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Comparison of Five Green Roof Treatments in Flint Michigan with Freidman's Two-Way Analysis of Variance by Ranks

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Published in the Journal of Architecture and Construction: Planners and designers are interested in evaluating the metrics and statistical differences between design treatments. This study addresses categories of design treatments for a rooftop at The Sylvester Broome Empowerment 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 investigators. The Friedman’s Two-way Analysis of Variance by Ranks statistical test was applied to examine significant differences between the five treatments (p ≤ 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 with the exception that the intensive green roof treatment was predicted to be significantly better than self-design rooftop (p ≤ 0.05).
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Journal of Architecture and Construction
Volume 3, Issue 1, 2020, PP 23-36
ISSN 2637-5796
Journal of Architecture and Construction V3 ● I1 ● 2020 23
Comparison of Five Green Roof Treatments in Flint Michigan
with Freidman’s Two-Way Analysis of Variance by Ranks
Wing Chi VincyTam1, Dr. Jon Bryan Burley*2, Dr. D. Bradley Rowe3, Dr. Trisha Machemer4,
1Environmental Design, School of Planning, Design, and Construction, Michigan State University,
E. Lansing Michigan, USA
2FASLA, Associate Professor, Landscape Architecture, School of Planning, Design, and Construction,
Michigan State University, E. Lansing, Michigan, USA
3Professor, Department of Horticulture, Michigan State University, E. Lansing, Michigan, USA
4Associate Professor, Urban and Regional Planning and Landscape Architecture, School of Planning,
Design, and Construction, Michigan State University, E. Lansing, USA
*Corresponding Author: Dr. Jon Bryan Burley, FASLA, Associate Professor, Landscape Architecture,
School of Planning, Design, and Construction, Michigan State University, E. Lansing, Michigan, USA
48824; E-mail: burleyj@msu.edu
INTRODUCTION
Interest is green roofs and roof tops has been of
interest to planners, designers, concerned
citizens, government officials, and clients
(Osmundson 1999). Utilizing the rooftop is
often a method of creating an inner-city
alternative social space (Pomeroy, 2012), and
part of a response in response to climate change
(Peck, 2008). Whittinghill and Rowe (2012)
describe some of the benefits associated with
green roofs. 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. Prior studies have shown the
benefits of urban green space. First, people are
more likely to visit an urban green space than a
native green area (Peters, Elands and Buijs,
2010). Secondly, people have a better sense of
the neighborhood and better relationship with
their neighbors if there are green spaces nearby
(Kuo et al.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 (Kuo et al. 1998). Moreover, green
roofs can boost worker creativity and help
provide different perspectives for work (Loder,
2014). In addition, a close proximity to a 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 and
Reames 2019, Sutton 2015), promote urban
ecosystem (Sutton, 2015), reduce storm water
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 concerning the specific
evaluation of various rooftop designs approach
lacking. The study addresses the different
ABSTRACT
Planners and designers are interested in evaluating the metrics and statistical differences between design
treatments. This study addresses categories of design treatments for a rooftop at The Sylvester Broome
Empowerment 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 investigators. The Friedman’s Two-way Analysis of Variance by Ranks statistical test was
applied to examine significant differences between the five treatments (p ≤ 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 with the
exception that the intensive green roof treatment was predicted to be significantly better than self-design
rooftop (p ≤ 0.05).
Keywords: landscape architecture, environmental design, sustainability, green architecture
Comparison of Five Green Roof Treatments in Flint Michigan with Freidman’s Two-Way Analysis of
Variance by Ranks
24 Journal of Architecture and Construction V3 ●I1●2020
categories (convention rooftop, self-design
rooftop, extensive green roof, semi-intensive
green roof, and intensive green roof) of rooftop
design treatments to determine to statistically
access the differences between design
treatments.
