Material quantities in building structures
and their environmental impact
by
Catherine De Wolf
B.Sc., M.Sc. in Civil Architectural Engineering
Vrije Universiteit Brussel and Université Libre de Bruxelles, 2012
Submitted to the Department of Architecture
in Partial Fulfillment of the Requirements for the Degree of
Master of Science in Building Technology
at the
Massachusetts Institute of Technology
June 2014
© 2014 Massachusetts Institute of Technology. All rights reserved.
Signature of Author:
Certified by:
Accepted by:
Department of Architecture
May 9, 2014
John A. Ochsendorf
Professor of Architecture and Civil and Environmental Engineering
Thesis Supervisor
Takehiko Nagakura
Associate Professor of Design and Computation
Chair of the Department Committee on Graduate Students
John E. Fernández
Professor of Architecture, Building Technology, and Engineering Systems
Head, Building Technology Program
Co-director, International Design Center, MIT
Thesis Reader
Frances Yang
Structures and Sustainability Specialist at Arup
Thesis Reader
“It is […] important to remember that unlike operational carbon emissions the embodied
carbon cannot be reversed”
Craig Jones, Circular Ecology
Material quantities in building structures and their environmental impact
by Catherine De Wolf
Submitted to the Department of Architecture in Partial Fulfillment of the Requirements for the Degree
of Master of Science in Building Technology on May 9, 2014.
Thesis Supervisor: John Ochsendorf
Title Supervisor: Professor of Architecture and Civil and Environmental Engineering
Abstract
Improved operational energy efficiency has increased the percentage of embodied energy in the
total life cycle of building structures. Despite a growing interest in this field, practitioners lack a
comprehensive survey of material quantities and embodied carbon in building structures. This
thesis answers the key question: “What is the embodied carbon of different structures?”
Three primary techniques are used: (1) a review of existing tools and literature; (2) a
collaboration with a worldwide network of design firms through conversations with experts and
(3) the creation of a growing interactive database containing the material efficiency and
embodied carbon of thousands of buildings.
The first contribution of this thesis is to define challenges and opportunities in estimating
greenhouse gas emissions of structures, expressed in carbon dioxide equivalent (CO2e). Two
key variables are analyzed: material quantities (kgmaterial/m2 or kgm/m2) and Embodied Carbon
Coefficients (ECC, expressed in kgCO2e/kgm). The main challenges consist of creating incentives
for sharing data, identifying accurate ECCs and resolving transparency while protecting
intellectual ownership. The main opportunities include using Building Information Models to
generate data, proposing regional ECCs and outlining a unified carbon assessment method.
The second contribution is the development of an interactive online tool, called deQo (database
of embodied Quantity outputs), to provide reliable data about the Global Warming Potential of
buildings (GWP, measured in kgCO2e/m2 and obtained by multiplying the two key variables).
Given the need for a long-term initiative, a framework is offered to create an interactive,
growing online database allowing architects, engineers and researchers to input and compare
their projects.
The third contribution is the survey of 200 existing buildings obtained through deQo. Two
general conclusions result from this survey of building structures: material quantities typically
range from 500 to 1500 kg/m2 and the GWP typically ranges between 200 and 700 kgCO2e/m2.
Conclusions from this survey include that healthcare buildings use more materials whereas
office buildings have a lower impact. Additionally, specific case studies on stadia, bridges and
skyscrapers demonstrate that the design approach can have a significant impact on the
embodied carbon of building structures.
Ultimately, this thesis enables benchmarking of the environmental impact of building
structures.
Key words: Embodied Carbon/Energy; Life Cycle Analysis; Database; Materials; Structures
Acknowledgments
First, I am very grateful to my advisor, Prof. John Ochsendorf for his perception, guidance and
enthusiasm during the development of this research and his support and friendship during my
Master studies at MIT. I am also thankful to my readers, Prof. John Fernandez and Frances
Yang (Arup), for their constructive suggestions during the development of this thesis. Their
willingness to give their time so generously has been very much appreciated.
My special gratitude goes to Frances Yang, Andrea Charlson and Kristian Steele (Arup) for
supervising my visiting research at Arup and offering me the opportunities to collaborate with
practitioners worldwide on the topic of this thesis. Also, I am especially thankful to Wolfgang
Werner (Thornton Tomasetti) whose collaboration was essential for the development of the
database. The thoughtful contributions of these talented engineers brought new perspectives to
my thesis.
For their help in the work towards this thesis, I am thankful in particular to the following
researchers and friends: Ornella Iuorio for her study of the literature of embodied carbon
coefficients; Mayce El Mostafa and Virginie Arnaud for their help in calculating the embodied
carbon of stadia and tall office buildings; Julia Hogroian for her work on the material quantities
in stadia; Eleanor Pence for her help coding the interactive database; Caitlin Mueller for her
valuable feedback and finally the Fall 2013 students in the “Building structural systems II” class
for their projects on skyscrapers.
Furthermore, I am very thankful to Kathleen Ross who always supported me and helped me
out with administrative tasks and travels.
My highest appreciation goes to John Ochsendorf and Frances Yang for giving me the chance
to discuss my work with world-class experts in structural engineering. The conversations with
leading experts were inspirational and brought more depth to this thesis. I am honored to have
met Edward Allen, Jörg Schlaich, William Baker, David Shook, Jim D’Aloisio, Kate Simonen,
Patrick McCafferty, Craig Jones, Roderick Bates, Alice Moncaster, Julian Allwood, the
SEAONC and SEI committees and many more.
I would like to thank the Arup and Thornton Tomasetti for their assistance with the collection
of my data.
This research was sponsored by the Belgian American Education Foundation, the KuMIT
project, the Harold Horowitz Award and Arup.
Finally, I thank my family and friends for always being there for me.
Contents
ABSTRACT
5
ACKNOWLEDGMENTS
6
CONTENTS
7
1.
9
INTRODUCTION
1.1.
1.2.
1.3.
1.4.
2.
Motivation
Definitions of concepts
Problem statement
Organization of thesis
STATE OF THE ART
2.1.
2.2.
2.3.
2.4.
3.
16
17
19
20
METHODOLOGY
23
Personal conversations with practitioners
Assessment of existing literature and tools
A new interactive database
Summary
CHALLENGES AND OPPORTUNITIES IN OBTAINING EMBODIED QUANTITIES
4.1.
4.2.
4.3.
4.3.1.
4.3.2.
4.4.
4.5.
5.
15
Material quantities
Embodied Carbon Coefficients (ECCs)
Examples of existing implementations
Summary
3.1.
3.2.
3.3.
3.4.
4.
9
10
12
13
Introduction
Getting material quantities
Accurate ECCs
Literature on ECCs
Applied ranges for ECCs
Implementation of a unified method
Summary
27
27
27
28
28
30
32
34
FRAMEWORK FOR A DATABASE
5.1.
5.2.
5.2.1.
5.2.2.
5.2.3.
5.2.4.
5.3.
5.4.
5.5.
5.5.1.
5.5.2.
5.6.
23
23
24
25
35
Introduction
Database specifications
General information
Structural information
Default versus entered ECCs
Contribution of a new database
Relational database
Web-based interface
Collaboration with industry
Revit plug-in developers
Industry and research database
Summary
35
36
36
39
42
42
44
44
46
46
47
48
7
6.
SURVEY OF EXISTING BUILDINGS
6.1.
6.2.
6.3.
6.3.1.
6.3.2.
6.3.3.
6.3.4.
6.4.
6.4.1.
6.4.2.
6.4.3.
6.4.4.
6.4.5.
6.5.
6.5.1.
6.5.2.
6.5.3.
6.5.4.
6.6.
7.
7.1.
7.2.
7.3.
49
Introduction
Existing building structures from the industry
Case Study I: Analysis of stadia
Description
Material quantities in stadia
Embodied carbon of stadia
Discussion of results
Case study II: Lessons from historic bridges
Description
Material quantities in historic bridges
Embodied carbon of historic bridges
Comparison Roman arch and Inca suspension bridge
Comparison with recent bridge designs
Case study III: Comparing tall buildings
Description
Material quantities in tall buildings
Embodied carbon of tall buildings
Discussion of the results
Summary
CONCLUSIONS
49
49
54
54
55
56
57
57
58
59
60
61
62
63
63
63
64
66
66
69
Discussion of results
Summary of contributions
Future research
69
71
72
BIBLIOGRAPHY AND REFERENCES
75
Part 1: General bibliography and references
Part 2: Stadia references
Part 3: Historic bridges references
Part 4: Tall building references
75
80
81
82
APPENDICES
85
Appendix A: Nomenclature
A.1. List of acronyms
A.2. Lexicon
Appendix B: Tables
B.1. Ten first projects in deQo
B.2. Analysis of stadia
B.3. Analysis of historic bridges
B.4. Analysis of tall buildings
85
85
86
88
88
89
90
92
8
1. Introduction
1.1. Motivation
Life cycle energy in buildings includes operational energy for heating, cooling, hot water,
ventilation, lighting on one hand and embodied energy for material supply, production,
transport, construction and disassembly on the other. The terms “embodied carbon” and
“Global Warming Potential” (GWP) refer to the equivalent in carbon dioxide of all lifecycle
greenhouse gas emissions and is expressed in weight of carbon dioxide equivalents (CO2e).
Many leading structural engineering and design firms are currently developing in-house
embodied carbon estimators to answer the following question: what is the embodied carbon for
different structures?
Craig Jones, co-founder of the Inventory of Carbon & Energy (Hammond & Jones, 2010),
highlights the importance “to remember that unlike operational carbon emissions the embodied
carbon cannot be reversed” (Circular Ecology, 2014). The key question of this thesis examines
embodied carbon for several reasons.
First, carbon reduction is needed now. As mentioned in the latest Intergovernmental Panel on
Climate Change (IPCC) report, substantial carbon reductions need to occur in the near future
in order to avoid extreme climate disruptions (IPCC, 2014). Embodied carbon savings in
building structures are an obvious opportunity to reduce the impacts in the short term. Next,
some buildings have a short lifetime, which results in a high percentage of embodied carbon in
the total environmental impact of a building. This is true for a diverse range of buildings, even
those most prized and lauded as architectural exemplars at the time of their construction. For
example, the Folk Art museum (Figure 1.1), built in 2001, will be torn down for an extension of
the MOMA after a lifespan of less than 15 years (New York Times, 2014).
Figure 1.1: Folk Art Museum and MOMA, New York City (New York Times, 2014)
Moreover, with the effective reduction of the operational carbon of buildings in future decades,
embodied carbon will become a more significant percentage of greenhouse gas emissions
caused by buildings. Furthermore, research in this field will help structural engineers and
architects to understand how to lower embodied carbon and fill this gap in literature (Dixit et
al., 2012). Finally, rating schemes such as LEED (USGBC, 2013) have begun including
embodied carbon in their credit system, though without defining baselines for benchmarking
(Yang, 2014).
9
It should be noted that this thesis is limited to structural material quantities. Cladding and other
non-structural materials are not considered for two reasons. First, structure accounts for the
greatest weight in buildings and contributes to about half of the total carbon emissions due to
materials (Webster et al., 2012). With a breakdown of embodied carbon for the different
elements in offices, hospitals and schools, Kaethner and Burridge (2012) demonstrate that the
super- and substructure together represent more than 50% of the total embodied carbon
emissions of buildings (Figure 1.2). Second, this helps to focus attention on a well-defined
quantity while still having a significant impact.
8% Finishes
4% Internal planning
4% Roof
13% External cladding
16% Construction
13% Substructure
42% Superstructure
71% Structure & Construction
29% Others
Figure 1.2: Average breakdown in building elements of embodied carbon in offices, hospitals and
schools, after (Kaethner and Burridge, 2012)
1.2. Definitions of concepts
Several key concepts are used regularly throughout this thesis. Since misunderstandings exist
around concepts such as “carbon”, “Embodied Carbon Coefficients” or “carbon equivalent”,
this section defines how they are interpreted in this work. Precise definitions can be found in
the nomenclature in appendix A.
The value for “embodied energy” is not the same as the value for “embodied carbon”. The
same amount of embodied energy can emit different intensities of greenhouse gases (GHG)
depending on the fuel used and the carbon emitted or absorbed by the materials processed. For
example, emissions occur in the chemical processing of cement, whereas carbon is sequestered
in wood. It is useful to account in terms of embodied carbon instead of embodied energy, as
CO2 contributes considerably to climate change. Also, measuring specifically in carbon helps to
compare the embodied with operational emissions. Carbon accounting therefore facilitates the
assessment of the whole life cycle impacts of buildings (Kaethner and Burridge, 2012).
The total embodied carbon of a building is often referred to as “Global Warming Potential”
(GWP). The GWP is expressed in kilograms of carbon dioxide equivalent per functional unit.
The carbon dioxide equivalent is noted “CO2e” and represents the equivalent in carbon dioxide
of the GHGs produced during the manufacturing and transportation of materials. The other
GHGs such as CH4, N2O, SF6, PFC and HFC can hence be converted to CO2 using conversion
factors in order to obtain a common unit for the environmental impact (IPCC, 2014), i.e. the
“carbon dioxide equivalent”.
10
A “functional unit” is a specified metric used to normalize the carbon footprint of buildings, in
order to compare ‘apples to apples’. For example, the useable floor area can be the functional
unit. The GWP is then measured in kgCO2e/m2. The number of occupants is another example of
a functional unit. The GWP is then measured in kgCO2e/occupant.
Two key variables are analyzed in this thesis: Structural Material Quantities (SMQ), expressed in
kg of material (kgmaterial or kgm) per functional unit (often m2), and Embodied Carbon
Coefficients (ECC), expressed in kg of CO2e (kgCO2e) per kg of material (kgm). Presently, there is
no clear standard for accurate ECC values and information on SMQ values for buildings is
scarce.
As illustrated in equation [1], the GWP (kgCO2e/m2) is obtained by multiplying the two key
variables: SMQ (kgm/m2) and ECC (kgCO2e/kgm), together.
GWP (kgCO2e/m2) = SMQ (kgm/m2) ! ECC (kgCO2e/kgm)
[1]
Figure 1.3 illustrates how the GWP of different materials can be added up for building projects
to define the embodied carbon.
Embodied Carbon or GWP
(kgCO2e/m2)
7"
Reinforcement
6"
Steel
5"
Concrete
4"
3"
2"
1"
Project F
Project E
Project D
Project C
Project B
Project A
0"
Figure 1.3: GWP divided into the composing materials of different building projects
In this thesis, “structure” refers to the structure of a building and implies the loadbearing part
of something built or constructed. When talking about a pattern, relation or organization, other
words, such as “framework”, are used.
11
1.3. Problem statement
This thesis aims to build literacy on the embodied carbon for different structures. Data is
collected in collaboration with a network of worldwide design firms. The research is conducted
in three primary streams:
1) Collect data from recently published literature on Life Cycle Assessments (LCA);
2) Collaborate with design and construction firms to build a useful database of their
projects;
3) Create an interactive growing database where participants can input projects to
include thousands of buildings worldwide.
Two necessary variables are introduced in section 1.2: SMQ (kgm/m2 ) conveys the amounts of
steel, concrete, wood, etc. and ECC (kgCO2e/kgm) expresses the carbon equivalent of these
materials. The former is sought from industry participants; the latter is computed with existing
LCA software and current literature. Developing confidence in the numbers for embodied
carbon of structures (GWP in kgCO2e/m2) requires a large amount of data. No framework or
reliable database exists yet assessing material efficiency and embodied carbon in structures. This
lack of information results in buildings using materials in a wasteful way with impunity.
However, to be able to rationally compare and assess projects, a wider set of input parameters
is needed beyond the two key variables. The first set of input parameters consists of general
project information such as the building location, typology and geometry. The second are
structural parameters such as material choices and quantities, structural systems, soil types and
loads. Outputs include ranges of GWP, illustrated in graphics comparing building projects or
categories (Figure 1.3). An intermediate result is better information on material efficiency.
This thesis has three main contributions. The first contribution is to define the challenges and
opportunities in obtaining the material quantities and estimating the embodied carbon of
structural materials. To obtain the key variables SMQ and ECC, many challenges occur in
existing tools and literature. However, by listing the challenges and offering possible solutions
and opportunities, this thesis clarifies which paths can be followed to reduce the embodied
carbon of building structures.
The second contribution of this thesis is the development of an interactive online tool to give
confidence in the GWP measurement of buildings. A framework is presented for a relational
database collecting both the embodied carbon of buildings, and their material quantities. The
idea is to create a worldwide online tool, which allows architects, engineers and researchers to
input their projects and compare it with others.
The third contribution is the survey of two hundred actual buildings taken from the database.
Additionally, a new unified embodied carbon assessment method is applied to specific case
studies, such as stadia, historic bridges and recent skyscrapers in order to critically analyze and
refine the process. Ultimately, this will enable benchmarking and comparisons of the
environmental impact of a wide range of projects.
12
1.4. Organization of thesis
The following chapter (Chapter 2) discusses the state of the art on material quantities, ECC
values and implementing the calculation of the GWP. Chapter 3 elaborates on the
methodology.
The Chapters 4 to 6 expand on the contributions and results of this thesis. First, Chapter 4
reviews the challenges and opportunities in obtaining material quantities and ECCs. Chapter 5
then develops a framework for an interactive database collecting data on existing building
projects. Finally, Chapter 6 surveys 200 actual buildings from industry and applies the defined
approach for estimating the embodied carbon of structures to three case studies: sport stadia,
historic bridges and tall office buildings.
Finally, Chapter 7 discusses the key contributions, takes conclusions and proposes paths for
future research.
13
14
2. State of the art
This chapter summarizes the state of the art on material quantities, ECCs and environmental
impact analysis tools. Gaps and challenges are highlighted in this chapter and will be addressed
in the following chapters. Chapter 2 is divided into three parts. The first two parts discuss the
literature on the two key variables: SMQ and ECC. The last part addresses existing tools to
implement the calculation of the GWP of buildings.
Figure 2.1 shows the wide range of results for embodied energy and carbon, illustrating the
need for an agreement on an accurate way to estimate the embodied energy and embodied
carbon of buildings. Cole and Kernan (1996) estimated the embodied energy is 4 to 9% of a 50
year life-cycle energy, whereas the Athena Institute of Sustainable Materials (2009) mentions 9
to 12% of a 60 year lifespan and Webster et al (2012) talk about 2 to 22% over 50 year. For the
embodied carbon, the numbers vary widely as well, from 11 to 80% depending on the source
(Simpson et al., 2010).
Cole & Kernan
1996
EE = 4-9%
of 50 yr life-cycle energy
Eaton & Amato
1998
Build Carbon Neutral
2007
EC = 37-43%
of 60 yr life-cycle carbon emissions
EC = 13-18%
of 60 yr life-cycle carbon emissions
Simon Group et al
2008
Athena
2009
EC = up to 80 %
of life-cycle carbon emissions
EE = 9-12%
of 60 yr life-cycle energy
Arup (Simpson et al)
2010
Webster et al
2012
EC = 11-50%
of 60 yr life-cycle carbon emissions
EE = 2-22%
of 50 yr life-cycle energy
Figure 2.1: Wide-ranging results for embodied carbon, after (Simpson et al., 2010)
15
2.1. Material quantities
In the 1890s, a tower design competition in London asked for material weight as one of the
criteria (Figure 2.2) and in the 1920s, Buckminster Fuller asked: “how much does your house
weigh?” (Lynde, 1890; Braham and Hale, 2013). However, material efficiency does not always
drive building design today. Indeed, as no framework yet exists to assess the embodied carbon
of a structure, many buildings may be consuming materials in a wasteful way with impunity.
Figure
Table 3. Unit direct construction costs for tall composite building structures
Unit Cost per Material
Unit Cost for Structural Members
Project
Material
*Won/m2
%
Str. Mem.
*Won/m2
%
Concrete
28,497
15.7
Core + Link
56,223
30.9
Reinf.
32,748
18.0
Column
37,023
20.4
Str. Steel
73,533
40.4
Beam/Girder
39,078
21.5
B(66F)
Deck
15,102
8.3
Outrigger
7,953
4.4
Precast
4,093
2.3
Slab
32,985
18.1
Formwork
27,866
15.3
Foundation
8,557
4.7
Total
181,839
100
Total
181,839
100
Concrete
28,189
15.9.
Core + Link
41,958
23.7
Reinf.
20,361
11.5
Column
34,997
19.3
Str. Steel
88,953
50.3
Beam/Girder
57,351
32.4
E(55F)
Deck
14,667
8.3
Outrigger
5,653
3.2
Formwork
24,740 competition
14.0
Slab
34,048
19.2
2.2: Particulars
of the design
for the London
tower
Foundation
2,905
1.6
Total
176,911
100
Total
176,911
100
Concrete
34,674
19.9
Core + Link
48,995
28.2
Reinf.
41,284
23.7
Column
36,476
21.0
Str. Steel
53,785
30.9
Beam/Girder
33,871
19.5
G(69F)
Deck
11,759
6.8
Belt Wall
13,973
8.0
Formwork
32,360
18.6
Slab
31,941
18.4
Foundation
8,605
4.9
Total
173,862
100
Total
173,862
100
* $1 # 1,200 Won
Unit Cost
Comparison
104.6
101.8
in 1890 (Lynde, 1890).
Recently, other studies have attempted to map material efficiency of tall buildings considering
the number of floors and structural systems (Cho et al., 2004; Elnimeiri and Gupta, 2009; Ali
100.0firms such as Arup
and Moon, 2007). Data on material quantities from leading structural design
and Thornton Tomasetti have been collected in the material quantity and the database of
embodied Quantity outputs (deQo), developed at the Structural Design Lab within the Building
Technology program at MIT (De Wolf and Ochsendorf, 2014; deQo, 2014).
In order to compare the construction costs of three
176,911 won/m2, respectively, giving differences of 4.6
buildings, the structural quantities of Table 2 are
and 1.8 %. The tallest G costs
3 even less2 than the fourteen
Cho ettransferred
al. (2004)
express
unit costs
material
quantities
volume
per
m ) more
for quantities
concrete and in
to direct
construction
for building
storyin
smaller
E. The G(m
utilized
relatively
2
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on therebar
price asand
of June,
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Formwork
of concrete and2.3,
reinforcement
with smaller
mass (kg
per m
) for
steel.
