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especially in developing nations like India. Between 1970 and 2010, global material consumption has
grown three fold from 22 billion tonnes to 70 billion tonnes and per capita has gone up from 7 tonnes
to 10 tonnes [1]. Domestic extraction of raw materials has also grown worldwide. It is estimated that
30 billion tonnes of raw materials are required to produce 10 billion tonnes of finished products.
Increase in demand for materials is primarily due to unprecedented growth in population which results
in Green House Gas (GHG) emissions entailing global warming along with other serious
environmental impacts. As observed by World Health Organisation [2], by 2030, 60-70% of the world
population will be in urban areas, exerting pressure on infrastructure development causing
sustainability imbalance. Simultaneously, technological advances in the field of material science and
material engineering continue to provide new generation building materials with enhanced properties
with traditional building materials still in use. With several material options available, selecting
suitable energy efficient building materials pose significant challenge to all the stakeholders of
construction industry. Further, environmental concerns associated with different life cycle stages of a
product significantly harm the environment.
According to the report generated by Organisation for Economic cooperation and Development-
OECD [3], global material consumption is in the order of 62 billion metric tonnes per year and
expected to reach 100 billion tonnes by 2030. This growth is primarily due to increase in global
demand for three major material groups namely, construction, energy and metal, accounting for about
80% of the total material extraction, impelling imbalance between material supply capacity and
demand. India being the second most populous country in the world, has to meet its housing and
infrastructure demands on a continuous basis. Considering the housing schemes like, ‘Housing for all
by 2022’, Indian government has to construct about 20 million houses in the next 5 years for people
belonging to economically weaker sections. This mega exercise is bound to exert enormous pressure
on environment and material requirement. As per available data, India consumes 4.6 billion metric
tonnes (about 7%) of the total global material extraction and expected to reach 14 and 27 billion
metric tonnes by 2030 and 2050 respectively. Current average material consumption per capita per
annum in India is about 4.2 tonnes and likely to touch 9.6 tonnes by 2030, which approximately is the
present global average excluding developed nations [4].
Engineering properties of construction materials play a vigorous role in assessing structural
integrity of a building and more or less well defined in terms of worldwide acceptance, measurement
and quantification. When it comes to measuring eco-properties of construction materials, there is no
such well-established equipment or specified technique. Most energy impact assessment methods
currently available for life cycle analysis consider embodied energy and embodied carbon as two
critical eco-properties along with energy consumed during transportation, maintenance and
decommissioning, as associated parameters. Embodied energy is associated with energy consumption
under cradle to cradle system boundaries, whereas embodied carbon gets associated with GHG
emissions into the atmosphere.
Energy, raw material extraction, product manufacturing and their impact on environment are
intricately connected giving rise to three important interactions between a) materials and embodied
energy (EE), b) EE, c) Global warming and materials. The synergic effect of three interactions results
in complex interaction phenomena called Sustainability Development Index (SDI) as discussed by Ajit
Sabnis et al. [5]. World Commission on Environment defines sustainable development as development
which meets the needs of present generations without compromising the needs of future generations.
According to Kibert [6], 40% of world’s energy flow and material are due to buildings. Total quantum
of material extracted from non-renewable sources thus becomes a realistic indicator of environmental
impact. This necessitates judicious usage of materials and minerals drawn from non-renewable
resources. Hence, selection of suitable construction materials from sustainability perspective attains
high importance.
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This paper discusses selection methodology of building materials for sustainable construction
using the concept of Figure of Merit (FoM) and an attempt made to provide a framework in assessing
the impact of construction materials on environment. Material selection for sustainable construction
involves in finding best match between design requirements based on function and material properties
with least environmental impact. Figure of Merit used here is a non-dimension number derived using
two engineering characteristics-modulus of elasticity and density and two cost stimulants-construction
cost per unit area and unit cost of materials. FoM values obtained are graphically represented to
quantitatively determine the sustainability quadrant and sustainability range within which materials
fall by plotting against other critical material parameters.
Sustainability assessment and Engineering design in buildings call for strategic economic decision
making in respect of selecting suitable construction materials and construction techniques that produce
optimum results in terms of sustainability. As suggested by Cabeza et al. [7], in addition to reducing
the embodied energy of materials, it is equally important to consider recycling potential of building
materials. Hence, there is a need for developing a tool which can assist the designer in adopting better
choice of materials with lower embodied energy and higher structural integrity.
