and nursery 

containers. Seeds is the least expensive installation method, or so call planting method 

among the other two (Snodgrass, & Snodgrass, 2006). However, it also takes to longest 

time for a seeded green roof to mature and it is challenging to have 100% plant coverage 

when matured (Snodgrass, &Snodgrass, 2006; Rowe, 2018). Depending on the climate, 

seeding is best to be sown in spring and fall using rapidly germinate seeds by hand or 

hydro-seeding technology (Snodgrass, & Snodgrass, 2006). Sedum album, 

Petrorhagia, and Dianthus are good plant choices for this planting method because they 

are hardy and easy to establish (Snodgrass, & Snodgrass, 2006). If sedum is used for this 

method, about 20 seeds per square foot are required to archive the even coverage and 

optimum appeal (Snodgrass, & Snodgrass, 2006). However, this method is hard to 

precisely deliver the landscape design look because species or weed use in the seed 

mixture may not be controllable (Snodgrass, & Snodgrass, 2006).  

 

10 

Cuttings is the most commonly use green roof installation method in Germany 

(Snodgrass, & Snodgrass, 2006). It is more expensive than seeding but cheaper than 

plugs (Snodgrass, & Snodgrass, 2006). It required 12 to 18 months to mature which is 

less time compared to seeding (Snodgrass, & Snodgrass, 2006). Cutting requires less 

labor than seeding, but more work to transport than plugs since it is more fragile and 

would require a refrigerated method to ensure the survival of plants (Snodgrass, & 

Snodgrass, 2006). 

           Plugs are plants that already established root system in plug trays, leading them to 

have more flexibility on the planting season lengthen from the last frost of spring to early 

fall depending on climates (Snodgrass, & Snodgrass, 2006). It is hardier then cutting 

since the rooted plugs already have sufficient energies transport, transplant, and establish 

(Snodgrass, & Snodgrass, 2006). It commonly takes around 12-16 months for plants to 

mature and the green roof achieves a full-coverage view (Snodgrass, & Snodgrass, 2016). 

           Nursery containers are usually used if green roof designs need more established 

plants in the beginning (Snodgrass, & Snodgrass, 2006). An established plant itself 

needed a deeper growing medium which is able to accommodate the additional mass 

from the root (Snodgrass, & Snodgrass, 2006). Other than the width of the growing 

medium, there are other factors needed to be considered when using this method. For 

example: system weight, where the total weight of root and soil that saturated around the 

root could lead to exceeding design specification (Snodgrass, & Snodgrass, 2006). 

 

 

 

 

11 

b.  Vegetated mats 

A vegetated mat is a thin layer of growing medium and pre-grown plants grown at 

ground level (Snodgrass, & Snodgrass, 2006; Rowe, 2018). The plants on vegetated mats 

are fully mature upon installation (Snodgrass, & Snodgrass, 2006). Vegetated mats are 

heavy, and it required to transport in refrigerated trucks if in hot weather (Snodgrass, & 

Snodgrass, 2006). They work well on sloped roofs (Snodgrass, & Snodgrass, 2006). Most 

company required to received orders of vegetated mats at least one year before 

installation (Snodgrass, & Snodgrass, 2006). 

c.  Modules 

 

Modules are discrete vegetated systems that pre-grown at ground level typically 

consist in black plastic trays or biodegradable materials such as coconut coir (Snodgrass, 

& Snodgrass, 2006; Rowe, 2018). It is the most expensive installation method among the 

other two (Snodgrass, & Snodgrass, 2006). Modules give higher accuracy of prediction 

of plants, and it is easy to be replaced because each module is a self-contained unit 

(Snodgrass, & Snodgrass, 2006). However, if modules are made with biodegradation 

material, they may decompose and fall apart when move (Rowe, 2018). It is easy to 

install, which labors could have no horticulture knowledge and install it just like 

installing other hardscapes, such as pavers (Snodgrass, & Snodgrass, 2006; Rowe, 2018). 

The biggest advantage of modules is that the roof would immediately become a green 

roof once install (Rowe, 2018). 

 

12 

 

 

From the above literature review reviewing different types of green roofs and plantings 

and construction of green roofs, we can see that the rooftop design option may be limit due to 

loading capacity and growing medium thickness. Therefore, before constructing a green roof, it 

is important to set a category of green roof design approach regarding desire outcomes. 

 

1.4 Benefits of Green Roofs  

Green roofs are vegetated rooftop involved with technology, aim at reducing the amount 

of lost green space caused by building contruction (Whittinghill, Rowe, 2011). Green roofs are 

promoted as the pioneer of “sustainable building practice” responding to environmental stresses 

we are facing (Sutton, 2015, p.1). They are potential aids on the effect of global warming, effect 

of urbanization, etc. Green roofs are always adopted for its ability on energy saving and heat 

island reduction (Getter, Rowe, Robertson, Cregg, & Andresen, 2009). However, green roofs are 

more than these that they could affect people psychologically and socially.  

 

1.4.1 Green roofs reduce stormwater runoff 

Reduce stormwater runoff is considered as the best eco-service provide by green roofs 

(Getter, Rowe, Andersen, 2007). Green roofs are often built for best management practices 

(BMPs) for urban stormwater since there are difficulties in managing water flow off from 

impervious surface in the urban area (Weiler, & Scholz-Barth, 2009; Whittinghill, Rowe, 

Andresen, & Cregg, 2015). With the increasingly rapid growth process of urbanization, 

permeable surface had been replaced by impervious surface, such as driveways and buildings, 

which changed the permeable nature of land, leading to increasing risk of flooding and decrease 

13 

 

groundwater recharge (Berndtsson, 2010; & Feitosa, & Wilkinson, 2016). Indeed, it is expected 

that 90% human will live in the urban by 2030 (Montgomery, 2003). Although urban sewer 

infrastructures were developed to handle stormwater runoff from impervious surface, limit of 

their handle exceeded in many cases especially in highly developed areas and cities (Weiler, & 

Scholz-Barth, 2009). Stormwater and sanitary sewers are separated in newer city, which 

stormwater would discharge into water stream directly, while sanitary would route to sewage 

treatment plants to clean and purify before releasing into water course (Weiler, & Scholz-Barth, 

2009). However, stormwater and sanitary sewers are combined into one system, they route to 

water treatment plants, resulting in overload and flooding (Weiler, & Scholz-Barth, 2009). The 

idea of sustainable development did not gain much attention until 1990s (Berndtsson, 2010). 

Strategy used for traditional stormwater management is to move water off-site into underground 

infrastructures, where BMPs decentralize stormwater to keep it on site to reuse and recycle, 

which alleviate peak flow rate, lengthen the time of concentration, and increase infiltration, 

resulting in allaying existing sewer loads (Weiler, & Scholz-Barth, 2009, p.31-32). With the 

needs of redesigning the urban hydrological cycle, green roofs seems to be the practical 

alternative because many of the BMPs such as stormwater ponds, retention basins, infiltration 

facilities, open channels, and treatment wetlands require lots of lands; creation of large green 

area in urban region is challenging due to high land price (Menten et al., 2005; & Berndtsson, 

2010). 

Green roof reduce stormwater runoff in three ways: (1) to delay the initial time of runoff 

by absorbing precipitation in the system, (2) to reduce total runoff by retaining part of 

precipitation, and (3) distributing runoff through long period of time by temporary storing 

precipitation in the substrate and slowly release excess water (Menten et al., 2005). Literature 

 

14 

found that the retention capability for green roofs on range from 75% for intensive green roofs to 

45% for extensive green roofs annually (Menten et al, 2005). Other studies conducted in 

Washington D.C. and Maryland found that green roof systems could reduce annual rainfall 

runoff addressing on inch rain fall event effectively at average of 85 to 90 percent. Especially 

with flat green roof with dry soil media, which provide maximize water storage capacity, which 

is around 100 percent of rainfall. (Weiler, & Scholz-Barth, 2009, p.31-32). As the “90 percent 

rule” is also being referred for green roof systems for storm water management (Weiler, & 

Scholz-Barth, 2009). Differences in magnitude of the retention could depending on lots of 

factors, such as structure of the green roof, depth of substrate, climate, plants selection, slope and 

amount of precipitation (Menten et al., 2005; Getter et al., 2007; Whittinghill, 2012). Depth of 

substrate plays the key role on the annual rainfall-runoff relationship of green roof, where 

intensive rooftop performs the best that there is a linear proportionally relationship between soil 

depth and peak flow reduction rate, but it depends on moisture condition of soil previously 

(Menten et al, 2005; & Castiglia Feitosa, & Wilkinson, 2016). Also, flat green roofs perform 

better of water retention than sloped green roofs (Cronk, 2012). Researchers found that negative 

relationship between slope of green roofs and retention value that when slope increase, retention 

rate decrease (Getter etal., 2007). In addition, Whittinghill (2012) found that plant selection has 

effect on rainwater retention, where prairies mix perform better then vegetable and herb mix 

(Whittinghill, 2012). 

Green roofs promote for their potentials on their environmental benefits (Berndtsson, 

2010). First half inch of precipitation is the most important when counting on rainfall on water 

quality, which green roofs may be useful on improve water quality. First half inch of rain is 

referred as the first flush, which it is traditionally a form of stormwater quality control. The first 

 

15 

flush in recognized to have lower water quality with concentrated and flushed off pollutants from 

fossil fuel combustion, byproducts of transportation, energy generation, industrial and 

manufacturing processes, leaves, and bird droppings (Berndtsson, 2010; & Weiler, & Scholz-

Barth, 2009). However, little studies pay attention on the quality of water runoff since rainwater 

is generally consider as non-polluted and acidic (Berndtsson, 2010). There are still debates 

concerning whether green roofs have the evident first flush effect. In addition, there is a question 

concerning a green roof ability to improve runoff quality (Berndtsson, 2010; Bliss, Neufeld, & 

Ries, 2008). Indeed, Berndtsson (2010) summarized 9 potential influential factors on water 

qualify of green roof runoff: (1) materials usage on the roof; (2) depth of soil; (3) type of 

drainage; (4) usage of chemical for maintenance; (5) greening; (6) precipitation; (7) wind 

direction; (8) sources of pollutants; and (9) physical chemical properties of pollutants 

(Berndtsson, 2010). Since these are nonpoint source pollutant, watersheds are in great risk. Also, 

stormwater runoff is the main cause of eutrophication and degradation of water quality due to 

excessive nitrogen, and phosphorus sourcing from fertilizers from agricultural fields and lawns, 

lead to watershed’s ecosystems collapse (Weiler, & Scholz-Barth, 2009, p.32-35). Green roofs 

improve water quality of urban rainwater runoff by absorbing pollutant, yet they could still 

release pollutant from soil and fertilizer usage (Teemusk, & Mander, 2007). As there are large 

difference between studies that some found green roofs reduce pollutant concentration, while 

other consider green roofs as contaminator for pollutant leading increase turbidity of runoff 

(Weiler, & Scholz-Barth, 2009; Berndtsson, 2010; Monterusso et al., 2002; Bliss et al., 2008; & 

Teemusk, & Mander, 2007; Krogulecki, 2014). 