Figure 2.3Figure
they compare
thestructural
structural steel
cost and different costs for different concrete strengths
steel amount, which appears to be the reason for the cost
quantities
for
various
story
heights.
As
Elnimeiri
and
Gupta
(2009)
express
it,
“good
are also taken into account in the process. Table 3 shows
saving. This fact shows the importance of selected structural
that
the
tallest
building,
G,
has
the
smallest
cost
of
materials for the economical
construction of
engineering revolves
around achieving efficiencystructural
and minimization
of material”.
173,862 won/m2, while B and E have 181,839 and
tall buildings.
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Structural
Fig. 1. Unit
structural 2.3:
steel quantities
steel quantities by number of stories (Cho et al., 2004)
Formwork costs occupy 14 to 18.6 % among total
structural expenses; horizontal structural members,
beams and slab, occupy 29.6, 51.6 and 37.9 % for B,
E and G, respectively. The high value of E occurs due
16
CTBUH 2004 October 10~13, Seoul, Korea
665
Extra cost for
lateral resistance
Columns and
bracing walls
Floor framing
Average weight of steel (kg/m2)
Structure cost
per unit floor area
Fazlur Khan (1980) introduced the notion of “premium for height” (Figure 2.4). With a
growing number of stories, the weight of steel in kg/m2 is not only increasing due to columns
and bracing walls, but also due to the increasing lateral wind loads. Ali and Moon (2007) and
Rizk (2010) give weights of steel in pounds per square feet (psf) versus the number of floors for
steel framed tall buildings. The Council on Tall Buildings and Urban Habitat (CTBUH) points
out it is often difficult to compare these material quantities, as some studies may include or
exclude the foundations, mezzanine floors, etc. (CTBUH Journal, 2010).
Number of stories
350
320 kg/m2
300
250
200
Premium
for height
150
100
120 kg/m2
50
0
10
20
30
40
50
60
70
80
90
100
Figure 2.4: Weights of steel per numbers of stories, after (Khan, 1980; Ali and Moon, 2007)
The scope of current studies tends to be narrowed down to a specific type of structure (e.g.
skyscrapers) or program (e.g. offices) (Amato and Eaton, 1998). Literature is lacking about the
ranges of material weights in typical buildings.
2.2. Embodied Carbon Coefficients (ECCs)
Similar uncertainty and gaps in data also characterize the literature that examines Embodied
Energy and Embodied Carbon. Moncaster and Symons (2013) describe the general lack of data
in the field of embodied carbon. Alcorn (1996) discusses the “Embodied Energy Coefficients”
(EEC, in MJ/kgmaterial) of building materials, while Dias and Pooliyadda (2004) define
“Embodied Carbon Coefficients” (ECC, in kgCO2e/kgmaterial). The phrase “Carbon Intensity
Factors” (CIF) is sometimes used interchangeably for the “Embodied Carbon Coefficients”
(ECC).
Various reports have analyzed the environmental impact of concrete (Vares and
Häkkinen,1998; Lagerblad, 2005; Collins, 2010; Struble and Godfrey, 1999; NRMCA, 2014), as
well as the impact of cement (Young, Turnbul and Russel, 2002). Other articles describe the
embodied energy of metals (Chapman and Roberts, 1983) and in particular steel (ISSF, 2013;
IISI, 2013; Eurofer, 2000; Stubbles, 2007; World Steel, 2014). Next to concrete and steel,
discussions exist on the embodied energy and carbon of other construction materials such as
timber (Pullen, 2000; Corrim, 2014). However, there is a significant variability in the results for
both EEC and ECC values.
17
There is a need for material manufacturers, such as the concrete, steel and timber industry, to
make the ECC data of their products more transparent and consistent (The Concrete Centre,
2013; Moynihan et al., 2012; Weight, 2011). However, each manufacturer puts forth a set of
assumptions, such as which life cycle stages to include. For example, taking into account the
carbon sequestration may be beneficial for the ECC value of timber, while taking into account
the end of life recycled content may be beneficial for the ECC value of steel (Weight, 2011).
Embodied Energy (EE) (MJ/kg)
Efforts exist to summarize the ECCs of common construction materials. In the United
Kingdom, the Inventory of Carbon and Energy (ICE) report from the University of Bath is one
of the most complete open source databases for ECCs (Hammond and Jones, 2010). Figure 2.5
illustrates the variability of the available data on the embodied energy of steel. The wide range
of available EEC/ECC values undermines useful comparisons of the environmental impact of
different buildings. The ICE report selects the best available embodied energy and carbon data.
However, there is still a need for values per country or region. The same concrete mix used in a
big city in China or a small town in the United States will not have the same coefficients if
factors such as transport are included (Ochsendorf, et al., 2011). In addition, the embodied
carbon in the ICE report is often underestimated by considering only the initial stage (‘cradle to
gate’) instead of the whole life cycle (‘cradle to grave’ or ‘cradle to cradle’). The life cycle stages
are defined in the TC350 European standards (Moncaster and Symons, 2013). In the Unites
States, the Carbon Working Group discusses the embodied carbon of common construction
materials. However, the group highlights the uncertainty and variability of available data quality
(Webster et al., 2012).
EE Scatter Graph - Steel
90
80
70
60
50
40
30
20
10
0
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Year of data
Figure 2.5: Variability of available embodied energy data of Steel (Hammond and Jones, 2010)
Several Life Cycle Inventory (LCI) and LCA tools exist to calculate impacts of single projects or
materials. The commercial software Gabi, EcoInvent and SimaPro are common practice for
LCA calculations, but can lack transparency due to protection of intellectual property (GaBi,
2013; EcoInvent, 2013; SimaPro, 2013). Furthermore, the Athena Institute of Sustainable
Materials has integrated LCI data at the building scale (Athena, 2009).
18
2.3. Examples of existing implementations
The following paragraphs illustrate several existing databases and tools for estimating embodied
carbon. The Athena Institute is a non-profit organization based in Canada that has integrated
LCI data into building industry specific tools: the Athena Eco Calculator (free) and the Athena
Impact Estimator (Athena, 2009). Also, EcoInvent provides thousands of LCI datasets in
various fields from agriculture to electronics (EcoInvent, 2013)
Furthermore, various companies have developed in-house tools focused on estimating the
embodied carbon of their projects. In 2013, Kieran Timberlake and PE International released
the Tally environmental impact tool (Tally, 2013) extracting data from Revit models (Revit,
2014). The SOM Environmental Analysis tool is a user-friendly embodied carbon calculator for
design projects (SOM, 2013).
In the United Kingdom, the non-profit Waste Reduction Action Program (WRAP) recently
launched a project-based database of embodied carbon (WRAP, 2014). WRAP asks users of the
web-interface to clearly mark building life cycle stages and to reference the LCA software used,
without asking specifically for material quantities (Charlson, 2012). The Royal Institution of
Chartered Surveyors (RICS) has started developing a range of benchmarks based on the
available data on embodied carbon in buildings (RICS, 2014).
Many leading structural engineering firms have also started the development of in-house
databases of structural material quantities or embodied carbon for their own projects. One
thoroughly developed example is the Arup Project Embodied Carbon and Energy Database
(PECD) mainly consisting of Arup buildings or projects from literature (PECD, 2013;
Kaethner and Burridge, 2012; Yang, 2013). Although PECD contains approximately 600
projects, the data scarcity, scattering and wide ranges of data still hinders the definition of a
baseline. Other companies, such as Thornton Tomasetti, have also developed a database of the
material quantities, extracted via a Revit plug-in, and the embodied carbon in their projects.
Studies demonstrate the need to inform not only designers and clients, but also governments
and the public of the need to develop solutions for carbon savings (Clark, 2013).
Table 2.1 gives a brief overview of companies and institutes working on similar problems. As
can be discerned from this table, the existing initiatives only look at one or two of the
parameters to estimate the embodied carbon of buildings. This thesis aims to bridge the gap
between the various influences.
19
Implementation
ECC
Material Quantities
Reports
Inventory of Carbon & Energy (ICE)
Structure and Carbon (Carbon working group)
Cole and Kernan, 1996
Eaton and Amato, 1998
Council of Tall Buildings and Urban Habitat (CTBUH)
Software
Athena
GaBi, SimaPro
SOM Environmental Analysis Tool
Tally beta tool
Build Carbon Neutral, 2007
Databases
Arup PECD
Thornton Tomasetti
WRAP
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
Table 2.1: Leading efforts in material quantity collection, ECC values, database implementation
2.4. Summary
Despite a growing interest in this field, designers and clients still lack a global embodied carbon
estimator (De Wolf et al., 2014).
Studies have attempted to map material efficiency of tall buildings considering the number of
floors and structural systems (Khan, 1980; Cho et al., 2004; Ali and Moon, 2007; Elnimeiri and
Gupta, 2009). Leading structural design firms such as Arup and Thornton Tomasetti collected
data on material quantities in their projects in-house.
Other studies are assembling data on ECCs, such as the ICE database of the University of Bath
in the United Kingdom (Hammond and Jones, 2010) or the Carbon Working Group in the
United States of America (Webster et al., 2013). There is a need for material manufacturers,
such as the concrete, steel and timber industry, to make the ECC data of their products more
transparent and consistent.
Several LCI/LCA software exist on the material and product scale, such as GaBi (GaBi, 2013),
EcoInvent (EcoInvent, 2013) and SimaPro (SimaPro, 2013), or on the building scale, such as
the Athena Institute of Sustainable Materials (Athena, 2009). The WRAP embodied carbon
20
database collects total carbon footprints of buildings, without asking for the material quantities
in the projects still (De Wolf and Ochsendorf, 2014; WRAP, 2014). The RICS hopes to develop
new benchmarks for embodied carbon based on these new data-points (RICS, 2014).
Overall, estimating the embodied carbon of building structures is data-intensive. However, the
available data on material quantities or ECCs are scarce and often unreliable. A general lack of
transparency hinders the usage ECC values available in the literature. Also, no baseline has been
defined for benchmarking material efficiency and embodied carbon in buildings. This thesis will
address these issues, by looking at the opportunities within the challenges. A framework for an
interactive database a survey of several hundreds of existing buildings will follow.
21
22
3. Methodology
The study of publicly available carbon data in Chapter 2 (Figure 2.1) illustrates the variability in
assumptions from different organizations. The existing literature is synthesized and the
published numbers on both key variables – the material quantities and the ECCs – are
compared in order to advise a unified method of estimating the GWP of buildings.
The methodology for estimating material quantities and the environmental impact of building
structures is threefold. First, one-on-one conversations with leading structural engineering and
design firms leads to a description of the current common practice and existing challenges in
estimating embodied carbon of their building projects. Further, existing literature and tools for
estimating the environmental impact of buildings are reviewed. Finally, the implementation of
an interactive interface and a relational database will unify the collection and processing of data.
3.1. Personal conversations with practitioners
To start, conferences and discussions with experts provide feedback from the professional
sectors of building design, engineering and construction. These interactions are held in the
form of personal conversations, presentations at conferences or open discussions in offices.
The design firms and experienced practitioners give a critical review of what should be queried
in a new database in order to legitimately compare the environmental impact of building
structures. These conversations with experts pave the way to accurate baselines for embodied
carbon while keeping the results easily accessible for the stakeholders.
Next to this critical review of the field, these interactions with practitioners also play a crucial
part in the gathering of data. These contacts with professionals deliver a significant amount of
data on material quantities in building projects. Leading structural engineering firms such as
Arup and Thornton Tomasetti have shared hundreds of projects with this research to analyze,
compare and validate the embodied carbon assessment method in their offices.
3.2. Assessment of existing literature and tools
As mentioned above, the available data are variable and often unreliable. It is therefore
important to thoroughly and critically review the challenges and opportunities arising from the
literature and existing tools. On one hand, (scarce) published numbers on material quantities in
buildings are listed. On the other hand, the different numbers for ECCs are compared and
evaluated. Finally, the current implementation of the actual estimation of the embodied carbon
of whole building structures is assessed.
In particular, this thesis uses and compares various existing embodied carbon estimating tools.
Various software or databases have been assessed (Table 3.1): the Athena Impact Estimator for
Buildings, the GaBi LCA software, the Tally tool developed by Kieran Timberlake and PE
23
International, the SOM Environmental Analysis Tool, the WRAP embodied carbon database,
etc. Very little has been written on the comparison of the available tools.
Company
Athena Sustainable Materials Institute
PE International
Kieran Timberlake & PE international
Skidmore, Owings & Merrill
WRAP
EC estimating tool
Impact estimater
GaBi Software
Tally
SOM Environmental Analysis Tool
WRAP Embodied Carbon Database
Reference
Athena, 2009
GaBi, 2013
Tally, 2013
SOM, 2013
WRAP, 2014
Table 3.1: Existing reviewed embodied carbon estimating tools
3.3. A new interactive database
Recognizing the need for a uniform method of assessing embodied carbon in buildings, this
research undertakes a long-term initiative to create an interactive, growing database of building
projects. The online interface allows architects, engineers and researchers to input data on the
material quantities and embodied impact of their projects.
The interactive web-based interface, where practitioners from industry can input data on their
projects from all around the world in a transparent way, is connected to a growing relational
database. While controlling the quality of the entered data, contribution of all industries is
encouraged. A “Wiki” approach with multiple participants facilitates the communication with
companies. The relational database is coded in MySQL, the interactive web-based interfaced in
html and php scripts make the connection between both.
The following example illustrates the working of the interactive database. A user inputs the
structural material quantities of an office building in London. Then, the participant can opt for
the default ECC value offered by the database or enter his/her own customized value. The
result will give the GWP of the project compared to other similar structures. Figure 3.1 shows
the current interface and database developed for the purpose of this thesis.
A transparent database composed of thousands of projects, will give participants a greater
confidence in the numbers for the GWP of buildings. Visualizing and comparing results will
increase the understanding of the environmental impact of various building types and structural
systems. Ultimately, the analysis of material quantities and embodied carbon will direct
architects and engineers towards designs with a lower embodied carbon.
24
WHAT?
deQo
HOW?
RESEARCH
HOW?
Database for Embodied Quantity Outputs
Search
Structural System & Material Choice
My Projects
PROBLEM
NEXT
New Project
Settings
Logout
Natural Hazard & Climate Zone
Building Life Cycle Stages
Included Building Components
Figure 3.1: Part of the interactive interface of the database
The following chapters will expand on the three main contributions of this thesis. Chapter 4
reviews the challenges and opportunities in the field of embodied carbon. Chapter 5 proposes a
framework for the interactive database. Chapter 6 illustrates the survey of over 200 existing
buildings. The results will be summarized, discussed and will lead to conclusions in Chapter 7.
3.4. Summary
The methodology can be summarized in three techniques: personal conversations with leading
experts, a review of the existing tools and literature and the development of a new interactive
database. The experts are structural engineers, architects, researchers and consultants. The
existing tools are databases such as WRAP, assessment tools such as Athena or LCA software
such as GaBi. The interactive database is composed of a web-based interface and a relational
database and will be discussed in more detail in Chapter 5. As a whole, these three techniques
led to the development of the challenges and opportunities in obtaining material quantities and
ECCs (Chapter 4), the framework for a new database (Chapter 5) and the survey of over 200
existing buildings (Chapter 6).
25
26
4. Challenges and opportunities in obtaining
embodied quantities
4.1. Introduction
While individual companies and researchers are developing their own in-house databases, it is
important to understand the challenges arising from carbon accounting. For an accurate,
complete and reliable database, it is essential to know the obstacles before it is possible to
overcome them. The thesis therefore addresses the lack of methodology or regulation divided
among three topics:
1. The first task is to collect material quantity data and assess their quality. This can allow
for comparisons across building types and structural systems.
2. The second goal is to propose standards for ECCs that are reasonably accurate but at
the same time do not require a complicated calculation from a complete LCA for each
material and each project.
3. The third topic addresses the implementation of the database. It includes unifying the
different methodologies in a transparent way while respecting intellectual property.
For each of the three problems identified, this thesis defines opportunities as well as challenges.
The opportunities illustrate the possibilities of the environmental impact database and can solve
part of the tasks in each topic, but challenges remain to be undertaken.
4.2. Getting material quantities
The first challenges consist in obtaining accurate material quantities and generating as much
data as possible. For accurate data, the scope of what is included should be very well defined
(for example, should the sub-structure be included?). Generating large amounts of data requires
incentives for architecture, engineering and construction firms to share their project
information. Indeed, hundreds of projects are needed to create a representative sample pool.
The opportunity in getting structural material quantities arise from Building Information
Models (BIM) such as Revit (Revit, 2014). Connecting Revit models to a database of material
quantities will generate data quickly in an automated way. Architecture and structural design
firms now almost always use BIM models for their projects. These 3D model based data
consequently makes a significant amount of data on material quantities in buildings available.
New design projects have a digital version of the amount of steel, concrete, timber or other
materials used in the building structure.
With the right incentives, these design firms can share the information on their project in a fast
and automated way with BIM, facilitating the collection of data on material choice and material
quantities in the building projects. Accordingly, a considerable amount of quantitative data is
already available in design firms and a user-friendly interactive web-interface should help
populate the database.
27
4.3. Accurate ECCs
4.3.1. Literature on ECCs
The definition of ECCs is an important and complex matter. Typically these data are obtained
from Life Cycle Inventory (LCI) databases. Many databases are available such as Bath
University’s ICE report (Hammond and Jones, 2010), Athena (Athena, 2009) and EcoInvent
(EcoInvent, 2013). In particular, the ICE presents ‘cradle-to-gate’ data for carbon and energy
impacts of building materials mainly in the United Kingdom.
Athena integrates average transportation distances (results customizable for different regions of
the United States of America) as well as impacts from construction, maintenance and
demolition (Athena, 2009). The tool helps designers evaluate environmental impacts without
developing detailed material quantity takeoffs. The EcoInvent datasets are based on industrial
data. The tool is compatible with most LCA and eco-design software tools (EcoInvent, 2013).
In order to understand the variability of ECCs among different databases, the values for
cement and concrete obtained by ICE and Athena are reported in Table 4.1. For concrete in
particular, the ECC can vary in a significant way depending on strength (Table 4.1, Figure 4.1
and Figure 4.2), cement quantity, percentage of fly ash (Figure 4.1) and blast furnace content.
Moreover, in the case of reinforced concrete the environmental impact of reinforcing bar
(rebar) has to be considered: the ICE suggests adding 0.77 for each 100kg of rebar per m3. With
different concrete strengths and rebar contents, the results vary widely per m3 (240 kg versus
788 kg, Figure 4.2). A critical study is needed to interpret this extreme variability to establish
reliability in the available concrete ECCs.
ICE
0.74
0.100
0.113
Cement
Concrete 16/20
Concrete 25/30
Athena
0.776
0.091
0.128
ECC for concrete
(kgCO2e/kgm)
Table 4.1: ECC for cement and concrete, data after (Hammond and Jones, 2010) and (Athena, 2009)
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
RC 20/25
(20/25 MPa)
RC 25/30
(25/30 MPa)
RC 28/35
(28/35 MPa)
RC 32/40
(32/40 MPa)
RC 40/50
(40/50 MPa)
0% fly ash
0.132
0.140
0.148
0.163
0.188
15% fly ash
0.122
0.130
0.138
0.152
0.174
30% fly ash
0.108
0.115
0.124
0.136
0.155
Figure 4.1: ECC for concrete, varying strengths and percentages of fly ash,
data after (Hammond and Jones, 2010)
28
kgCO2e
for 1 m3 of concrete
800
700
600
500
400
300
200
100
0
16/20 MPa
20/25 MPa
25/30 MPa
28/35 MPa
32/40 MPa
40/50 MPa
0% rebar
240
257
271
288
317
362
1% rebar
425
442
456
473
502
547
2% rebar
535
552
567
583
612
658
3% rebar
665
682
697
713
742
788
Figure 4.2: Embodied carbon for a 1m3 of concrete at varying strengths and percentages of rebar, data
after (Hammond and Jones, 2010)
Next to concrete, the ECC values for steel products also present an important variation, as
illustrated in Figure 4.3 for various steel products and different recycled contents.
3.50
3.00
ECC for steel
(kgCO2e/kgm)
2.50
2.00
1.50
1.00
0.50
0.00
UK Typical - EU
59% Recycled
R.O.W. Typical 35.5% Recycled
World Typical 39% Recycled
Primary - 100%
hypothetical virgin
General
1.46
2.03
1.95
2.89
Bar & Rod
1.40
1.95
1.86
2.77
Coil (Sheet)
1.38
1.92
1.85
2.74
Coil (Sheet Galv.)
1.54
2.12
2.03
3.01
Figure 4.3: ECC for steel products at varying recycling contents,
data after (Hammond and Jones, 2010)
29
Table 4.2 proposes average ECC values after the ICE database (Hammond and Jones, 2010)
and EcoInvent (EcoInvent, 2013). The opportunity lies in the definitions of average numbers
per location. If the database can propose an agreement for ECC standards, it can allow
practitioners to use both average and more sophisticated customized values.
Material
ECC in kgCO2e/kg
0.11*
0.13*
1.1
2.6
1.2
2.5
1.7
Standard
High Strength
Sections (beams, columns)
Sheeting
Studs
Plates
65% recycled content
Concrete1
Steel2
Rebar3
*The
Carbon coefficients for concrete can vary in a significant way depending on strength, cement quantity,
percentage of fly ash and blast furnace content, in this table two values are provided that can be applied
respectively for normal concrete (C20/25 - C28/35 and 30% fly ash) and high strength concrete (C32/40 C40/50 and 30% fly ash). This does not include reinforcing steel in the concrete.
1after (Hammond and Jones, 2010);
2after (EcoInvent, 2014).
3after (GaBi, 2013)
Table 4.2: Evaluation of ECCs for a set of structural materials, in collaboration with Ornella Iuorio
4.3.2. Applied ranges for ECCs
This section discusses a choice of default ECCs, based on a critical review of databases,
software and design scheme guides of leading companies. Figure 4.4 illustrates the results for
unreinforced concrete, from different sources such as the ICE database, GaBi, Athena, The
Concrete Centre. The deQo database follows the most reliable source or an average of the most
reliable numbers.