2. AN OVERVIEW OF FIGURE OF MERIT (FOM)
Figures of Merit (FoM) have varying definitions depending on a context and are being extensively
used in several engineering fields to rank the most suitable alternative amongst the available options.
FoM in engineering designs is used to find out material suitability, compare utility, applicability and
design options. In commercial sectors, FoM helps to decide upon the dependability of a particular
brand.
Studies carried out by Kima et al. [8] in the field of thermoelectric materials adopt principle of
Figure of Merit to predict the efficiency of thermoelectric materials. Jeffrey O. Grady, in his book
System Management: Planning, Enterprise Identity, and Deployment, Second Edition, classifies risks
as low, medium and high, based on the Figure of Merit values. Studies reveal many such examples of
FoM applications and formulations using engineering parameters. Varun et al. [9], Prakash et al. [10]
proposed a sustainability index based on Figure of Merit for renewable energy sector with renewable
energy options. Prioritization of sustainable electricity generation methods considered two critical
parameters, net energy and carbon dioxide emissions. Based on FoM rankings, they concluded that
electricity generated by the wind power is most sustainable.
Filetin and Galinec [11] proposed use of FoM in material selection processes and observe that
Figure of Merit to be a mathematical expression where inputs are some of the important engineering
characteristics of a material and the output data validating these characteristics. Thus by comparing the
Figures of Merit of different materials, assessment can be made as to which material is better suited
for a given condition. Several combinations of characteristics are suggested by Filetin and Galinec
considering important characteristics of materials. Suggested combinations by Filetin and Galinec,
contained two critical parameters, elasticity modulus and density of material, playing predominant
roles.
Bleek [12] presented the concept of ‘Material Intensity Per Service Unit (MIPS)’ and evolved an
indicator based on the utilization of natural resources for their consumption in a finished form at the
end of a supply chain. MIPS-was defined by as inverse of resource productivity and the proposed
equation comprised ecological rucksacks of all input materials and number of utilities the finished
product offers. Mancini et al. [13] successfully applied MIPS concept for evaluating the sustainability
of diets based on the use of natural resources along the supply chain in thirteen European countries.
Roldán and Valdés [14] outlined a methodology of developing a Figure of Merit for evaluating
sustainable development using social, environmental and economic indicators and applied it to
different regions of Mexico without taking into account any of the engineering characteristics of
materials.
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Dixit et al. [15] in their review paper on embodied energy computation methods observe variation
in methods being adopted for data collection of energy inputs and product manufacturing processes
leading to incompleteness and inaccuracies of these methods. Most modern building materials
available in the market today tend to become energy intensive due to processes and long distance
transports, as observed by Reddy [16]. Dixit et al. [17] suggests embodied energy of construction
materials depend on product’s manufacturing processes and identifies ten different system boundaries
for embodied energy computation.
Ajit Sabnis and Pranesh [18] used Figure of Merit (FoM) in material selection including cost
function and further integrated it with other energy indicators in developing a new Sustainability
Development Index (SDI), a tool that helps assessing sustainability levels of buildings in percentage.
Nguyen et al. [19] developed a sustainability development indicator called TPSI for tall buildings
above twenty floors. ‘Tall-Building Projects Sustainability Indicator-TPSI’ drew a threshold line for
twenty floors or sixty meters height. Their findings showed beyond 20 stories, the eco-efficiency of
buildings reduce dramatically in terms of structural and economics aspects. Pilon et al. [20] presented
a methodology using the concept of FoM to screen the composite materials containing phase change
materials (PHM) for energy efficient buildings with crack resistant concretes. Schrader and Rickman
[21] refer to particle type, particle size, particle shape, and density as four types of measurements
required for constructing a FoM equation.
3. FORMULATION OF FOM EQUATION
There are no stipulated guidelines available in construction industry for deriving the FoM equations.