Green spaces and green infrastructures play
important roles in social activities and
environment events. While they promote social
cohesion, it is also important to look into social
interaction and place attachment (Peters Elands
and Buijs 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 et al. 2017). 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 storm water runoff (Weiler and
Scholz-Barth, 2009). Researchers found that its
efficiency on lengthen the time of concentration,
increase infiltration, resulting in reduced
workloads for existing sewer systems and
decreasing risk of watershed safety by
decentralizing storm water, which green roofs
keep storm water on site to reuse and recycle it
(Weiler and Scholz-Barth, 2009). It was
determined vegetation roofs, especially an
extensive green roof, could hold reduce around
85% to 90% annual rainfall addressing on one
inch falling event (Weiler and Scholz-Barth,
2009). These prior studies support the positive
correlation between neighborhood connections
to green spaces/rooftops and the positive
attributes of vegetated roofs in the environment.
This proposed study focuses specifically on
comparing various rooftop design treatments.
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 and Kyung-Ho,
2018).With the large amounts of rooftop spaces
in a cities, and known environmental and social
benefits of green roofs, 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 and Reames 2019),
and to create and improve urban ecosystems
(Sutton,2015).
Green roofs are not a new phenomenon. They
have been constructed for thousands of years to
protect people from arduous weather (Peck,
2008). The history of green roofs is presented by
Peck (2008). Jim 2017).Subsequently, the era of
modern green roof began around
1960sGermany, 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
Comparison of Five Green Roof Treatments in Flint Michigan with Freidman’s Two-Way Analysis of
Variance by Ranks
Journal of Architecture and Construction V3 ● I1 ● 2020 25
less growing media (Peck, 2008), which
composed by relatively thin and light growing
media profile (Forschungsgesellschaft
Landschaftsentwicklung--Landschaftsbau
2018). Then, the system had been heavily
studied by German institutions and found
numbers of positive attributes in storm water
management, plant survivability, fire
retardation, and energy conservation (Peck,
2008).Green Roof Guidelines- Guidelines for
the Planning, Construction and Maintenance of
Green Roofs (Forschungsgesellschaft
LandschaftsentwicklungLandschaftsbau 2018),
is 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). Snodgrass and
McIntyre (2010) describe contemporary issues
and best practices to construct green roofs.
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 States have begun to follow the
European model concerning green roofs, to
encourage and reward practice green roofs in
their lands (Snodgrass and Snodgrass 2006). For
example, green roofs are installed on city halls
of Chicago and Toronto (Snodgrass and
Snodgrass 2006). Leadership in Energy and
Environmental Design (LEED), a green building
certification program developed by the U.S.
Green Building Council, had included green
roof as one of the sustainable practices to obtain
a higher reward (Snodgrass and Snodgrass
2006).Recent studies to address the benefits of
green roofs include: reduce storm water runoff
(Feitosa Wilkinson, 2016, Whittinghill Rowe
Andresen and Cregg 2015Krogulecki 2014,Cronk
2012, Berndtsson 2010, Weiler and Scholz-Barth,
2009, Bliss Neufeld Ries 2008, Getter Rowe
Andersen, 2007, Teemusk andMander 2007,
Mentens, Raes Hermy 2006), green roofs as tools
to alleviate global warming(Matlock and Rowe
2016, Whittinghill Rowe Schutzki and Cregg
2014, Rowe 2010, Getteret al. 2009 , Sailor,
2008), green roofs in noise reduction(Pittaluga,
2012, Van Renterghem and Botteldooren
2009,Van Renterghem and Botteldooren 2008,
Öhrström, 1991), wildlife habitat and biodiversity
enhancement (Partridge and Clark 2018,
Rumble Finch andGange2018; Washburn et al.
2016,Cook-Patton 2015, Eakin, Campa, Linden,
Roloff, Rowe, & Westphal, 2015,Sutton 2015,
Maclvor, and Lundholm 2011,Monsma, 2011,
Burghardt Tallamy Philips and Shropshire, 2010,
Lundholm et al.2010, Nagase and Dunnett
2010,Wilsey et al. 2009, Spehnet al. 2000,
Yachi and Loreau, 1999), and green roofs as
urban parks benefiting social connections
(Mesimakiet al. 2017, Kazmierczak, 2013,
Arnberger and Eder, 2012aPeters Elands and
Buijs 2010, Peck 2002, Kuo et al. 1998,).