ECC of concrete
(kgCO2e/kgm)
0.25
ICE Bath University
0.2
GaBi 2006
0.15
The Concrete Centre
Athena 2003
0.1
deQo
0.05
20
Low
30
Medium
50
High
Concrete Strengths (MPa)
Figure 4.4: ECC of low, medium and high strength concrete from various sources
30
Not only do these amounts depend on location (transport from extraction site to construction
site), but also vary as a function of material composition. For example, for an ECC of
reinforced concrete, numbers depend significantly on the mixes. Indeed, different cement
contents, fly ash replacements, or rebar contents will have a considerable impact on the value of
the ECC. However, to simplify the approach to estimating the GWP of buildings, an average
ECC range can be determined. Figure 4.5 proposes average values for the ECC of reinforced
concrete from low to high strength concrete and from 0 to 5% of rebar.
ECC of concrete
(kgCO2e/kgm)
0.3
0.25
0% rebar
0.2
2% rebar
5% rebar
0.15
0.1
20
30
40
50
Concrete Strength (MPa)
Figure 4.5: Average ECC of reinforced concrete
ECC of steel
(kgCO2e/kgm)
The same analysis is conducted for steel values (Figure 4.6), differentiating hotrolled steel and
rebar. The ICE database gives the value for steel in the United Kingdom; Athena is applied to
North America; SimaPro gives a general value for both hotrolled and rebar steel; and GaBi
incorporates different global values. As can be discerned from Figure 4.6, the values are very
different from one source to another.
2.00
1.80
1.60
1.40
1.20
1.00
0.80
0.60
0.40
0.20
0.00
Hotrolled Steel
Rebar
ICE Bath Athena 2003 GaBi 2006
University
SimaPro
deQo
Figure 4.6: ECC for hotrolled and rebar steel from various sources
31
ECC of glulam
(kgCO2e/kgm)
A similar comparison was established for timber as a structural material. Figure 4.7 gives a
summary of the ECC values for timber (Arup, 2008).
1
0.8
0.6
0.4
0.2
0
UK
Germany
Australia
Canada
Global
Global
v2.0
2006
2007
2003
2014
2014
Bath ICE
GaBi
RMIT
Athena
Arup study
deQo
Figure 4.7: ECC of glued laminated timber from various sources
Having made this overview of material quantities and ECCs, a more critical evaluation is
possible for the GWP results for building projects in section 4.4.
4.4. Implementation of a unified method
The last topic in this chapter is the implementation of a database with material quantities and
embodied carbon. To define the challenges in this field, the first step is to analyze existing
embodied carbon estimator tools (Table 4.3). Current developments are mainly design-oriented.
Usually, tools do not give a specific indication of a baseline for benchmarking. A databaseoriented tool is needed to shift away from the design process towards disclosure of projects
after construction, in order to give an idea how the embodied carbon of a new design will
compare to a typical building of the same typology and structural system.
Tools
Advantages
• Uses BIM output
TALLY beta version
• Design oriented
SOM Environmental • Basic default assumptions
Analysis Tool
• Option for customized details
Athena Carbon
• Established estimator
Estimator
• No LCA expertise required
• Uses BIM output
ARUP PECD
• Hundreds of projects available
Disadvantages
• Control what BIM includes?
• Transparency
• No Normalized metrics (kg/m2)
• Linear modeling of ECCs
• No BIM connection
• Transparency
• Control what BIM includes?
• Transparency
Table 4.3: Review of used and tested tools
Two important aspects contradict one another: the need for transparency and the protection of
intellectual property. Indeed, if a comparative database divulges all projects, the risk exists that
companies will use it to demonstrate “lower” embodied carbon compared to their competitors,
which could result in skewed data-points. Also ownership of data should be taken into account.
An option would be to allow anonymous data input, which then undermines the transparency.
32
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4.5. Summary
The main challenges discussed in this chapter are the following.
• The creation of incentives for companies to share data on their building projects.
• The identification of accurate default ECC values considering various locations.
• The resolution of data transparency while protecting intellectual ownership.
Nevertheless, these challenges also lead to following opportunities.
• The compatibility of data collection with Building Information Modeling tools allows
for the generation of hundreds to thousands of datapoints.
• The proposal for an agreement on accurate ECC values will facilitate the calculation of
the embodied carbon of buildings.
• A unified methodology for calculating the GWP of buildings will define reference
buildings for assessing the embodied carbon of building structures.
Moreover, this chapter offered default ECCs based on the existing literature. Results for
concrete range between 0.1 and 0.2 kgCO2e/kg. With 2% of rebar, it can range between 0.13 and
0.23. With 2% of reinforcement, the value ranges between 0.18 and 0.28. For steel, a distinction
is made between rebar (around 1.7 kgCO2e/kg) and hotrolled steel (around 0.8 kgCO2e/kg). Note
that these values are used mostly in projects in the United States, but can vary with the location
or material specification. Glued laminated timber has an ECC ranging between 0.1 and 0.8
kgCO2e/kg.
34
5. Framework for a database
5.1. Introduction
The second contribution of this thesis is to create a framework for a database of building
projects. Indeed, efforts exist to create an embodied carbon database of materials, such as the
Inventory of Carbon & Energy (Hammond and Jones, 2010). However, until very recently, no
database of buildings existed. This research proposes a framework for a worldwide, transparent
and interactive database where architects, engineers and other stakeholders can input data about
their building projects, more precisely about the material quantities and embodied carbon in
their building structures.
In 2014, WRAP launched a database collecting embodied carbon in buildings (WRAP, 2014).
However, they do not collect material quantities. This method requires a priori knowledge of
the embodied carbon in a building project. Also, the collected carbon results in the WRAP
database originate from various studies, making different assumptions. The embodied carbon
calculated with different tools can therefore not always be compared equally. Therefore, this
chapter will propose a framework for a complete database including material quantities together
with the embodied carbon of building structures. The database elaborated in this Chapter is
named “deQo” or “database of embodied Quantity outputs”.
The input and output parameters should be compatible with other databases such as WRAP,
Project Embodied Carbon Database (PECD), etc. and use existing, international listings, classes
and standards. The database should contain a significant amount of data entered with
comparable assumptions.
Figure 5.1 illustrates the framework for an interactive database. On one side (Figure 5.1, left),
the web-based interface is created to collect data on material quantities in building projects.
Architects and engineers can input data on their projects on this interactive interface (deQo,
2014). The user can access this part online and can make different queries.
Platform 1
COLLECT
Platform 2
PROCESS
Platform 3
STORE
HTML
PHP
MySQL
web-interface
connection
database
accessible by user
inaccessible by user
inaccessible by user
Figure 5.1: Framework for an interactive database
On the other side (Figure 5.1, right), a relational database, inaccessible to the user, stores the
project data. This database in MySQL is connected to the HTML web-interface through a PHP
script (Figure 5.1, center), processing the data back and forth.
35
The main aims of the relational database are the following:
• Build literacy on typical embodied carbon of structures;
• Offer a large data population beyond a single company;
• Compare project options (material choice, structural system, etc.) transparently;
• Shape a baseline for benchmarking in embodied carbon;
• Ultimately allow designers, industry and education to optimize design solutions.
This chapter is contains six sections and a summary. In section 5.2, the database specifications
are elaborated: what should be included in the in- and output parameters? In addition, section
5.3 details a framework for the relational database itself. In section 5.4, the interactive webinterface and tool to query results are illustrated. Furthermore, section 5.5 suggests the
collaboration with industry and possibilities for connections with Building Information Models
(BIM) plug-ins. Finally section 5.6 summarizes the contributions of this database.
5.2. Database specifications
This section explains the general framework of the database and expands on the features and
options that the database should include in order to be useful for the industry. The in- and output parameters of the database will be discussed. The collected information is divided in two
groups (Table 5.1): general and structural information. A future integration of operational
energy, maintenance and financial cost is possible.
1.
General Information
Credits, location, program, geometry
2.
Structural Information
Material choice, structural systems, material quantities
BIM, BOQ, etc.
Embodied Carbon Coefficients
Default or entered by user
Results
Material Quantities or GWP ranges
Comparative charts
Table 5.1: Framework for a database
5.2.1. General information
The database input asking for general information (Figure 5.2 and Figure 5.3) contains the
following input parameters: project name and source information (which can be held
anonymous); the date of design, construction, completion and/or publication; building stage;
location specifying region, country and town; program; architect, engineer and contractor;
accredited rating scheme and applied building code. These parameters are selected carefully
after reviewing existing tools and assessing the need for a universal tool in the industry. The
main drivers for this relatively concise interface were transparency, the ability to normalize by
different functional units, the accurate estimation of ECCs, the integration of material
quantities in carbon assessments, the compatibility with other existing databases, the capability
to compare projects legitimately and the aim to take conclusions on low-carbon design
strategies.
36
General information (1)
Upload photo
Date
Location
Building type (choose all that apply)
Figure 5.2: Interface, “General information” section, part 1
37
General information (2)
Geometry
Figure 5.3: Interface, “General information” section, part 2
The project name has to be entered, even if the contributor can choose to stay anonymous. The
source has to be clearly noted, in order to be able to post-verify the data. In case the
contributors wish to highlight their project, they are able to upload an image of their building
and must specify the source of the image for later publication purposes. The program or type
of building, i.e. residential, office, recreational, healthcare etc., are an important factor. Indeed, a
hospital has different requirements and therefore different material quantities than an office.
Geometry analysis includes aspects such as height and number of floors. The geometry has a
mandatory entry: the total useable net floor area (m2 or sf). Indeed, to be able to normalize the
data, a functional unit should divide the absolute values of material quantities (kg or lbs) and
embodied carbon (kgCO2e) in structures. However, another functional unit should be used if
more appropriate, for example the number of seats in stadia or the number of fulltime
occupants for schools. The gross floor area is asked when the total useable net floor area is
unknown. A percentage of this value can be used as an approximation of the net floor area.
38
5.2.2. Structural information
The second set of input parameters contains the structural information (Figure 5.4) of the
building projects. The structural system is divided into vertical, horizontal and lateral systems.
Then, the material choices and material quantities are requested. Furthermore, the user needs to
specify which building components are included. Resilience towards earthquake and other
natural hazards are taken into account. Alongside this information, factors such as the climate
zone are entered. Figure 5.4 illustrates the interface asking about the structural information of a
newly entered building project.
Structural information (1)
Structural system
Material choice
Buidling components included
Natural hazard and climate zone
Figure 5.4: Interface, “Structural information” section, part 1
A main material is selected for vertical, horizontal and lateral loads before specifying the
structural system. Table 5.2 illustrates the available structural systems the user can pick from.
39
Material
Concrete
Structural System
Vertical
In-situ wall
In-situ column
Precast column
Other
Steel
Studs & panel wall
Steel column
Diagrid
Timber
Studs & panel wall
Solid column
Glue laminated column
Solid stacked wall
Other
Masonry
Brick Wall
Concrete Block Wall
Other
Horizontal
In-situ 1-way spanning
In-situ 2-way spanning
In-situ flat slab
Ribbed and waffle slab
Post-tensioned band beams (long span)
Post-tensioned flat slab
Precast hollow core (composite)
Precast hollow core (non-composite)
Precast long span (composite)
Other
Composite metal decking
Non-composite metal decking
Beam & decking
Truss & decking
Diagrid
Other
Solid timber slab
Timber joists & decking
Solid beams & girders
Glue laminated beams & girders
Timber truss & girders
Other
Vaults
Other
Lateral
Shear wall
Rigid frame
Infill wall
Other
Bracing
Diagrid
Other
Shear wall
Bracing
Other
Shear wall
Other
Other
Table 5.2: Main Materials and corresponding structural systems
Table 5.3 illustrates the list of building components. The user selects which components are
included in the analysis. Non-structural building components are added in order to make the
database expandable to non-structural material quantities in the future.
Building components included
Foundations
Basement retaining walls
Lowest floor construction
Frame
Upper floors
Roof
Stairs and ramps
External walls
Windows and external doors
Internal walls and partitions
Wall finishes
Floor finishes
Ceiling finishes
Fittings, furnishings and equipment
Services
Roads, paths and paving
External drainage
External services
Structural
✓
✓
✓
✓
✓
✓
✓
✓
Non-structural
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
Table 5.3: Structural and non-structural building components included
40
Before the material quantities are entered, the source of these data is specified (dwgs, BIM, bill
of quantities, etc.). For the material quantities, only the materials that have been selected in
‘material choice’ and ‘structural system’ will be displayed (Figure 5.5). They can either be
entered in absolute values (in kg) or relative values (kg per appropriate functional unit, usally
m2). If only the absolute value is given, this value is normalized. The absolute value is divided
by the functional unit. In most cases, the functional unit will be the useable floor area, given in
the general information section. The relative material quantities are consequently expressed in
kilograms per square meter. Also, the applied life cycle stages entered in order to make ‘applesto-apples’ comparisons for the GWP results.
Structural information (2)
Material quantities
Embodied Carbon Coefficients
Life Cycle Stages
Figure 5.5: Interface, “Structural information” section, part 2
41
Additional, optional information can be added such as the structural grid, typical span, the
foundation and ground types (Table 5.4). If information is known on these types, it is useful to
compare material quantities of structures with similar grounds/foundations. Also, the loads can
be entered: dead and live load in kN/m2 as well as the wind, snow and seismic loads. The
database will ask whether the dead load is superimposed or total. Instead of entering a number
for the live load, a use type can also be specified.
A
B
C
D
E
S1
S2
Rock or other rock-like geological formation, including at most 5 m of weaker material at the surface.
Deposits of very dense sand, gravel, or very stiff clay, at least several tens of meters in thickness,
characterized by a gradual increase of mechanical properties with depth.
Deep deposits of dense or medium dense sand, gravel or stiff clay with thickness from several tens to
many hundreds of meters.
Deposits of loose-to-medium cohesion less soil (with or without some soft cohesive layers), or of
predominantly soft-to-firm cohesive soil.
A soil profile consisting of a surface alluvium layer with v s values of type C or D and thickness varying
between about 5 m and 20 m, underlain by stiffer material with v s > 800 m/s.
Deposits consisting, or containing a layer at least 10 m thick, of soft clays/silts with a high plasticity index
(PI 40 or more) and high water content
Deposits of liquefiable soils, of sensitive clays, or any other soil profile not included in types A – E or S 1
Table 5.4: Ground types
5.2.3. Default versus entered ECCs
The scope of the project location is worldwide. The goal is to include hundreds to thousands of
structures globally and to define default ECCs for location zones, such as countries and regions.
ECCs are computed considering the location of the building.
However, the user can enter his/her own ECC calculations when citing the source clearly. The
GWP can then be calculated by multiplying the SMQs with the ECCs. It is important to clearly
state the assumptions users make when entering their own project data. For example, if they
enter the ECCs, they should state clearly which life cycle stages are included and reference the
source of their calculations (GaBi, SimaPro, etc.). The quality assessment of the data will
depend on these assumption specifications.
5.2.4. Contribution of a new database
The proposed framework for a new database results from the review of existing carbon
estimating tools and conversations with experts. Table 5.5 summarizes the contribution of the
parameters collected deQO and compares the parameters to those in the existing tools
reviewed in Chapter 4.
The reasons for incorporating these parameters in the database, summarized in the second
column of Table 5.5, are the following: data should be as transparent as possible
(“transparency”) while protecting proprietary rights (“intellectual property”); data should be
compatible with other tools (“compatibility”); data should allow accurate ECC estimation
(“ECC”); data should be comparable (“comparison”) and therefore normalized
42
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
Table 5.5: Motivation and comparison of deQo parameters with existing tools
43
ICE
✓
✓
✓
✓
✓
✓
Compatibility
Comparison
Comparison
Design
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
EcoInvent
✓
✓
SimaPro
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
GaBi
Design & Normalization
ECC
Comparison
Comparison
Comparison
Normalization
Comparison
Comparison
Comparison
✓
✓
✓
✓
✓
✓
✓
✓
✓
✓
Athena
✓
Thornton Tomasetti database
✓
PECD
Transparency
Compatibility
Transparency
Transparency
Transparency
Transparency
Transparency
Intellectual property
Design
ECC & Design
Design
Compatibility
Normalization
Normalization
Normalization
Normalization
Design
Normalization
Design
Design
Why is this parameter
important?
Tally environmental impact
SOM environmental analysis
deQo
General Information
Project name
Metric and imperial units
Architect
Engineer
Contractor
Client
Publication
Anonymity
Date
Location
Program
Volume
Total useable floor area
Total gross floor area
Height
Number of stories
Story height
Number of occupants
Wall to floor ratio
Plan shape
Structural Information
Structural system
Material choice
Building components
Natural hazard zone
Climate zone
Material quantities
ECCs
Life cycle stages
Additional notes
Other aspects
Work with BIM
Projects globally
Projects across firms
Building scale
WRAP
(“normalization”); and data should say something about design strategies (“design”). The
parameters are selected carefully in order to have a limited number of questions in the interface
while enabling a complete analysis of material quantities and embodied carbon in buildings.
✓
5.3. Relational database
A relational database has been created to collect all the entered information. This means that all
the data are set in tables related to each other. Through a php script, the MySQL database and
html interface are connected. Figure 5.6 illustrates how the data are stored and how they can be
viewed, edited and exported.
Figure 5.6: Relational database, accessed through phpMyAdmin
All the input parameters discussed above, such as the material quantities, embodied carbon
coefficients and total floor area are related to each other and can be exported to spreadsheets or
used directly within the MySQL database.
The simple multiplication, illustrated by equation 2, is performed within the relational database
and stored for comparison with other projects.
GWP (kgCO2e/m2) = Relative SMQ (kgm/m2) ! ECC (kgCO2e/kgm)
[2]
5.4. Web-based interface
The web-interface is aiming at clarity and transparency. As the database becomes more useful
with a higher quantity of data, the access to it should be easy and the input parameters should
be well defined. The list of input parameters should therefore be short (yet complete) so that
the input process is fast.
44
The access to the database through the web-interface is granted after an (open-source)
registration (in order to insure data quality). Although the name of the participants will be
published, the individual projects can either be kept anonymous or highlighted following the
WHAT?
HOW?
RESEARCH
PROBLEM
NEXT
HOW?
request of the contributor.
The first page
of the interface
is shown
in Figure 5.7.
deQo
DATABASE FOR EMBODIED QUANTITY OUTPUTS
embodiedco2.scripts.mit.edu
Urban Modeling Interface
Implementing Embodied Carbon & BIM models
urbanmodellinginterface.ning.com
3
Figure 5.7: Register for deQo (deQo, 2014)
In the interactive web-interface, the user can click on the ‘Search’ button to illustrate the ranges
of results already entered in the database (Figure 5.8). On the y-axis of the search tool, either
“Material Quantities” or “Global Warming Potential” can be shown.
Figure 5.8: Search tool
45
The relational database should report results separately by building type, building component,
material, structural system, life cycle stage, location, loading, average floor height, span, total
height and number of floors. Finally, the rating scheme a building received can also be listed as
another filtering factor to give an idea how well low embodied carbon projects are rewarded.
A specific approach needs to be followed
for protecting
the anonymity
of building
projects. For
PROBLEM
LITERATURE
NEXT
WHY?
PROBLEM
RESULTS
example, if a data-point has a height of 800 meters and a location set in Dubai, it is publicly
known to be the Burj Khalifa (Figure3.5.9,
right). If anothercalculating
project is 1776
feet
tall and
located
Implementation:
the
GWP
of structures
in New York City, confidential data on the Freedom tower (Figure 5.9, left) will be given away.
It is therefore important to give the results only in ranges (of material quantities, embodied
Challenge:
carbon or even height).
Resolve data transparency while protecting intellectual ownership
“Location: New York City;
Height: 1776 ft”
“Location: Dubai;
Height: 2,722 ft”
20
Figure 5.9: Freedom tower (Dunlap, 2014), Burj Khalifa (photograph by the author)
In this thesis, all input parameters are expressed in metric units. However, clicking on ‘imperial’
instead of ‘metric’ allows all data entries and results to show in the appropriate unit for the user.
5.5. Collaboration with industry
5.5.1. Revit plug-in developers
WHY?
PROBLEM
LITERATURE
NEXT
PROBLEM
RESULTS
PROBLEM
WHY?
PROBLEM
RESULTS
In order to collect
a considerable
amount LITERATURE
of data on material
quantities,NEXT
collaboration with
plug-in developers for Building Information 1.
Models
(BIM)
is necessary.
An example of such a
Getting
Material
Quantities
Getting
Material
Quantities impact of
tool is the recently developed Revit plug-in1.for
estimating
the environmental
buildings. By using Revit models of their
projects, Arup and Thornton Tomasetti were able to
Opportunity:
1.
Getting Material Quantities
Opportunity:
BIM models
tocurrent
generate
material
quantity
data5.10).
contribute hundredsUsing
of projects
to the
deQo
database
(Figure
WHY?
PROBLEM
LITERATURE
NEXT
PROBLEM
RESULTS
Using BIM models to generate material quantity data
Opportunity:
Using BIM models to generate material quantity data
Tally tool (Tally, 2014)
PECD (PECD, 2013)
(Schumaker et al., 2014)
Figure 5.10: Databases and tools using Revit for collecting material quantities
17
46
17
17
5.5.2. Industry and research database
The growing database is an important step towards an agreement for benchmarking. Indeed,
the database will define baselines for building structures in order to measure a project’s
efficiency in terms of material use or carbon emissions.
To create such a database, this research relies on voluntary data input from the leading firms in
the industry, such as engineering offices and contractors. Furthermore, any data to feed into the
database will have to be generated according to a universal set of rules (e.g. on boundary
conditions and embodied carbon coefficients) to allow for meaningful comparisons and
statistical analysis.
Figure 5.11 illustrates the collaboration between MIT and WRAP as well as participation
opportunities for other companies. The deQo tool collects not only embodied carbon of
building structures, but also their material quantities. With an agreement on corresponding
ECCs, a connection can occur with the WRAP database, that is collecting solely the embodied
carbon of buildings. Industry can participate by adding to the ‘Bill of Materials Database’ as
well as to the ‘Project Embodied Carbon Database’. The more industry participates to both
initiatives, the more accurate conclusions will be on material efficiency in structures and
benchmarking of embodied carbon.