FoM, in the present discussion, is constructed using two critical reference engineering properties and
two construction industry cost stimulants as described in section 1. These four parameters in the FoM
equation are intricately connected and influence material selection. Jiao et al. [22] developed modified
Input-output based analysis to compute EE of materials and systems by relating cost data and
demonstrated strong correlation between EE and cost of materials. In construction, though high
material strength and low material density are preferred, they need not be always the most suitable
selection criteria. Cost of materials and cost of implementation also play a vital role. For completing
the sustainability assessment of a building, FoM has to be further integrated with other critical eco
parameters. This is in consistency with the suggestion made by Ashby [23] to consider Mass,
Embodied Energy and Embodied carbon in the selection strategy of materials.
FoM is a non-dimensional parameter and designated as ZFOM
3.1. FoM Objective
Objective of developing the ZFOM for various construction materials is to effectively integrate them
with cost parameters and validate them with other parameters namely embodied energy, embodied
carbon and density. It is a well-established fact that cost of materials increase due to various process
involved during the life cycle of a product starting from energy consumed during raw material
extraction, transporting the raw material to the factory, processes involved in processing and refining
of raw materials, manufacturing of a product, packing and lastly its transport to the construction site.
Further, higher material density entails higher transportation cost which in turn results increased
greenhouse gas emissions
3.2. Constructing FoM Equation
Figure of Merit (ZFOM) for various construction materials is derived using the following equation.
ZFOM = E/ρ x Cm x 1/Ca (1)
Where;
E = Elasticity modulus in GPa,
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ρ = Material density in kg/m3
,
Cm = Material cost in INR / m3
and
Ca = Cost of construction in INR/m2
On substitution, FoM emerges as a non-dimensional numerical value. Cost in the present
discussion is taken in INR for illustration. FoM equation can be applied to any location and applicable
currency be deployed. ZFOM values for some critical construction materials in Indian scenario are
computed and tabulated in Table 1. Computation of ZFOM takes into account, range of E-values from
standard data tables, cost of construction materials and cost of construction prevailing in one of the
Indian metros, Bangalore. Cost of construction per unit area of a ‘ready to occupy’ building is found to
be in the range of INR 20000-65000 (US $ 350 – 1100) per square meter.
Table 1 FoM (ZFoM) Values of Construction Materials
4. EMBODIED ENERGY (EE)-CONSTRUCTION MATERIALS
Assessing energy impact of building materials on environment based on embodied energy (EE) has
been the focus of study for the past several decades. Useful relationship between building materials,
construction processes, and their environmental impacts has also been established. As observed by
Langston and Langston [24] the process involved in the actual assessment of EE is a complex process
and involves numerous data from various sources. EE is typically measured as a quantity of
nonrenewable energy consumed per unit of material or a subsystem constituting a building system.
Though EE measurement is considered as a reasonable impact indicator, it should be weighed along
with durability and performance characteristics of materials. Further, as suggested by several
researchers, there is no specific widely accepted EE computing methodology accurately and hence
Density
Kg/m3 L H L H
1 Aluminium 2700 68.00 82.00 22.15 87.28 54.71
2 Brass 8500 110.00 120.00 60.42 215.40 137.91
3 Low Carbon steel 7800 200.00 215.00 12.49 43.87 28.18
4 Stainless steel 8000 189.00 210.00 64.25 233.30 148.78
5 Polypropyline 910 0.90 1.55 0.21 1.19 0.70
6 Polyethelene(HDPE) 960 0.62 0.86 0.12 0.53 0.32
7 Polycarbonate 1210 2.00 2.44 1.06 4.23 2.64
8 PVC 1580 2.14 4.14 0.53 3.38 1.96
9 Epoxy 1400 2.35 3.08 2.93 12.56 7.75
10 Ceramic Tiles Dry 2000 350.00 400.00 17.62 65.81 41.72
11 Bricks in Clay 1st Qlty 2080 10.00 50.00 0.04 0.74 0.39
12 Stabilised mud bricks 1850 0.70 1.00 0.00 0.01 0.00
13 Stone (Hard) 2880 35.00 50.00 0.04 0.20 0.12
14 Granite (Polished) 2880 50.00 60.00 2.91 11.43 7.17
15 Sand stone 2200 25.00 40.00 3.34 17.45 10.39
16 Marble 2500 60.00 80.00 5.03 21.94 13.49
17 Concrete 2400 15.00 25.00 0.05 0.27 0.16
20 Cement Mortar wet 1900 2.00 3.00 0.05 0.27 0.16
21 Glass(Soda-lime) 2500 68.00 72.00 5.71 19.74 12.72
21 Hard Wood 940 20.60 25.20 0.62 2.46 1.54
22 Soft Wood(sawn) 550 8.40 10.30 0.36 1.43 0.89
23 Plywood 700 6.90 13.00 0.53 3.28 1.91
24 MDF 500 2.00 4.00 0.13 0.85 0.49
25 Gypsum Plaster Boards 800 1.50 3.50 0.10 0.74 0.42
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variations in EE values are unavoidable [25, 26, 27, 28,]. Embedded in the measure of EE, are the
associated ramifications of greenhouse gasses, resource depletion, global warming and biodiversity
reduction.