While there has been much interest in the
properties of green roofs, very little effort has
been focused upon assessing statistically the
differences in various treatments from a multi-
variate perspective. This study investigates a set
of these treatments.
METHODOLOGY
The experimental design for this study is to
develop 5 design scenarios with different
rooftop design approaches using the rooftop on
an existing infrastructure at The Sylvester
Broome Empowerment Village, located in Flint,
Michigan. The site is located at 4119 Saginaw
St., Flint, MI. 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 Empowerment Village. This two-story
structure is nearly a hundred years old. It is open
to the public. The building has four rooftop
levels (Figure 1) of which the bottom three are
considered for a green roof. The low three
levels comprise0.84 acres, this undeveloped roof
is the first treatment, Currently the accessibility
to the rooftop is through some classroom
windows (Figure 2). A second treatment is a
client-based design with a teaching greenhouse
and plaza space on the lowest roof level with
access to the roof from the ground floor to the
greenhouse (Figures 3 and 4).
Comparison of Five Green Roof Treatments in Flint Michigan with Freidman’s Two-Way Analysis of
Variance by Ranks
26 Journal of Architecture and Construction V3 ●I1●2020
Figure1. Birdseye view of a conventional rooftop (treatment 1), the existing condition where the lower three
levels are further examined with green roof treatments. (Copyright © 2019 Wing Chi Vincy Tam all right
reserved used by permission).
Figure2. There is an accessibility challengeon accessing to the rooftop through some classroom windows.
(Copyright © 2019 Wing Chi Vincy Tam all right reserved used by permission).
Figure3. Birdseye view of a client-self-designed rooftop (treatment 2). (Copyright © 2019 Wing Chi Vincy Tam
all right reserved used by permission).
Comparison of Five Green Roof Treatments in Flint Michigan with Freidman’s Two-Way Analysis of
Variance by Ranks
Journal of Architecture and Construction V3 ● I1 ● 2020 27
Figure4. An outdoor teaching area for maximum 20 students. (Copyright © 2019 Wing Chi Vincy Tam all right
reserved used by permission).
Figure 5 presents an extensive green roof
treatment (treatment 3). Such treatments are
usually not open to public (Peck, 2008), so it
would not have the designer features in
treatment 2, but rather the treatment contains
planting with extensive greening. Goals of this
design approach are:
Reduce storm water 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
Figure5. Birdseye view of an extensive green roof (treatment 3). (Copyright © 2019 Wing Chi Vincy Tam all
right reserved used by permission).
Treatment 4 is a semi-intensive green roof
(Figure 5). This design approach attempts to
create a social space and encourage engagement
with the outside. The goals of this design
approach are:
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
Encourage social interaction by having
gathering space
Allowing group activity or outdoor
classroom by having plaza space
Family friendly by having children
entertaining facilities
Comparison of Five Green Roof Treatments in Flint Michigan with Freidman’s Two-Way Analysis of
Variance by Ranks
28 Journal of Architecture and Construction V3 ●I1●2020
This semi-intensive green roof is divided into
two parts: quiet area, and active area. The
reading area, as shown in figure 14, 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. Active
area includes interactive children entertaining
equipment a viewing bar, a multi-purpose area,
a flower bed, a dry garden, and a fire pit with
sofa
Figure5. Birdseye view of a semi-intensive green roof (treatment 4). (Copyright © 2019 Wing Chi Vincy Tam all
right reserved used by permission).
The fifth treatment is an extensive green roof
design (Figure 6). This design approach intends to
create 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 storm water 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.
Nature preservation, storm water 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 storm water management, clean energy,
and ecology.
Figure6. Top view of an intensive green roof. (Copyright © 2019 Wing Chi Vincy Tam all right reserved used by
permission).