A way to create an incentive to add more data to the database is to reward the carbon
accounting in rating systems such as LEED. Also, a simple ‘release of information’ can be
signed by a company to allow its employees to add data about their projects. The companies’
logos can be added to the ‘contributors’ section on the web-interface.
Material Quantities
x
Embodied Carbon
Coefficients (ECC)
=
Embodied Carbon
Bill of Materials
Database
deQo
Materials Efficiency
ECC
Project Embodied
Carbon Database
Benchmarking
Figure 5.11: Collaboration deQo & WRAP databases and participation opportunities
47
5.6. Summary
In this chapter, a framework is developed for a database collecting material quantities and the
environmental impact of building projects. The database developed for the purpose of this
thesis focuses on embodied carbon of building structures, but is designed with possibilities to
expand to operational carbon and non-structural elements.
While working with existing tools and databases such as WRAP, Tally or the SOM
environmental analysis tool, the database for embodied quantity outputs (deQo) is a framework
for future development. As the field of embodied carbon needs to mature in the coming
decade, the various existing tools will merge in one way or another to compare and combine
the available data.
The deQo tool proposes in this chapter aims to help the industry to develop new benchmarks
for embodied carbon in their structural projects. In comparison with other available tools,
deQo attempts to offer a succinct but complete interface to allow meaningful comparisons of
the environmental impact of buildings. By also looking at the material quantities, deQo can lead
to more material efficiency in design.
48
6. Survey of existing buildings
6.1. Introduction
This chapter summarizes the results of the data collected through deQo. A survey of the 200
existing building projects will be presented. Different normalizations, filters and presentations
of the material quantities and embodied carbon will lead to conclusions.
Additionally, the developed approach is applied on case studies. The first case study compares
nine stadia to assess the impact of their design strategies on the environment. The second case
study compares two historic bridges with opposite sustainability strategies in order to learn
lessons from history. The third case study compares skyscrapers worldwide.
6.2. Existing building structures from the industry
This section shows the results of the material quantities and embodied carbon of real existing
buildings from the industry, all fully or nearly completed. Some projects are collected through
literature review, but most projects are shared by leading design firms such as Arup, Thornton
Tomasetti through the deQo interface.
Figure 6.1 illustrates the concrete, hotrolled and rebar steel for ten projects entered in the deQo
database. A wide range appears already. An obvious trend is that healthcare buildings tend to
have the highest amount of material. Only the government building has a greater number. In
fact, this government project is an imposing city hall containing a high amount of concrete. The
lowest material weights are in office buildings.
2000
1800
SMQ
(kg/m2)
1600
1400
rebar steel
1200
hotrolled steel
1000
concrete
800
600
400
200
0
Figure 6.1: Material quantities in the ten first projects entered in deQo by program
49
Figure 6.1 shows that in some cases iconic design (such as the government city hall) can have a
significant impact on the material efficiency.
The companies also entered ECCs, verified with the appropriate coefficient values of the
corresponding location. The results for the GWP of the building projects can be obtained by
multiplying these coefficients with the material quantities, as shown in Figure 6.2.
500
450
400
GWP
(kgCO2e/m2)
350
rebar steel
300
hotrolled steel
250
concrete
200
150
100
50
0
Figure 6.2: Embodied carbon in the ten first projects of deQo
Steel having a higher ECC than concrete, the contribution of the different materials to the total
number shifts compared to the material quantity analysis. Hence, these charts give a better
understanding of the environmental impacts of the structures.
Figure 6.3 gives an overview of 44 individual projects, ranked again by program. Healthcare
buildings are still using a considerable amount of materials, but a wider variety of office
buildings appear. Indeed, the embodied carbon of office buildings can vary by height
(skyscraper versus low-rise), material use (steel, timber, concrete, composite) or location (city
center, distance to material extraction). A new type is the residential building, where much
higher quantities are observed. This study also counts in the partitioning walls, which explains
this jump. A warehouse is mainly driven by structural efficiency, as the partitioning doesn’t have
to be as thorough as in residential buildings, which explains the lower impacts.
50
600
GWP
(kgCO2e/m2)
500
400
300
200
100
Car Parking
Central Utility Plant
Government
Healthcare
Healthcare
Healthcare + Office
Office
Office
Office
Office
Office
Office
Office
Office
Office
Office
Office
Office
Office
Office
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Residential
Warehouse
Warehouse
0
Figure 6.3: Total embodied carbon per program of 44 individual building projects
In the studies above, the projects were sorted by program. When continuing this analysis on a
greater number of building structures, the projects are moreover sorted by structural system,
height, number of occupants, location, etc. Figure 6.4 shows the same building projects ranked
by structural systems. The results show that concrete structures vary from 100 till 450
kgCO2e/m2, masonry from 225 till 575 kgCO2e/m2, steel from 80 till 475 kgCO2e/m2 and timber
from 70 till 490 kgCO2e/m2. The most common values are 275 kgCO2e/m2 for masonry and 175
kgCO2e/m2 for timber. Much higher variations exist for concrete, steel and composite structures.
600
GWP
(kgCO2e/m2)
500
400
300
200
0
Composite
Composite
Composite
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Concrete
Masonry
Masonry
Masonry
Masonry
Masonry
Masonry
Masonry
Masonry
Masonry
Masonry
Masonry
Masonry
Masonry
Masonry
Masonry
Steel
Steel
Steel
Steel, diagrid
Timber
Timber
Timber
Timber
Timber
Timber
Timber
Timber
Timber
Timber
Timber
100
Figure 6.4: Total embodied carbon per structural system of 44 individual building projects
51
The same graphical results can be obtained for other parameters, such as location, height, date,
number of floors, number of occupants. However, due to intellectual property rights, the
following results, including 200 projects from industry, will be shown in ranges, rather than
individual projects. Moreover, the box-and-whiskers graphical representation facilitates the
visualization of the ranges, outliers, minimum and maximum. For example, Figure 6.5 gives an
overview of different programs and the corresponding material quantity ranges. The boxes give
the standard ranges with a line indicating the median. The whiskers indicate the minimum and
maximum, where the crosses indicate the outliers, excluded from the analysis.
9000
8000
SMQ
(kg/m2)
7000
6000
5000
4000
3000
2000
Mixed use
Sports &
Entertainment
Residential
Healthcare
Government
Education
Hospitability
0
Commercial
1000
Figure 6.5: Ranges of material quantities for 200 real projects per program category
Figure 6.6 illustrates another way of organizing the data, i.e. by structural system. The 200 actual
projects are divided in concrete, steel and composite structures.
8000
SMQ
(kg/m2)
7000
6000
5000
4000
3000
2000
1000
0
Concrete
Steel
Composite
Figure 6.6: Ranges of material quantities for real projects per structural system
52
The same graphical representation of the GWP demonstrates the ranges of the embodied
carbon of buildings by program (Figure 6.7) or structural system (Figure 6.8).
4000
GWP
(kgCO2e/m2)
3500
3000
2500
2000
1500
1000
Mixed use
Sports &
Entertainment
Residential
Healthcare
Government
Education
Commercial
0
Hospitability
500
Figure 6.7: Real projects per program category, ranges of embodied carbon
As expected, the healthcare ranges are slightly higher, as are cultural and hospitability (hotels,
which are similar to residential buildings). All buildings range on average between 250 and 700
kgCO2e/m2. These ranges are a first step towards benchmarking of building projects for their
environmental impact.
Figure 6.8 divides the 200 projects in concrete, steel, timber and composite structures. Next to
a few outliers, the ranges are visualized with the boxes. A wider variety of results exist for the
steel buildings. As expected, the timber structures have a lower GWP than other structural
types. It is important to note that these numbers consider the ‘cradle to construction’ stages and
not the end of life.
4000
GWP
(kgCO2e/m2)
3500
3000
2500
2000
1500
1000
500
0
Concrete
Steel
Timber
Composite
Figure 6.8: Real projects per structural system, ranges of embodied carbon
53
In the following sections, several case studies will be analyzed in more depth. The first part
discusses the analysis of stadia, the second part historic bridges and the third part tall office
buildings.
6.3. Case Study I: Analysis of stadia
The first section introduces the studied sport stadia. The second section presents the material
quantities used in this case study. The third section calculates the embodied carbon of the
projects. Finally, the results are discussed.
6.3.1. Description
Most stadia in this study are partially covered, while some have a retractable roof. All stadia
were constructed between 2000 and 2011. Table 6.1 illustrates the stadia in this case study.
Stadium
Millennium Stadium
Allianz Stadium
Joao Havelange Olympic St.
London Olympic Stadium
Wembley Stadium
Aviva Stadium
Australia Sydney Stadium
Emirates Stadium
Beijing Olympic Stadium
Jaber Al Ahmad Stadium
Location
Cardiff, Wales
Munich, Germany
Rio de Janeiro, Brazil
London, England
London, England
Dublin, Ireland
Sydney, Australia
London, England
Beijing, China
Kuwait, Kuwait
Date
2007
2005
2007
2011
2007
2010
2000
2006
2008
2010
Structural Engineer
WS Atkins
Arup
Andrade Rezende
Buro Happold
Mott Stadium Consortion
Buro Happold
Sinclair Knight Merz
Buro Happold
Arup
Schlaich Bergermann & Partner
Table 6.1: List of sport stadia with location, date of completion and structural engineer
The material quantities and embodied carbon vary with the sizes of the sport stadia. It is
therefore necessary to normalize the results. Two methods are used for normalizing: per area or
per seat. Also, when comparing the final results, the presence of a (partial or retractable) roof
should be taken into account. Table 6.2 gives the number of seats and type of roof. The ‘area
per seat ratio’ is given in order to comprehensively interpret the results. Also, the sources for
material quantities are given in Table 6.2 and can be found in part 2 of the references.
Stadium
Millennium Stadium
Allianz Arena
Joao Havelange Olympic St.
London Olympic Stadium
Wembley Stadium
Aviva Stadium
Australia Sydney Stadium
Emirates Stadium
Beijing Olympic Stadium
Jaber Al Ahmad Stadium
Area (m2)
40,000
37,600
34,250
61,575
79,578
66,460
160,000
122,000
254,600
400,000
# Seats
74,500
68,000
45,000
80,000
90,000
51,700
110,000
60,355
91,000
65,000
Area/Seat
0.54
0.55
0.76
0.77
0.88
1.29
1.45
2.02
2.80
6.15
Roof
Retractable
Partially covered
Partially covered
Partially covered
Retractable
Partially covered
Partially covered
Partially covered
Partially covered
Partially covered
References
[1], [2]
[3]
[4]
[5]–[8]+[14]
[9], [10]
[11]–[13]
[14]
[15], [16]
[17]–[19]+[14]
[20]–[22]
Table 6.2: List of sport stadia with area/seat ratio, number of seats, roof type and references
54
6.3.2. Material quantities in stadia
A comparison of the material quantities in steel and concrete is conducted primarily through a
thorough literature review (references can be found in Table 6.2). Figure 6.9.a indicates the
material quantities in kg normalized per area in m2. The results demonstrate that most stadia
range from 800 kg/m2 to 3000 kg/m2. However, both the Beijing Olympic and the Allianz
Stadium have relatively high concrete and steel quantities, compared to the other stadia (up to
ten times higher).
Nonetheless, the ‘area/seat’ ratio reveals a significant difference: the Allianz stadium with a
ratio of 0.55 m2/seat can receive the same number of spectators on a much smaller area than
the Beijing stadium with a ratio of 2.80 m2/seat. This means that the comparison per square
meter is inequitable: the total material quantity of the Allianz is divided by an area that is 5.68
times smaller than the Beijing stadium for the same amount of spectators. This results in a
much higher normalized material quantity. Therefore, it may be more useful to consider the
material quantities normalized by the number of seats, which gives a better evaluation of the
fulfillment of the function. Figure 6.9.b illustrates the material quantities divided by the number
of seats. The material quantities range from 500 to 4000 kg per seat, except for the Beijing
Olympic Stadium or “Bird’s Nest.” The material quantity per seat in the Beijing Olympic
stadium is approximately ten times higher than in the London Olympic Stadium.
Material Quantities per Seat
Material Quantities per Area
8,000
16,000
7,000
14,000
12,000
10,000
Jaber Al Ahmad
Beijing Olympic
Emirates
Australia Sydney
Jaber Al Ahmad
Beijing Olympic
Emirates
Australia Sydney
0
Aviva
0
Wembley
2,000
London Olympic
1,000
Joao Havelange
4,000
Allianz Arena
2,000
Aviva
6,000
Wembley
3,000
steel per seat
8,000
Allianz Arena
steel per area
rebar per seat
Millenium
rebar per area
4,000
concrete per seat
London Olympic
SMQ (kg/seat)
5,000
Millenium
SMQ (kg/m2)
concrete per area
Joao Havelange
6,000
Figure 6.9: Material Quantities in kg: (a) normalized per square meter; (b) normalized per seat
55
6.3.3. Embodied carbon of stadia
Figure 6.10 illustrates the embodied carbon or GWP of the sport stadia. For projects based in
the United Kingdom and Australia, the values of the ICE database are followed. For projects in
America, the values of the Carbon Working Group are used. For the Beijing, Munich and
Kuwait projects, an LCA of the materials is performed using GaBi (Gabi, 2013). The numbers
are illustrated in Table 6.3.
ECC
Concrete
Hotrolled steel
Rebar steel
United Kingdom
0.10-0.13
0.88-0.89
1.71
Brazil
0.13
0.88
Kuwait
0.15
0.71
China
0.17
0.88
Germany
0.13
0.88
Australia
0.15
0.89
1.71
Table 6.3: ECCs used for this study
Steel has a higher ECC than concrete. For the same material weights, steel will therefore have a
higher impact in the total embodied carbon. Consequently, these embodied carbon charts give a
better understanding of the environmental impacts of the stadia, compared to the charts of
material quantities. Nevertheless, similar trends appear. The high use of steel and concrete
results in a high embodied carbon in the stadia.
Embodied Carbon per Seat
Embodied Carbon per Area
3,500
1,400
3,000
EC concrete per area
EC concrete per seat
Figure 6.10: GWP of stadia: (a) normalized per square meter; (b) normalized per seat
56
Jaber Al Ahmad
Beijing
Emirates
Millenium
Jaber Al Ahmad
Emirates
Beijing Olympic
Australia Sydney
0
Aviva
0
Wembley
500
Joao Havelange
200
London Olympic
1,000
Allianz Arena
400
Aviva
1,500
Australia
600
EC steel per seat
2,000
Wembley
800
London
EC steel per area
EC rebar per seat
Allianz Arena
GWP (kgCO2e/m2)
2,500
Joao Havelange
EC rebar per area
1,000
Millenium
GWP (kgCO2e/m2)
1,200
6.3.4. Discussion of results
The method of normalization (by area or by seat) has an important influence on the
interpretation on the results. A stadium showing both high material usage and a high embodied
carbon is the Beijing Olympic Stadium. By comparing both types of normalization, a better
understanding of the numbers for GWP emerges. Nevertheless, as the results by seat give a
better representation of the function of stadia, this method is preferred. Both key variables
result in clear trends in the different stadium design strategies.
Comparing material quantities and embodied carbon in stadia illustrates the difficulty of this
field. Indeed, a simple shift in functional unit from kgCO2e per m2 to kgCO2e per seat changes
radically the comparison. Also, the lack of available data on both variables, the material
quantities and the embodied carbon coefficients, can question the reliability of the results.
While this research is very data-intensive, the case studies of the stadia demonstrate the
simplicity and transparency of the proposed approach in equation [1].
The results show that design strategies for stadium structures have a significant impact on their
embodied carbon footprint. For example, the “Bird’s Nest” had an esthetic design pattern
inspired by Chinese-style 'crazed pottery' (National Stadium, 2014), which resulted in a high
material use and embodied carbon.
6.4. Case study II: Lessons from historic bridges
This section presents two complete opposite design solutions for sustainable historic: Inca
suspension bridges and Roman arch bridges (Figure 6.11). Both bridges are made from local
materials, but the design approach is fundamentally different: where Roman stone arch bridges
are created to be permanent and have a life time of several thousands of years, the Peruvian
communities rebuild the suspension grass bridges every year. This comparative analysis will
illustrate the trade-off between lightweight temporary bridges versus heavy permanent bridges
in terms of embodied carbon. The key question is: “What can historic bridges teach us on
sustainability?”
Moreover, the comparison between the permanent and temporary structures can raise the
question on the lifetime engineers and architects should consider for their designs. Indeed,
temporary and reusable structures could compensate a less durable approach.
The chosen case studies are the Roman stone arch “Pont Saint Martin” in Aosta, Italy, and the
last remaining Inca suspension grassbridge “Keswha-Chaka” in Huinchiri, Peru. They both
have a single span around 30 meters. It is important to note that this analysis is meant to be
comparative. The historic analysis require assumptions on the materials and construction
methods, so that it is not accurate to talk about absolute numbers. The absolute values are not
as relevant as the comparison between the cases, so that a conclusion can follow around the
differences between permanent and temporary bridge structures.
57
“What
difference
in embodied
carbon
and and
material
weight
between
historichistoric
“Whatis isthethe
difference
in embodied
carbon
material
weight
between
“What
is
the
difference
in
embodied
carbon
and
material
weight
between
historic
bridges
and recent
bridge
designs?”
bridges
bridge
designs?”
“What is and
the recent
difference
in embodied
carbon and material weight between historic
bridges and recent bridge designs?”
bridges and recent bridge designs?”
6.4.1.
Description
The
studies
chosen
areare
the the
Roman
stone
archarch
Pont Pont
Saint Saint
Martin
in Aosta,
Italy, Italy,
Thecase
case
studies
chosen
Roman
stone
Martin
in Aosta,
Thethe
case
studies
chosen
are
the
Roman
stone
arch
Pont
Saint
Martin
in Aosta,
Italy,
and
last
remaining
Inca
suspension
grassbridge
Keswha-Chaka
in
Peru.
The
case
studies
chosen
are
the
Roman
stone
arch
Pont
Saint
Martin
in Huinchiri,
Aosta,
Italy,
and
the
last
remaining
Inca
suspension
grassbridge
Keswha-Chaka
in Huinchiri,
The the
Roman
stone
arch “Pont
Saint
Martin”
crosses
the Keswha-Chaka
Lys river
in Aosta,
Northern
Italy andPeru.
and
last
remaining
Inca
suspension
grassbridge
in
Huinchiri,
Peru.
They
have
a single
span
around
meters.
isKeswha-Chaka
important
to note
that
this
analysis
and
the
last
remaining
Inca
suspension
grassbridge
inaround
Huinchiri,
Peru.
They
both
have
a27single
span
around
30 meters.
It is
important
to
note
that
this analysis
wasboth
built
between
B.C.
and
A.D.
1430
(Figure
6.11,ItIt left).
With
a span
35.6
meters,
it is
They
both
have
a
single
span
around
30
meters.
is
important
to
note
that
this
analysis
They
both
have
a
single
span
around
30
meters.
It
is
important
to
note
that
this
analysis
isis
meant
to
be
comparative.
The
historic
bridges
require
a
certain
number
of a of
to be span
comparative.
The historic
bridges
require
a made
certain
number
themeant
largest known
of Roman bridges.
The single
span arch
is mostly
of gneiss,
is meant
meant to
be
comparative.
The
historicbridges
bridgesrequire
require
number
of
is
comparative.
The
historic
asuspension
certain
number
of
assumptions
onbe
thethe
materials
construction
methods,
that
itathat
iscertain
not
to talk
local stonetomaterial
and
filledand
with
soil
(Blake, 1947).
Theso
Inca
bridge
“Keshwaassumptions
on
materials
and
construction
methods,
so
it isaccurate
not accurate
to talk
assumptions
on
thematerials
materials
and
construction
methods,
so
that
it not
is not
accurate
to crosses
talk
assumptions
on
the
and
construction
methods,
so
that
it
is
accurate
to
talk
chaka”
(which
translates
as
grass-bridge)
between
the
villages
of
Huinchiri
and
Quehue
about
absolute
numbers.
The
absolute
values
are
not
as
relevant
as
the
comparison
about absolute numbers. The absolute values are not as relevant as the comparison
about
absolute
numbers.
Thethe
absolute
values
are
not
as
relevant
as
the
comparison
about
absolute
numbers.
The
values
are
as
relevant
asdifferences
the
comparison
a 30 meters
wide
canyon
over
River
innot
Peru
(Figure
6.11,
right).
The between
lightweight
between
thethe
cases,
so so
that
a absolute
conclusion
can
follow
around
the
between
cases,
that
a Apurimac
conclusion
can
follow
around
the
differences
between
between
the
cases,
so
that
a
conclusion
can
follow
around
the
differences
between
construction
is
composed
of
braided
cables
for
the
floor
and
handrails,
connected
with
vertical
between
the
cases,
so
that
a
conclusion
can
follow
around
the
differences
between
permanent
and
temporary
bridge
structures.
permanent
and
temporary
bridge
structures.
grass ropes and
and
fixed
at both
sidesstructures.
with
stone abutments. The villages at both sides of the rivers
permanent
andtemporary
temporary
bridge
structures.
permanent
bridge
6.5.1.
Description
6.5.1.
Description
come together in a yearly three-day festival to rebuild the grass bridge
after
they
throwing
the
6.5.1.
Description
6.5.1.
Description
old grass bridge into the river (Ochsendorf, 1996).
> 1000
years
1 year
> 1000
years
1 year
High
initial
cost
Low
initial
cost
> 2000 years 1 year
High
initial
cost
Low
initialinitial
cost cost
High initial
cost
Low
Low maintenance
High
maintenance
High initial cost Low initial
cost
Low
maintenance
Highquality
>reuse)
2000
years
1maintenance
year
High quality
stone
(EoL
Low
plants
(washed away)
Low
maintenance
High
maintenance
Low
maintenance
cost
High
maintenance
>reuse)
2000
years
1 year
High
quality
stone
Low
quality
plants(washed
High
initial
cost
Low
initial
cost
High
quality
stone
(EoL
Low
quality
(washed
away)away)
>reuse)
2000
years
1 plants
year
Local
material
Local
material
High
quality
stone
(EoL
Low
quality
plants
End
of
Life
reuse
Washed
away
yearly
High
initial
cost
Low
initial
cost
Low
maintenance
cost
High
maintenance
Local
material
Local
material
High
initial
cost
Low
initial cost
Local
material
Local
material
Local material
Local
material
High
quality
stone
Low
quality
plants
Low
maintenance
cost
High
maintenance
Span
35.6after
mcost
30 mafter
Low maintenance
High
maintenance
Images
[8]Span
Images
[12]
th
End
of
Life
reuse
Washed
away
yearly
27
B.C.