From sustainability point of view, construction materials can be defined as those materials which
have low ecological impacts, which minimize resource use, impart no health risks and do not
compromise durability aspects. These materials in their finished form consume enormous energy
before they reach the point of implementation. Energy consumed during several processes involved in
transforming raw materials into finished products, is directly proportional to greenhouse gas emissions
leading to Global warming. Buildings contribute almost 40% of CO2 emissions and are major
contributors to the greenhouse gas (GHG) emissions.
Construction materials display wide range of embodied energy variations and emit GHGs with
varying magnitudes in their life cycle. Appropriate selection of construction materials play a vital role
in cutting down carbon dioxide emissions and make buildings more sustainable. Studies carried out
based on embodied energy and embodied carbon for impact assessment have their own limitations due
to varying geographic locations and local climatic conditions.
Alcorn and Baird [29] modified energy coefficients using hybrid analysis while applying to New
Zealand to avoid inaccuracies and limitations embedded in energy values. Buchanan and Honey [30],
while investigating the total energy consumption by a building and its impact on global warming, used
energy coefficients suggested by Baird and Chan (1983). Noteworthy contributions have been made
by several researchers including Adalberth [31] [32], Pullen [33], Crawford and Treloar [34] and
Lenzen et al. [35] in the past for assessing the impact of built environment on natural environment
taking into consideration the embodied energy and carbon emissions.
Table 2 shows embodied energy, embodied carbon, density and mean FoM values for construction
materials.
Table 2 EE, EC, FoM Values for Construction materials
MATERIAL
EE
MJ/kg
EC
kgCO2/kg
Density
kg/m
3
Mean
FoM
Aluminium 218.00 8.24 2700 54.71
Brass 80.00 4.39 8500 137.91
Low Carbon steel 20.10 1.37 7800 28.18
Stainless steel 56.70 6.15 8000 148.78
Polypropyline 115.10 3.93 910 0.70
Polythelene(HDPE) 76.70 1.57 960 0.32
Polycarbonate 112.90 6.03 1210 2.64
PVC 77.20 2.61 1580 1.96
Epoxy 139.00 5.91 1400 7.75
Ceramic Tiles 12.00 0.74 2000 41.72
Clay Bricks 3.00 0.23 2080 0.39
CSEB 0.83 0.084 1850 0.00
Stone (Hard) 1.00 0.056 2880 0.12
Granite 11.00 0.64 2880 7.17
Sand stone 1.00 0.058 2200 10.39
Marble 2.00 0.116 2500 13.49
Concrete 0.75 0.1 2400 0.16
Cement Mortar wet 1.10 0.171 1900 0.16
Glass(Soda-lime) 15.00 0.86 2500 12.72
Hard Wood 10.00 0.30 940 1.54
Soft Wood(sawn) 7.40 0.19 550 0.89
Plywood 15.00 0.42 700 1.91
MDF 11.00 0.37 500 0.49
Gypsum Plaster Boards6.75 0.38 800 0.42
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5. FOM APPLICATION IN MATERIAL SELECTION
Material selection criteria in the present discussion are explained in the following paragraphs through
FoM Charts developed using FoM, EE, EC and Density properties. FoM charts in principle are
classified as FoM-Quadrant Charts, FoM-Range Charts and FoM-Eco Charts. Quadrant charts identify
materials based on suitability and design; Range charts identify material range within the imposed
limits of FoM and EE and, Eco charts identify materials from sustainability point of view.