Comparison of Five Green Roof Treatments in Flint Michigan with Freidman’s Two-Way Analysis of
Variance by Ranks
Journal of Architecture and Construction V3 ● I1 ● 2020 29
To evaluate the 5 treatments, a list of 36
variables ranging across 7 aspects, including
accessibility, plant, function, habitat value,
active maintenance, water efficiency, and
program are presented in Table 1.The variables
are assessed with Friedman‘s Two-Way
Analysis of Variance by Ranks to compare all
treatments across multiple variables. This
experimental design had been used on several
past landscape studies, including: Feng et al.
(2018), Feng et al. (2017),Lin et al. (2017),
Burley et al. (2016), et al. (2016),Wang et al.
(2015), Wang Burley and Partin (2013)
Hallsaxton and Burley, 2011; Hallsaxton and
Burley; 2010, Keefe and Burley 1998; Burley
1996, and Burley et al. (1988). Burley, Li, and
He (2020) published a technical report
concerning this methodology. The treatments
are assessed in the flowing steps
1. All treatments across blocks are going to
rank from smallest to largest by the author
by observation (Daniel, 1978). Treatments
would receive same ranking it the author
thinks they rank the same. For example, the
author found the best and the worst
treatments rank 1 and 5 accordingly, the
other three treatment would all rank 3;
2. Sum up within each treatment;
3. Apply 2= (12
+12
=1 )3+ 1 (1)
Where:
b equals blocks
K equals numbers of treatments
R equals sum for ranks in each treatment
4. Since there are ties, apply 12
=1 /
(21) to justify xr2 (2)
Where:
=3
= the number of observations tied for a given
rank in the th block.
5. Apply || (+1)
6 to determine
which scenarios is better than the other,
where,
and are the th and th treatment rank
totals
is the value from a table provided in Daniel‘s
book, corresponding to /(1)
(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 (Daniel, 1978).
Table1. The list of variables employed in assessing the treatments.
Aspect
Variable
Accessibility
Entrance
ADA accessible
Safety
Plant
Shading
Diversity of plants
Present of plant in number
Function
Reduce storm water 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
Comparison of Five Green Roof Treatments in Flint Michigan with Freidman’s Two-Way Analysis of
Variance by Ranks
30 Journal of Architecture and Construction V3 ●I1●2020
Habitat value
Provide habitat for wildlife
Promote biodiversity
Active maintenance
Minimal or no irrigation
Do not require chemical inputs, such as fertilizers, pesticides, or
herbicides
Water efficiency
No permanent irrigation
Program
Seating
Table
Gathering space
Viewpoint/ observation deck
Children playing equipment
Encourage social interaction
Improve public health
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
RESULTS
Table 2 presents the ranks of the five treatments;
while Table 3 presents the sum of the rankings
for each treatment. The results from equations
3,4, and 5 suggest that at least one treatment is
significantly different than at least one other
treatment (p <0.05). In the multiple compassion
test, the results suggest a difference between
treatments larger than 37.7001 are significant.
The self-design rooftops, extensive green roofs,
semi-intensive green roofs, and intensive green
roofs are statistically significantly better than
conventional rooftops (p <0.05). In Addition,
the intensive green roof is statistically
significantly better than self-design rooftopp
<0.05).
Table2. Variables in rankings
Aspect
No.