–
A.D.
14
15
century
today
Information
after
[6],
[7]
Information
after
[10]
High
quality
stone
Low
quality
plants
High quality stone Low quality plants
Lys
Apurimac
Local
material
Local
material
ofPont
Life
reuse
Washed
yearlyyearly
FigureEnd
6.11:
Martin
(left)
andaway
Keshwa-Chaka
(right)
End
of Saint
Life
reuse
Washed
away
Aosta, Italy Huinchiri, Peru
Local
material
Local
material
Local
Local material
Segmental
stonematerial
arch Suspension
grass bridge
Case Study
1 year
Case Study
> 1000 years
Case Study
Pont
Saint
Martin
Keshwa-Chaka
Span
35.6
m Span
Span
30
m30 m
Span
35.6
m
Span
Span
35.6
m
30
m
th
Span
35.6
m
Span
30
m - today
th
th
27
B.C.
A.D.
14 15
15 century
century
27
B.C.
– A.D.
14
15century
century
- today
27 B.C.
–– A.D.
14
- today
th
27 B.C.
– A.D.
14 15
- today
Lys
Apurimac
Lys
Apurimac
LysLysApurimac
Apurimac
Aosta,
Italy
Huinchiri,
Peru
Aosta,
Italy
Huinchiri,
Peru
Aosta,
Italy
Huinchiri,
Aosta,
Italy
Huinchiri,
Peru Peru
Segmental
stone
arch
Suspension
grass
bridge
Segmental
stone
arch
Suspension
grass
bridgebridge
Segmental
stone
arch
Suspension
grass
bridge
Segmental
stone
arch
Suspension
grass
The two bridges have a single span with similar length. However, the Roman arch Pont Saint
Martin is working
in compression
and designed
a permanent(right)
lifetime,
1 2 3 4where the Inca Bridge
Figure
39: Pont Saint Martin
(left) andfor
Keshwa-Chaka
Keswha-Chaka is working in tension and designed for a lifespan of one year. The Roman arch
1 2 3 4 1 2 3 4
Figure
39:that
Pont
Saint
Martin
(left)
and
Keshwa-Chaka
uses high quality
stone
could
be
reused
at(left)
the end
life of the(right)
structure
opposed to the
Figure
39:
Pont
Saint
Martin
andof
Keshwa-Chaka
(right)as
1low
quality
grass
the Inca Bridge, which is washed away every time the old bridge is
Aosta,
Wikipedia,
Mayused
2013, in
http://nl.wikipedia.org/wiki/Aosta
thrown in the river. Nevertheless, both bridge designs have a sustainable approach that current
1 Aosta,
engineers
and
architects
can learn from: they use local material and offer59efficient
1bridge
Wikipedia,
MayMay
2013,
http://nl.wikipedia.org/wiki/Aosta
Aosta,
Wikipedia,
2013,
http://nl.wikipedia.org/wiki/Aosta
solutions to the design problem (Ochsendorf, 2004).
> 1000 years
High initial cost
Low maintenance
High quality stone (EoL reuse)
1 year
58
Low initial cost
High maintenance
Low quality plants (washed away)
Case Study
59
59
59
6.4.2. Material quantities in historic bridges
Case Study
Study
Case
Vault,
spandrel
walls, Abutments
Abutments 9070
9070
kg
Vault,
spandrel
walls,
Abutments
9070
kg
Vault,
spandrel
Abutments
9070
Vault,
walls,
Abutments
9070
kg
Vault,spandrel
spandrelwalls,
walls,
Abutments
kg
Vault,
spandrel
kg kg
PONT
SAINT
MARTIN
KESHWA-CHAKA
PONT
SAINT
MARTIN
KESHWA-CHAKA
PONT
SAINT
KESHWA-CHAKA
pavimentum
parapets
Stone
ECC
0.056
pavimentum
&
parapets
Stone
ECC0.056
0.056
pavimentum
&
Stone
––––ECC
pavimentum
parapets
Stone
ECC
0.056
pavimentum&
&&parapets
parapets
Stone
–– ECC
0.056
pavimentum
&
Stone
ECC
0.056
33 –– 1790
686
m
1790
Vertical
ropes
Twisted
cords,
cm
686
m
Vertical
Twisted
cords,
cm
686
Vertical
Twisted
cords,
333–
686
m
––1790
1790
Vertical
ropes
Twisted
cords,
cm
Vault,
spandrel
walls,
Abutments
– Twisted
9070
kg
Vault,
spandrel
walls,
Abutments
kgcords,
686
m
1790
Vertical
55 cm
686
m
ttttt Vertical
ropes
Twisted
cords,
cm5555cm
Local
gneiss
–
ECC
0.017
Floor/handrails
Braided
cables,
6
x
45
m
Local
gneiss
ECC
0.017
Floor/handrails
Braided
cables,
6xxx45
45
m
Local
gneiss
Floor/handrails
Braided
cables,
m
Local
gneiss
–
ECC
0.017
Floor/handrails
Braided
cables,
45
pavimentum
& parapets
parapets
Stone – ECC–0.056
pavimentum
&
Stone
Local
gneissspandrel
ECC
0.017
Floor/handrails
Braided
66 xx45
m
Vault,
walls, Floor/handrails
Abutments
9070
kg cables,
Local
gneiss
––––ECC
0.017
Braided
cables,
4566
m
3
3
Filling
3630
Puna
grass
–
ECC
0.01
Filling
3630
kg
Puna
grass
–
ECC
0.01
3630
Puna
–– ECC
0.01
686&
mparapets
1790 tt 3630
Vertical
floor
&
handrails
––3630
Filling
3630
kg
Puna
grass
ECC
0.01kg
686
m
–– 1790
Vertical
ropes,
& grass
handrails
3630
kg
pavimentum
Stone
ECC
0.056
Filling
3630
Puna
grass
–– ECC
0.01
Filling
kg–
grass
ECC
0.01
3 ––
780
m
Deck cords,
225
kg
780
m
1248
Deck
225
kg
Local780
gneiss
ECC
0.017
Twisted
diameter
55 cm
780
Deck
225
kg
Local
gneiss
––3333m
ECC
0.017
Twisted
diameter
cm for
for ropes
ropes
m
1248
Deck
225
kg
686
–1248
1790
Vertical
ropes,225
floor
&
handrails
– 3630 kg
780
m
–31248
1248
Deck
kg
780
m
––
ttttt t Deck
kg
Soil
–
ECC
0.023
Sticks/matted
reeds
Soil
–
ECC
0.023
Sticks/matted
reeds
Filling
Braided
6
x
45
m
for
floor
and
rails
Filling
Braided
cables,
m
for
floor
and
rails
Soil
–
Sticks/matted
reeds
Soil
–
ECC
0.023
Sticks/matted
reeds
LocalSoil
gneiss
– ECC
0.017 Twisted cords,Sticks/matted
diameter 5 cmreeds
for ropes
Soil
ECC
0.023
––ECC
0.023
Sticks/matted
reeds
Case
Study
Case
CaseStudy
Study
Case
Study
First, the material quantities are estimated, based on geometry descriptions in publications,
drawing and construction video’s. The sources for the two bridges can be found in part 3 of the
references. The ECCs are estimated based on the material descriptions and the ICE database
(Hammond and Jones, 2010). The calculations are summarized in (Figure 6.12).
780m
m33 ––Filling
1248 tt Braided
Puna grass
780
1248
Puna
– ECC
0.01
cables,
6 x0.01
45 m for floor and rails
3 – 1248
Soil
ECC
0.023
Deck
– 225kg
Soil
ECC
0.023t Puna
Deckgrass
780––m
– ECC 0.01
Sticks
matted reeds
Sticks –&225kg
Soil – ECC 0.023 Deck
Sticks
&
matted
Figure
images after
after [4],
[4], [5],
[5],[9],
[9],[10],
[10],[11]
[11]
Figure6.16:
6.16:Weight/ECC
Weight/ECCPont
PontSaint
Saint Martin
Martin &
& Keshwa-Chaka,
Keshwa-Chaka, reeds
images
Figure
6.12:
Weight/ECC
Saint
Martinquantities
& Keshwa-Chaka,
images
after
[4], [5],are
[9],illustrated
[10], [11] inin
The
calculation
of
material
in the Pont
Saint
Martin
are
illustrated
Theresults
resultsof
ofthe
the
calculationPont
of the
the
material
quantities
Saint
Martin
Table
Table6.4.
6.4.An
Anextended
extendedcalculation
calculation can
can be
be found
found in appendix B.4.a.
The results of the calculation of the material quantities in the Pont Saint Martin are illustrated in
Parts
Volume
Material
Density
Weight Weight
Weightper
permeter
meter
Parts 6.4. An extended
Volume
Material
Density
ECC
Table
calculation
can be found
in appendix
B.4.a. Weight
Vault
Parts
Vault
Spandrel
Spandrelwalls
walls
Vault
Pavimentum
Pavimentum
Spandrel walls
Parapets
Parapets
Filling
Pavimentum
Filling
Parapets
Filling
mm3 3
kg/m
kgCO2e/kg
kg
kg/m33
kg
270
Gneiss
2610
0.017
704700
Volume
Material
Density
ECC
Weight
270
Gneiss
2610
704700
3
m3
kg/m
kgCO2e
/kg
kg
390
Gneiss
2610
1017900
390
Gneiss
2610
0.017
1017900
270
Gneiss
2610
0.017
704700
42
Limestone
2500
0.017
105000
42
Limestone
2500
105000
390
Gneiss
2610
0.017
1017900
26
Gneiss
2610
67860
26
Gneiss
2610
0.017
67860
780
Soil
1600
1248000
42
Limestone
2500
0.017
105000
780
Soil
1600
0.023
1248000
26 Calculation
Gneiss
2610ECC for 0.017
67860
Table
Pont Saint
Saint Martin
Martin
Table6.4:
6.4: Calculation weights
weights and
and
780
Soil
1600
0.023
1248000
kg/m
kg/m
22443
Weight per 22443
meter
kg/m
32417
32417
22443
3344
3344
32417
2161
2161
39745
3344
39745
2161
39745
The
the
quantities
infor
Keshwa-Chaka
bridge are
areillustrated
illustrated
Table 6.4:of
Calculation
weights
and ECC
Saint Martinbridge
Theresults
resultsofofthe
thecalculation
calculation
of
the material
material
quantities
thePont
Keshwa-Chaka
ininTable
6.5.
An
extended
calculation
can
be
found
in
appendix
B.4.b.
Table 6.5. An extended calculation can be found
B.4.b.
Parts
Material
Density
ECC
Weight bridge
Weight
permeter
meter
The
calculation
of
the material
quantities in the
Keshwa-Chaka
are per
illustrated
Partsresults of the Volume
Volume
Material
Density
ECC
Weight
Weight
33
33
m
kg/m
kg
/kg
kg
kg/m
CO2e
m
kg/m
kg
/kg
kg
kg/m
CO2e
in Table 6.5. An extended calculation can be found in appendix
B.4.b.
Abutments
Abutments
Cables
Cables
Vertical
VerticalRopes
Ropes
Deck
Deck
//
1.98
1.98
0.6
0.6
0.45
0.45
Stone
Stone
Puna
Punagrass
grass
Puna
Punagrass
grass
Sticks
Sticks
2500
2500
395
395
395
395
59
500
500
0.056
0.056
0.01
0.01
0.01
0.01
0.01
0.01
9070
9070
302
302
3630
3630
121
121
Table
for Keshwa-Chaka
Keshwa-Chaka
Table6.5:
6.5:Calculations
Calculations sheet
sheet weights
weights and
and ECC
ECC for
Parts
Abutments
Cables
Vertical Ropes
Deck
Volume
m3
/
1.98
0.6
0.45
Material
Stone
Puna grass
Puna grass
Sticks
Density
kg/m3
2500
395
395
500
ECC
kgCO2e/kg
0.056
0.01
0.01
0.01
Weight
kg
9070
Weight per meter
kg/m
302
3630
121
Table 6.5: Calculations sheet weights and ECC for Keshwa-Chaka
6.4.3. Embodied carbon of historic bridges
Now that the weights and ECCs are determined, the Global Warming Potential (GWP) is given
by multiplication. The total weight of the different parts have been divided by the span, in order
to obtain a “linear” GWP, i.e. the GWP per meter of length of the bridge for the sake of
comparison. Considering the Roman arch has a lifespan of more than 2000 years, where the
Inca suspension bridge is less permanent, the lifetime of the bridges should be taken into
account while looking at the Global Warming Potential. The “linear” GWP is divided by the
number of years for which it has been standing to obtain an “annual” GWP. The results are
shown in Table 6.6 for Pont Saint Martin and in Table 6.7 for the Keshwa-Chaka bridge.
Parts
Material
Vault
Spandrel walls
Pavimentum
Parapets
Filling
Gneiss
Gneiss
Limestone
Gneiss
Soil
Weight / meter
(kg/m)
22442.68
32417.20
3343.95
2161.15
39745.22
Total
GWP / meter
(kgCO2/m)
381.53
551.09
56.85
36.74
914.14
1940.34
GWP / meter /year
(kgCO2/m/y)
0.19
0.28
0.03
0.02
0.46
0.97
Table 6.6: GWP of Pont Saint Martin
For the Keshwa-Chaka, the bridge is divided in a permanent and a temporary part. Indeed, the
abutments are not rebuilt every year. This is the permanent part, which is divided by the
number of years that the bridge has been in use (600 years). The suspended part, the grass
bridge itself, is divided by one, as it requires the whole construction and material supply again
every year. The “linear” and “annual” GWP are given in Table 6.7.
Parts
Material
Abutments
Cables
Vertical Ropes
Deck
Stone
Puna grass
Puna grass
Sticks, matted reeds
Weight / meter
(kg/m)
302.33
GWP / meter
(kgCO2/m)
16.93
GWP / meter / year
(kgCO2/m/y)
0.03
121.00
1.21
1.21
Total
18.14
1.24
Table 6.7: GWP of Keshwa-Chaka
60
If comparing the “linear” GWP without taking into account the lifespan, the Roman arch has
an embodied carbon (1940 kgCO2/m) more than 100 times higher than the Inca suspension
bridge (18 kgCO2/m). However, if dividing the permanent parts by the years that the bridge has
been in use, the Inca Bridge has a higher embodied carbon (1.24 kgCO2/m/y) than the Roman
arch (0.97 kgCO2/m/y).
6.4.4. Comparison Roman arch and Inca suspension bridge
In Table 6.8, the comparison of both bridges is illustrated, with both the “linear” and the
“annual” GWP compared.
Pont Saint Martin
Keshwa-Chaka
> 2000 years 1 year
High initial cost Low initial cost
Low maintenance cost High maintenance
High quality stone Low quality plants
End of Life reuse Washed away yearly
Local material – Gneiss & Soil Local material – Stone & Puna grass
Embodied Carbon .
1940.34 kgCO2/m 18.14 kgCO2/m
0.97 kgCO2/m/y 1.24 kgCO2/m/y
Table 6.8: Comparison Pont Saint Martin and Keshwa-Chaka, images from (Foer, 2013; O’Connor,
1993; The Last Handwoven bridge, 2013)
The first number shows that the Roman arch Pont Saint Martin has an embodied carbon of
1940 kgCO2/m or a factor hundred more than the Inca suspension bridge Keshwa-Chaka with
an embodied carbon of 18 kgCO2/m. When taking the lifespans into account, the Roman arch
has a slightly lower embodied carbon than the Inca Bridge.
When comparing both bridges, other aspects than embodied carbon, span and lifespans would
need to be taken into account. The load capacity of the Roman arch is much higher (car traffic
instead of pedestrian loads). Moreover, the Inca suspension bridges are also subject to a lot of
lateral movements, especially during consequent wind loads. The Inca suspension bridge is part
of a cultural heritage and community energy and vitality. Additionally, the bridge would
probably last longer, at least up to two years, than the one-year lifespan it is given due to the
annual festivities.
In both cases, the (linear or annual) GWP value is very low in general. The use of local
materials, traditional manufacturing and efficient design has a significant impact on the
embodied carbon. These low environmental impacts can teach current engineers and architects
about efficient design.
61
6.4.5. Comparison with recent bridge designs
A comparison with recent bridges puts previous results in perspective. Figure 6.13 illustrates
the material quantities of recent bridges with various spans (Clune, 2013). However, recent
bridges are road bridges with multiple lanes carrying much heavier live loads than the historic
counterparts discussed in this case study, so that the comparison is only theoretical.
Oakland Bay Bridge
Sydney Harbor Bridge
Figure 6.13: Recent Bridges, material quantities (Clune, 2013)
The bridge with the most similar span (around 45 m) has a mass of 500 kg/m2. This bridge has
the lowest embodied carbon (best case!) among the recent bridges. With a width similar to Pont
Saint Martin (which allows traffic), i.e. 6 m, the mass becomes 83 kg/m. An ECC for steel of
1.77 gives an embodied carbon of 147.5 kg CO2/m. If we consider a lifetime of 50 years, the
“annual” GWP becomes 2.95 kg CO2/m/y, which is three times more than the two historic
bridges. The upper bound of the range, a cable-stayed bridge, has a “linear” GWP of 590 kg
CO2/m and an “annual” GWP of 11.8 kg CO2/m/y. These numbers do not include nonstructural materials or maintenance. Indeed, recent bridges often require a new layer of asphalt
every twenty years or a new layer of protective paint.
Though paving materials and maintenance are not included in results for recent bridges, the
GWP is still ten times higher than for the two historic bridges (Table 6.9). The Oakland Bay
Bridge, San Francisco, (Figure 6.14) has a mass of 2100 kg/m2 and a width of 17.5m. The
“linear” mass is of 120 kg/m. Multiplying with the ECC gives an embodied carbon of 212.4 kg
CO2/m, and dividing with the lifetime of the bridge of 76 years, gives 2.8 kg CO2/m/y.
Pont Saint Martin
0.97 kgCO2/m/y
Keshwa-Chaka
1.24 kgCO2/m/y
Oakland Baybridge
2.8 kgCO2/m/y
Recent bridge range
2.8-11.8 kgCO2/m/y
Table 6.9: Comparison of “annual” Global Warming Potential
Figure 6.14: Oakland Bay Bridge, San Francisco, United States (photograph by the author)
62
6.5. Case study III: Comparing tall buildings
This section discusses the material quantities and embodied carbon in tall buildings. A
comparison of tall landmark buildings worldwide is illustrated by ten case studies.
6.5.1. Description
The ten skyscrapers considered in this study are listed in Table 6.10, with their location, date of
completion, structural engineer, structural system, height and sources (see part 4 in references).
Name
30 St Mary Axe
The United Tower
The Shard
Al Hamra Firdous
Willis Tower
World Financial Center
Location
London
Kuwait
London
Kuwait
Chicago
Shanghai
Date
2004
2011
2012
2011
1974
2008
Structural Engineer
Arup
WSP Cantor Seinuk
WSP Cantor Seinuk
SOM
SOM
Leslie E. Robertson
Taipei 101
Taipei
2004
One World Trade Center
Shanghai Tower
Burj Khalifa
New York
Shanghai
Dubai
2014
2014
2010
Thronton Tomasetti;
Evergreen Engineering
WSP Cantor Seinuk
Thornton Tomasetti
SOM
Structure
Steel Diagrid
Reinf. Concrete
Reinf. Concrete
Reinf. Concrete
Steel
Trusses &
columns
Composite
Hybrid
Concrete
Buttressed Core
Height (m)
Refs.
180
240
306
413
443
492
[1] – [4]
[5] – [10]
[11] – [16]
[17] – [20]
[21]
[22] – [24]
508
[25] – [26]
546
632
828
[27]
[28] – [33]
[34] – [41]
Table 6.10: Case studies for tall buildings
The height of the skyscrapers varies from 180 m for 30 St Mary Axe or “Gherkin” in London
till 828 m for the Burj Khalifa in Dubai. As demonstrated by Khan (see section 2.1), the height
of tall buildings influences the material quantities. Therefore, the results are always shown in
graphics with increasing building height from left to right (or from top to bottom in case of
Table 6.10). All buildings have been completed between 2004 and 2014, except for the Willis
Tower in Chicago, in order to see how recent buildings relate to older skyscrapers.
6.5.2. Material quantities in tall buildings
Figure 6.15 gives the material quantities normalized by floor area. As opposed to the previous
calculations in this thesis, the gross floor area has been used, as the internal floor area was not
always available for the ten towers. The sources (Bibliography and references, part 4) are mostly
publications, bill of quantities or design office documents.
Although the sources used to collect the data were fairly reliable, the accuracy could be
improved. For example, The United Tower and The Shanghai Tower were both constructed
with reinforced concrete, which has a certain percentage of steel. Therefore to obtain more
accurate results the exact percentage of reinforcement bars in the concrete should be known.
When this percentage was not known for the different cases, a general average of steel
percentage in the reinforced concrete was taken.
63
3,000
SMQ (kg/m2)
2,500
2,000
concrete per area
rebar per area
1,500
steel per area
1,000
500
0
Figure 6.15: Material quantities normalized per gross floor area
6.5.3. Embodied carbon of tall buildings
To have a better understanding of the environmental impact of the tall buildings, the used
ECCs were adapted to each region: the United Kingdom, the United States, the Middle East
and China. Based on the ICE coefficients, LCA calculations adapted the ECCs to include
transportation for the different countries. The modification consisted in the multiplication of
the original transportation input by a ratio taking into account the surface area of the country.
Then, a review of the concrete mix proportions used in every country was performed. The
collection of data represented many challenges during this step.