 

 

16 

1.4.2 Green roofs as tools to alleviate global warming 

Carbon dioxide is often referring as one of the primary greenhouse gasses leading to the 

effect of global warming. Green roofs could alleviate global warming by reducing carbon 

dioxide in the atmosphere by (1) photosynthesis (Rowe, 2010), and (2) heat insulation on 

individual buildings (Whittinghill, Rowe, Schutzki, & Cregg, 2014; Rowe, 2010). 

Green roofs reduce carbon dioxide by using plants. Even though the ability of carbon 

sequester of green roofs could not compare to old forests, they are still better perform then flat-

top rooftops (Getter, 2009). Plants naturally sequester carbon dioxide into biomass and soil 

subtracts by photosynthesis (Rowe, 2010). Besides, green roofs reduce heat island effects, 

leading to reduction of demands on the usage of heating and air-conditioning, resulting in less 

carbon dioxide release from generating power for HVACs (Getter et al., 2009; Rowe, 2010). The 

process of terrestrial carbon sequestration refers to the process photosynthesis remove carbon 

dioxide into biomasses of plants, making green roofs became man-made carbon sinks (Getter et 

al., 2009). However, this man-made ecosystem of the green roof will reach its carbon 

equilibrium at one point that carbon the system absorbs for plant growth would equal its release 

by plant decomposition (Rowe, 2010). Heat island effects in urban areas made green roofs 

becoming more critical on alleviating global warming because urban areas tend to have higher 

temperatures than rural areas, there are higher carbon dioxide concentrations in urban areas 

(Whittinghill et al., 2014).  

Researchers have discovered the green roofs ability to capture carbon dioxide is 

dependent on plant species selection, the complexity of plant community, age of plants, and 

depth of subtracts (Getter et al., 2009; Whittinghill et al., 2014). Whittinghill et al. (2014) found 

 

17 

that woody plants perform better to sequester carbon than sedums and prairies. Indeed, 

ornamental landscapes systems on rooftop perform as well as if they are in-ground, while sedum 

and prairies system does not appear to be as well-perform due to soil and substrate on green 

(Whittinghill et al., 2014). Also, shading by full plant canopy maximize the cooling effect, it is 

found that engineered soil made by crushed porcelain and foamed glass could maximize the 

effect (Matlock, 2015). 

Although green roof capture carbon dioxide, it is essential to consider the carbon cost of 

having a green roof. The embodied energy is the energy used to construct a green roof. Carbon 

payback periods of green roofs are ranging from 15 years to less than 3 years, which the length 

of period decreases when there is a more complex plant community (Whittinghill et al., 2014). A 

research on green roof performance on building’s energy-saving had studied on an individual 

building, implemented with EnergyPlus, which is a building energy simulation model supported 

by the US Department of Energy, found a reduction of 2% of electricity and 9-11% of natural 

gas usage (Sailor, 2008). Reduction of fossil fuel usage directly related to the reduction of carbon 

dioxide production since carbon dioxide is a by-product of fossil fuel combustion (Rowe, 2010). 

1.4.3 Green roofs in noise reduction 

 

Noise is directly related to humans’ negative health effects. People are more susceptible 

to have depression if they are surrounded by noise (Öhrström, 1991). As urbanity is continue 

growing rapidly, traffic noise annoyance is one of the major issues we have nowadays 

(Renterghem, & Botteldooren, 2008; & Montgomery, 2003). Although things had been done 

toward to the issue, such as sound barriers near highways, new types of road surface layers to 

eliminate noise productions, and houses as sound barriers, the expectation of quiet still have not 

 

18 

been met (Renterghem, & Botteldooren, 2009). Green roofs could be very useful when creating 

very quiet environment especially in the urban area (Renterghem, & Botteldooren, 2008; 

Renterghem, & Botteldooren, 2009). Multiple studies found the high sound absorption capability 

of green roofs, especially when compare with traditional conventional rooftops (Pittaluga, 2012; 

Renterghem, & Botteldooren, 2008; & Renterghem, & Botteldooren, 2009). Green roofs have 

their acoustic performance in two ways-in and out of the building: (1) to absorb outdoor noise, 

and (2) to insulate outdoor noise for indoor environments (Pittaluga, 2012). It is found that there 

is a linear relationship between the green roof effect on sound absorption and amount of green 

coverage on the rooftop (Renterghem, & Botteldooren, 2008). Nevertheless, the green roof effect 

performs the best at 6”, which is the maximum depth of the substrate of an extensive green roof, 

and the effect does not amplify once it excesses the thickness (Renterghem, & Booteldooren, 

2008). Renterghem, & Booteldooren (2009) also found positive effect on green roof and noise 

absorption on increase on traffic speed on light vehicles when there is sufficient presence of 

green roofs.  

 

1.4.4 Wildlife habitat and biodiversity enhancement 

 

Human activities altered the composition of biological community and ecosystem 

property, causing increasing rate of species invasions, endangered, and extinctions globally 

(Hooper, Chapin, Ewel, Hector, Inchausti, Lavorel, & Sveriges, 2005). With range of ecosystem 

services provided by green roofs, including establishing an urban ecosystem and providing 

habitat for urban biodiversity, green roofs should be adapted to enhance these great services been 

provide to the urban communities (Cook-Patton, 2016; Rumble, Finch, & Gange, 2018; Eakin, 

2012). When the one of the rule of thumbs of deploying a green roof is to keep plants alive, plant 

 

19 

composition on green roof design is important since study found that plant diversity affect 

survivability, sustainability and functionality of green roofs (Sutton, 2015, p.7; Nagase, & 

Dunnett, 2010; & Lundholm, Macivor, Macdougall, & Ranalli, 2010).  

Since planting on green roofs serve multiple purpose, such as aesthetics, extent rooftop 

longevity, provide and improve functions of green roofs, selecting the right mixture of planting 

trait get difficult (Maclvor, & Lundholm, 2011; & Cook-Patton, 2015). Plant selections on green 

roofs are different than if they are on ground-level, plants needs to be more vigorous, stress-

tolerance, and less nutrient-reliant to be selected due to the stressful and harsh growing 

environment on rooftops with high exposure to wind and solar radiation, and maybe disturbing 

environment (Snodgrass, & Snodgrass, 2006; Nagase, & Dunnett, 2010). Succulents are 

commonly plant on green roofs because of its evergreen nature making green roof “look” green 

all year-round (Nagase, & Dunnett, 2010; Lundhlm, Heim, Tran, & Smith, 2014). While studies 

found that there is a position relationship between plant composition and degree of ecosystem 

functioning, there is a movement to employ other living-form of plants, such as grasses and forbs 

(Lundholm et al., 2010; Spehn, Joshi, Schmid, Diemer, & Korner, 2000; & Maclvor, & 

Lundholm, 2011). Indeed, growing condition of plants affect ecosystem services provided by 

green roofs, for example, roof surface has the highest temperature on conventional rooftops, 

average of 10oC temperature reduction occurs on rooftops with only growing medium, additional 

average of 2oC temperature reduction occurs on rooftops with monocultural plantings. Finally, an 

additional average of 1.5oC temperature reduction occurs on rooftops with multispecies plantings 

(Lundholm et al., 2010). At least 7cm of subtract is recommended for sedum community 

development (Getter, 2009). In is also found that a minimum 13cm of is required for survival of 

most green roof plant species (Vandegrift, 2018). Spehn et al. also found that multispecies-

 

20 

communities product a significant higher amount of biomass and canopy height than 

monoculture communities (Spehn et al., 2001). Plants grow better in multispecies ecosystem 

than monoculture ones because of complementary usage of resources since the “insurance” 

hypothesis says insurance ecosystems would against decline in bios functioning because species 

richness provide better chance if some of them fail to function due to bad germination, growth or 

survival, etc., other of them could still maintain the ecosystem (Spehn et al., 2000; Yachi, 

Loreau, 1999).  

Other than plant species and traits, plant origin is another consideration for plant 

selection. Researchers found that native plants and exotic plants have different effect toward the 

ecosystem (Cook-Patton, & Agrawal, 2014; Wilsey, Teaschner, Daneshgar, Isbell, & Polley, 

2009; & Burghardt, Tallamy, Philips, & Shropshire, 2010). Even though diverse plant 

communities composed with either native or exotic plants produce higher biomass and seed 

production than if those are in monocultural plant communities, yielding behavior between 

exotic plants and native plants are different causing exotic plants suppress native plants on seed 

production if they grow together (Cook-Patton, & Agrawal, 2014; Wilsey et al., 2009). Indeed, 

exotic species replaced native species and dominated in many systems, but species diversities 

decline more in exotic monocultural greenings than native ones (Wilsey et al., 2009). Also, 

exotic plants attract fewer arthropod than native plants (Cook-Patton, & Agrawal, 2014). 

According to “more individual hypothesis,” a higher plant species richness increase the ability of 

the productive site the support more a larger pollution of each species, which, in this case, more 

arthropod species means the site is being more productive and higher chance on rare species 

observation (more individual hypothesis, Srivastava, & Lawton, 1998). Another research team 

found a similar result with lepidopteran communities that exotic plants communities supported 

 

21 

significantly fewer caterpillars and less species richness than native plants communities even if 

those exotics were with close relatives with native plants (Burghardt et al., 2010). 

Green roofs act as habitats by the plant communities supporting the cascade effect 

through food webs to support lives of urban animals (Cook-Patton, 2015; Haddad, Crutsinger, 

Gross, Haarstad, Knops, & Tilman, 2009) There is a strong effect between plant species richness, 

herbivore richness because when the biomass increase, there is more resources and habitat spaces 

for animals, then these resources will travel through trophic levels (Haddad et al., 2009; & Cook-

Patton, 2015). Researchers found correlation between vegetation cover and arthropod richness on 

green roofs; no effect of roof height and distance to habitat on ground level, on the arthropod 

richness on green roofs (Schindler, Griffith, & Jones, 2011). Monsma (2011) also found similar 

result that spider abundance and richness is effected by proportion of vegetation cover of green 

roofs (Monsma, 2011). 

Existence of invertebrate communities make green roofs more biological valuable than 

conventional rooftops (Partridge, & Clark, 2018). Invertebrates, including spiders, arthropods, 

and insects are commonly see on green roofs, which are key and foundational organism for 

terrestrial food wed on converting plants into protein in providing food higher trophic levels 

(MacIvor, & Ksiazek, 2015). A research found green roofs bring positive effect on increasing 

habitat connectivity for avian community by providing supplementary resources (Eakin, Campa, 

Linden, Roloff, Rowe, & Westphal, 2015). While green roofs are visited by bird because of 

abundance arthropod food supplies (Partridge, & Clark, 2018), avian usage of rooftop habitats 

primarily on the summer (Washburn, Swearingin, Pullins, & Rice, 2016). Indeed, majority of 

avian found on green roofs are insectivores during migration period, while are rarely found on 

conventional rooftops (Partridge, Clark, 2018). 

