embodied energy assessment and comparisons for a residential building using conventional and...

CASE STUDY

Embodied Energy Assessment and Comparisons for a ResidentialBuilding Using Conventional and Alternative Materials in IndianContext

K. Naveen Kishore • J. S. Chouhan

Received: 29 March 2013 / Accepted: 5 May 2014

� The Institution of Engineers (India) 2014

Abstract Building sector is responsible for 40 % of the

primary energy use and 24 % of carbon dioxide emissions

in India. The main source of green house gas emissions

from buildings is due to energy consumption. This paper

aims to assess the embodied energy index and environ-

mental impact of a two storied residential building. The

study proposes various alternative materials which can be

used in day to day construction in order to mitigate the

environmental impact and climate change due to con-

struction activity in India. Two types of construction

techniques have been considered for the study, namely load

bearing and reinforced concrete framed construction.

Embodied energy and carbon dioxide emissions of walling

and roofing components using conventional and alternative

materials has also been analyzed and compared. The

comparison is done based on two parameters namely,

embodied energy/m2 and CO2 emissions per unit of floor

area. The study shows that bricks, cement and steel are the

three major contributors to the energy cost of constructing

a building by conventional methods. A conventional two

storied load bearing structure is 22 % more energy efficient

when compared to a reinforced concrete structure. It has

also been observed from the study that use of alternative

material in the building envelope gives embodied energy

savings between 50 and 60 % for a two storey load bearing

structure and 30–42 % for a two storey reinforced concrete

structure. Hence a load bearing construction is certainly a

better alternative to RC framed construction for up to two

storied structures in terms of embodied energy and envi-

ronmental impacts.

Keywords Embodied energy � Conventional materials �Alternative materials � CO2 emissions �Load bearing construction � RC framed construction �Low energy buildings

Abbreviations

RCC Reinforced concrete (framed) construction

LBS Load bearing structure (construction)

FCB Fired clay bricks

FAB Fly ash bricks

HCB Hollow concrete blocks

SCB Soil cement blocks

ACB Aerated concrete blocks

FSR Filler slab roof

RSR RC ribbed slab roof

PBR Prefabricated brick panel roof

PJR RC plank & joist roof

BMTPC Building Materials Technology Promotion

Council

IS Indian Standards

Introduction

The building sector represents around 40 % of the primary

energy use [1] throughout the world, which makes them the

single most energy intensive sector [2]. The construction

sector in India is responsible for the largest share of CO2

emissions (24 %) into the atmosphere [3] and a primary

K. Naveen Kishore (&)

Corporate Institute of Science and Technology, Hathaikheda,

Anand Nagar, Bhopal 462021, Madhya Pradesh, India

e-mail: [email protected]

J. S. Chouhan

Samrat Ashok Technological Institute, Vidisha,

Madhya Pradesh, India

123

J. Inst. Eng. India Ser. A

DOI 10.1007/s40030-014-0075-x

energy use of nearly 41 % [4]. About 80 % of the above

emissions are resulting mainly from industrial/production

processes of four energy intensive building materials,

namely—cement, burnt clay bricks, lime and steel.

According to a survey by development alternatives the

demand for cement is expected to increase from 92.5

million tones in 2000 to 202 million tones in 2020. The

demand for steel is expected to increase from 9.6 to 23

million tones and for bricks from 61 to 89 billion during the

same period. The CO2 emissions due to cement production

is expected to increase from 85 million tones in 2000 to

186 million tones in 2020. The CO2 emissions due to

production of steel is expected to increase from 23 to 55.2

million tones and for bricks from 18 to 26 billion during the

same period [5].

A study conducted by development alternatives also

shows that the increasing demand for building materials in

the construction sector is a direct outcome of the galloping

demand for housing on a continuing growth trend of 2.4 %

per annum aggregate cumulative growth rate [5]. Nearly 2

million residential buildings are built every year in India

[6]. Most of the buildings are built using the conventional

materials like clay bricks, cement and steel. The increased

consumption of these building materials is also due to a

switch over from the conventional load bearing construc-

tion to RC framed construction even for two storied resi-

dential structures, where load bearing construction would

prove more economical.