Variable
Conventional
Self-
Design
Extensive
Semi-
intensive
Intensive
Accessibility
1
Entrance
4.5
2
4.5
2
2
2
ADA accessible
4.5
3
4.5
1.5
1.5
3
Safety
3
3
3
3
3
Plant
4
Shading
4.5
4.5
3
2
1
5
Diversity of plants
5
4
1
3
2
6
Present of plant in
number
5
4
1.5
3
1.5
Function
7
Reduce storm water
runoff
4.5
4.5
1
3
2
8
Renewable energy
production
4.5
2
4.5
2
2
9
Conserve energy
4.5
4.5
1.5
3
1.5
10
Reduce heat island
effect
5
4
1.5
3
1.5
11
Promote water
infiltration
4.5
4.5
1
3
2
12
Reduce pollutant
loading
5
4
1.5
3
1.5
13
Rainwater recycle
5
1
3
3
3
14
Increase longevity
of roofing
membranes
4.5
4.5
2
2
2
15
Reduce carbon
footprint
5
4
1.5
3
1.5
16
Reduce noise
pollution
4.5
4.5
1.5
3
1.5
Comparison of Five Green Roof Treatments in Flint Michigan with Freidman’s Two-Way Analysis of
Variance by Ranks
Journal of Architecture and Construction V3 ● I1 ● 2020 31
17
Provide on-site
education
5
2
4
3
1
18
Provide on-site
research value
5
3
2
4
1
Habitat value
19
Provide habitat for
wildlife
5
4
1
3
2
20
Promote
biodiversity
5
4
1
3
2
Active
maintenance
21
Minimal or no
irrigation
2
2
2
4
5
22
Do not require
chemical inputs,
such as fertilizers,
pesticides, or
herbicides
2
2
2
4
5
Water efficiency
23
No permanent
irrigation
2
2
2
4.5
4.5
Program
24
Seating
4.5
3
4.5
1.5
1.5
25
Table
4.5
1
4.5
2
3
26
Gathering space
4.5
3
4.5
1.5
1.5
27
Viewpoint/
observation deck
4.5
3
4.5
2
1
28
Children playing
equipment
4
2
4
1
4
29
Encourage social
interaction
5
3
4
1.5
1.5
30
Improve public
health
5
4
2
2
2
31
Encourage
volunteerism
5
4
3
1.5
1.5
32
Promote
neighborliness and
social inclusion
5
3
4
1.5
1.5
33
Provide views for
people within the
building
5
4
2
2
2
34
Encourage for
outdoor activities
5
3
4
1.5
1.5
35
Improve
surrounding human
mental health
5
4
2
2
2
36
Being influential
and encouraging for
having green
infrastructure
5
4
2
2
2
Table3. Sum in ranking of each scenario
Conventional
Self-design
Extensive
Semi-intensive
Intensive
Sums
161.5
118
95.5
90
75
2= ( 12
36×5×5+1×161.52+1182+95.52+
902+752
3
×
36
×
5+1=50.35
(3)
Since there are ties occurs, text statistic has been
justified by dividing 2 , by
12
=1 /(21)
where,
=3
= the number of observations tied for a
given rank in the th block.
There are 27 two-way ties, 12 three-way ties,
and one five-way ties, therefore,
1232×27+333×12+535×1
36×5×521= 0.868056 (4)
Then, we calculate adjusted 2 value by,
2=50.35 ÷ 0.868056 =58.003 (5)
Comparison of Five Green Roof Treatments in Flint Michigan with Freidman’s Two-Way Analysis of
Variance by Ranks
32 Journal of Architecture and Construction V3 ●I1●2020
Then, the 2adjusted for ties is 58.0032.
A numerical value for assessing the null
hypothesis is needed and is determined by using
a table that contain chi-square value of 2 (1−)
with k-1 degree of freedom, provided by Daniel
(Daniel, 1978). If 2is greater or equal than the
determined value, the null hypothesis will be
rejected (Daniel, 1978). In this study, the
experiment-wise error rate of α equal to 0.05
and k equal to 5. The value of 20.99 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);
 +1
6 (6)
Where,
and are the th and th treatment rank
totals
is the value from a table provided in
Daniel‘s book, corresponding to /( 1)
(Daniel, 1978).