22 

 

1.4.5 Urban parks benefit in social connection 

 

The nature of green roof – soothing and calming, are good resources for horticultural 

therapy (Peck, 2002, p.10). There are opportunities of converting green roofs to be social nodes. 

Indeed, researchers have found that neighborhood social ties (NSTs) depend on the amount of 

informal social interaction that takes place (Kuo, Sullivan, Coley, & Brunson, 1998). In addition, 

there is a direct relationship between the level of greenness of a common social space and NSTs 

(Kuo et al., 1998).  

Green space and green infrastructure promote social cohesion that plays important roles 

in engaging people (Peters, Elands, & Buijs, 2010). The idea of the “common living room” 

increases opportunity of casual interaction among people and boosts the sense of well-being 

among people at the same time (Mesimaki, Hauru, Kotze, & Lehvavirta, 2017).  Recognition is 

built on regular contact (Kazmierczak, 2013), which is an essential factor for developing 

neighborhood social ties. By being recognized, users of an urban open space can increase their 

familiarity and casual interaction opportunities with others in the city, creating tighter 

community and neighborhood bonds. These factors are why it is important to consider the effect 

of recognition on social interaction and place attachment.  

Green infrastructure adds social benefits to a neighborhood. There is a positive 

relationship between public green space quality and community attachment (Arnberger, & Eder, 

2012). Green space quality is also a factor for drawing people to a public space. The amount of 

greenness in a social space has direct impacts on NSTs (Kuo et al., 1998). NSTs depends on the 

amount of informal social interaction (Kuo et al., 1998). While an abandoned common space 

discourages people to be there, a successful placemaking strategy uses plants to attract people 

 

23 

(Kuo et al., 1998). A common social space in a neighborhood with more plants encourages 

people spending time outdoors to stay in the public space (Kuo et al., 1998). Their study found 

that residents living near a green common space boost the feeling of belonging and attachment 

for residents in a neighborhood (Kuo et al., 1998). There is a stronger relationship among 

neighborhood residents as well as increased willingness to help one another if the neighborhood 

has a green social common space (Kuo et al., 1998). Because greening the common space has 

such a positive effect on the neighborhood, rooftops that are usually abundant and forgotten are 

an alternative social common space in a highly populated and dense city. 

With the literature reviewed, rooftops are having many potentials, transforming barren 

conventional rooftops to other kinds of roofscapes which could attribute to society and the 

environment. 

 

 

 

 

 

 

24 

CHAPTER TWO: METHODOLOGY 

The experimental design of this study is to develop 5 design scenarios with different rooftop 

design approach using the rooftop on an existing infrastructure at The Sylvester Broome 

Empower Village, located in Flint, Michigan. 

 

2.1 Design Scenario Description 

The methodology is based on 5 design scenarios: conventional rooftop, which is also the 

existing rooftop; self-design rooftop, extensive rooftop, semi-intensive rooftop, and intensive 

rooftop. These 5 design scenarios are based on the existing rooftop, known green roof category: 

extensive, semi-intensive, and intensive (FLL, 2002); and imaginary rooftop design approach if 

not designed by a professional. The intensive design scenario was used for course LA817 

Environmental Design Studio at Michigan State University. The following sections will 

introduce the five design treatments: existing site, self-design rooftop, extensive green roof, 

semi-intensive green roof, and intensive green roof accordingly. 

 

2.1.1 Existing site 

The site is located at 4119 Saginaw St., Flint, MI (43.052800, -83.694300). Flint has the 

7-th highest population density in Michigan, laying on M-475, M-69, and M-75. The 

building itself is owned by The Sylvester Broome Empower Village. Its vision is to 

transform Flint into a just and equitable city by developing and investing in youth. The 

 

25 

organization offer summer day camp, adult literacy program, SKY after-school program, 

and other educational program related to youth and adult. 

 

Figure 1: Location of the Sylvester Broome Empower Village in Flint, Michigan. (Copyright © 

2019 Wing Chi Vincy Tam all right reserved used by permission) 

This two-story structure is nearly a hundred years old. It is open to the public. The 

designated design area for this study has three level, with a total of 0.84 acres. Designated 

design area is indicated in figure 2.  

 

26 

 

Figure 2: Aerial view of designated existing design site. (Google, n.d., Retrieved October 15, 

2019, from https://www.google.com/maps/@43.0524912,-83.6954075,17z.) 

There are severe accessibily and safety challenges in the existing site, which indicated in 

figure 3 to figure 7. The rooftop could not be accessed excpet for climbing out from window in 

the computer lab, as describe in figure 3. Therefore, a proper entrance is requie. Also, there is 

about a 3 foot height differential between level one and level two rooftop without any ramp or 

stair giving visitors accessing to level two, as described in figure 4. There is a ladder for 

climbing up but it is not ADA accessible. Nevertheless, there is no railing on level three roofing. 

There is a possibily of falling. Accessibility and safty improvement is needed if the area is 

developed. 

 

27 

Figure 3: Accessibility challenge on accessing to the rooftop. (Copyright © 2019 Wing Chi 

Vincy Tam all right reserved used by permission). 

 

 

Figure 4: Accessibility challenge on level two rooftop. (Copyright © 2019 Wing Chi Vincy Tam 

all right reserved used by permission). 

 

28 

 

Figure 5: A latter giving access from level two to level three roofing. (Copyright © 2019 Wing 

Chi Vincy Tam all right reserved used by permission). 

Figure 6: No railing on level three rooftop. (Copyright © 2019 Wing Chi Vincy Tam all right 

 

reserved used by permission). 

 

29 

Figure 7 demonstrtate accessibility for exisiting conditions. The green shawdow indicates an 

area that is accesible for the user. The yellow shawdow indicates an area that is inaccessible to 

use, and requires some climbing to be there. The red shawdow indicates an area which is not 

accessible to users. 

 

 

Figure 7: Accessibility indication on existing rooftop. (Google, n.d., Retrieved October 15, 2019, 

from https://www.google.com/maps/@43.0524912,-83.6954075,17z.) 

Other than existing site challenges, renewable energy and outdoor classroom are design 

orientation lead to design programs of experiential design approaches present below.  

 

 

30 

2.2 Study scenario 

2.2.1 Conventional rooftop 

This design approach is based on existing site condition. Figure 8 is a birdseye view of the 

design treatment as there was no extra design work performed to the rooftop (Figure 8). 

 

Figure 8: Birdseye view of a conventional rooftop. (Copyright © 2019 Wing Chi Vincy Tam all 

 

right reserved used by permission). 

 

2.2.2 Self-design rooftop 

As people may utilize the space that fit their needs without hiring landscape architects, green 

roof professionals, or urban planners, they place items to fill the space. This design (Figures 9-

31 

 

12) approach imitates a utilized rooftop spatial response to the property by user. Design goals 

and objectives are: 

•  Enriching educational opportunity by creating outdoor classroom 

•  Encourage urban sustainability by establishing rainwater harvesting system 

•  Promote urban agriculture by building green house 

•  Create special relationship with proper planting layout 

•  Encourage social connection by creating gathering area 

•  Provide entertainment facilities 

•  Generate renewable energy by installing solar panels 

• 

Improving accessibility by having an entrance accessing to the roof 

Figure 9: Birdseye view of a self-design rooftop. (Copyright © 2019 Wing Chi Vincy Tam all 

 

right reserved used by permission). 

32 

 

 

Figure 10: An outdoor teaching area for maximum 20 students. (Copyright © 2019 Wing Chi 

Vincy Tam all right reserved used by permission). 

 

 

33 

Figure 11: A corridor connecting active and quite area. (Copyright © 2019 Wing Chi Vincy Tam 

all right reserved used by permission). 

 

Figure 12: The active area. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by 

 

permission). 

 

34 

 

Other than, solar panels laying on top level of the roof, this self-design rooftop is divided 

into a quite area (figure 10) and an active area (figure 12), connecting by a corridor composed by 

planting pots (figure 11). The quite area has an outdoor classroom with maximum capacity of 20 

students (figure 10). The active area has a greenhouse for urban agriculture, seats and tables for 

gathering, a swing for entertainment, a water harvesting system, and special planting pots layout 

to emphasize spatial relationship (figure 12).  

 

2.2.3 Extensive green roof 

Extensive green roofs are usually not open to public (Peck, 2008), so it would not have much 

design element but planting with extensive greening. Goals of this design (Figure 13) approach 

are: 

•  Reduce stormwater runoff, heat island effect, pollutant loading, carbon footprint, noise 

pollution 

•  Provide habitat for wildlife 

• 

Improve surrounding human mental health by providing meadow view for people within 

the building; and 

• 

Increase longevity of roofing membranes 

 

 

35 

Figure 13: Birdseye view of an extensive green roof. (Copyright © 2019 Wing Chi Vincy Tam 

 

all right reserved used by permission). 

 

2.2.4 Semi-intensive green roof 

This design approach is aim at creating social space and encouraging builder user of that 

building to be outdoor since they could watch from windows that lots of facilities and activities 

could be done/ happening on rooftop. Below are goals and objectives of this design approach 

(Figures 14-23): 

• 

Improving accessible challenge by designing ADA path from first level rooftop to second 

level rooftop 

•  Generate renewable energy by applying solar panels 

•  Addressing accessibility issue by having proper door entrance 

 

36 

•  Encourage social interaction by having gathering space 

•  Allowing group activity or outdoor classroom by having plaza space 

•  Family friendly by having children entertaining facilities 

 

 

 

Figure 14: Birdseye view of a semi-intensive green roof. (Copyright © 2019 Wing Chi Vincy 

Tam all right reserved used by permission). 

This semi-intensive green roof is divided into two parts: quiet area, and active area. The 

reading area, as shown in figure 15, is the quiet area that is partly enclosed by walls and a foot-

tall fence to create a quiet, and enclosed feeling. Flower plots in are employed to sit in the 

reading area to create an inclusive atmosphere and to emphasize on spatial relationship.  

 

37 

 

Figure 15: A reading area. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by 

permission). 

Active area includes interactive children entertaining equipment (figures 16 & 20), a viewing 

bar (figure 19), a multi-purpose area (figure 21), a flower bed, a dry garden (figure 22) and a fire 

pit with sofa (figure 23). 

 

 

38 

Figure 16: An interactive children entertaining facility / interactive chess area with seats aside for 

guardians to supervise their children alongside.(Copyright © 2019 Wing Chi Vincy Tam all right 

reserved used by permission). 

  

 

Figure 17: Perspective overlooking from second level to first level rooftop along the end of a 

ramp. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by permission). 

 

39 

Figure 18: Perspective overlooking from first level to second level rooftop along the end of a 

ramp. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by permission). 