Previous studies have shown that for buildings con-

structed in temperate or cold regions, the major part of the

energy use in buildings is in embodied energy (10–20 %)

and operating energy (80–90 %) [7–9]. The energy used

for on-site construction, demolition at the end of its life

accounts for only 1 % in the overall life cycle energy.

Thus, embodied and operating energy of the building are

two important phases of energy use in a building’s life

cycle. Embodied energy is the energy needed for produc-

tion and transportation of materials. The embodied energy

of a building depends on the quantity of materials used in

its construction and their embodied energy values/unit

weight of the material. It is seen that building envelopes

have a significant potential in bringing down the embodied

energy in a building because they contribute a major pro-

portion (walls 46 % and roofs 16 %) of the materials used

in residential buildings [10]. For a sustainable future, the

buildings need to be constructed in a manner that they use

minimum natural resources and also cause low environ-

mental impact on the surroundings. Therefore alternatives

to the conventional building materials like cement, bricks

have to be used. This can result in considerable energy

savings as well as reduction of CO2 emissions.

This paper aims to assess and compare the embodied

energy index and environmental impact of a two storied

residential building using conventional and alternative (low

energy) building material. Several potential alternative

walling units and roofing systems have been analyzed and

compared with conventional materials used in construction.

The building is evaluated for its embodied energy with the

existing conventional materials namely fired clay bricks,

cement and steel. For the modified cases, alternative (low

energy and cost effective) materials like fly ash bricks,

hollow concrete blocks, soil cement blocks and cellular

concrete blocks are used for masonry walls. Filler slabs,

RC ribbed slabs, prefabricated brick panels and RC plank

and joist are used as alternatives for roofs.

Literature Review

Previous researches from open literature show many case

studies of embodied energy and environmental impact in

the context of the developed or cold countries. But only a

few case studies exist in the Indian context. Three case

studies in the context of the cold countries and two in the

Indian context have been reported [11]. In the context of

the cold countries, a three bedroom semi detached house in

Scotland was examined for five main construction materi-

als namely, wood, aluminium, glass, concrete and ceramic

tiles for their respective embodied energy and their

respective environmental impacts [12]. The embodied

energy content of the various materials used for construc-

tion was estimated to be 227.4 GJ. Concrete, timber and

ceramic tiles were the three major energy intensive mate-

rials. The conclusions from the study shows that concrete is

the most energy intensive material not only in terms of the

quantity consumed but also in terms of the associated

environmental impacts. Concrete and mortar, together are

responsible for 99 % of the total CO2 emissions resulting

from the construction. The embodied energy and CO2

implications of building construction have been evaluated

in New Zealand [13]. They have made a detailed analysis

of the net carbon emissions resulting from construction of

buildings using different construction materials. The con-

clusions from the study show that significant decrease in

embodied energy CO2 emissions can be achieved if there is

a shift from using steel, concrete and aluminium to greater

use of wood as an alternative in construction. A detailed

analysis was performed on the energy consumption and

CO2 emission due to housing construction in Japan [14].

Total energy required and CO2 emissions/m2 of area for

different types of constructions have been compared. The

conclusions from the study show that energy consumption for

the construction of wooden single family houses (3 GJ/m2)

scores over steel and reinforced concrete (RC) construction

of multi-storeyed family houses (8–10 GJ/m2) in terms of

energy requirements and CO2 emissions. The life cycle


123

assessment of office buildings constructed in China using

steel and concrete has been reported [15]. The observations

show that embodied energy and environmental impacts of

steel framed structures were superior to the concrete

framed structures.