5.1. FoM - EE Quadrants
Hammond and Jones [36] [37], Alcorn and Baird [29], Reddy and Jagdish [38] have made notable
contributions in terms of computing energy values for several construction materials and tabulating
them. While most metals show higher embodied energy, building materials under polymer and
ceramic classification show lower and mid-range values. In the present discussion, it is attempted to
classify construction materials under four groups namely; 1) Most suitable, 2) Not Suitable, 3)
Materials where FoM matters most and 4) Materials where EE matters most. FoM value of 30 and EE
value of 30 MJ/kg are imposed as baseline values on the basis of best range energy data from ICE
inventory [36], material profile. These limits are shown as horizontal and vertical lines demarking four
quadrants. Concept of four quadrants is explained by taking materials under metal and ceramic
classifications.
Figures 1 and 2 are scattered graphs showing FoM and Embodied energy values for materials
under Metals and Ceramics category taken from Table 1 for illustration. In Figure 2, both X and Y
axes are in log scale. Two dotted lines representing baseline values of FoM and EE, separating four
quadrants are fixed at 30 and 30 MJ/kg respectively. FoM values up to 30 are considered to be Low-
Range Values, 30 to 75 as Mid-Range and above 75 as High-Range. Similarly, Embodied Energy
values of construction materials up to 30 MJ/Kg are considered as Low-Range, 30 to 60 MJ/kg as mid-
Range and above 60 MJ/kg as high-Range. Normalizing the graph with the above characteristics, we
have materials falling in four quadrants namely;
Figure 1 FoM-EE Acceptability Criteria for Metals
Q1: Lower FoM, Lower EE – Most suitable
Q2: Lower FoM, Higher EE- Choice of materials if FoM matters the most
Q3: Higher FoM, Lower EE – Choice of materials if EE matters the most.
Q4: higher FoM, Higher EE- Not suitable
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From Figure 1, it is observed that Steel falls in Q1 with low FoM value and low embodied energy
and hence becomes most suitable. Its suitability enhances when recycled steel is used. Average
embodied energy of virgin steel is about 12 to 15 % higher than 50% recycled steel [36]. Other three
metals namely Stainless steel, Brass and Aluminium fall in quadrant 4 and hence not suitable as
sustainable construction materials. However, Aluminum has a low FoM as compared to Brass and
Stainless steel and virgin Aluminium has an embodied energy 15 times higher compared to
predominantly recycled Aluminium [36]. Hence Aluminium, being closer to baseline separating Q1
and Q2, can be considered as suitable material. Selection criteria for aluminium is also viewed from
recyclability, lightness, low maintenance, low energy and mid-range FoM parameters.
From Figure 2, it is observed that most construction materials under ceramic classification
generally fall in Q1. For example, CSEB-Compressed Stabilized Earth Blocks with least embodied
energy value of and least FoM become most suitable. Since Ceramic tiles in the market are available
with several choices, it is possible to choose a ceramic tile which satisfies low FoM and low embodied
energy criteria. In case of ceramic tiles or vitrified tiles, cost of material plays a vital role in
determining FoM value.
Figure 2 FoM-EE Acceptability Criteria for Ceramics
5.2. FoM Range Values
Figures 3, 4 and 5 show range values of FoM from Table 1 and graphically represented as floating
columns. Values falling in low and mid-range are represented by yellow fields and those falling in
high FoM range are represented by blue fields. It is observed from Figure 3 that Aluminium, Low
carbon steel and Structural steel fall in the low and mid-range zones of FoM and embedded in yellow
fields. Thus, with low FoM values, these materials become more suitable compared to Brass and
Stainless steel with high FoM values embedded in blue fields. But it can also be interpreted that, Brass
and Stainless steel with FoM values falling in the mid-range, can be used as suitable construction
materials.
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Figure 3 FoM Range Values for Metals
Referring to Figure 4, natural stone floor materials and concrete, falling in the yellow field with
low to negligible FoM become more suitable flooring materials as compared to ceramic tiles falling in
blue field. Figure 5, represents FoM values for three masonry materials commonly used in Indian
construction industry as illustration. It is interpreted from the chart that, CSEBs, Concrete and Clay
bricks falling in yellow field are more suitable as construction materials. Higher range values of FoM
are for wire cut bricks which are nearly fourfold expensive than conventional 1st
quality clay bricks
and hence blue field.