 

Figure 19: A viewing bar with 7 seats. (Copyright © 2019 Wing Chi Vincy Tam all right 

 

reserved used by permission). 

 

40 

Figure 20: An Interactive child playing facility. (Copyright © 2019 Wing Chi Vincy Tam all 

right reserved used by permission). 

 

Figure 21: A multi-purpose area. (Copyright © 2019 Wing Chi Vincy Tam all right reserved 

 

used by permission). 

 

41 

Figure 22: A dry garden. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by 

permission).  

 

Figure 23: A fire pit with sofas. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used 

 

by permission). 

 

42 

2.2.5 Intensive green roof 

This design approach (Figures 24 - 29) is aim at creating an alternative of urban park, and a 

multi-functional space provides social, educational, and environmental value, which is also 

hoping to be influential to surrounding encouraging other building owners to utilize their rooftop 

and invest in green roof. The design criteria are: 

•  Generate renewable energy by applying solar panels; 

•  Reduce stormwater runoff by building it with special soil profile; 

•  Provide social opportunities by provide gathering space and seats; 

•  Provide educational opportunities by provide real time footage of butterfly garden with 

monitors and monitoring cameras; 

•  Encourage nature preservation by creating a man-made habitat for butterflies and provide 

educational programs about renewable energy and preservation of nature to visitors; and 

• 

Improving accessible challenge by designing ADA path from first level rooftop to second 

level rooftop. 

 

 

 

43 

Figure 24: Top view of an intensive green roof. (Copyright © 2019 Wing Chi Vincy Tam all 

 

right reserved used by permission). 

 

44 

Nature preservation, stormwater management, and energy efficiency are the three 

concepts that had been applied to the design. The site becomes not only a gathering site for 

youths and their families, but a biological spot for natural species (butterfly) and an 

educational spot for the community to have a better understanding about stormwater 

management, clean energy, and ecology. 

The butterfly garden facilitates the site to become an educational and ecological spot. It is 

designated for nature preservation and educational purposes that there are two monitoring 

cameras, recording real time footage of the butterfly garden and providing it on monitors in the 

secret garden, as shown in figure 25. 

Figure 25: A butterfly garden. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used 

 

by permission). 

 

45 

The sectet garden (Figure 26) is a partlialy enclosed space prviding 4 sofa seats and two 

wall-mounted monitors provide real-time footage that is capture in the butterfly garden, allowing 

visitors to learn about the nearby butterfly garden, biodoversity, and urban ecosystem. 

 

Figure 26: A secret garden. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by 

 

permission). 

 

 

46 

Figure 27: Ramp with railing alongside. (Copyright © 2019 Wing Chi Vincy Tam all right 

reserved used by permission). 

 

 

Figure 28: Plaza with a two-level creative seating element which encourage user to interact 

(Copyright © 2019 Wing Chi Vincy Tam all right reserved used by permission). 

 

47 

Aluminum planting grates are employed to maximize walkable and planting area and to 

emphasize visual differences (Figure 29). An aluminum planting grate allow people to walk on it 

while having sedum to plant underneath it. The design was inspired by the green roof on ASLA 

headquarters in Washington, D.C. 

Figure 29: Maximize walkable are and visual difference with use of two flooring materials: deck 

and aluminum planting grate. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by 

 

permission) 

2.3 Data collection 

This research will compare 5 rooftop design approach scenarios as listed and described in 

above sections: a conventional rooftop, a self-design rooftop, an extensive green roof, a semi-

intensive green roof, and an intensive green roof. The conventional rooftop scenario is the 

existing rooftop; others four scenarios are designed by the investigator, Wing Chi Vincy Tam. In 

order to evaluate these scenarios, a list of 36 variables ranging in 7 aspects, including 

 

48 

accessibility, plant, function, habitat value, active maintenance, water efficiency, and program 

are selected by the author, as describe in table 2.  

Data will be treated with Friedman test to compare multiple variables, which had been 

used on many studies on landscape architecture (Burley, Li, & He, 2020; Feng, Burley, 

Machemer, Korkmaz, & Villanueva, 2018; Feng, Burley, Machemer, & Korkmaz, 2017; Lin, 

Burley, Nieratko, & Machemer, 2017, Burley, Li, Ying, Tian, & Troost, 2016; Wang, Burley, & 

Partin, 2013; Hallsaxton, Burley, 2011; Hallsaxton, Burley; 2010; Keefe, Burley, 1998; Burley, 

1996; & Burley, Johnson, Larson, & Pecka, 1988). Data will treat in following steps: 

1.  All treatments across blocks are going to rank from smallest to largest by the author by 

observation (Daniel, 1978), which means the smaller score is a better score and the larger 

score is a poorer score. Treatments would receive same ranking if the author thinks they 

rank the same. For example, if the middle three treatments are all tied, they would all 

rank 3; while the best treatment rank 1 and the worst treatment rank 5; 

2.  Sum up within each treatment. 

3.  Apply (cid:1)(cid:2)(cid:3) = (

(cid:5)(cid:3)
(cid:6)(cid:7)((cid:7)(cid:8)(cid:5)(cid:9) ∑ (cid:12)(cid:13)(cid:3)

(cid:7)(cid:13)(cid:14)(cid:5)

(cid:9) − 3(cid:17)((cid:18) + 1(cid:9) (Equation 1), where, 

b equals blocks 

K equals numbers of treatments 

R equals sum for ranks in each treatment 

4.  Since there are ties, apply 1 − ∑ (cid:12)(cid:13)(cid:3)

(cid:6)(cid:13)(cid:14)(cid:5)

(cid:21)(cid:13) /(cid:17)(cid:18)((cid:18)(cid:3) − 1(cid:9) (Equation 2) to justify xr

2, where, 

(cid:21)(cid:13) = (cid:24)(cid:25)(cid:13)(cid:26) − (cid:24)(cid:25)(cid:13) 
(cid:25)(cid:13) = the number of observations tied for a given rank in the (cid:27)th block. 

 

49 

5.  Apply |(cid:12)(cid:13) − (cid:12)(cid:13)(cid:29)| ≥ (cid:31) (cid:6)(cid:7)((cid:7)(cid:8)(cid:5)(cid:9)

!

   (Equation 3) to determine which scenarios is better than 

the other, where, 

(cid:12)(cid:13) and (cid:12)(cid:13)" are the (cid:27)th and (cid:27)′th treatment rank totals 
(cid:31) is the value from a table provided in Daniel’s book, corresponding to ∝/(cid:18)((cid:18) − 1(cid:9) 

(Daniel, 1978); 

6.  Find z score from Daniel’s book (Daniel, 1978) 

7.  Calculate differences between each scenario; and 

8.  Compare results from step 5 and step 7, if the result from step 7 is larger than result from 

step 5, there is enough different showing these two scenarios have nonidentical effects. 

 

The p-value is set at 0.05. The null hypothesis of this study is all design approach 

scenarios have identical effect (Daniel, 1978); the research hypothesis is at least one scenario 

have larger value then at least one scenario (p≤0.05) (Daniel, 1978). 

This is a preliminary study that will reach across different rooftop design approaches for 

purpose of understanding how each design approaches weight on design aspects. 

Table 2: Variables 

Aspect 

No. 

Variable 

Accessibility 

 

 

Plant 

 

1 

2 

3 

4 

5 

Accessible entrance to the roof 

ADA accessible 

Safety 

Shading 

Diversity of plants 

50 

 

Table 2 (cont’d) 

 

Function 

 

 

 

 

 

 

 

 

 

 

 

Habitat value 

 

Active 
maintenance 

 

Water efficiency 

Program 

 

 

 

 

 

 

 

 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

 

Present of plant in number 

Reduce stormwater runoff 

Renewable energy production 

Conserve energy 

Reduce heat island effect 

Promote water infiltration 

Reduce pollutant loading 

Rainwater recycle 

Increase longevity of roofing membranes 

Reduce carbon footprint 

Reduce noise pollution 

Provide on-site education 

Provide on-site research value 

Provide habitat for wildlife 

Promote biodiversity 

Minimal or no irrigation 

Do not require chemical inputs, such as fertilizers, 
pesticides, or herbicides 

No permanent irrigation 

Seating  

Table 

Gathering space 

Viewpoint/ observation deck 

Children playing equipment 

Encourage social interaction 

Improve public health 

51 

Table 2 (cont’d) 

 

 

 

 

 

 

 

2.4 Variable Rating Criteria 

31 

32 

33 

34 

35 

36 

Encourage volunteerism 

Promote neighborliness and social inclusion 

Provide views for people within the building 

Encourage for outdoor activities 

Improve surrounding human mental health 

Being influential and encouraging for having green 
infrastructure  

All treatments are going to process in ranking from smallest to largest (Daniel, 1978), which 

means the smaller number in the rank, better that treatment design on that variable. Below 

present ranking criteria of each variable respectively following their orders on above table (Table 

2). 

 

1.  Accessible entrance to the roof 

If there is a proper accessible entrance from the building to the roof, such as a doorway, 

that treatment will rank the lowest; if there is no proper accessible entrance, that 

treatment will rank the highest. 

2.  ADA accessible 

There are two contents to compare across all treatments. 

a.  Entrance. If there is no ADA accessible entrance from the building to the roof. 

b.  Accessibility to the whole design area by wheelchairs. For example, if there is any 

ramp at where the elevation change. 

52 

If a treatment fails criteria (a), that treatment will immediately rank the highest because 

an entrance is the most immediate component for anyone who wants access to the roof. If 

a treatment success on both criteria (a) and (b), that treatment will rank the lowest. If a 

treatment only success on criteria (a), that treatment will rank in between the highest and 

the lowest. 

3.  Safety 

Prevention of people falling from the roof, such as at least 3-foot tall wall. 

4.  Shading 

Plants provide shades. The more shrubs and trees the treatments have on-site, the smaller 

it ranks. 

5.  Diversity of plant 

The higher diversity of plants a treatment has, the smaller it ranks. 

6.  Present of plant in number 

The more plant a treatment has, the smaller it ranks. 

7.  Reduce stormwater runoff 

Studies (Getter et al., 2007; Menten et al., 2005; Whittinghill, 2012) found that green 

roofs could reduce stormwater runoff. Ranking depends on plant coverage of treatment, 

the higher percentage of plant coverage, the smaller that treatment ranks. 

8.  Renewable energy production 

If that treatment produces any kind of renewable energy, such as solar energy, that 

treatment will rank the smallest. Otherwise, it will rank the highest. 

9.  Conserve energy 

 

53 

Studies (Getter et al., 2009; Rowe, 2010) found green roofs conserve energy by reducing 

the demand for HVACs. The more plant present on a treatment, the smaller that treatment 

ranks.  

10. Reduce the heat island effect 

Studies (Rowe, 2010; Whittinghill, Rowe, Schutzki, & Cregg, 2014) shows that the 

presence of plant reduce heat island effect. This variable will evaluate by the percentage 

of plant cover of the roof. The higher percentage, the smaller number of rankings that 

treatment is. 