In the Indian context, the embodied energy requirements

of three types of buildings namely, single storey and double

storey load bearing structures and four storey (RC framed)

structures has been evaluated [16]. The embodied energy/

m2 of floor area has been quantified to be between 3 and 5

GJ/m2 of floor area. It has been concluded that bricks,

cement and steel are the three major contributors to the

energy cost of constructing the three types of buildings.

Hence in order to reduce the indirect energy use in these

buildings, due to the construction materials, either alter-

natives for brick, cement and steel have to be found or

vigorous energy conservation measures in these segments

of industry have to be initiated. The embodied energy in

conventional and alternative building materials have been

analyzed [17]. A detailed analysis of the energy involved in

the manufacture, transportation of these materials has been

presented. Also an analysis on the embodied energy in

different types of building systems such as masonry,

roofing systems and the building types have been quanti-

fied. It is concluded from the study that among the masonry

(walling) units, soil cement blocks are the most energy

efficient in comparison to burnt clay brick and concrete

block masonry units, giving energy savings between 68 and

76 %. Among the roofing systems Mangalore tile roof and

Ferro cement roofs have the lowest embodied energy giv-

ing a savings between 70 and 80 %. Use of soil cement

block masonry and stabilized mud block (SMB) filler slab

roof has led to a 62 % savings in embodied energy when

compared to a multi storied RCC framed structure. The

results from these studies are confined only to the use of

soil cement blocks and filler slab roofs in buildings as

alternative materials. The effect of other alternative walling

and roofing systems on the embodied energy of different

building types has not been quantified. The embodied

energy of an adobe house have been evaluated in the Indian

context [18]. The house is constructed using low energy

materials like soil, sand, cow dung, etc. An embodied

energy reduction of nearly 50 % was achieved compared to

a conventional building built with cement, bricks and steel.

A summary of the embodied energy study and analysis in

Indian context is presented in Table 1 below:

Based on the studies conducted in the Indian context the

following observations have been made from the above table:

• For a floor area ranging from 50 to 130 sq m, a double

storey LB structure is more economical than a single

storey LB structure and a four storey RCC structure, in

terms of embodied energy [16].

• For a floor area ranging from 130 to 200 sq m a four

storey RCC structure is more economical as the

embodied energy is between 530 and 600 GJ. For the

same floor area, a two storey LB structure has an

embodied energy between 530 and 740 GJ [16].

• It has been indicated that to reduce the embodied

energy use in a building, alternatives for brick, steel

and cement have to be used in buildings [16].

• A two storey conventional LB structure has an embodied

energy of 2.92 GJ/m2. In contrast to this a two storey LB

structure, having similar floor area, using alternative

materials like soil cement blocks (for walls), filler slab (for

roof) has an embodied energy of 1.61 GJ/m2. This is 45 %

less than its conventional counterpart [17].

Many of the above studies only focus on quantifying the

embodied energy content of existing buildings. Some

studies suggest use of wood as an alternative for reducing

the embodied energy content in buildings. But wood is not

a feasible alternative in the Indian context, due to its high

costs. Thus from the above studies it is concluded that in

order to identify potential building alternatives for con-

ventional buildings, there is a need to quantify and com-

pare the embodied energy of all available alternative

Table 1 Overview of literature study (Indian context)

Type of building Materials used No. of

floors/

storey, s

Area, m2 Embodied energy

per unit area,

GJ/m2

CO2 emissions,

t/m2Reference

Load bearing (conventional) Brick, cement, steel 1 50–200 4.1–5 NA [16]

Load bearing (conventional) Brick, cement, steel 2 50–200 3.7–4.2 NA [16]

R.C. framed (conventional) Brick, cement, steel 4 50–200 3.1–4.3 NA [16]

R.C. framed (conventional) Brickwork for walls, Roof—RC

solid slab, mosaic floor finish

8 5120 4.21 0.21 [17]

Load bearing (conventional) Brickwork for walls, Roof- RC

solid slab, Mosaic floor finish

2 150 2.92 0.15 [17]

Load bearing (alternative) Soil cement block wall, filler slab

roof, terracotta tile floor finish

2 161 1.61 0.08 [17]


123

walling units and roofing systems on a residential building.