For example, no reliable source on the exact concrete mix of the World Financial Center,
Shanghai, was found. Therefore, published information on high strength concrete was used,
since this is the type of concrete used in the tower. The common water/cement ratio used for
concrete lies between 0.45 and 0.6. However in the case of the high strength concrete, the
water/cement ratio lies between 0.3 and 0.4. Consequently, the average value of 0.35 was used
with a gravel-content of 950 kg/m³. Moreover, the typical cement content for this type of
concrete varies between 350 to 500 kg/m³ of cement. Hence, a value of 450 kg/m³ of cement
was selected and by applying the water cement ratio chosen the amount of water was calculated
to be 157 kg. The water content is slightly lower than the usual water portion found in regular
concrete due to the addition of plasticizers.
64
In the case of the United Tower in Kuwait, the main inputs used in the Life Cycle Assessment
were extracted from the Bill of Quantities (BOQ) obtained from the client, United Real Estates.
All information on the construction and the structure of the tower in Kuwait is confidential,
and therefore it is difficult to obtain accurate information. From the BOQ, the main reinforced
concrete quantities were extracted. However, the additional information regarding the structural
system was obtained from construction magazines published in the Gulf. The only information
on the exact concrete mix in the BOQ available was the Specification 03300. Therefore,
technical papers published in Kuwait were used to adjust the cement content and water/cement
ratio in the LCA sheet. Moreover, The BOQ does not specify the proportion of reinforcement
in the concrete. Therefore it was assumed that steel reinforcement represents 0.5 percent of the
reinforced concrete.
One of the challenges of this research is to be very transparent about the data used and the
assumptions made. Therefore, the case studies are analyzed with different ECCs, given in Table
6.11. The values of the various sources are comparable in order of magnitude. The recycling
and the reuse phases of the materials were not taken into account. Consequently, to assure the
accuracy of the numbers found, a comparison is performed with the values from the ICE
database and the Carbon Working Group. The results for the embodied carbon of tall buildings
are shown in Figure 6.12.
ECC
Concrete
Hotrolled steel
Rebar steel
United Kingdom
0.16
0.89
1.7
Middle East
0.15
0.71
1.7
China
0.17
0.88
1.7
United States
0.13
0.88
1.7
Table 6.11: ECCs used for this study
500
GWP (kgCO2e/m2)
450
400
350
300
EC concrete per area
250
200
EC rebar per area
150
EC steel per area
100
50
0
Figure 6.16: Embodied carbon per area of tall buildings
65
The results show the highest impact from concrete and reinforcement for the Al Hamra
Firdous Tower and the United Tower, both in Kuwait. The Taipei 101 tower also represents a
higher impact due to concrete quantities used for the construction. The 30 St Mary Axe or
“Gherkin” in London has the lowest embodied carbon impact. It used a steel diagrid to
enhance the structural efficiency of the tower. It should be noted that, though it was
constructed in 1974, the Willis tower has the second lowest impact.
6.5.4. Discussion of the results
The high emissions for the Kuwait towers can s be
linked to the structural system of the
36-43 Swiss NY 04-10-06 16.03 Sida 39
skyscrapers. The architectural shape of the Al Hamra Tower (Figure 6.17.a.) requires more
concrete than the other tall buildings. Also, the reinforced concrete structure with the concrete
core in the United Tower (Figure 6.17.b.) was designed to accommodate the architectural wave
feature of the building. The architectural design did not take into account material reduction.
S
n
b
a
c
f
a
p
p
l
Plan of the 18th storey,
with denotation of the grid
of the raised floor.
Figure 6.17: (a) Al Hamra (photograph by the author), (b) United Tower (KPF, 2012), (c) Gherkin
(Munro, 2006) The real thing!
introduced, this increases the change in
column
angle and with
the spreading
The design of the steel diagrid in the 30 St Mary Axe
Tower
or it“Gherkin”
(Figure 6.17.c.)
effect of vertical column loads.
In
the
Swiss
Re
building
all
these
hodemonstrates that integrating sustainable design and structural
engineering starting from the
rizontal forces are carried by perimeter
hoops at
node tall
level, which
also
concept stage influences the embodied carbon emissions
ofeachthe
buildings
and that iconic
The shape of the tower
provide equilibrium for any asymmetric
design is not incompatible with embodied carbon reductions.
is influenced by the
or horizontal loading conditions. The
combination of these geometrical actions
results in compression in the hoops at
the top of the building, where the columns are more steeply angled and lighter loaded, to very significant tension ➤
Office division
(note: showing poss
variations of office
planning layout).
physical environment of
the city. The smooth
flow of wind around the
building was one of the
main considerations.
6.6. Summary
This chapter surveys over 200 existing buildings as well as historic and recent case studies. The
survey of material quantities in buildings designed by leading engineering firms was conducted
and the results of the ECCs in Chapter 4 lead to a range of embodied carbon values for various
building types and different structural systems. Then, three case studies illustrated the process
in sport stadia, historic bridges and tall buildings.
66
NR 3 • 2004 • NYHETER OM STÅLBYGGNAD
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v
b
c
e
in
m
li
t
s
it
in
c
s
STÅLBYGGN
The survey of existing buildings demonstrated that the highest weight of material come from
concrete, where the highest impacts are mainly due to concrete and hotrolled steel. The survey
reveals that healthcare buildings have the highest amount of material (range between 1000 and
2300 kg/m2), followed by residential buidlings (range between 1500 and 1800 kg/m2), whereas
office or government buildings have the lowest amount of material (range between 500 and
1500 kg/m2). The GWP shows similar trends with typical values between 100 and 1000
kgCO2e/m2. The various structural systems, such as concrete, steel, timber and composite, were
compared. Timber had the lowest cradle-to-site impact.
The case studies of the stadia illustrated an important aspect of estimating the GWP of
buildings: the choice of functional unit. Dividing the total amount of materials by area or by
seat resulted in different conclusions. When normalizing by seat, the Beijing Olympic Stadium
was shown to have an impact ten times higher than the London Olympic Stadium.
The case studies of the historic bridges showed that recent bridge design can take lessons from
history. The Keshwa Chaka Inca bridge illustrates temporary low-carbon design as opposed to
the Roman arch Pont Saint Martin using a permanent low-carbon design.
Finally, the case studies of the tall buildings illustrate the impact of structural design on the
material quantities and embodied carbon in structures. The results range from 250 to 2500
kg/m2 for the material quantities and 50 to 450 kgCO2e/m2 for the GWP.
“How much does your building weigh Mr. Foster?” – An Art Commissioners film
This chapter is the first attempt in research in answering this question asked by an Art
Commissioners film and by many structural engineers and architects.
67
68
7. Conclusions
“ There’s only one creature capable of leaving a footprint that size…”
From King Kong movie
7.1. Discussion of results
This thesis has three types of results: (1) a critical review, (2) a new database and (3) a survey
analysis. First, this research synthesizes the challenges and opportunities for collecting material
quantities and embodied carbon. Second, to collect this information, it develops a framework
for a database. Third, a survey of 200 real building projects formulates an understanding of the
material efficiency and life cycle impact of actual buildings.
(1) The first part of this thesis discusses the challenges and opportunities in estimating the
embodied carbon in structures. In order to obtain the Global Warming Potential
(GWP), Structural Material Quantities (SMQ) are multiplied by Embodied Carbon
Coefficients (ECC). For each of these three parameters, one main challenge and one
main opportunity are defined.
For the material quantities, the industry needs incentives to share enough data on their building
projects. Confidence in the results on material efficiency relies on voluntary data input from the
leading firms in the industry, such as design offices, engineering firms and contractors.
Motivations are necessary for stakeholders to spend additional time entering the material
amounts in the database. However, BIM models such as Revit offer the opportunity to collect
thousands of projects in an automated way. Linking Revit models to the database will generate
thousands of data on material quantities in buildings.
Another challenge is to identify accurate ECC values. The available numbers vary widely, due in
part to different life cycle stages included. Most currently available ECCs are cradle-to-gate.
Therefore, parts of the life cycle such as transportation, construction or demolition are omitted.
However, there is an opportunity to define default ECCs, based on the existing literature. For
unreinforced concrete, ECCs range between 0.1 and 0.2 kgCO2e/kg depending on the strength.
For reinforced concrete, the values lie between 0.13 and 0.23 kgCO2e/kg for 2% rebar and
between 0.18 and 0.28 kgCO2e/kg for 5% rebar. Average values for steel are 1.7 kgCO2e/kg for
rebar and 0.8 kgCO2e/kg for hotrolled steel. Values shift according to varying location,
manufacturing, transportation, fly ash replacement, recycled content, etc.
After obtaining these two key variables, calculating the GWP itself presents challenges. Indeed,
many firms request that their data be kept confidential. However, protecting the intellectual
ownership of companies critically compromises comprehensive transparency. Nonetheless, a
unified methodology will facilitate benchmarking of embodied carbon in structures. The
opportunity lies in defining a universal assessment of the GWP, by obtaining the two key
variables, SMQ and ECC, in a transparent way. Using the database developed in part (2) and
the survey in part (3), a greater confidence in the numbers on embodied carbon in building
structures will identify reference buildings for comparison.
69
(2) The second part of this thesis synthesizes the opportunities developed in part (1) into a
new database, called “deQo” or “database for embodied Quantity outputs”. This thesis
establishes a framework for this database collecting material quantities and embodied
carbon of building projects.
A relational database is developed in MySQL connected to an html web-interface through php
scripts. The deQo tool collects not only the embodied carbon, in addition to the work from the
WRAP embodied carbon database (WRAP, 2014), but also the amounts of steel, concrete,
timber and other materials in building structures. The interface targets structural materials, but
the database was designed to expand to all building materials.
Many leading engineers are developing methods for estimating the embodied carbon of their
projects, such as the SOM environmental analysis tool (SOM, 2013) or the Tally environmental
impact tool (Tally, 2014). The review of these existing tools and conversations with leading
experts have defined the parameters in deQo.
The field of life cycle impacts of buildings is maturing and the existing efforts will likely soon
merge into a comprehensive approach. This database is a first step towards an agreement on
ranges for material weights and embodied carbon in typical buildings. In the long term, deQo
will offer the industry a basis for benchmarks on material efficiency as well as low-carbon
buildings.
(3) The third part of this thesis analyzes a survey of over 200 buildings collected through
deQo developed in part (2). A unified methodology (GWP = SMQ ! ECC) is applied to
the data from the survey and to three case studies in more detail.
A survey of 200 existing buildings reveals the material efficiency and the carbon impact of
structures. As can be expected, healthcare buildings have the highest material amounts between
1000 and 2300 kg/m2 and the highest embodied carbon between 300 and 800 kgCO2e/m2.
Residential buildings also have high impacts, with material quantities ranging from 1100 to 1900
kg/m2 and GWP values ranging from 250 to 750 kgCO2e/m2. The lowest impacts can be found
in office and government buildings with material quantities between 500 and 1500 kg/m2 and
GWP between 200 and 1000 kgCO2e/m2. In general, the typical embodied carbon in structures
ranges from 100 to 1000 kgCO2e/m2. Additionally, the different structural systems are compared,
with timber having the lowest impact when taking into account cradle-to-site life cycle stages.
Furthermore, detailed case studies illustrate three important aspects on comparing embodied
carbon and material efficiency in buildings. The first case study analyzes stadia. The study
illustrates the importance of an appropriate functional unit. Indeed, when the material
quantities are normalized by floor area, stadia have a lower impact compared to other building
types in the survey. However, for a more comprehensive view on the GWP of stadia, the
material quantities can be divided by number of seats as a functional unit. The Beijing Olympic
Stadium or “Bird’s Nest” shows the highest amount of materials and impact, up to ten times
higher than the London Olympic Stadium. Results therefore debate whether the floor area is
the best choice as a functional unit. Another option for comparing the embodied carbon across
building types is the number of total occupants, focusing on the service of the building rather
than the geometry.
70
The second case study is the comparison of two historic bridges: the Inca grass bridge “Keshwa
Chaka” and the Roman stone arch “Pont Saint Martin”. The trade-offs between temporary and
permanent structures raise the question of what the total lifespan of buildings should be.
Lessons learned from these historic structures are the following: using local materials and
manufacturing and using force paths to shape structures. These strategies are followed in both
the temporary and permanent options.
The last case study consists of tall buildings. The material quantities range widely from 250 to
2500 kg/m2 as does the embodied carbon from 130 to 450 kgCO2e/m2. The structural system
revealed itself crucial to lower the impact on the environment.
Taken as a whole, the three contributions (1), (2) and (3) offer a new understanding of
material efficiency and the life cycle impact of building structures.
The critical review of the current challenges in part (1) has helped to develop a transparent,
interactive, growing database in part (2). This database is crucial in the comparison of existing
buildings in part (3). The combination of all results provides confidence in the numbers for
material quantities and GWP of building structures.
7.2. Summary of contributions
This thesis answers the following key question: “What is the embodied carbon for different
structures?” The answer to this question is important for multiple reasons. First, unlike
operational carbon, embodied carbon is permanent. Lowering the latter therefore leads to
immediate savings in carbon emissions. Moreover, the percentage of embodied carbon in the
whole building life cycle is becoming significant with increasing operational energy efficiency
and shortening building lifespans. Finally, structural engineers and architects need a transparent
way of comparing the life cycle impact of their projects against reference buildings, especially
since rating schemes started incorporating embodied carbon in their credits.
The major contribution of this thesis is to pave the way to a more unified method for collecting
material quantities, defining accurate ECC ranges and calculating the GWP of building
structures. The results discussed in Section 7.1 are a first attempt to estimate the material
efficiency and environmental impact of buildings in a transparent way. An understanding of the
emissions of buildings will become as intuitive as the CO2 emissions of cars. For comparison,
driving from Philadelphia to Boston (480km) would generate 104 kg of carbon, whereas the
construction of the One World Trade Center or “Freedom Tower” generated 100,000,000 kg
of carbon.
First, the challenges and opportunities encountered in existing literature and tools are analyzed.
Three aspects are studied: the two key variables, SMQ and ECC, and an equation calculating
the GWP. Separating the current practice in three topics develops a transparent approach. With
a critical review of current literature and tools, this thesis creates a basis for a more unified and
transparent methodology.
71
Second, the synthesis of the opportunities rising from the challenges led to a framework for a
new database. Indeed, a new interactive, growing database was created to collect thousands of
building projects from leading structural design firms. The database of embodied Quantity
outputs or “deQo” incorporates the simple method multiplying two key variables to obtain the
GWP.
Third, deQo already collected over 200 existing projects from worldwide architecture or
structure companies. The survey of these projects contributed to a new understanding of
material efficiency and environmental impact of structures. The results for building structures
are normalized material weights ranging on average between 500 and 2500 kg/m2 and
normalized embodied carbon ranging on average between 250 and 750 kgCO2e/m2.
This thesis lays the groundwork that industry and research needs for benchmarking embodied
carbon in buildings. All of this work is motivated by the prospect that ultimately, designers will
incorporate Global Warming Potential as one of the factors to take into account in their design
process.
7.3. Future research
Based on the approach developed in this thesis, the following paths are open for exploration:
•
Integrate Building Information Modeling (BIM) in carbon estimating tools
While this thesis used BIM such as Revit through the data collection from practitioners,
ultimately, there is a need for integrating BIM models directly into the database in order to
compute thousands of projects at the time. Plugging in Revit software will allow benchmarking
through comparison of thousands of projects across companies.
•
Dynamic alternative to the GWP
The measure of the GWP, i.e. “carbon dioxide equivalent”, is a static way of measuring the
environmental impact of buildings. However, Kendall (2014) demonstrates this static
measurement could skew the results, because methane tends to disappear with the years as
opposed to carbon dioxide emissions. Converting gases such as methane to the equivalent in
carbon dioxide is consequently a static simplification of a dynamic phenomenon. Though this
thesis used GWP as the most feasible, currently available assessment method, future research
can explore how to integrate complex dynamic parameters such as the instantaneous climate
impact (ICI) or the cumulative climate impact (CCI). These factors would better reflect the
dynamic aspect of greenhouse gases.
•
Expanding to non-structural materials and to operational carbon
The thesis is limited to structural materials only and the embodied life cycle stages. The method
can be extrapolated to non-structural materials such as cladding and services. Also, combining
the embodied and operational carbon will give a complete view of the whole life cycle impact
of buildings.
72
•
Extrapolating on the urban scale
ENERGY
ENERGY
This thesis looks at the embodied carbon on the material and building scale. However, current
research efforts exist to implement embodied carbon at the urban scale. The “Urban Modeling
Interface” or “umi” (umi, 2014), developed in the building technology program at MIT,
simulates the life cycle impact of neighborhoods. A buildings’ massing model is associated with
selected materials from a database. The result is a visualization ofDESIGNING
the LCA
impacts
yearE
THE
E URBAN
ENER
RGYper
LIFECYCL
(Figure 7.1).
EMB
BODIED ENERGY
Y
0
10
20
30
40
50
60
70
80
90
100
110
1
0
100
20
30
40
5
TIME
Figure 15: Em
mbodied and operation energy
Figure 7.1: Massing model and yearly impact visualization in “umi” after (umi, lifec
2014;
Cerezo,
cycle time
functio
ons 2013)
•
Figure 16: Life c
hypotheeti
Theconceptual
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b
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Incorporate embodied carbon in design, starting at the initial
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Architecture answers a combination of many different boundary conditions.
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cannot be analyzed in isolation from other design factors. This thesis offers an objective
otal lifecycle
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ned by the p
carbon in architecture, starting at the initial concept scheme.
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This ‘crossing po
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both present the same value.
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First, a study is necessary on the followed strategies in low impact stbuildings
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er
exploring the successful case studies, themes will appear in the ddesign
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esigned to last a very long time, operation
o
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nergy tends
analysis should determine how embodied carbon correlates with
financial cost. Balancing
actor. Therefore, it is not possible to evaluate thee relative imp
po
fa
material and construction cost with financial advantages due to accreditation
will
pave
the
way
energy withou
ut defining a specific tem
mporal framew
work.
to a cost efficient strategy for low impact buildings. Third, it is crucial to take into account how
strategies for decreasing embodied carbon in buildings interact with other variables in the
design process. Indeed, a method that lowers the embodied carbon of a building could in some
cases undermine the operational energy, the structural efficiency, the functionality or the spatial
C impacts
CERE
EZOrelate
DAVILA - to
MDesS
M
Thesis ( Energy and Env
experience of the architecture. Further research can explore how life cycleCARLOS
these other parameters. The relationship of embodied carbon to other criteria will identify its
importance in the design process.
73
Matl
Quants
ECC
Values
1. GWP
1.  Patterns in low
embodied carbon
design
B)
2. vs. financial cost
3. vs. other design
parameters
S y n t h e s i s
Project 1
Project 2
Project 3
Project 4
Project 5
…
Project 10
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Project 100
…
Growing
Multi-scale
-
3. Case Studies
2. Benchmarks
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A)
Objective
A n a l y s i s
1_Research_Objectives
Figure 7.2: Further research
The objective analysis in this thesis combined with a future multi-scale synthesis will lead to a
new design approach in architecture. The qualitative and quantitative assessment of embodied
life cycle impacts of buildings will develop new design criteria. While leaving all design options
open to architects and engineers, the expanded knowledge will inform designers and their
clients on the impact of their choices. These new guidelines will create opportunities for
reducing the embodied carbon in the built environment.
•
Making the business case
Finally, research on embodied carbon alone is not enough to incorporate change in design. Not
only structural engineers and architects should be informed of low-carbon design strategies, but
also the government and the public. It is important to make the business case for lowering the
embodied carbon of structure, either by informing, rewarding through rating schemes such as
LEED and BREEAM or by legislation.
“Informing both government and the media of the need for the right legislation, and the long-term cost benefits of
this, is probably as important in the delivery of significant change as developing the actual solutions to deliver
energy and carbon savings in buildings.” – David Clark (CLARK, 2013)
74
Bibliography and references
The references and bibliography of this thesis can be found hereunder. Part 1 gives the general
bibliography and references in alphabetical order. Part 2, 3 and 4 give the references specific to
the case studies. A detailed list of references for the material quantities in the stadia, historic
bridges and tall buildings enhances the transparency of the applied method.
Part 1: General bibliography and references
Alcorn, A. (1996). “Embodied Energy Coefficients of Building Materials.” Centre for Building Performance
Research, Victoria University of Wellington, Wellington.
Ali, M. M. and Moon, K. S. (2007) “Structural Developments in Tall Buildings: Current Trends and
Future Prospects.” Architectural Science Review, 50 (3): pp. 205–223.
Amato, A. and Eaton, K. (1998) “A comparative Life Cycle Assessment of Modern Office Buildings.”
The Steel Construction Institute, Berkshire.
Arup (2008) “Structural Scheme Design Guide.” Arup, Internal report, London.
Athena Sustainable Materials Institute. (2009) “Impact Estimator for Buildings.” Accessed
November 15, 2013. http://www.athenasmi.org
Baker, William, Skidmore, Owings and Merrill, personal conversation with John Ochsendorf and
Catherine De Wolf, Cambridge (MA), October 23, 2013.
Blake, M.E. (1947) Ancient Roman Construction in Italy forom the Prehistoric Period to Augustus. Washington:
Carnegie Institution, 421p.
Braham, W. W. and Hale, J. A. (2013) “1929 Richard Buckminster Fuller. 4D Time Lock.” in:
Rethinking Architectural Technology, London: Routledge, pp. 42-46.
Build Carbon Neutral. (2007) “Estimate the embodied CO2 of a whole construction project.”
Accessed December 1, 2013. http://buildcarbonneutral.org
Cerezo, C. (2013) “Designing The Urban Energy Life Cycle. A framework and a tool for embodied
energy accounting and conservation.” Masters in Design Studies thesis, advisor: Christoph Reinhart,
Harvard University, Cambridge (MA).
Chapman, P. F. and Roberts, F. (1983) Metal Resources and Energy. Oxford: Butterworth-Heinemann,
256p.
Cho, H.-W., Roh, S.-G., Byun, Y.-M. and Yom, K.-S. (2004) “Structural Quantity Analysis of Tall
Buildings.” CTBUH Conference: Tall Buildings in Historical Cities – Culture & Technology for Sustainable Cities,
Seoul, October 10–13, pp. 662-668.
Clark, D.H. (2013) What color is your building? Measuring and reducing the energy and carbon footprint of buildings.