11. Promote water infiltration 

By absorbing and retaining rainwater, green roofs promote water infiltration and increase 

the quality of stormwater (Berntsson, 2010; Teemusk, &Mander, 2007; Weiler, &Scholz-

Barth, 2009). Therefore, the higher percentage of plant coverage on-site, the smaller that 

treatment will rank.  

12. Reduce pollutant loading 

Green roofs could absorb pollutants (Teemusk, & Mander, 2007). Therefore, the higher 

percentage of plant coverage, the smaller that treatment ranks. 

13. Rainwater recycles 

If a treatment has rainwater recycling facilities on-site, it will rank the smallest. If a 

treatment does not have any rainwater recycling facility on-site, but rainwater could use 

for irrigation, it will rank the next. 

14. Increase longevity of roofing membranes 

 

54 

Green roofs can extend the life of rooftops (Snodgrass, & Snodgrass, 2016). Therefore, if 

a treatment is considered a green roof, it will rank the smallest. If not, it will rank the 

highest. 

15. Reduce carbon footprint 

Implementation of green roofs could lead to less HVACs usage, resulting in carbon 

footprint reduction (Getter et al., 2009; Rowe, 2010). Also, plant natural sequesters 

carbon dioxide into its biomass by photosynthesis (Rowe, 2010). Therefore, the more 

plants a treatment has, the smaller it ranks. 

16. Reduce noise pollution 

Studies (Pittaluga, 2012; Renterghem, & Botteldooren, 2009; Renterghem, & 

Botteldooren, 2008) found plants could reduce noise pollution. The more plant a 

treatment has, the smaller it ranks. 

17. Provide on-site education 

The more educational facilities or opportunities installed or could be install, such as 

outdoor classrooms and research programs, the smaller that treatment rank. 

18. Provide on-site research value 

The more research value a treatment has, the smaller it ranks. 

19. Provide habitat for wildlife 

Studies (Schindler et al., 2011; Monsma, 2011) found a positive correlation between the 

proportion of vegetation cover of green roofs and spices richness. Therefore, the more 

plants a treatment has, the smaller it ranks. 

20. Promote biodiversity 

 

55 

Plant communities have a cascade effect on promoting biodiversity by supporting urban 

animal lives through food webs. Therefore, the more plant a treatment has, the smaller it 

will rank. 

21. Minimal or no irrigation 

The least irrigation that treatment needs, the smaller it ranks.  

22. Do not require chemical inputs, such as fertilizers, pesticides, or herbicides 

If a treatment requires these chemical inputs, the more it needs, the higher it will rank.  

23. No permanent irrigation 

If a treatment requires permanent irrigation, it will rank the highest. Otherwise, the 

treatment will rank the lowest. Usually, permanent irrigation related to plant presence and 

water requirement of plant selections.  

24. Seating 

The more seats a treatment provides, the smaller it ranks. 

25. Table 

The more tables a treatment provides, the smaller it ranks. 

26. Gathering space 

If a treatment does not have an area for visitors to stay and gather, that treatment will 

rank the highest. If a treatment has a destinated and designed area that encourages 

gathering and social interaction, that treatment will rank the lowest. If a treatment has an 

area that people could stay or seat, but not encouraging people interaction, that treatment 

will rank in between. 

27. Viewpoint/observation deck 

 

56 

If a treatment is accessible by visitors, the higher destined locations they are to be 

viewpoints/observation decks, the smaller that treatment ranks. 

28. Children playing equipment 

If a treatment has any children playing equipment on site, the more it has, the smaller it 

ranks. 

29. Encourage social interaction 

The more elements that would encourage social interaction, such as children playing 

equipment, gathering area, and seats a treatment has, the smaller it ranks.  

30. Improve public health 

Green roofs provide numbers of services improve public health, including reduce 

stormwater runoff (Weiler, & Scholz-Barth, 2009), alleviate global warming (Rowe, 

2010; Whittinghill et al., 2014), and reduce noise pollution (Renterghem, & Botteldooren, 

2008; Renterghem, & Botteldooren, 2009). Therefore, if a treatment is considered as a 

green roof, it will rank the smallest. If it is not considered as a green roof but still 

provides opportunities for people to spend time outdoor, that treatment will rank the next. 

If a treatment provides neither of the functions nor opportunity, it will rank the largest.  

31. Encourage volunteerism 

Volunteerism could use for site maintenance. The more maintenance treatment might 

require, the smaller it ranks. 

32. Promote neighborliness and social inclusion 

Green roofs promote social inclusion and increase neighborhood social ties as green 

instructions (Peter et al., 2010; Kuo et al., 1998). A study (Kuo et al.,1998) found that the 

more greenness in a social space, the closer neighborhood social ties. Also, urban open 

 

57 

spaces increase casual social opportunity which leads to tighter neighbor social bond 

(Kazmierczak, 2013; Mesimaki et al., 2017). Therefore, if a treatment is being accessible 

to visitors, the greener it is, the smaller it ranks. If a treatment is not being accessible but 

it is still green, that treatment will rank the next because having “quality green” nearby 

could encourage increase neighborhood social ties (Kuo et al., 1998). If a treatment is not 

being accessible and green, it will rank the highest.  

33. Provide views for people within the building 

If a treatment could provide “green views” for people within the building, it will rank the 

smallest. If there is something that could look at, but not green, it will rank the next. 

34. Encourage for outdoor activities 

If a treatment has elements that encourage people to go to the site and stay, such as 

interactive playing elements, reading area, fire pit, and observation deck, it will rank the 

smallest. If a treatment only allows people to access the area but it does not has any 

attractive element for leading visitors to be there for outdoor activity, it will rank the 

next. If a treatment is not accessible, it will rank the largest.  

35. Improve surrounding human mental health 

If a treatment is considered as a green roof, it will rank the smallest. If a treatment is not 

considered as a green roof but still encourage neither outdoor activities nor social 

interactions, it will rank the next. 

36. Being influential and encouraging for having green infrastructure 

If a treatment is utilizing the roof and it is considered as a green roof, it will rank the 

smallest. If a treatment is not utilizing the roof, it will rank the highest. If a treatment is 

utilizing the roof, but it is not designed as a green roof, it will rank in between. 

 

58 

CHAPTER THREE: RESULT 

To process Friedman test, all treatments are going to rank from smallest to largest 

(Daniel, 1978), as shown (Table 3). 

Table 3: Variables in rankings 

Aspect 

No.  Variable 

Conventional  Self-

Extensive  Semi-

Intensive 

Design 

intensive 

Accessibility  1 

Accessible 
entrance to the 
roof 

4.5 

ADA accessible  4.5 

4.5 

2 

2 

4.5 

1.5 

1.5 

2 

3 

3 

4.5 

4 

4 

3 

3 

1 

1.5 

4.5 

1 

2 

4.5 

4.5 

1.5 

4 

1.5 

4.5 

1 

59 

3 

2 

3 

3 

3 

2 

3 

3 

3 

3 

1 

2 

1.5 

2 

2 

1.5 

1.5 

2 

2 

3 

4 

5 

6 

7 

8 

9 

Safety 

Shading 

Diversity of 
plants 

Present of plant 
in number 

Reduce 
stormwater 
runoff 

Renewable 
energy 
production 

Conserve 
energy 

10  Reduce heat 
island effect 

11 

Promote water 
infiltration 

 

3 

4.5 

5 

5 

4.5 

4.5 

4.5 

5 

4.5 

Plant 

Function 

 

 

Table 3 (cont’d) 

 

12  Reduce 

pollutant 
loading 

13  Rainwater 

recycle 

14 

Increase 
longevity of 
roofing 
membranes 

5 

5 

4 

1 

4.5 

4.5 

1.5 

3 

2 

15  Reduce carbon 

5 

4 

1.5 

footprint 

16  Reduce noise 

4.5 

4.5 

1.5 

17 

18 

19 

20 

pollution 

Provide on-site 
education 

Provide on-site 
research value 

Provide habitat 
for wildlife 

Promote 
biodiversity 

Habitat 
value 

Active 
maintenance 

21  Minimal or no 

irrigation 

22  Do not require 

chemical inputs, 
such as 
fertilizers, 
pesticides, or 
herbicides 

5 

5 

5 

5 

2 

2 

Water 
efficiency 

23  No permanent 

2 

irrigation 

Program 

24 

Seating  

25  Table 

4.5 

4.5 

26  Gathering space  4.5 

 

60 

2 

3 

4 

4 

2 

2 

2 

3 

1 

3 

4 

2 

1 

1 

2 

2 

2 

4.5 

4.5 

4.5 

3 

3 

2 

3 

3 

3 

4 

3 

3 

4 

4 

4.5 

1.5 

2 

1.5 

1.5 

3 

2 

1.5 

1.5 

1 

1 

2 

2 

5 

5 

4.5 

1.5 

3 

1.5 

Table 3 (cont’d) 

 

 

3 

2 

3 

4 

4 

3 

4.5 

4 

4 

2 

3 

4 

2 

1 

1 

4 

1.5 

1.5 

2 

1.5 

1.5 

2 

1.5 

1.5 

4 

2 

2 

2 

3 

4 

4 

2 

4 

2 

1.5 

1.5 

2 

2 

2 

2 

4.5 

4 

5 

5 

5 

5 

5 

27  Viewpoint/ 
observation 
deck 

28  Children 
playing 
equipment 

29  Encourage 

social 
interaction 

30 

Improve public 
health 

31  Encourage 

volunteerism 

32 

33 

Promote 
neighborliness 
and social 
inclusion 

Provide views 
for people 
within the 
building 

34  Encourage for 

5 

5 

5 

35 

outdoor 
activities 

Improve 
surrounding 
human mental 
health 

36  Being 

influential and 
encouraging for 
having green 
infrastructure  

 

61 

Secondly, to determine if Ho is true or false by calculating the test statistic in summing 

ranking in each scenario, as shown on Table 4. If Ho is true, sums are close, and neither small 

nor large rank should show a tendency toward a scenario. However, if Ho is false, at least one 

scenario has sufficient differences in sum from the other. 

 

Table 4: Sum in ranking of each scenario 

 

Conventional 

Self-design 

Extensive 

Semi-

Intensive 

intensive 

Sums 

161.5 

118 

95.5 

90 

75 

 

Thirdly, set the risk level alpha (α) in 0.05, which is associated with null hypothesis, meaning 

that there is 95% chance that the null hypothesis can be accepted. 