Figure 4 FoM Range Flooring Materials Figure 5 FoM Range Masonry Materials
5.3. FOM-EE Comparison
Embodied Energy and Embodied Carbon coefficients published by University of Bath [19], are used
in the present discussion to assess energy impact of construction materials on global warming. It is
now an established fact that greenhouse gasses such as Carbon dioxide and other detrimental
pollutants are embedded within the materials. As observed by Hammond and Jones [37], in order to
quantify the total embodied energy, assessment based on ‘Cradle to Site’ principle needs to be applied
systematically including stages from raw material extraction to processing to transportation to delivery
at construction site stages.
Figures 6 and 7 depict Embodied energy and Figure of Merit profiles interpreting suitability of
construction materials in terms of sustainability. Mean FoM and embodied energy values for metals
and ceramics are drawn from Table 2 and graphically represented as column charts for comparison
between materials under respective categories. For example, from Figure 6, low carbon steel with
embodied energy value of 20.10 MJ/kg and FoM value of 28.2 falls in the lower range of FoM and
hence more sustainable. Stainless steel with high embodied energy and high FoM value is not
sustainable as compared to low carbon steel. Similar analogy can be applied for materials under
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ceramic category, Figure 7. Ceramic tile with high FoM value and high embodied energy though is not
a great material from sustainability point of view but in lower ranges, it can be considered as a suitable
material depending on the function it has to perform in the buildings.
Figure 6 FoM vs EE for Metals Figure 7 FoM vs EE for Ceramics
5.4. FoM-EC Comparison
Carbon dioxide (CO2) is anthropogenic and available in plenty in the atmosphere. As one of the
greenhouse gasses, it poses a great concern in mitigating global warming. Global warming results in
the increase of average global temperature and affects macro and micro climates of eco-system.
Embodied Carbon expressed in terms of per unit weight, gives an indication of its impact on global
warming. Figures 8 and 9 show graphs for mean FoM and Embodied carbon values for ceramics and
metals as illustration, taken from Table 2. It is gathered from these graphs, materials with lower FoM
are more suitable in sustainable construction. For example, natural stones and concrete fall in lower
range values of Figure of Merit and hence recommended as sustainable flooring materials as compared
to ceramic or vitrified tiles (Fig 8). Stainless steel displays high Figure of Merit and high embodied
carbon. Hence it cannot be considered as sustainable material (Fig 9).
Figure 8 FOM vs EC for Ceramics Figure 9 FOM vs EC for Metals
5.5. FOM-Density Comparison
Mean FoM and material density for Metals and ceramics, drawn from Table 2 are plotted and
represented in Figures 10 and 11 respectively. In metal category, brass and stainless steel display high
density and high FoM characteristics and become unsuitable as construction materials. However, low
carbon steel and aluminium fall in low and mid-range zone of FoM and hence become more suitable
as construction materials (Fig 10). In case of materials falling under ceramics category, most materials
except ceramic tiles fall below FoM baseline and are suitable as construction materials (Fig 11).
11. Ajit Sabnis and M R Pranesh
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Uutilising ceramic tiles in buildings has to be reviewed along with other considerations (section 5.1)
while decision making.
Figure 10 FOM vs Density for Metals Figure 11 FoM vs Density for Ceramics
6. FOM APPLICATION-SUBSYSTEM SELECTION
6.1. Formwork as a Subsystem
Building as a system involves several subsystems as its components. Each subsystem encompasses
many materials and processes like Foundation, Structural frame, Reinforcement, Structural Steel,
Joinery, Flooring, Masonry, Plastering, Glazing, Formwork, Water proofing. The concept of Figure of
Merit can be applied to any subsystem for its assessment. As an illustration, Formwork is analysed and
assessed for its suitability. In Indian scenario, three types of formwork systems are in practice.
Conventional formwork where the main sheathing is of steel floor plates and supporting shoring
consists of adjustable steel props and spans. In ply formwork, sheathing material is replaced with
plywood. In the third system, sheathing material made of aluminium floor plates.