London: RIBA Publishing, 263p.
75
Clune, R. (2013) “Algorithm Selection in Structural Optimization.” PhD thesis, advisor: John
Ochsendorf, Massachusetts Institute of Technology, Cambridge (MA).
Cole, R. J. and Kernan, P. C. (1996) “Life-Cycle Energy Use in Office Buildings.” Building and
Environment, 31 (4), pp. 307-317.
Collins, F. (2010) “Inclusion of carbonation during the life cycle of built and recycled concrete:
influence on their carbon footprint.” International Journal of Life Cycle Assessment, 15 (6), pp. 549-546.
CTBUH (2010) “Tall Buildings, Structural Systems and Materials.” CTBUH Journal: Tall Buildings in
Numbers (2), pp. 40-41.
Darling, D. (2004) The Universal Book of Mathematics, New York City: Wiley, 90p.
De Wolf, C., Iuorio, O. and Ochsendorf, J. (2014) “Structural Material Quantities and Embodied
Carbon Coefficients: Challenges and Opportunities.” Sustainable Structures Symposium, Corey Griffin (ed.),
Portland: Portland State University, April 17-18, pp. 309-328.
De Wolf, C. and Ochsendorf, J. (2014) “Participating in an Embodied Carbon Database. Connecting
structural material quantities with environmental impact.” The Structural Engineer, 2 (February), pp. 30-31.
deQo (2014) “database for embodied Quantity outputs.” available at embodiedco2.scripts.mit.edu
Dias, W. P. and Pooliyadda, S. P. (2004) “Quality based energy contents and carbon coefficients for
building materials: A System approach.” Energy 29, pp. 561-580.
Dixit M.K., Fernández-Solís J.L., Lavy S. and Culp C.H. (2012) “Need for an embodied energy
measurement protocol for buildings: A review paper.” Renewable and Sustainable Energy Reviews, 16 (6), pp.
3730-3743.
Dunlap, D.W. (2014) “1 World Trade Center Is a Growing Presence, and a Changed One.” The New
York Times, Accessed June 12, 2014. http://cityroom.blogs.nytimes.com/2012/06/12/1-world-tradecenter-is-a-growing-presence-and-a-changed-one/
Eaton, K. J. and Amato, A. (1998) “A Comparative Life Cycle Assessment of Steel and Concrete
Framed Office Buildings.” Journal of Constructional Steel Research, 46, 1-3.
EcoInvent (2013) “EcoInvent.” Swiss Centre for Life Cycle Inventories, Accessed December 13, 2013.
http://www.ecoinvent.ch
Elnimeiri, M. and Gupta, P. (2009) “Sustainable Structure of Tall and Special Buildings.” CTBUH 2nd
Annual Special Edition, Tall Sustainability, Wiley, 17 (5), pp 881-894.
Eurofer, (2000) “European Steel Industry and Climate Change.” European Confederation of Iron and Steel
Industry.
GaBi (2013) “GaBi 4 extension database III: steel module and GaBi 4 extension database XIV:
construction materials module.” PE International, Accessed December 1, 2013. www.gabi-software.com
Hammond, G. and Jones, C. (2010). “Inventory of Carbon & Energy (ICE), Version 1.6a.” Sustainable
Energy Research Team (SERT), Department of Mechanical Engineering, Bath: University of Bath.
76
IISI (2013) “The measure of our sustainability, Report of the world steel industry 2004.” International
Iron and Steel Institute (IISI), Accessed September 12.
http://www.worldsteel.org/dms/internetDocumentList/bookshop/Sustainability_Report2004/docume
nt/2004%20Sustainability%20Report.pdf
IPCC (2014), “Climate Change 2014: Mitigation of Climate Change.” International Panel for Climate Change
(IPCC), Geneva, Accessed April 15, 2014. www.ipcc.ch.
ISSF (2013) “ISSF - Stainless steel LCI spreadsheet.” Institute of Stainless Steel Forum (ISSF), Brussels,
Accessed September 12, 2013. http://www.worldstainless.org/Files/issf/non-imagefiles/PDF/GeneralIntroductiontostainlesssteelLCI1.pdf
Iuorio, O., Landolfo, R. and Ochsendorf, J. (2013) “Embodied Carbon of Lightweight Steel
Structures.” Proceeding of XXIV Congresso C.T.A.: The Italian steel days, pp. 333-340.
Kaethner, S. and Burridge, J. (2012) “Embodied CO2 of structural frames.” The Structural Engineer,
May, pp. 33-40.
Kendall A. (2014) “Climate change mitigation: Deposing global warming potentials.” Nature Climate
Change, 4(5), Nature Publishing Group, a division of Macmillan Publishers Limited, pp. 331-332.
Khan F. R. and Rankine J. (1981) Tall building systems and concepts. New York City: American Society of
Civil Engineering, 1337p.
KPF (2012) “United Tower.” Accessed November 11, 2014. www.kpf.com/project.asp?S=1&ID=246
Lagerblad, B. (2005) “Carbon Dioxide Uptake During Concrete Life Cycle - State of the Art.” Swedish
Cement and Concrete Research Institute, CBI, Stockholm.
Lynde, F. C. (1890) Descriptive Illustrated Catalogue of the sixty-eight competitive designs for the Great Tower for
London. London: The Tower Company, St. Stephen's Chambers.
Marmon, J., Naugle, M. and Werner, W. (2014) “Buildings instead of Landfills: recycled plastic waste
in concrete structures.” Sustainable Structures Symposium, Corey Griffin (ed.), Portland: Portland State
University, April 17-18, pp. 247-260.
Moncaster, A.M. and Symons, K.E. (2013) “A method and tool for ‘cradle to grave’ embodied
carbon and energy impacts of UK buildings in compliance with the new TC350.” Energy and Buildings 66,
Cambridge (UK), pp. 514-523.
Moynihan M.C. and Allwood J.M. (2012) “The flow of steel into the construction sector.” in:
Resources, Conservation and Recycling 68, Cambridge: University of Cambridge, pp. 88-95.
Munro, D. (2006) “Swiss Re’s Building, London.” Arup, London, Accessed November 11, 2012, 8p.
www.epab.bme.hu/oktatas/2009-2010-2/v-CA-B-Ms/FreeForm/Examples/SwissRe.pdf
National Stadium (2014) “National Stadium (Bird’s Nest).” Arup, Accessed on April 30, 2014.
www.arup.com/projects/chinese_national_stadium.aspx
77
New York Times (2014), “Moma to raze ex American folk art museum building.” New York Times,
Accessed on April 16, 2014. www.nytimes.com/2013/04/11/arts/design/moma-to-raze-ex-americanfolk-art-museum-building.html?pagewanted=all&_r=0
Ochsendorf, J., Norford, L., Brown, D., Durschlag, H., Hsu, S. L. and Love, A. (2011). “Methods,
Impacts and Opportunities in the Concrete Building Life Cycle, Research Report R11-01.” Concrete
Sustainability Hub, Department of Civil and Environmental Engineering. Cambridge (MA): Massachusetts
Institute of Technology
Ochsendorf, J.A. (2004) “Sustainable Structural Design: Lessons from History.” Structural Engineering
International, 3, pp. 192-194.
Ochsendorf J.A. (1996) “Inca Suspension Bridges.” Department Report 96-8, Department of Civil and
Environmental Engineering, Cornell University.
PECD (2013) “Project Embodied Carbon Database.” Arup, In-house used tool.
Pullen S. (2000) “Estimating the Embodied Energy of Timber Building Products.” Journal of the Institute
of Wood Science, 15 No. 3 (87), pp. 147-151.
Reap, J., Roman, F., Duncan, S. and Bras, B. (2008) “A survey of unresolved problems in life cycle
assessment, Part 2: impact assessment and interpretation.” International Journal of Life Cycle Assessment,
13(4), pp. 290-300.
Revit (2014) “Building design and construction software.” Autodesk, Accessed April 1, 2014.
www.autodesk.com/products/autodesk-revit-family/overview
RICS (2014) “Methodology to calculate embodied carbon in a building’s construction life cycle.” Royal
Institution of Chartered Surveyors, data courtesy of Atkins, London.
Rizk, A. S. (2010) “Structural Design of Reinforced Concrete Tall Buildings.” CTBUH Journal, (1), pp.
34-41.
Sauven, Edward, Buro Happold, personal conversation with John Ochsendorf and Catherine De Wolf,
London, November 15, 2012.
Schlaich, Jörg, Schlaich Bergermann & Partner, personal conversation with John Ochsendorf and
Catherine De Wolf, Cambridge (MA), October 4, 2012.
Schumaker, J. (2014) “Embodied Carbon Efficiency Tool.” Thornton Tomasetti, Accessed on April 19,
2014. www.thorntontomasetti.com/blog/post/20-Embodied-Carbon-Efficiency-Tool
SEAONC Sustainable Design Committee and SEI Sustainability Committee (2013) “For
practicing structural engineers to provide comments to improve MIT Database Inputs Template.”
Report by Frances Yang, San Francisco.
SimaPro (2013) “The world’s most widely used LCA software.” SimaPro UK Ltd., Accessed November
12, 2013. www.simapro.co.uk
Simpson, S., Cousins, F., Ayaz, E. and Yang, F. (2010) “Zero Carbon Isn’t Really Zero: Why
Embodied Carbon in Materials Cannot be Ignored.” Design Intelligence. Arup, Accessed December 1,
78
2013. www.slideshare.net/enginayaz/zero-carbon-isnt-really-zero-why-embodied-carbon-in-materialscant-be-ignored
Smith, B.P. and Feldson (2008) “Whole Life Carbon Footprinting”, Simons Developments, The
Structural Engineer, 86 (6) pp. 15-16.
SOM (2013) “Environmental Analysis Tool™.” Skidmore, Owings & Merrill, Accessed August 30, 2013.
www.som.com/publication/environmental-analysis-tool-tm
Struble, L. and Godfrey, J. (1999) “How Sustainable is Concrete? International workshop on
sustainable development and concrete technology.” Chicago: University of Illinois.
Stubbles, J. (2007) “Carbon 'Footprints' in U.S. Steelmaking.” Steel Manufacturers Association (SMA),
Accessed August 30, 2013. http://66.39.14.41/archive/20071120.htm
Tally (2013) “Revit add-in Tally™ (beta version). Real Time Environmental Impact tool. revised Tally
Revit Application.” Kieran Timberlake Research Group, Accessed December 30, 2013.
www.kierantimberlake.com/pages/view/95/tally/parent:4
The Concrete Centre (2013) “Embodied carbon dioxide (CO2e) of concretes used in buildings.” mpa
The Concrete Centre on behalf of the Sustainable Concrete Forum, London.
Umi (2014) “Urban Modeling Interface.” Accessed on May 3, 2014. urbanmodellinginterface.ning.com
USGBC (2013) “LEED v4 for Building Design And Construction.” U.S. Green Building Council or
USGBC, Washington D.C., 154p.
Vares, S. and Häkkinen, T. (1998) “Environmental burdens of concrete and concrete products.”
Technical Research Centre of Finland, VTT Building Technology, Espoo, Accessed July 20, 2013.
http://www.tekna.no/ikbViewer/Content/739021/doc-21-10.pdf
Webster M. D., Meryman H., Slivers A., Rodriguez-Nikl T., Lemay L. and Simonen K. (2012)
“Strucutre and Carbon – How Materials Affect the Climate.” SEI Sustainability Committee, Carbon Working
Group, American Society of Civil Engineers or ASCE, Reston.
Weight D.H. (2011) “Embodied through-life carbon dioxide equivalent assessment for timber
products.” Institution of Civil Engineers Energy 164, Issue EN4, pp. 167–182.
Wise, C., Pawlyn, M. and Braungart, M. (2013) “Living in a materials world.” Eco-engineering, Nature,
494, pp. 172-175.
Wolfgang, Werner and Dugum, Hussam, Thornton Tomasetti, personal conversation with John
Ochsendorf and Catherine De Wolf, Cambridge (MA), July 29, 2013.
WRAP (2014) “Embodied Carbon Database.” UK Green Building Council or UKGBC, Accessed April 14,
2014. http://ecdb.wrap.org.uk
Yang, F. (2014) “Benchmarking Embodied Impact Performance of Structure.” Sustainable Structures
Symposium, Corey Griffin (ed.), Portland: Portland State University, April 17-18, pp. 131-146.
Yang, Frances, Arup, personal conversation with Catherine De Wolf, San Francisco, July 11, 2013.
79
Yang, F., Shook, D., Williams, P. and De Wolf, C. (2013) “Embodied carbon: a meeting of the
minds and collaboration opportunities.” Arup, SOM, Webcor, MIT, Conference, July 1, San Francisco.
Young, S. B., Shannon T. and Russell A. (2002) What LCA can tell us about the cement industry. Five
winds international; World business council for sustainable development, 117p.
Part 2: Stadia references
This section gives the references for the stadia. The material quantities were cross-referenced
with the following sources. They are classified per stadium.
Millenium Stadium, Cardiff
[1] Design Build Network (2014) “Millennium Stadium, Wales.” Accessed April 2, 2014.
www.designbuild-network.com/projects/millennium-stadium-wales/
[2] Millennium Stadium (2014) “Facts and Figures.” Accessed April 2, 2014.
www.millenniumstadium.com/information/facts_and_figures.php.
Allianz Arena, Munich
[3] Allianz Arena (2014) “Nuts and Bolts.” Accessed April 15, 2014. www.allianzarena.de/en/fakten/detaillierte-zahlen/
Joao Havelange Olympic Stadium
[4] Design Build Network (2014) “João Havelange Olympic Stadium, Brazil.” Accessed April 2,
2014. www.designbuild-network.com/projects/joao-havelange/.
London Olympic Stadium
[5] Buro Happold (2013) “London 2012 Olympic Stadium.” Accessed April 20, 2013.
www.burohappold.com/projects/project/london-2012-olympic-stadium-132/.
[6] Detail Das Architecturportal (2012) “London 2012 – Olympic Stadium.” www.detailonline.com/architecture/news/london-2012-olympic-stadium-019389.html, Detail Magazine
7+8/2012, 2012.
[7] National Geographic Channel (2012) “London’s Olympic Stadium.” Accessed August 20,
2012. natgeotv.com/uk/londons-olympic-stadium.
[8] Sauven, Edward, engineer at Buro Happold, personal conversation with John Ochsendorf and
Catherine De Wolf, London, November 13, 2012.
Wembley Stadium
[9] Design Build Network (2014) “Wembley Stadium, London, United Kingdom.” Accessed
April 2, 2014. www.designbuild-network.com/projects/wembley/.
[10] Wembley (2014) “Stats and Facts.” Accessed April 2, 2014.
www.wembleystadium.com/Press/Presspack/Stats-and-Facts.
Aviva Stadium
[11] Design Build Network (2014) “Aviva Stadium, Ireland.” Accessed April 2, 2014.
www.designbuild-network.com/projects/aviva-stadium/.
80
[12] Kilsaran Build “Case Study: Architectural Concrete at the Aviva Stadium.” Report.
[13] McGuirk, Laura, engineer at Kilsaran Build, in personal conversation with Julia Hogroian and
Catherine De Wolf, March 18, 2014.
Australia Sydney Stadium
[14] Cullen J., Carruth M.A., Moynihan M., Allwood J.M. and Epstein D. (2011) “Learning
legacy Lessons learned from the London 2012 Games construction project.” Cambridge
University, Olympic Delivery Authority, 031.
Emirates Stadium
[15] Association for Project Management (2014) “Emirates Stadium: More Than a World Class
Stadium.” Arcadis, AYHplc, Accessed April 2, 2014.
www.apm.org.uk/sites/default/files/Arcadis_Presentation_(Resized).pdf.
[16] Design Build Network (2014) “Emirates Stadium, United Kingdom.” Accessed April 2, 2014.
www.designbuild-network.com/projects/ashburton /.
Beijing National Stadium
[17] Arup (2012) “Chinese National Stadium.” Accessed August 20, 2012.
www.arup.com/Home/Projects/Chinese_National_Stadium.aspx
[18] Chinese Architect (2012) “Beijing National Stadium.” Accessed August 20, 2012.
www.chinesearchitecture.info/OLYMPICS/OL-001.htm.
[19] Design Build Network (2014) “Beijing National Stadium, ‘The Bird’s Nest’, China.” Accessed
April 2, 2014. www.designbuild-network.com/projects/national_stadium/.
Jaber Al-Ahmad Stadium
[20] Kharafi Group (2012) “Al-Sheikh Jaber Al-Ahmad International Sports Stadium, Kuwait.”
Accessed August 20, 2012. www.makharafi.net/buildings.html.
[21] Kuwait City (2012) “Jaber Al-Ahmad International Stadium (60,000).” Accessed August 20,
2012. skyscrapercity.com/showthread.php?t=283227.
[22] Stadiony (2012) “Jaber Al-Ahmad International Stadium.” Accessed August 20, 2012.
stadiony.net/projekty/kuw/jaber_al_ahmad_stadium.
Part 3: Historic bridges references
This section gives the references for the historic bridges. The material quantities were crossreferenced with the following sources. They are classified per bridge.
[1]
[2]
Clune, R. (2013) “Algorithm Selection in Structural Optimization.” PhD thesis, Massachusetts
Institute of Technology, Cambridge (MA).
Ochsendorf, J.A. (2004) “Sustainable Structural Design: Lessons from History.” Structural
Engineering International, 3, pp. 192-194.
81
Pont Saint Martin
[3] Blake, M.E. (1947) “Ancient Roman Construction in Italy forom the Prehistoric Period to
Augustus”, Washington.
[4] Frunzio G. and Monaco M. (1998) “An approach to the structural model for masonry arch
bridges: Pont Saint Martin as a case study.” Centro Interdipartimentale di Ingegneria per I Beni Culturali,
Università Federico II, Napoli, paper in book (Sinopoli [9])
[5] Gneiss rockpack, Geology superstore, Accessed May 10, 2013.
www.geologysuperstore.com/product/hornblende-gneiss-rock-pack-1772
[6] O’Connor, C. (1993) Roman Bridges. Cambridge University Press, 235p.
[7] O’Connor, C. (1993b) Development in Roman stone arch bridges. University of Queensland, Australia.
[8] “Pont Saint Martin”, Locali dautore, Accessed May 2, 2013.
http://www.localidautore.com/paesi/pont-saint-martin-1678.aspx
[9] Sinopoli, A. (1998) “Arch Bridges: History, Analysis, Assessment, Maintenance and Repair”, 2nd
International Conference, Venice, 6-9 October 1998, pp. 231-238.
Keshwa-Chaka bridge
[10] Foer J. (2013) “The Last Incan Grass Bridge. The sixth hidden wonder of South America.” Slate,
Accessed May 13, 2013.
www.slate.com/articles/life/world_of_wonders/2011/02/the_last_incan_grass_bridge.html
[11] Ochsendorf J.A. (1996) “Inca Suspension Bridges.” Department Report 96-8, Department of Civil
and Environmental Engineering, Cornell University.
[12] “The Last Handwoven bridge.” Accessed May 2, 2013. www.atlasobscura.com/places/lasthandwoven-bridge
Part 4: Tall building references
Alia, M. M. and Moona, K. S. (2007) “Structural Developments in Tall Buildings: Current Trends and
Future Prospects.” Architectural Science Review, 50(3), pp. 205-223, Accessed October 22.
www.tandfonline.com/doi/pdf/10.3763/asre.2007.5027
30 St Mary Axe
[1] Aldersey-Williams, H. (2011) “Towards biomimetic architecture.” Accessed October 15,
2012. www.nature.com/nmat/journal/v3/n5/full/nmat1119.html
[2] Arup (2012) “30 St Mary Axe.” Accessed October 15, 2012.
www.arup.com/Home/Projects/30_St_Mary_Axe/
[3] Munro, D. (2006) “Swiss Re’s Building, London.” Arup, London, 8p., Accessed November 11,
2012. www.epab.bme.hu/oktatas/2009-2010-2/v-CA-B-Ms/FreeForm/Examples/SwissRe.pdf
[4] Freiberger, M. (2007) “Perfect buildings: the maths of modern architecture.” Plus Magazine,
March, Accessed November 1, 2012.
www.rigb.org/assets/uploads/docs/PLUS_MAGAZINE_Perfect%20buildings.pdf
The United Tower
[5] KPF (2012) “United Tower.” Accessed November 11, 2012.
www.kpf.com/project.asp?S=1&ID=246
[6] El Mostafa, Hakam, KIPCO Group, U.R.E., Personal conversation on October 20, 2012.
[7] United Tower (2012) “We love the clouds.” 48p., Accessed November 2, 2012.
http://www.unitedtowers.net/AxCMSwebLive/upload/utbrochure1_1172.pdf
[8] Unitedtowers.net (2012), Accessed October 20, 2012. www.unitedtowers.net/
82
[9]
Perime (2012) “United Tower”, Sharq, Kuwait, Accessed November 2, 2012.
www.perime.com/projects.cfm
[10] UN Data (2012) Accessed November 2, 2012.
data.un.org/CountryProfile.aspx?crName=KUWAIT#Environment
The Shard
[11] Ferguson, H. (2012) "Building the Shard." Ingenia, September, 24-30.
[12] Kennett, S. (2013) "The Shard: Foot of the Mountain." Building.co.uk, Accessed September 11,
2013. www.building.co.uk/the-shard-foot-of-the-mountain/3162661.article
[13] Moazami, K. (2008) and Ahmad Rahimian. "Shard at London Bridge Tower."
STRUCTUREmag, June, Accessed September 10, 2013.
www.structuremag.org/article.aspx?articleID=694
[14] Moazami, K., Parker, J., and Giannini, R. (2010) “Unique Hybrids at London Tallest.”
CTBUH 8th World Congress: Steel-Concrete-Steel, Dubai.
[15] Thompson, P. (2010) "Shard's Giant Core Shoots up." Steel Construction News 7187: 1-3.
[16] WSP (2013) “The Shard.” London: WSP.
Al Hamra Firdous Tower
[17] Agarwal, R., Noor, A., Lindsay, H., Neville, M., Mazeika, A., and Sarkisian, M. (2007)
“Sculpted High-rise, The Al Hamra Tower.” SOM, Council on Tall Buildings and Urban Habitats:
Structural Engineers World Congress, Bangalore, India.