Then, this equation has been applied (Daniel, 1978), 

(cid:1)(cid:2)(cid:3) = (

(cid:5)(cid:3)
(cid:6)(cid:7)((cid:7)(cid:8)(cid:5)(cid:9) ∑ (cid:12)(cid:13)(cid:3)

(cid:7)(cid:13)(cid:14)(cid:5)

(cid:9) − 3(cid:17)((cid:18) + 1(cid:9) (Equation1) 

Where, 

•  b equals blocks 

•  K equals numbers of treatments 

•  R equals sum for ranks in each treatment 

Therefore, as describe in Table 4,  

 

62 

(cid:1)(cid:2)(cid:3) = (

(cid:5)(cid:3)

(cid:26)!×&×(&(cid:8)(cid:5)(cid:9)×(161.5(cid:3) + 118(cid:3) + 95.5(cid:3) +90(cid:3) + 75(cid:3)(cid:9) − 3 ×36 × (5+ 1(cid:9) = 50.35 

(Equation 1.2) 

Since there are ties occurs, text statistic has been justified by dividing (cid:1)(cid:2)(cid:3) , by 

1 − ∑ (cid:12)(cid:13)(cid:3)

(cid:6)(cid:13)(cid:14)(cid:5)

(cid:21)(cid:13) /(cid:17)(cid:18)((cid:18)(cid:3) − 1(cid:9) (Equation 2) 

where, 

•  (cid:21)(cid:13) = ∑(cid:25)(cid:13)(cid:26) − ∑(cid:25)(cid:13) 
•  (cid:25)(cid:13) = the number of observations tied for a given rank in the (cid:27)th block. 

There are 27 two-way ties, 12 three-way ties, and one five-way ties, therefore, 

1 − .(cid:3)/0(cid:3)1×(cid:3)2(cid:8).(cid:26)/0(cid:26)1×(cid:5)(cid:3)(cid:8).&/0&1×(cid:5)

(cid:26)!×&×(&30(cid:5)(cid:9)
Then, we calculate adjusted (cid:1)(cid:3) value by, 

= 0.868056 (Equation 2.2) 

(cid:1)(cid:3) = 50.35÷ 0.868056 = 58.0032 

Then, the (cid:1)(cid:2)(cid:3)adjusted for ties is 58.0032. 

Then, required value for rejecting the null hypothesis is needed to determine by using a table that 

contain chi-square value of (cid:1)(cid:3)((cid:5)06(cid:9) with k-1 degree of freedom, provided by Daniel (Daniel, 
1978). If (cid:1)(cid:2)(cid:3)is greater or equal than the determined value, the null hypothesis will be rejected 

(Daniel, 1978). In this study, the experimentwise error rate of α equal to 0.05 and k equal to 5. 

The value of (cid:1)(cid:3)7.88 with 35 degrees of freedom is 57.342. Since 58.0032 is greater than 57.342, 

at least one treatment is significantly different than another treatment.  

In order to determine which scenario is better than the other, multiple-comparison procedure for 

use with Friedman test apply (Daniel, 1978). The equation is (Daniel, 1978); 

 

63 

|(cid:12)(cid:13) − (cid:12)(cid:13)(cid:29)| ≥ (cid:31) (cid:6)(cid:7)((cid:7)(cid:8)(cid:5)(cid:9)
!

 (Equation 3) 

Where, 

•  (cid:12)(cid:13) and (cid:12)(cid:13)" are the (cid:27)th and (cid:27)′th treatment rank totals 
•  (cid:31) is the value from a table provided in Daniel’s book, corresponding to ∝/(cid:18)((cid:18) − 1(cid:9) 

(Daniel, 1978). 

In this study, experimentwise error rate of 9 equal to 0.05, which  

(cid:31) = 9 ÷ (cid:18)((cid:18) − 1(cid:9) 

(cid:31) = 0.05÷ 5(5 −1(cid:9) = 0.0025 

(cid:31)-score for 0.0025 is 2.81, found in a table in Daniel book. 

Therefore, after applied multiple comparison procedure for use with Friedman test apply, 

2.81 (cid:26)!×&×(&(cid:8)(cid:5)(cid:9)

!

= 37.7001 (Equation 3a) 

Differences between five design scenarios are listed in Table 5. According to previous 

statements and calculations, we can find differences between conventional rooftops and all of the 

other rooftop design approaches since their differences are larger than 37.7001 (Equation 3a). 

There are also differences between self-design rooftops and intensive green roofs, since their 

difference are larger than 37.7001 (Equation 3a).  

Table 5: Design Scenarios Difference 

Combinations of Design Scenarios 

Difference 

 

 

 

64 

Table 5 (cont’d) 

Conventional & Self-design 

Conventional & Extensive 

Conventional & Semi-intensive 

Convention & Intensive 

Self-design & extensive 

Self-design & Semi-intensive 

Self-design & Intensive 

Extensive & Semi-intensive 

Extensive & Intensive 

Semi-intensive & Intensive 

 

43.5 

66 

71.5 

86.5 

22.5 

28 

43 

5.5 

20.5 

15 

As a result, one can determine self-design rooftops, extensive green roofs, semi-intensive 

green roofs, and intensive green roofs are statistically significantly better than conventional 

rooftops. Nevertheless, intensive green roofs are statistically significantly better than self-design 

rooftops.  

 

 

 

65 

CHAPTER FOUR: DISCUSSION 

4.1 Evaluation Between Theory and Reality 

 

The performance of green roofs was predicted to do better than conventional rooftops and 

self-design rooftops when the researcher was reading the literature about the effects of rooftops 

on energy and water efficiency, environmental, psychological, and social interaction. Green 

roofs are obviously more advantageous than the other non-green-roof designs, not only on 

reducing stormwater runoffs and heat island effects, but also design programs, responses from 

the societies, plantings, and accessibilities. In addition, it was predicted that the intensive green 

roof scenario was the best rooftop design approach because there are lots of possibilities 

concerning designing the area. It has fewer regulations regarding to weight load than the other 

approaches. Also, this scenario addressed educational, environmental, nature preservation, and 

energy generation program elements. As a result, the assumption is partly correct.  

           The results for each individual scenario show my assumption is somewhat correct. Based 

on just the sum of the rankings, the intensive green roof scenario performs the best since it has 

the lowest sum of ranking. Then the semi-intensive green roof, the extensive green roof, and the 

self-design rooftop. Finally, the conventional rooftop scenario ranked the least. In contrast, the 

sum of ranking compared the performance of each scenarios. The Friedman test interpreted 

results statistically. The result of Friedman test supported the notion that the self-design rooftop, 

the extensive green roof, the semi-intensive green roof, and the intensive green roof scenarios are 

statistically better than the conventional rooftop scenario. However, Friedman test did not 

confirm that the self-design rooftop, the extensive green roofs, the semi-intensive green roofs, 

and the intensive green roofs are different on their performance. They had not shown remarkable 

 

66 

statistical differences. Under this circumstance, the researcher could still confirm intensive green 

roofs are statistically better than self-design rooftops. This result has slightly differed from the 

assumption, but still validate that conventional rooftops should be converted into alternative 

social spaces or stormwater management tools. From the rankings, we can see that once a 

conventional rooftop is converted into a usable space, it would rank higher with most of the 

variables employed in the study.  

           In this research, rooftop design approaches had been evaluated to determine which is 

better comprehensively by comparing 5 rooftop design approach scenarios in 36 variables 

ranging from 7 aspects by Friedman test.  

4.1.1 Green Roofs as social-inclusive areas 

Greenspaces, including urban green space and native green areas, are places for people to 

spend their leisure time. Urban green space can serve as a place that it brings diverse 

communities together, often communities with varying socio-economic backgrounds 

(Krellenberg, Welz, Reyes-Packe, 2014). People are more likely to be in a “green” common 

social space in a neighborhood than in abandoned spaces (Kuo et al., 1998). A nationwide study 

of 11238 randomly selected adults in Denmark examined the influence on user motivations and 

distance to urban park on the park usage of urban parks, using a survey. The survey found that 

people are more willing to visit an urban park than a native park (Schipperjin et al., 2010). In 

addition, a research study on urban park concentrating on what it means to different ethnic group 

and their behaviors towards different types of parks, using surveying, observation, and interview 

methods in five selected urban parks in Netherland, found that urban parks are inclusive places 

that offer opportunities to all ethnic groups to spend their leisure time (Peter et al., 2010).  

 

67 

4.1.2 Green Roofs in the Biosphere Concept 

Green roofs are being referred as the green lungs in urban and suburban areas since they 

provide lots of environmental, economic, climate, social, and technical advantages comparing to 

traditional conventional rooftop (Schrader, Böning, 2006). While rapid urbanization and 

expansion of urban sprawl caused habitat fragmentation, opportunities of green roofs to reserve 

urban biosphere and function as urban habitat networks should be explored (Kim, 2004). Indeed, 

green roofs had been adopted to a habitat network project in Seoul, South Korea, as 

steppingstones to connect fragment habitats and build biosphere networks (Kim, 2004). The 

project is divided into four categories: urban green belt biosphere reserve, urban green corridor 

biosphere reserve, urban green area cluster biosphere reserve, and urban region biosphere 

reserve; creating green space equivalent to 27.5% of Seoul administrative district (Kim, 2004). 

Since 42% of the city is covered with buildings, which is impossible to link fragment habitats 

without utilizing rooftops. As Seoul is facing a challenge in the storage of green space, 

converting these rooftops into green roofs would create green space equivalent to 30% of the 

area (Kim, 2004). The green belt project is designed to outskirt 15-25km from the center of 

Seoul. Green corridors: one circulates with the green belt, two divide the belt from north to 

south, and from east to west (Kim, 2004). Green roofs in inner Seoul play in for the area cluster 

that six sites, including Seoul form a large-scale green area cluster when various species 

inhabitant there (Kim, 2004). Finally, Seoul and its surrounding existing and implemented green 

areas lined to define the region as a biosphere reserve zone (Kim, 2004). Green roofs are being 

recognized on their excel of being providers of eco-services. They are employed to be elements 

of “building-integrate habitat” and biotopes in the case in Seoul. They are applications of the 

biosphere reserve concept. 

 

68 

Green roofs are no longer just build for humans to overcome arduous weather like our 

ancestors, they provide services to human, man-made environments, ecosystems, and nature. As 

this result of this study found that conventional rooftop performs the worst and many studies and 

cases found and prove advantageous of green roofs, these spare barren rooftops should have 

more attention from the public. 

           Innovation green roof constructions and designs in the future could regreen metropolis, 

like the habitat network project in Seoul. As green roofs are being increasingly popular to 

address challenges on urban sustainability development, supports from governments such as 

revising building codes and other beneficial policies would play a key role in pushing forward 

the movement of green roofs. With overseeing abilities from planners and landscape architects, a 

green roof would no longer be just an individual rooftop. Its effect would be bigger, to connect 

with other green roofs, nearby green areas, and over the globe. 

 

4.2 Limitation 

           This study has a limited sampling size, in which a larger one could increase the accuracy 

of this study. Each rooftop design approach has only one design provided for comparison.  Also, 

except the conventional rooftop scenario is adopted from the existing site, the other scenarios all 

depend on designed rooftops, which designed by the investigator, Wing Chi Tam. These designs 

may be subjective. Even though there are 65 variables selected from 7 aspects, which are chosen 

by the author, and it may be personal and not being comprehensive enough. In addition, the error 

rate is set at 5%, which if it is set at a different rate, the result might be different. 