In this paper a residential building is evaluated for its

embodied energy with the existing conventional materials

namely fired clay bricks, cement and steel and its modified

cases using alternative (low energy and cost effective)

materials like fly ash bricks, hollow concrete blocks, soil

cement blocks and cellular concrete blocks for masonry

walls and filler slabs, RC ribbed slabs, prefabricated brick

panels and RC plank and joist for roofing systems.

Methodology

The case study building is a generic two-storey RC framed

residential structure (Figs. 1, 2) built in 2009 and having a

usable floor area of 126 m2. The building is built using

RCC for columns, beams and slabs and clay fired bricks as

in fills for walls.

The quantity of materials used in construction has been

estimated from the technical drawings of the existing

building. The embodied energy values of the different

building materials are taken from literature [19–21]. They

have been compiled from standard research publications

and presented in Table 2. The embodied energy of the

building has been calculated by summing up the product of

the quantity of materials and their embodied energy values.

The properties and specifications of materials and roofing

systems used for the case study building are presented in

Table 3. The embodied energy for the roofing systems has

been worked from the literature [22]. The properties of

materials have been compiled from literature [23–27].

Costs of materials have been worked out as per the latest

rates of building materials in the Indian market [28]. Based

on the studies of different alternative building materials

and systems, alternative options for construction were

worked out and have been listed in Table 4.

BMTPC has developed several cost effective and energy

efficient building materials and systems conforming to IS

codes. They include both walling units and roofing sys-

tems. To study the embodied energy savings of the building

with different alternative materials, the same house is

modified for the different options available for alternative

walling units and roofing systems. The embodied energy

demand of the conventional building which is constructed

using fired clay bricks for walls and RCC for roof is esti-

mated first and it is taken as the base case. The building is

then modified by replacing fired clay bricks for walls with

the alternative materials or blocks, namely fly ash, hollow

concrete, soil cement and cellular concrete separately with

a block thickness of 20 cm. The conventional RCC roof is

replaced with alternative roofing systems namely, filler

slab, RC ribbed slab, prefab brick panel and RC plank and

joist. A roof thickness of 11 cm is considered for all roof

types. Cement pozzolona mortar is used in all alternative

building options. The comparisons are done for two types

of construction techniques, namely load bearing construc-

tion and RCC framed construction. Embodied energy

demand of the modified building is then compared with the

base case. The comparisons have been done based on two

parameters namely, embodied energy/m2 and CO2 emis-

sions (in kg)/m2 of floor area. Results have been tabulated

in the form of tables and graphs.

Results and Discussions

Embodied Energy

Based on the technical drawings used in this study, steel,

concrete, mortar and bricks together contribute to about

80 % of the materials used in the building and hence are

regarded as energy intensive materials (Fig. 3). The total

embodied energy of the structure (Base case) amounts to

about 392 GJ (3.1 GJ/m2). This is comparable well with

and is close to the results obtained by the study [17],

(Table 1) where a similar two storey conventional load

bearing structure has an embodied energy of 438 GJ (2.92

GJ/m2). It is also close to the results obtained by the study.

[16] where a RCC framed structure with floor area between

50 and 200 m2 has an embodied energy between 3.1 and 4

GJ/m2. The embodied energy breakup of the materials used

in construction is presented in Table 5. If the same building

is built using load bearing construction technique the sav-

ings in embodied energy (Table 6) amount to nearly 22 %

using conventional materials (Fig. 4). This is because the

use of steel as a structural material is reduced by nearly

50 % in a load bearing structure. This compares well with

the results obtained by Venkatarama Reddy and Jagadish

[17], where a conventional load bearing structure is com-

pared with a RCC framed structure and a energy saving of

20 % is obtained. The embodied energy savings become

more significant, between 50 and 60 %, when alternative

materials are used (Fig. 5) in place of conventional mate-

rials in a load bearing construction. This also compares

well and is close to the results obtained by the study [17]