In this study, experiment wise error rate of
equal to 0.05, which
=÷(1)
= 0.05 ÷ 551= 0.0025 -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,
2.8136×5×(5+1)
6=37.7001 (7)
Table4. Design Scenarios Difference
Combinations of Design Scenarios
Difference
Conventional & Self-design
43.5
Conventional & Extensive
66
Conventional & Semi-intensive
71.5
Convention & Intensive
86.5
Self-design & extensive
22.5
Self-design & Semi-intensive
28
Self-design & Intensive
43
Extensive & Semi-intensive
5.5
Extensive & Intensive
20.5
Semi-intensive & Intensive
15
DISCUSSION/CONCLUSION
Based upon the sum of the rankings, intensive
green roof scenario performs the best, then the
semi-intensive green roof, the extensive green
roof, and the self-design rooftop. This is the
typical approach when designers often evaluate
projects; yet the statistical approach reveal
different insights. As might be suspected, the
conventional rooftop scenario ranked the least;
however statistically some of the designs are not
significantly different. The result of Friedman‘s
Two-Way Analysis of Variance by Ranks 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 roof top scenario. In contrast the
test did not confirm that the self-design roof top,
the extensive green roofs, the semi-intensive
green roofs, and the intensive green roofs are
different on their performance. They had not
shown remarkable statistical difference. Under
this circumstance, one could still confirm
intensive green roofs are statistically better than
self-design roof tops. This result is slightly
differed from might be expected. Designers
often observe much in the differences between
various design treatments and may interpret the
treatments with more separation and distinction
between each other; yet statistically, they are
somewhat equal. Each treatment offers
something different. Statistically there is no
best design; but statistically, there is a least
preferred design. From the better performing
green roof treatments there is not enough
separation to identify statistically the best
treatment.
This study has a limited sampling size; it is just
one green roof study, with five treatments. Each
rooftop design approach has only one design
provided for comparison. These designs are
quite subjective. Even though there are 36
variables selected from 7 aspects, which where
Comparison of Five Green Roof Treatments in Flint Michigan with Freidman’s Two-Way Analysis of
Variance by Ranks
Journal of Architecture and Construction V3 ● I1 ● 2020 33
chosen by the study team, and it may be a
personal perspective with bias, not being as
comprehensive or as thoughtful as it could be
with the input of other scholars. In addition, the
error rate is set at 5%, which if it is set at a
different rate, the results might be different.
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.
For building owners, urban planners/designers,
developers, and government officials, it is
beneficial to appreciate underused spaces, such
as rooftop environments. Rooftops can be
retrofitted, re-designed, and adjusted. The
variables presented in Table 1, can provide an
initial program list to assess design alternatives.
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 poorest
environments in these five scenarios. Intensive
green roofs are better than self-design rooftops.
However, there are insufficient statistically
results to confirm if self-design rooftops,
extensive green roofs, semi-intensive green
roofs, and extensive green roofs are different
from each other.
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Citation: Wing Chi VincyTam et.al, Comparison of Five Green Roof Treatments in Flint Michigan with
Freidman’s Two-Way Analysis of Variance by Ranks”, Journal of Architecture and Construction, 2020, 3(1),
pp. 23-36.
Copyright: © 2020 Wing Chi VincyTam et.al, This is an open-access article distributed under the terms of
the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction
in any medium, provided the original author and source are credited.
... The Friedman methodology was applied to study green roof design alternatives [41]. The location of the research is in the Sylvester Brooms Empowerment Village in Flint, Michigan. ...
... It is an open house, now with a history of nearly 100 years. The building has a total of four roofs [41]. The five designs mainly include conventional, self-design, extensive, semi-intensive, and intensive. ...