 

69 

4.3 Recommendation 

 For all building owners, urban planners, developers, and government, it is beneficial to 

appreciate spaces that we have and maximize its use. Rooftops could be retrofit, design, and 

adjust scenarios base on the calculation of this study, which conventional rooftops could be more 

advantageous if they convert to social nodes or stormwater runoff alleviation tools.  

Future study is recommended to have a larger sample size and to have more samples 

come from reality to let this study become more comprehensive. 

 

4.4 Conclusion 

There could be many possibilities toward rooftops, which could bring many attributes to 

the societies and natural environment. This study focusses on comparing five rooftop design 

approach scenarios: conventional rooftops, self-design rooftops, extensive green roofs, semi-

intensive green roofs, and extensive green roofs, with the quantitative method. The result shows 

that conventional rooftops are the worst ones in these five scenarios. Intensive green roofs are 

better than self-design rooftops. However, there are insufficient statistical results to confirm if 

self-design rooftops, extensive green roofs, semi-intensive green roofs, and extensive green roofs 

are different from each other. 

 

 

 

70 

 

 

 

 

BIBLIOGRAPHY 

 

71 

 

BIBLIOGRAPHY 

 

Arnberger, A., & Eder, R. (2012). The influence of green space on community attachment of 

urban and suburban residents. Urban Forestry & Urban Greening, 11(1), 41-
49.doi:10.1016/j.ufug.2011.11.003 

Bliss, D. J., Neufeld, R. D., & Ries, R. J. (2009). Storm water runoff mitigation using a green 
roof. Environmental Engineering Science, 26(2), 407-418. doi:10.1089/ees.2007.0186 

Burghardt, K. T., Tallamy, D. W., Philips, C., & Shropshire, K. J. (2010). Non‐native plants 

reduce abundance, richness, and host specialization in lepidopteran 
communities. Ecosphere, 1(5), 1-22. doi:10.1890/ES10-00032.1 

Burley, J.B.  1996.  Designing to preserve wildlife.  Landscape Design 9(10):16-23. 

Burley, J.B., S. Johnson, P. Larson and B. Pecka. 1988.  Big Stone granite quarry habitat 

design:  HSI reclamation application.  ASSMR Conference Proceedings, PA., 161-169. 

Burley, J.B., N. Li, J. Ying, H. Tian, and S. Troost. 2016.  Chapter 3: Metrics in master planning 

low impact development for Grand Rapids, Michigan.  Egren, M.(ed.) in: Sustainable 
Urbanization.  Intech Rijeka, Croatia, 61- 86. 

Burley, J. B., Li, X., & He, S. (2020). Metrics Evaluating Multivariate Design Alternatives: 
Application of the Friedman’s Two-way Analysis of Variance by Ranks: A Personal 
Reflection. Whitemud Academics: Perrinton, MI, USA, 36. 

Castiglia Feitosa, R., & Wilkinson, S. (2016). Modelling green roof stormwater response for 

different soil depths. Landscape and Urban Planning, 153, 170-
179.doi:10.1016/j.landurbplan.2016.05.007 

Cook-Patton, S. C.  2015. “Plant Biodiversity on Green Roofs.” P.193-210. In: R. Sutton (ed.). 

Green roof ecology. Springer, NewYork, NY. (ISBN 978-3-319-14982-0) 

Cook-Patton, S. C., & Agrawal, A. A. (2014). Exotic plants contribute positively to biodiversity 

functions but reduce native seed production and arthropod richness. Ecology, 95(6), 
1642-1650. doi:10.1890/13-0782.1 

Cronk, E. (2012). Stormwater retention capabilities of steep sloped, extensive green roof 

systems. Michigan State University. Environmental Design. 

Czemiel Berndtsson, J., Lund University, Avdelningen för Teknisk vattenresurslära, Lunds 

universitet, & Division of Water Resources Engineering. (2010). Green roof performance 
towards management of runoff water quantity and quality: A review. Ecological 
Engineering, 36(4), 351-360. doi:10.1016/j.ecoleng.2009.12.014 

 

72 

Daniel, W. W. (1978). Applied nonparametric statistics. Boston: Houghton Mifflin. 

Eakin, C. J. (2012). Assessing wildlife habitat contributions of green roofs in urban landscapes 

in Michigan and Illinois, USA: measuring avian community response to green roof 
factors. Michigan State University. Fisheries and Wildlife.. 

Eakin, C. J., Campa, H., Linden, D. W., Roloff, G. J., Rowe, D. B., & Westphal, J. (2015). Avian 

response to green roofs in urban landscapes in the midwestern USA. Wildlife Society 
Bulletin, 39(3), 574-582. doi:10.1002/wsb.566 

Feng, M., J.B. Burley, T. Machemer, A. Korkmaz, M.R. Villanueva.  2018. Earthquake spatial 

mitigation: Wenchuan China and Los Banos, Philippines Case Studies.  GSTF Journal of 
Engineering Technology (JET)5(2): p. 10. 

Feng, Mengwen, J. B. Burley, T. Machemer, and Armagan Korkmaz. 2017.  Spatial mitigation 

treatments: Wenchuan earthquake case study. 3rdAnnual International Conference on 
Urban Planning and Property Development (UPPD 2017). Global Science & Technology 
Forum (GSFT), 68-75. 

Forschungsgesellschaft Landschaftsentwicklung--Landschaftsbau. (2004). Guideline for the 

planning, execution and upkeep of green-roof sites: Roof-greening guidelines, January 
2002 edition ; with Methods to be employed when investigating vegetation substrates and 
aggregate-type drainage materials used at roof-greening sites, 1995 edition with 
supplements dated January 2002 ; and, Procedure for investigating resistance to root 
penetration at green-roof sites, 1999 edition with editorial changes dated January 2002. 
Bonn: Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau e.V. 

Getter, K. L. (2009). Extensive green roofs: carbon sequestration potential and species 

evaluations. Michigan State University. Horticulture.  

Getter, K. L., Rowe, D. B., & Andresen, J. A. (2007). Quantifying the effect of slope on 

extensive green roof stormwater retention. Ecological Engineering, 31(4), 225-231. 
doi:10.1016/j.ecoleng.2007.06.004 

Getter, K. L., Rowe, D. B., Robertson, G. P., Cregg, B. M., & Andresen, J. A. (2009). Carbon 
sequestration potential of extensive green roofs. Environmental Science & Technology, 
43(19), 7564-7570. doi:10.1021/es901539x 

Google Maps. (n.d.). Retrieved October 15, 2019, from 

https://www.google.com/maps/@43.0524912,-83.6954075,17z. 

Haddad, N. M., Crutsinger, G. M., Gross, K., Haarstad, J., Knops, J. M. H., & Tilman, D. (2009). 

Plant species loss decreases arthropod diversity and shifts trophic structure. Ecology 
Letters, 12(10), 1029-1039. doi:10.1111/j.1461-0248.2009.01356.x 

 

73 

Hallsaxton, M., and J.B. Burley.  2011.  Residential interior occupant health criteria review and 

assessment in Holland, Michigan.  International Journal of Energy and Environment, 
5(5): 704-713. 

Hallsaxton, M. and J.B. Burley. 2010.  Residential interior occupant health criteria in West 

Michigan. Panagopoulos, T., T. Noronha, and J. Beltrao, (eds.) in: Advances In 
UrbanRehabilitation andSustainability 3rd WSEAS International Conference on 
UrbanRehabilitation And Sustainability (URES '10)University of Algarve, Faro, 
PortugalNovember 3-5, 2010, 2010:42-48. 

Hooper, D. U., Chapin, F. S., Ewel, J. J., Hector, A., Inchausti, P., Lavorel, S., . . . Sveriges 

lantbruksuniversitet. (2005). Effects of biodiversity on ecosystem functioning: A 
consensus of current knowledge. Ecological Monographs, 75(1), 3-35. doi:10.1890/04-
0922 

Jim, C.Y. (2017). An archaeological and historical exploration of the origins of green roofs. 

Urban Forestry & Urban Greening, 28, 32-42. doi:10 1016/j.ufug.2017.06.014 

Kazmierczak, A. (2013). The contribution of local parks to neighbourhood social ties. Landscape 

and Urban Planning, 109(1), 31-44. doi:10.1016/j.landurbplan.2012.05.0076 

Keefe, P.S. and J.B. Burley.  1998.  Post-mining predictive visual quality assessment: a 

methodology.  Throgmorton, D., J. Nawrot, J. Mead, J. Galetovic, and W. Joseph (eds.) 
In: Proceedings Fifteenth Annual Meeting American Society for Surface Mining and 
Reclamation: Mining--Gateway to the Future!  May 17-21, 1998, St. Louis, Missouri, 
The American Society for Surface Mining and Reclamation :752-760. 

Kim, K. (2004). The application of the biosphere reserve concept to urban areas: The case of 

green rooftops for habitat network in seoul. Annals of the New York Academy of 
Sciences, 1023(1), 187-214. doi:10.1196/annals.1319.010 

Krellenberg, K., Welz, J., & Reyes-Päcke, S. (2014). Urban green areas and their potential for 

social interaction – A case study of a socio-economically mixed neighbourhood in 
Santiago de Chile. Habitat International, 44, 11-21. doi:10.1016/j.habitatint.2014.04.004 

Krogulecki, K. S. (2014). Effects of Green Roof Plant Selection on Enhancing Stormwater 

Quality Under Steep Sloped Roof Conditions. Michigan State University. Environmental 
Design-Master of Arts. 

Kuo, F. E., Sullivan, W. C., Coley, R. L., & Brunson, L. (1998). Fertile ground for community:    

Inner-city neighborhood common spaces. American Journal of Community Psychology, 
26(6), 823-851. doi:10.1023/A:1022294028903 

Lin, Wan-Chu, J. B. Burley, P. Nieratko, T. Machemer. 2017.  Railroad station arrival cognition: 

way-finding at the East Lansing train station. 3rdAnnual International Conference on 
Urban Planning and Property Development (UPPD 2017). Global Science & Technology 
Forum (GSFT), 91-97. 

 

74 

Loder, A. (2014). ‘There's a meadow outside my workplace’: A phenomenological exploration 
of aesthetics and green roofs in Chicago and Toronto. Landscape and Urban Planning, 
126, 94-106. doi:10.1016/j.landurbplan.2014.01.008 

Lundholm, J., Heim, A., Tran, S., & Smith, T. (2014). Leaf and life history traits predict plant 

growth in a green roof ecosystem. PloS One, 9(6), e101395. 
doi:10.1371/journal.pone.0101395 

Lundholm, J., Macivor, J. S., Macdougall, Z., & Ranalli, M. (2010). Plant species and functional 

group combinations affect green roof ecosystem functions. PloS One, 5(3), e9677. 
doi:10.1371/journal.pone.0009677 

Matlock, J. M. (2015). A critical evaluation of green roof substrate components. Michigan State 

University. 