where a 55 % savings is obtained by comparison (Table 1)

of a two storey load bearing structure with alternative

materials (soil cement blocks) with a conventional two

storey load bearing structure. In Table 7 the comparisons

of embodied energy for conventional and alternative load

bearing construction options is shown. For a RC framed

construction the savings (Fig. 6) with alternative materials

vary between 30 and 42 %. Table 8 shows the comparisons

for embodied energy for conventional and alternative RC

framed construction options. The combination of soil

cement blocks ? filler slab roof is the most energy


123

efficient with an embodied energy consumption of 160 GJ

which amounts to a 60 % savings in embodied energy for a

load bearing construction. This is followed by the combi-

nation of cellular concrete blocks ? filler slab roof which

consumes about 170 GJ of embodied energy corresponding

to 57 % savings. Soil cement blocks score over cellular

concrete block in terms of energy efficiency because they

do not require any external plastering, although both have

nearly the same embodied energy values per m3 of

masonry. Among the alternatives, the combination of

alternative walling units with RC plank and joist roofing

option is the most energy expensive, but they also give a

minimum savings of about 30 % for RC framed

construction.

Environmental Impacts (CO2 Emissions)

The environmental impacts for the different construction

options are presented in Table 9. The conventional RC

framed construction is expensive in terms of environmental

impact. A conventional load bearing construction is more

eco friendly in comparison to a conventional RC framed

Fig. 1 Ground floor plan

(conventional-base case)


123

Fig. 2 First floor plan

(conventional-base case)

Table 2 Embodied energy coefficients and quantity of key building materials used in the construction of the building (base case)

Sl. no. Name of material Quantity Embodied energy, MJ

1 Cement 27.97 t 4,200

2 Bricks 12,425.00 nos 4,250

3 Sand 107.15 m3 175

4 Aggregates 57.72 m3 200

5 Steel (reinforcement) 3.63 t 42,000

6 Steel (M.S grills) 0.30 t 42,000

7 Lime (slaked) 0.16 t 5,630

8 Hard wood (Sal) 0.22 t 1,800

9 Particle board 0.45 t 8,000

10 Glass 0.15 t 25,800

11 Aluminium 0.03 t 237,000

12 Marble 6.27 t 2,000

13 Ceramic tiles 0.65 t 2,500

14 White cement 0.25 t 7,800

15 Paint (enamel and primer) 0.02 t 80,000

16 Kota stone (for parking and utility area) 2.03 t 500


123

Table 3 Properties of masonry materials/roofing systems/mortar-plasters

Type of

component

Name of building component Description/specifications Embodied

energy

per unit

volume,

MJ/m3)

No. of

blocks

per unit

volume

Weight of

masonry/m3

(Density),

kg/m3

Cost, Rs/m3 CO2

emissions,

kg/m3

Reference

Wall Brick masonry Type: Conventional 2,550 600 1,700 3,900 250 [17, 19, 21, 29]

Size—230 9 110 9 75

Composition—Clay

As per IS 2,691

Clay fly ash brick masonry

(clay, flyash and lime)

Type: Alternative 1,392 600 1,270 2,400 136 [19, 21, 25]

Size—230 9 110 9 75

Composition—Clay, fly ash,

lime

As per IS 13757

Hollow concrete block

masonry (with 10 %

cement, sand, coarse

aggregates)

Type: Alternative 971 63 1,200 2,646 95 [17, 19, 26]

Size—400 9 200 9 200

Composition—10 % cement,

sand, coarse aggregates

As per IS 2185 (part 1)

Soil cement block masonry

(8 % cement and soil)

Type: Alternative 810 230 1,900 3,680 79 [17, 23]