Table 3 EE, EC and FOM Values for Formwork
Source: Ajit and Pranesh [2]
Table 3 shows values of Embodied Energy (EE), Embodied Carbon (EC) per unit area along with
mean FoM (ZFOM) for all the three systems.
EE /m2
EC/m2
MJ kgCO2e
Conventional
Formwork with Timber joists, Adjustable
steel props and spans, Steel floor plates
for sheathing.
229 18.43 9.38
Plywood
As above but resin coated Plywood as
sheathing material.
234 18.81 19.37
Aluminium
As in conventional formwork but with
Aluminium floor plates for slabs.
15.6 2.5 1.01
Formwork
System
ZFOMMaterial Specification
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Figure 12 FoM vs EE for Formwork Figure 13 FoM vs EC for Formwork
EE and EC values for all the three systems are plotted against respective values of FoM and
represented in Figures 12 and 13. FoM values for three formwork systems are computed using
equation 1 separately adopting detailed process analysis of Life Cycle. Interpretation of graphs for
suitability of a formwork system shows that Aluminium formwork with lowest Figure of Merit is most
suitable from sustainability consideration as compared to other two systems. Aluminium floor plates
allow high repeatability, recyclability and help us in avoiding plastering activity. Though capital
investment on aluminium formwork is very high, considering 100 repetitions, aluminium formwork
per repetition becomes highly economical. Plywood system with five repetitions and high FoM value
is not preferred as sustainable system of formwork. There are many multi-story buildings where,
aluminium and conventional formwork systems are applied in combination for optimization. From
both EE and EC criteria, it is seen that lower FoM serves as an indicator of a better sustainable system.
7. DISCUSSION
Concept of Figure of Merit (FoM) is applied in selecting building materials suitable for sustainable
construction. Application of FoM is common in aeronautical, automobile and electronic industries
where high strength materials with low density are preferred. Present discussion takes into account
four critical parameters namely, Elasticity Modulus, Material Density, Cost of materials and Cost of
construction per unit area. These are integrated to express a unique dimensionless value called Figure
of Merit, designated as ZFOM. Selection of parameters for the evaluation of Figure of Merit is not a
rigid decision. For different aspects, the parameterization shall vary to best suit the condition. Based
on the requirements of the situation, the characteristics are selected so that a suitable Figure of Merit is
obtained.
Values of ZFOM and EE of building materials are used to group building materials in four quadrants
namely most sustainable, not sustainable, materials where FoM matters the most and materials where
EE matters the most. These are graphically represented in Fig 1, 2. As an illustration, metals and
ceramics are taken from the material chart and classification made. It is observed from the plots that
most metals except steel fall in ‘not sustainable quadrant’ due to their high embodied energy and high
ZFOM. In case of materials under ceramics, most of them come under ‘most suitable quadrant’ due to
their low ZFOM and low EE. Four quadrants in Fig 1, 2 are separated by two base lines representing
two base values of FoM and EE at 30 and 30 MJ/kg respectively.
Advantage of ascribing base values to FoM is to identify materials falling in different ranges with
FoM perspective. FoM value between 0-30 considered as low range, 30-75 as mid-range and above 75
as high range. From FoM perspective, materials displaying lower ZFOM have better suitability in
sustainable construction. Validation of proposed FoM concept is carried out by comparing and plotting
FoM vs EE, FoM vs EC and FoM vs Density for metals and ceramics as illustration-Figures 6 to 11.
13. Ajit Sabnis and M R Pranesh
http://www.iaeme.com/IJCIET/index.asp 215 editor@iaeme.com
There are several formwork systems, water proofing systems; many envelop systems, plastering
methodologies that can be adopted to complete a building. What is essential under these circumstances
is a tool that addresses these variations and helps in selecting a suitable subsystem. FoM concept as
applied to selection of a suitable subsystem is discussed using Formwork as example.Studies carried
out by Reddy B.V.V and Jagdish, K.S [38] show that by using alternative sustainable construction
materials and technologies, significant reduction in energy consumption, to the extent of about 30%
can be achieved. The present study proposes use of Figure of Merit as a reasonable and practical tool
to assess the suitability of construction materials leading to a sustainable solution.