[18] Gonchar, J. (2012) "Al Hamra Firdous Tower." Architectural Record, May.
[19] Haney, G. (2009) "Al Hamra Firdous Tower." Architectural Design, Mar.-Apr. 2009, pp. 38-41.
[20] Sarkisian, M., Aybars, A., Neville, M., and Mazeika A. (2012) "Sculpting a Skyscarper."
Civil Engineering—ASCE 82.9, pp. 52-61. Business Source Complete.
Willis Tower
[21] SkycraperPage (2014) “Willis Tower.” SkyscraperPage.com, Accessed May 1, 2014.
http://skyscraperpage.com/cities/?buildingID=5
World Financial Center
[22] Vertigo (1999) “The strange new world of the contemporary city.” Rowan Moore (ed.),
Laurence King, Glasgow.
[23] Construction Technology (2012) “Tall Buildings-Shanghai World Finance Center,
Ahmedabad.” Cept University.
[24] Arcelor Mittal (2012) “Shanghai World Financial Center.” Accessed October 10, 2012.
www.constructalia.com/english/case_studies/china/shanghai_world_financial_center
Taipei 101
[25] Skyscrapercenter (2014) “Taipei 101.” Skycsrapercenter.com, Accessed May 1, 2014.
www.skyscrapercenter.com/taipei/taipei-101/117/
[26] Concretepumping (2014) “World Record Pumping Height Achieved on Tallest Building
2004”, Accessed May 1.
http://concretepumping.com/dictionary/index.php/WORLD_RECORD_PUMPING_HEIG
HT_ACHIEVED_ON_TALLEST_BUILDING_2004
83
One World Trade Center
[27] Tweeten, L. and Maltby, E. (2014) “Inside the tower, The top of America Exclusive: the
inside story of building one world trade center.” Time Magazine, March 17.
Shanghai Tower
[28] CTBUH YPC (2013) Presentation – Shanghai Tower. Presentation by the Young Professionals
Committee of the Council on Tall Buildings on May 22, 2013 at the Chicago Architecture
Foundation, Chicago, IL, USA. (www.youtube.com/watch?v=riRVkoUEBP4)
[29] Jacobson, C. (2012) “A New Twist on Supertall: An American firm approaches the design of
its 121-story, mixed use tower now rising in Shanghai as a vertical collection of
neighborhoods.” Architectural Record, May, Accessed October 1, 2012.
archrecord.construction.com/projects/portfolio/2012/05/Shanghai-Tower.asp
[30] Xia, J., Poon, D. and Mass, D.C. (2010) “Case Study: Shanghai Tower.” CTBUH Technical
Paper.
[31] Gensler Design Update (2010) “Shanghai Tower.” Gensler Publications, Accessed October 1,
2012. gensler.com.
[32] Gu, J.P. (2012) “Shanghai Tower: Re-Thinking the Vertical City.” CTBUH Technical Paper.
[33] Zhu, Y., Poon, D., Zuo, S. and Fu, G. (2012) “Structural Design Challenges of Shanghai
Tower.” CTBUH Technical Paper.
Burj Khalifa
[34] Baker, W.F., and Pawlikowski, J.J. (2012) “Higher and Higher: The Evolution of the
Buttressed Core.”
[35] Baker, W.F. (2012) “The World’s Tallest Building - The Burj Khalifa”
[36] Baker, W.F. (2012) “The Burj Khalifa Triumphs - Engineering an Idea: The Realization of the
Burj Khalifa”
[37] Abdelrazaq, A. “Design and Construction Planning of the Burj Khalifa.” Dubai, UAE
[38] Abdelrazaq, A. “Validating the Structural Behavior and Response of Burj Khalifa: Synopsis of
the Full Scale Structural Health Monitoring Programs.”
[39] Aldred, J. “Burj Khalifa - A new high for high performance concrete.”
[40] Baker, W.F., Skidmore, Owings & Merrill LLP, “Tall Buildings and the Burj Khalifa” Interview,
Accessed October 20, 2012. http://chicagowindowexpert.com/2010/04/22/bill-baker-ofskidmore-owings-merrill-llp-tall-buildings-and-the-burj-khalifa/
[41] SOM (2012) “Burj Khalifa - ARCHITECT OFFICIAL PROJECT PAGE”, Accessed October
20, 2012. www.som.com/project/burj-khalifa-formerly-burj-dubai
84
Appendices
Appendix A: Nomenclature
A.1. List of acronyms
BIM
BOM
BOQ
BREEAM
CCI
CIF
CO2e
deQo
ECC
EEC
GHG
GWP
html
ICE
ICI
IPCC
KPF
LCA
LCI
LEED
MIT
MySQL
PECD
php
RICS
SOM
SQM
umi
WRAP
Building Information Models
Bill of Materials
Bill of Quantities
Building Research Establishment Environmental Assessment Methodology,
available at: http://www.breeam.org
Cumulative Climate Impact
Carbon Intensity Factor, synonym of ECC
Carbon dioxide equivalent
database of embodied Quantity outputs,
available at: embodiedco2.scripts.mit.edu
Embodied Carbon Coefficient
Embodied Energy Coefficient
Greenhouse Gases
Global Warming Potential
HyperText Markup Language
Inventory of Carbon & Energy (Hammond and Jones, 2010)
Instantaneous Climate Impact
Intergovernmental Panel on Climate Change
Kohn Pedersen Fox Associates,
available at: www.kpf.com
Life Cycle Assessment
Life Cycle Inventory
Leadership in Energy and Environmental Design,
available at: http://www.usgbc.org/leed
Massachusetts Institute of Technology
Open-source relational database management system,
named after co-founder Michael Widenius's daughter, My
and SQL stands for Structured Query Language
Project Embodied Carbon Database,
developed by Arup and Climate Earth (Yang, 2014)
Hypertext PreProcessor (backronym), a server-side scripting language
Royal Institution of Chartered Surveyors,
available at: www.rics.org
Skidmore, Owings & Merrill LLP,
available at: www.som.com
Structural Material Quantities
urban modeling interface
Waste Reduction Action Program, developed the wrap embodied carbon database,
available at: ecdb.wrap.org.uk
85
A.2. Lexicon
Carbon Dioxide Equivalent
(CO2e)
The “equivalent” in carbon dioxide of all emitted
greenhouse gases (GHGs).
Carbon Dioxide (Only the CO2) ≠ Carbon Dioxide
Equivalent (CO2e), which converts all GHGs to the
“equivalent” in CO2.
For example, 1 lbs of methane (CH4) is equivalent to 21
lbs of carbon dioxide (CO2).
Cradle to Gate
The life cycle stages from the material extraction till the
finished product.
Cradle to Site
The life cycle stages from the material extraction till the
product arrives on site.
Cradle to Grave
All the life cycle stages: material extraction, processing,
product manufacturing, transport to site, construction,
use, demolition and either reuse/recycling/landfill.
All the life PROBLEM
cycle stagesLITERATURE
of a building
are illustrated
RESULTS
NEXT in
Figure A.1.
PROBLEM
WHY?
Why embodied?
CRADLE
GATE
Based on [CLARK, What Colour is your Building?]
SITE
GRAVE
Figure A.1: Life cycle stages of a building, based on
(CLARK, 2013)
4
Operational energy
Energy used for the heating, cooling, hot water,
ventilation and lighting of a building.
Embodied energy
Energy used for the material extraction, material
processing and product manufacturing, the transport of
products to the construction site, the construction of a
building and the demolition at the end of life. It is all
the life cycle energy excluding the operational energy.
86
Whole life cycle energy
Whole life cycle energy = operational energy +
embodied energy (definition a)
Sometimes, the transport of the building occupants (≠
transport of product), for example commuting of
employees for an office building, and their consumption
are also considered. The definition of whole life cycle
energy then also contains these aspects.
Whole life cycle energy = operational energy +
embodied energy + transportation energy +
consumption energy (definition b)
In this thesis, when talking about the whole life cycle
energy, definition (a) is implied.
Embodied carbon
Embodied Energy ≠ Embodied Carbon
Embodied carbon corresponds to the emitted
greenhouse gases (GHGs) to produce the embodied
energy. ‘Carbon’ is not the same as ‘energy’, as the
GHG emissions depend on the fuel used and the
carbon emitted or absorbed by the materials processed
too. For example, processing cement can emit CO2,
where timber sequestrates CO2.
Functional unit
A specified metric used to normalize the carbon
footprint of buildings in order to compare ‘apples to
apples’. For example, the useable floor area can be the
functional unit, so that the total embodied carbon is
divided by the total useable floor area. The GWP is
consequently measured in kgCO2e/m2. The number of
occupants is another example of a functional unit. The
GWP is then measured in kgCO2e/occupant.
Global Warming Potential
Measure of embodied carbon of a building project,
expressed in kg of carbon dioxide equivalent (kgCO2e)
per functional unit (usually m2).
87
Appendix B: Tables
B.1. Ten first projects in deQo
Program
Office, high rise
Government
Healthcare
Healthcare
Healthcare + Office
Office
Office, high rise
Office, mid rise
Central Utility Plant
Car Parking
Location
London, UK
New Port Beach, USA
San Francisco, USA
San Francisco, USA
LA, USA
CA & Mexico
USA
Seattle, USA
LA, USA
USA
Structural System
Steel, diagrid
Composite
Concrete
Concrete
Concrete
Concrete
Composite
Concrete
Composite
Concrete
Area (m2)
47,850
8,705
46,755
4,849
6,821
7,870
8,367
89,354
6,538
181,951
Table B.1: Ten projects entered through deQo, name made anonymous
Table B.2 gives the material quantities divided into sub- and superstructure and divided by
material: concrete (C), hotrolled steel (S) and reinforcement bar (R).
Substructure
kg/m2
C
S
R
Program
Office, high rise
Government
Healthcare
Healthcare
Healthcare + Office
Office
Office, high rise
Office, mid rise
Central Utility Plant
Car Parking
262
507
827
627
236
287
776
979
210
0
0
0
0
0
0
0
0
0
9
9
70
24
38
10
14
26
7
Superstructure
kg/m2
C
S
195
175
317
112
488
66
404
153
305
75
112
71
111
25
215
45
645
179
518
16
Total
kg/m2
R
4
10
11
13
9
13
4
5
21
24
C
195
579
995
1231
932
348
398
991
1624
728
S
175
112
66
153
75
71
25
45
179
16
R
4
19
21
83
33
51
13
19
47
31
Table B.2: Material quantities of the 10 projects in Table B.1.1.
Source
ECC
Program
Office, high rise
Government
Healthcare
Healthcare
Healthcare + Office
Office
Office, high rise
Office, mid rise
Central Utility Plant
Car Parking
LCA
Arup
Arup
Arup
Arup
Arup
Arup
Arup
Arup
Arup
C
0.16
0.14
0.10
0.15
0.15
0.15
0.11
0.12
0.08
0.15
ECC
kgCO2e/kg
S
0.89
1.41
0.56
1.40
1.42
1.38
1.49
1.48
1.04
1.88
R
0.89
0.57
0.57
0.57
0.57
0.56
0.57
0.57
0.43
0.57
GWPper material
kgCO2e/m2
C
S
R
31
156
4
83
157
11
101
37
12
185
215
47
139
106
19
52
98
29
42
37
8
124
66
11
130
187
20
107
30
17
GWPtotal
kgCO2e/m2
190
251
150
447
263
179
87
201
337
155
Table B.3: ECCs used for the materials and GWP of the 10 projects in Table B.1.1.
88
B.2. Analysis of stadia
unit
location
floor area
number of seats
area/seat
total steel
total rebar
total concrete
steel per area
rebar per area
concrete per area
steel per seat
rebar per seat
concrete per seat
ECC steel
ECC rebar
ECC concrete
EC steel per area
EC rebar per area
EC concrete per area
EC steel per seat
EC rebar per seat
EC concrete per seat
m2
m2/seat
kg
kg
kg
kg/m2
kg/m3
kg/m2
kg/seat
kg/seat
kg/seat
kgCO2e/kg
kgCO2e/kg
kgCO2e/kg
kgCO2e/m2
kgCO2e/m2
kgCO2e/m2
kgCO2e/seat
kgCO2e/seat
kgCO2e/seat
Millenium
Cardiff
40,000
74,500
0.54
12,000,000
4,000,000
40,000,000
300
100
1,000
161
54
537
0.88
1.71
0.13
264
171
130
142
92
70
Allianz
Munich
37,600
68,000
0.55
20,000,000
Joao H.
Rio de J.
34,250
45,000
0.76
2,700,000
London
London
61,575
80,000
0.77
10,700,000
Wembley
London
79,578
90,000
0.88
23,000,000
256,800,000
532
0
6,830
294
0
3,776
0.88
1.71
0.13
468
0
888
259
0
491
96,000,000
79
0
2,803
60
0
2,133
0.88
1.71
0.13
69
0
364
53
0
277
102,000,000
174
0
1,657
134
0
1,275
0.89
216,000,000
289
0
2,714
256
0
2,400
0.88
1.71
0.13
254
0
353
225
0
312
0.10
155
0
159
119
0
122
Table B.4: Data on stadia, five first stadia
unit
location
floor area
number of seats
area/seat
total steel
total rebar
total concrete
steel per area
rebar per area
concrete per area
steel per seat
rebar per seat
concrete per seat
ECC steel
ECC rebar
ECC concrete
EC steel per area
EC rebar per area
EC concrete per area
EC steel per seat
EC rebar per seat
EC concrete per seat
m2
m2/seat
kg
kg
kg
kg/m2
kg/m3
kg/m2
kg/seat
kg/seat
kg/seat
kgCO2e/kg
kgCO2e/kg
kgCO2e/kg
kgCO2e/m2
kgCO2e/m2
kgCO2e/m2
kgCO2e/seat
kgCO2e/seat
kgCO2e/seat
Aviva
Australia
Emirates
Beijing Jaber Al A.
Dublin
Sydney
London
Beijing
Kuwait
66,460
160,000
122,000
254,600
400,000
51,700
110,000
60,355
91,000
65,000
1.29
1.45
2.02
2.80
6.15
5,000,000
12,000,000
3,000,000
110,000,000
1,965,000
10,000,000
10,000,000
84,000,000 210,000,000 144,000,000 1,300,000,000 288,000,000
75
75
25
432
5
0
63
82
0
0
1,264
1,313
1,180
5,106
720
97
109
50
1,209
30
0
91
166
0
0
1,625
1,909
2,386
14,286
4,431
0.88
0.89
0.88
0.88
0.71
1.71
1.71
1.71
1.71
1.71
0.11
0.15
0.13
0.17
0.19
66
67
22
380
3
0
107
140
0
0
139
197
153
868
137
85
97
44
1,064
21
0
155
283
0
0
179
286
310
2,429
842
Table B.5: Data on stadia, five last stadia
89
B.3. Analysis of historic bridges
B.3.a. Calculations Pont Saint Martin
Legend
Span
31.4 m
Life time
2000 years
drawing
other
literature
Material
Gneiss
Limest.
Soil
Parts
ECC
0.017
0.017
Density
2610
2500
0.023
1600
Vault
Spandrel
Volume
m3
270
390
Pavi.
Parapets
Filling
42
26
780
Material
Gneiss
Gneiss
Limeston
e
Gneiss
Soil
http://geology.about.com/cs/rock_types/a/aarockspecgrav.htm
http://geology.about.com/cs/rock_types/a/aarockspecgrav.htm
http://soils.usda.gov/sqi/assessment/files/bulk_density_
sq_physical_indicator_sheet.pdf
Density
kg/m3
2610
2610
ECC
kgCO2e/kg
0.017
0.017
Weight
kg
704700
1017900
Weight
kg/m
22443
32417
GWP
kgCO2e/m
382
551
GWP
kgCO2e/m/y
0.19
0.28
2500
2610
1600
0.017
0.017
0.023
105000
67860
1248000
3344
2161
39745
Total
57
37
914
1940
0.03
0.02
0.46
0.97
Table B.6: Calculations Pont Saint Martin
The Pont Saint Martin has a span of approximately 35.6 m with a rise of one-third of the
span. The width of the bridge is 5.8m (4.6m between parapets) and the height is 12m (13.6m
when counting the parapet). The main material used in the bridge is blocks of local gneiss
(O’Connor, 1993).
Based on the drawings and descriptions in (Frunzio and Monaco, 1998; Sinopoli, 1998]), the
volumes of different parts of the Roman arch could be determined. The detailed calculations
are shown in attachment. The volume of the vault, spandrel walls, pavimentum and parapets,
which are made of stone, is 686 m3. The densities of the stones (Alden) are set at 2610 and 2500
kg/m3. This part weights 1790 tonnes. The interior part of the bridge, which is filled by 780 m3
of soil, with a density of 1600 kg/m3 (Soil, 2008), weights 1248 tonnes.
The ECC factors given by (Hammond and Jones, 2010) for gneiss and limestone are 0.017
kgCO2/kg and 0.023 kgCO2/kg for soil.
90
B.3.b. Calculations Keshwa-Chaka
Legend
Span
30 m
Life time
600 years
drawing
other
literature
Material
Stone
Puna
Sticks
ECC
0.056
0.01
0.01
Density
2500
395
500
Parts
Volume
m3
/
1.98
0.6
0.45
Material
Abutments
Cables
Ropes
Deck
Stone
Puna
Puna
Sticks
Density
kg/m3
2500
395
395
500
ECC
kgCO2e/kg
0.056
0.01
0.01
0.01
Weight
kg
9070
Weight
kg/m
302
GWP
kgCO2e/m
16.93
GWP
kgCO2e/m/y
0.03
3630
121
1.21
1.21
Total
18.14
1.24
Table B.7: Calculations Keshwa-Chaka
To calculate the embodied carbon of the 30 meter long Keshwa-chaka, a description of the
construction components is necessary.
The strands of grass used to braid are 45 centimeters (18 inch) long. Over 15240 meters (50000
feet) of grass cord are produced every year. The grass comes from the local mountainside and is
manufactured by twisting it by hand. The twenty-four cords are one centimeter (3/8 inch) thick
and almost 60 meters (200 feet) long. These cords are twisted into ropes with a diameter of five
centimeters (two inches). Next, these ropes are themselves braided in six 45 meters long cables.
These are the main structural elements of the grass bridge itself. This first part takes one day
and the help of all villagers to accomplish (Ochsendorf, 1996).
The second day of the festival, only adult male villagers work on the cutting of the old bridge
and the installation of the cables by minimizing the sag in the middle and wrapping and tying
them around the stone abutments. The stone abutments are masonry of 9070 kilogram (20000
pounds).
The last day, the Chaka-Camayoc or bridge-keeper ties the floor cables together and adds the
vertical cords between the floor and the handrails. He adds sticks and matted reeds to create a
deck on the floor (Ochsendorf, 1996).
The weight of one cable and decking is 907 kg (4100 pounds – 14*150 pounds = 2000 pounds).
The total weight of the bridge is 8000 pounds, which is 3630 kg. The stone abutments are 9070
kg (Ochsendorf, 1996). The grass used for the Keshwa-chaka is cut of the local mountainsides
and is typically the Puna grass found in the Andes. The ECC is similar to that of straw, 0.01
kgCO2/kg (Hammond and Jones, 2010).
91
B.4. Analysis of tall buildings
unit
Location
Date
Structural Engineer
Structural System
Floor area
Height
Number of floors
Total steel
Total rebar
Total concrete
Steel per area
Rebar per area
Concrete per area
ECC steel
ECC rebar
ECC concrete
EC steel/area
EC rebar/area
EC concrete/area
m2
m
kg
kg
kg
kg/m2
kg/m2
kg/m2
kgCO2e/kg
kgCO2e/kg
kgCO2e/kg
kgCO2e/m2
kgCO2e/m2
kgCO2e/m2
Mary Axe
United T. The Shard
Al Hamra
Willis
London
Kuwait
London
Kuwait
Chicago
2004
2011
2012
2011
1974
Arup
WSP
WSP
SOM
SOM
Steel
Reinforced
Reinforced
Diagrid
Concrete
Hybrid
Concrete
Steel
74,300
98,000
126,712
195,000
416,000
180
240
306
413
443
41
59
87
80
111
8,358,000
752,781 12,671,200
50,000
76,000
187,035
2,936,146
9,800,000
9,351,736 146,807,304 77,040,896 490,000,000 132,115,200
112
8
100
0
0
3
30
50
0
126
1,498
608
2,513
318
0.89
0.71
0.89
0.71
0.89
1.70
1.70
1.70
1.70
1.70
0.16
0.15
0.16
0.15
0.16
100
5
89
0
0
4
51
0
85
0
20
225
97
377
51
Table B.8: Data on stadia, five last stadia
unit
Location
Date
Structural
Engineer
Structural System
Floor area
Height
Number of floors
Total steel
Total rebar
Total concrete
Steel per area
Rebar per area
Concrete per area
ECC steel
ECC rebar
ECC concrete
EC steel/area
EC rebar/area
EC concrete/area
m2
m
kg
kg
kg
kg/m2
kg/m2
kg/m2
kgCO2e/kg
kgCO2e/kg
kgCO2e/kg
kgCO2e/m2
kgCO2e/m2
kgCO2e/m2
WFC
Shangai
2008
Leslie E.
Robertson
Associates
Trusses &
columns
381,600
492
101
13,861,826
4,748,813
237,440,637
36
12
622
0.88
1.70
0.17
32
21
106
Taipei 101
TaiPei
2004
Thronton T.;
Evergreen
Engineering
1WTC
New York
City
2014
Shanghai
Burj Khalifa
Shanghai
2014
Dubai
2010
WSP
Thornton T.
Composite
193,400
508
106
Hybrid
325,279
546
82
48,000,000
Concrete
521,000
632
128
SOM
Buttressed
Core
334,000
828
162
28,390,000
489,600,000
381,600,000
148
0
1,173
0.88
1.70
0.13
130
0
153
739,820,000
574,480,000
85
1,420
0.88
1.70
0.17
0
0
241
1,720
0.71
1.70
0.15
60
0
258
2,532
0.88
1.70
0.17
0
0
430
Table B.9: Data on stadia, five last stadia
92