Size- 230 9 190 9 100

Composition—8 % cement

and soil

Aerated concrete block

masonry (cement, fine

aggregates and aluminium)

Type: Alternative 819 63 750 3,150 80 [19, 27]

Size—400 9 200 9 200

Composition—cement, fine

aggregates and aluminium

As per IS 2185 (part 3)

Type of

component

Name of building component Description/specifications Embodied

energy per unit

area, MJ/m2

Cost, Rs/m2 CO2

emissions,

kg/m2

Reference

Roof RCC slab (110 mm thick, in

M15 CC)

Type: Conventional 640 1,150 63 [19, 21]

Size—10 m2 area

Composition—M15 CC-cement,

sand, aggregates in ratio (1:2:4)

As per IS-456

Filler slab roof (110 mm

thick, M15 CC with

Mangalore tiles as infill)

Type: Alternative 350 582 34 [22]

Size—10 m2 area

Composition—M15 CC-cement,

sand, aggregates in ratio (1:2:4),

Mangalore tiles as filler material

As per IS-456

RC ribbed slab roof (50 mm

thick in M20 CC)

Type: Alternative 491 979 48 [20, 22]

Size—10 m2 area

Composition—M20 CC cement, sand,

aggregates in ratio (1:1.5:3) for

slab, RC ribs

As per IS-456

Prefabricated brick panel roof

(110 mm thick in M20 CC)

Type: Alternative 426 927 42 [20, 22]

Size—10 m2 area

Composition—Brick panels for slab,

30 mm of M20 CC slab over brick

panels

As per IS-456

R.C. plank & Joist roof

(110 mm thick in M20 CC)

Type: Alternative 506 1,043 49.6 [20, 22]

Size—10 m2 area Composition-R.C.

planks, RC joits, 30 mm of M20 CC

slab over R.C. planks As per IS-456


123

construction, giving a 20 % reduction in the CO2 emis-

sions. Among the alternatives, Soil cement blocks and

cellular concrete blocks have the least environmental

impact corresponding to a 53–55 % reduction in the CO2

emissions when compared to conventional construction

methods.Fig. 3 Embodied energy break up (conventional RCC-base case)

Table 5 Embodied energy breakup of materials (conventional RCC

structure-base case)

Sl. no. Name of material Total embodied energy, MJ

1 Cement 117,464

2 Bricks 52,806

3 Sand 18,751

4 Aggregates 11,544

5 Steel (reinforcement) 152,453

6 Steel (M.S grills) 12,600

7 Particle board 3,627

8 Glass 3,870

9 Aluminium 5,925

10 Marble 12,542

Table 3 continued

Type of

component

Name of building

component

Description/specifications Embodied per

unit volume,

MJ/m3

No. of blocks

per unit

volume

Weight of

masonry/m3

(Density), kg/m3

Cost,

Rs/

m3

CO2

emissions,

kg/m3

Reference

Mortar/

Plaster

Cement plaster (1:6 CM) Type: conventional 1,268 2,777 124 [19, 21]

Size—1 m2 area

Composition—CM-1:6 cement, sand

As per IS-269, 383

Cement pozzolona mortar

(20 % fly ash based- 1:6

CM)

Type: Alternative Size—1 m2 area 918 2,355 90 [17, 19]

Composition- CPM-(0.8:0.2):6 Cement

(80 %), pozzolona (20 %), sand As per

IS-1489, 383

Table 4 Alternative options for construction

Sl. no. Parameter Conventional

(base case)

Alternative (modified case)

Option 1 Option 2 Option 3

1 Type of construction RC framed Load bearing (conventional) Load bearing (alternative) RC framed (alternative)

2 Building material

(a) Wall (masonry) Clay bricks Clay bricks FAB FAB

HCB HCB

SCB SCB

ACB ACB

(b) Roof RCC solid slab RCC solid slab FSR FSR

RSR RSR

PBR PBR

PJR PJR

(c) Mortar (for joints/

plasters)