8. CONCLUSION
Based on the results presented, following conclusions are drawn:
Lower value of Figure of Merit represents higher suitability of building materials and systems in
sustainable construction
Selection of materials cannot be done only with embodied energy, embodied carbon perspective but to
be integrated with other critical engineering and cost characteristics of materials
Selection of materials for sustainable construction to be made taking recyclability, reuse parameters
into consideration
Different alternative solutions can be identified using FoM tool.
It is possible to modify the building footprint with better sustainability level at the drawing board stage
before commencement of actual construction.
9. ACKNOWLEDGEMENTS
The authors acknowledge their gratification to the authorities of Jain University for extending
cooperation in the present research.
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![Building Materials Assessment for Sustainable Construction Based on Figure of Merit as a Concept
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especially in developing nations like India. Between 1970 and 2010, global material consumption has
grown three fold from 22 billion tonnes to 70 billion tonnes and per capita has gone up from 7 tonnes
to 10 tonnes [1]. Domestic extraction of raw materials has also grown worldwide. It is estimated that
30 billion tonnes of raw materials are required to produce 10 billion tonnes of finished products.
Increase in demand for materials is primarily due to unprecedented growth in population which results
in Green House Gas (GHG) emissions entailing global warming along with other serious
environmental impacts. As observed by World Health Organisation [2], by 2030, 60-70% of the world
population will be in urban areas, exerting pressure on infrastructure development causing
sustainability imbalance. Simultaneously, technological advances in the field of material science and
material engineering continue to provide new generation building materials with enhanced properties
with traditional building materials still in use. With several material options available, selecting
suitable energy efficient building materials pose significant challenge to all the stakeholders of
construction industry. Further, environmental concerns associated with different life cycle stages of a
product significantly harm the environment.
According to the report generated by Organisation for Economic cooperation and Development-
OECD [3], global material consumption is in the order of 62 billion metric tonnes per year and
expected to reach 100 billion tonnes by 2030. This growth is primarily due to increase in global
demand for three major material groups namely, construction, energy and metal, accounting for about
80% of the total material extraction, impelling imbalance between material supply capacity and
demand. India being the second most populous country in the world, has to meet its housing and
infrastructure demands on a continuous basis. Considering the housing schemes like, ‘Housing for all
by 2022’, Indian government has to construct about 20 million houses in the next 5 years for people
belonging to economically weaker sections. This mega exercise is bound to exert enormous pressure
on environment and material requirement. As per available data, India consumes 4.6 billion metric
tonnes (about 7%) of the total global material extraction and expected to reach 14 and 27 billion
metric tonnes by 2030 and 2050 respectively. Current average material consumption per capita per
annum in India is about 4.2 tonnes and likely to touch 9.6 tonnes by 2030, which approximately is the
present global average excluding developed nations [4].
Engineering properties of construction materials play a vigorous role in assessing structural
integrity of a building and more or less well defined in terms of worldwide acceptance, measurement
and quantification. When it comes to measuring eco-properties of construction materials, there is no
such well-established equipment or specified technique. Most energy impact assessment methods
currently available for life cycle analysis consider embodied energy and embodied carbon as two
critical eco-properties along with energy consumed during transportation, maintenance and
decommissioning, as associated parameters. Embodied energy is associated with energy consumption
under cradle to cradle system boundaries, whereas embodied carbon gets associated with GHG
emissions into the atmosphere.
Energy, raw material extraction, product manufacturing and their impact on environment are
intricately connected giving rise to three important interactions between a) materials and embodied
energy (EE), b) EE, c) Global warming and materials. The synergic effect of three interactions results
in complex interaction phenomena called Sustainability Development Index (SDI) as discussed by Ajit
Sabnis et al. [5]. World Commission on Environment defines sustainable development as development
which meets the needs of present generations without compromising the needs of future generations.
According to Kibert [6], 40% of world’s energy flow and material are due to buildings. Total quantum
of material extracted from non-renewable sources thus becomes a realistic indicator of environmental
impact. This necessitates judicious usage of materials and minerals drawn from non-renewable
resources. Hence, selection of suitable construction materials from sustainability perspective attains
high importance.](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)