MacIvor, J. S., & Lundholm, J. (2011). Performance evaluation of native plants suited to 

extensive green roof conditions in a maritime climate. Ecological Engineering, 37(3), 
407-417. doi:10.1016/j.ecoleng.2010.10.004 

Mentens, J., Raes, D., & Hermy, M. (2006). Green roofs as a tool for solving the rainwater 

runoff problem in the urbanized 21st century? Landscape and Urban Planning, 77(3), 
217-226. doi:10.1016/j.landurbplan.2005.02.010 

Mesimäki, M., Hauru, K., Kotze, D. J., & Lehvävirta, S. (2017). Neo-spaces for urban livability? 

urbanites’ versatile mental images of green roofs in the Helsinki metropolitan area, 
Finland. Land use Policy, 61, 587-600. doi:10.1016/j.landusepol.2016.11.021 

Monsma, J. L. (2011). A Comparison of Insect and Spider Species Presence and Composition 

Across Multiple Vegetated Roof Systems. Michigan State University. Environmental 
Design. 

Monterusso, M. A., Rowe, D. B., Rugh, C. L., & Russell, D. K. (2002, August). Runoff water 

quantity and quality from green roof systems. In XXVI International Horticultural 
Congress: Expanding Roles for Horticulture in Improving Human Well-Being and Life 
Quality 639 (pp. 369-376) 

Montgomery, M. (2003). United nations world urbanization prospects: The 2001 

revision. Population and Development Review, 29(3), 530 

Nagase, A., & Dunnett, N. (2010). Drought tolerance in different vegetation types for extensive 

green roofs: Effects of watering and diversity. Landscape and Urban Planning, 97(4), 
318-327. doi:10.1016/j.landurbplan.2010.07.005 

Öhrström, E. (1991). Psycho-social effects of traffic noise exposure. Journal of Sound and 

Vibration, 151(3), 513-517. doi:10.1016/0022-460X(91)90551-T 

Osmundson, T. (1999). Roof gardens: history, design, and construction. WW Norton & 

Company. 

 

75 

Ouldboukhitine, S., Belarbi, R., & Djedjig, R. (2012). Characterization of green roof 

components: Measurements of thermal and hydrological properties. Building and 
Environment, 56, 78-85. doi:10.1016/j.buildenv.2012.02.024 

Partridge, D. R., & Clark, J. A. (2018). Urban green roofs provide habitat for migrating and 

breeding birds and their arthropod prey. PloS One, 13(8), e0202298. 
doi:10.1371/journal.pone.0202298 

Peck, S. W. (2008). Award-winning green roof designs: Green roofs for healthy cities. Atglen, 

PA: Schiffer Pub. 

Peters, K., Elands, B., & Buijs, A. (2010). Social interactions in urban parks: Stimulating social 

cohesion?. Urban Forestry & Urban Greening, 9(2), 93-100. 
doi:10.1016/j.ufug.2009.11.003 

Pittaluga, I., Schenone, C., & Borelli, D. (2012). Sound absorption of different green roof 

systems. Proceedings of Meetings on Acoustics, 14(1) doi:10.1121/1.3685875 

Pomeroy, J. (2012). Room at the top-the roof as an alternative habitable / social space in the 

Singapore context. Journal of Urban Design, 17(3), 413-424. 
doi:10.1080/13574809.2012.666176 

Rowe, D. B. (2011). Green roofs as a means of pollution abatement. Environmental 

Pollution, 159(8), 2100-2110. doi:10.1016/j.envpol.2010.10.029 

Rowe, D. (2018). Green roofs: plant production and installation methods©. Acta Horticulturae, 

(1212), 97–100. doi: 10.17660/actahortic.2018.1212.19 

Rumble, H., Finch, P., & Gange, A. C. (2018). Green roof soil organisms: Anthropogenic 

assemblages or natural communities? Applied Soil Ecology, 126, 11-20. 
doi:10.1016/j.apsoil.2018.01.010 

Saadatian, O., Saadatian, E., Sopian, K., Salleh, E., Lim, C. H., Riffat, S., . . . Sulaiman, M. Y. 
(2013). A review of energy aspects of green roofs. Renewable and Sustainable Energy 
Reviews, 23, 155-168. doi:10.1016/j.rser.2013.02.022 

Sailor, D. J. (2008). A green roof model for building energy simulation programs. Energy & 

Buildings, 40(8), 1466-1478. doi:10.1016/j.enbuild.2008.02.001 

Sanchez, L., & Reames, T. G. (2019). Cooling detroit: A socio-spatial analysis of equity in green 

roofs as an urban heat island mitigation strategy. Urban Forestry & Urban Greening, 44, 
126331. doi:10.1016/j.ufug.2019.04.014 

Schindler, B. Y., Griffith, A. B., & Jones, K. N. (2011). Factors influencing arthropod diversity 

on green roofs. Cities and the Environment, 4(1), Article 5-20 pp. 

 

76 

Schrader, S., & Böning, M. (2006). Soil formation on green roofs and its contribution to urban 

biodiversity with emphasis on collembolans. Pedobiologia - International Journal of Soil 
Biology, 50(4), 347-356. doi:10.1016/j.pedobi.2006.06.003 

Schipperijn, J., Ekholm, O., Stigsdotter, U. K., Toftager, M., Bentsen, P., Kamper-Jørgensen, F., 

& Randrup, T. B. (2010). Factors influencing the use of green space: Results from a 
Danish national representative survey. Landscape and Urban Planning, 95(3), 130-137. 
doi:10.1016/j.landurbplan.2009.12.010 

Shafique, M., Kim, R., & Kyung-Ho, K (2018). Green roof for stormwater management in a 

highly urbanized area: The case of seoul, korea. Sustainability, 10(3), 584: 
doi:10.3390/su10030584 

Snodgrass, E. C., & McIntyre, L. (2010). The green roof manual: A professional guide to design, 

installation, and maintenance. Portland: Timber Press. 

Snodgrass, E. C., & Snodgrass, L. L. (2006). Green roof plants: A resource and planting guide. 

Portland, Or: Timber Press. 

Spehn, E. M., Joshi, J., Schmid, B., Diemer, M., & Korner, C. (2000). Above-ground resource 

use increases with plant species richness in experimental grassland 
ecosystems. Functional Ecology, 14(3), 326-337. doi:10.1046/j.1365-2435.2000.00437.x 

Srivastava, D. S., & Lawton, J. H. (1998). Why more productive sites have more species: An 

experimental test of theory using Tree‐Hole communities. The American 
Naturalist, 152(4), 510-529. doi:10.1086/286187 

Sutton, R. K.  2015. “Introduction to Green Roof Ecosystems.” P.1-26. In: R. Sutton (ed.). 

Green roof ecology. Springer, NewYork, NY. (ISBN 978-3-319-14982-0) 

Tabares-Velasco, P. C., & Srebric, J. (2011). Experimental quantification of heat and mass 

transfer process through vegetated roof samples in a new laboratory setup. International 
Journal of Heat and Mass Transfer, 54(25), 5149-5162. 
doi:10.1016/j.ijheatmasstransfer.2011.08.034 

Teemusk, A., & Mander, Ü. (2007). Rainwater runoff quantity and quality performance from a 

greenroof: The effects of short-term events. Ecological Engineering, 30(3), 271-277. 
doi:10.1016/j.ecoleng.2007.01.009 

The Sylvester Broome Empowerment Village. (n.d.). Retrieved from https://sbev.org/. 

Tian, Y., & Jim, C. Y. (2011). Factors influencing the spatial pattern of sky gardens in the 

compact city of hong kong. Landscape and Urban Planning, 101(4), 299-309. 
doi:10.1016/j.landurbplan.2011.02.035 

Vandegrift, D. A. (2018). Expanding the Plant Palette for Green Roofs. Michigan State 

University.  

 

77 

Van Renterghem, T., & Botteldooren, D. (2008). Numerical evaluation of sound propagating 

over green roofs. Journal of Sound and Vibration, 317(3), 781-799. 
doi:10.1016/j.jsv.2008.03.025 

Van Renterghem, T., & Botteldooren, D. (2009). Reducing the acoustical façade load from road 

traffic with green roofs. Building and Environment, 44(5), 1081-1087. 
doi:10.1016/j.buildenv.2008.07.013 

Wang, M.  R. Q. Hyde, J.B. Burley, A. Allen, and T. Machemer.  2015.  Low-impact housing: 

River Rouge, Michigan.  Housing and Society: 1-14. 

Wang, Y. J. B. Burley, and S. Partin.  2013.  Case study: post-mining and lands-use planning and 

design: an overview. Journal of Mining Reclamation 2(1):114-135. 

Washburn, B. E., Swearingin, R. M., Pullins, C. K., & Rice, M. E. (2016). Composition and 

diversity of avian communities using a new urban habitat: Green roofs. Environmental 
Management, 57(6), 1230-1239. doi:10.1007/s00267-016-0687-1 

Weiler, S. K., & Scholz-Barth, K. (2009). Green roof systems: A guide to the planning, design, 

and construction of landscapes over structure. Hoboken, N.J: John Wiley & Sons. 

Whittinghill, L. J. (2012). Vegetable production using green roof technology and the potential 

impacts on the benefits provided by conventional green roofs. Michigan State University. 
Horticulture. 

Whittinghill, L. J., & Rowe, D. B. (2012). The role of green roof technology in urban 

agriculture. Renewable Agriculture and Food Systems, 27(4), 1-9. 
doi:10.1017/S174217051100038X 

Whittinghill, L. J., Rowe, D. B., Andresen, J. A., & Cregg, B. M. (2015). Comparison of 

stormwater runoff from sedum, native prairie, and vegetable producing green 
roofs. Urban Ecosystems, 18(1), 13-29. 
doi:http://dx.doi.org.proxy2.cl.msu.edu/10.1007/s11252-014-0386-8 

Whittinghill, L. J., Rowe, D. B., Schutzki, R., & Cregg, B. M. (2014). Quantifying carbon 

sequestration of various green roof and ornamental landscape systems. Landscape and 
Urban Planning, 123, 41-48. doi:10.1016/j.landurbplan.2013.11.015 

Wilsey, B. J., Teaschner, T. B., Daneshgar, P. P., Isbell, F. I., & Polley, H. W. (2009). 
Biodiversity maintenance mechanisms differ between native and novel exotic‐
dominated communities. Ecology Letters, 12(5), 432-442. doi:10.1111/j.1461-
0248.2009.01298.x 

Yachi, S., & Loreau, M. (1999). Biodiversity and ecosystem productivity in a fluctuating 
environment: The insurance hypothesis. Proceedings of the National Academy of 
Sciences of the United States of America, 96(4), 1463-1468. doi:10.1073/pnas.96.4.1463 

 

78