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Multiple studies have quantified the ecosystem services of green infrastructure for both public and environmental health. This study evaluates and compares accessibility of low-income and marginalized communities to the cooling benefits of green roofs in Detroit, MI in the context of the urban heat island effect and the City’s current heat relief system of dedicated cooling centers. Regions of the city were evaluated for their vulnerability to the urban heat island effect, which can be alleviated by green roofs due to raised surface albedo and evaporative cooling. Spatial data regarding land surface temperature, income, and race were used to locate where green roof ecosystem services are most needed and how communities within these regions are categorized demographically. Existing green roof efforts were mapped to determine whether siting has occurred where ecosystem services are most needed and how socioeconomic factors might be related to the locations of urban heat island-mitigating green infrastructure. Analysis of the spatial data in this study revealed most low-income residents are within walking distance from cooling centers, but not included in the Detroit Future City Urban Green Neighborhoods, while green roofs specifically were in the affluent part of Detroit's urban core, where the population is predominantly white. The methodology employed here can be applied to evaluate urban greening plans in other cities. More here https://urbanenergyjusticelab.com/research/publications/
Article
Read for free until May the 13th 2018: https://authors.elsevier.com/a/1Wmmq3JGmQz8ER Green roofs provide a range of ecosystem services, from stormwater retention to thermal insulation. They can also provide habitat for biodiversity, remediating land lost in development. However, few extensive green roofs are designed with this benefit in mind and, as such, biodiversity often does not reach its full potential. In particular, the soil ecology of green roofs is poorly understood, despite soil microorganisms having a large impact on nutrient cycling and thus plant diversity. In particular, whilst there are studies describing the soil microarthropods and microbial communities present on green roofs, little is known about how these species arrive there. This paper aims to determine how soil microarthropods and microbes colonise green roofs and which species survive post-construction, to inform green roof technosol design and to understand if remediation of impoverished green roof soils is possible. To do this, we conducted a preliminary study by analysing green roof construction materials (substrates and Sedum plugs) for microarthropods, bacteria and fungi before constructing a new green roof. We then monitored survival and independent colonisation over eleven months. Whilst green roof substrates were a poor source of colonisation, Sedum plugs showed potential as a vehicle for colonisation by microbes and, especially, by soil microarthropods. However, the majority of the species present within Sedum plugs were not adapted to the harsh conditions of the green roof, resulting in high mortality. Two ubiquitist species, the Collembola species complex Parisotoma notabilis and a mite of the family Scutoverticidae survived in high abundance after the eleven month sample period, and the functional role of these species on a green roof should be investigated. Some species colonised independently during the study, highlighting that microarthropods and microbes in green roofs consist of a mix of anthropogenic assemblages and natural communities. Mycorrhizal fungi were extremely successful, independently colonising almost all Sedum plants by the end of the study. However, the absence of arbuscules suggests that this colonisation may not have a benefit to plant growth in this instance. Demonstrating that the succession of soil organisms is influenced by the communities present in construction materials has implications for substrate design, demonstrating that soil organisms may be inoculated onto green roofs to provide functioning technosols. In addition, the independent colonisation of mycorrhiza in this study stimulates discussion about the role of commercially applied mycorrhizal fungi in green roof construction.
Book
This book provides an up-to-date coverage of green (vegetated) roof research, design, and management from an ecosystem perspective. It reviews, explains, and poses questions about monitoring, substrate, living components, and the abiotic, biotic, and cultural aspects connecting green roofs to the fields of community, landscape, and urban ecology. The work contains examples of green roof venues that demonstrate the focus, level of detail, and techniques needed to understand the structure, function, and impact of these novel ecosystems. Representing a seminal compilation of research and technical knowledge about green roof ecology and how functional attributes can be enhanced, it delves to explore the next wave of evolution in green technology and defines potential paths for technological advancement and research.
Article
The origin of green roof could be interpreted as old wine in new bottle and traced to antiquity. Archaeological and historical records and contemporary geographical-ecological assessments provide ample evidence to interpret the birth and progressive evolution of the cultural heritage. Studies in different places find early shelters using different natural materials. Humans living in harsh climates need particularly effective weather-proof enclosures to survive. The Arctic region with natural resource deprivation furnished the cradle for green roof initiation and refinement. The versatile and rather ubiquitous earth, widely used since Neolithic times to build dwellings, offered learning opportunities regarding properties and applications. The primitive flimsy conical shelters were sealed by earth daubing, permitting nature’s seed rain to establish a vegetative cover to form the spontaneous meadow roof as green roof precursor. Subsequent progression to the house form, separating walls from roofs, required innovations to enhance weather-proofing and durability. Cutting from natural meadows mat-like sods with soil bound by dense fibrous roots into portable strips for roofing was better than plastering. Tantamount to transferring the sod ecosystem en masse from nature to roof, it permitted instant vegetation establishment and bypassed the erosion-vulnerable bare-earth stage. The invention denoted birth of the intentional sod roof. The materials and construction methods of the traditional multiple-layered sod roof are explained with the help of preserved technology. Employing research findings, eighteen hypothesized ecosystem services of sod roofs are identified and explained vis-à-vis modern counterparts.