Cement mortar (1:6) Cement mortar (1:6) Cement pozzolona

mortar (1:6)

Cement pozzolona

mortar (1:6)


123

Table 6 Embodied energy breakup of materials (conventional LBS)

Sl. no. Name of material Total embodied energy, MJ

1 Cement 86,789

2 Bricks 77,988

3 Sand 17,717

4 Aggregates 7,904

5 Steel (reinforcement) 76,227

6 Steel (M.S grills) 12,600

7 Particle board 3,627

8 Glass 3,870

9 Aluminium 5,925

10 Marble 12,542

Fig. 4 Embodied energy break up (conventional LBS)

1.441.59 1.52

1.611.38

1.53 1.461.55

1.271.43 1.36

1.441.351.5 1.43

1.52

2.44 2.44 2.44 2.44

3.17 3.17 3.17 3.17

0

0.5

1

1.5

2

2.5

3

3.5

Filler slab R.C thinribbedslab

Brickpanel

RC.Plank& joist

Em

bodi

ed e

nerg

y (

in G

J/m

2 )

Fly Ash

HCB

SCB

ACB

Conventional(LoadBearing)(Burnt clay+RCC roof)

Conventional (RCFramed)(Burnt clay+RCC roof)

Fig. 5 Embodied energy comparisons for LBS

Table 7 Embodied energy comparisons for conventional and alter-

native options (LBS)

Sl. no. Type of construction Embodied energy per

unit area, GJ/m2

1 Conventional (RCC)

(Burnt clay ? RCC roof)

RCC roof

3.17

RCC roof

2 Conventional (LBS)


2.44

Alternative (load bearing

structure with cement

pozzolona mortar)

Filler

slab

R.C thin

ribbed slab

Brick

panel

R.C. plank

& joist

3 FAB 1.44 1.59 1.52 1.61

4 HCB 1.38 1.53 1.46 1.55

5 SCB 1.27 1.43 1.36 1.44

6 ACB 1.35 1.50 1.43 1.52

2.022.17 2.1 2.19

1.962.11 2.04 2.13

1.852.01 1.94 2.021.92

2.08 2.01 2.1

3.17 3.17 3.17 3.17

0

0.5

1

1.5

2

2.5

3

3.5

Filler slab R.C thinribbed slab

Brick panel RC.Plank &joist

Em

bodi

ed e

nerg

y, G

J/m

2

Fly Ash

HCB

SCB

ACB

Conventional (RC Framed)(Burnt clay+RCC roof)

Fig. 6 Embodied energy comparisons for RCC

Table 8 Embodied energy comparisons for conventional and alter-

native options (RCC structure)

Sl. no. Type of construction Embodied energy per

unit area, GJ/m2

1 Conventional (RC Framed)


RCC roof

3.17

Alternative

(RC framed structure

with cement

pozzolona mortar)

Filler

slab

R.C thin

ribbed slab

Brick

panel

R.C. plank

& joist

2 FAB 2.02 2.17 2.1 2.19

3 HCB 1.96 2.11 2.04 2.13

4 SCB 1.85 2.01 1.94 2.02

5 ACB 1.92 2.08 2.01 2.10


123

Conclusions

In this paper, the embodied energy demand for a residential

building of usable floor area of 126 m2 is analyzed with

existing conventional (FCB, steel, concrete) and alternative

materials (Walling units—FAB, HCB, SCB, ACB and

roofing systems—FSR, RSR, PBR, PJR) and techniques.

The study is aimed at quantifying how the present con-

struction methods are energy intensive and cause serious

environmental impact. The study is done for load bearing

construction and RC framed construction techniques. The

conventional RC framed construction is most expensive in

terms of energy and environmental impacts. The embodied

energy amounts to 3.11 GJ/m2 and the CO2 emissions

Table 9 Comparative summary of CO2 emissions for different construction types

Sl. no. Type of construction Total CO2 emissions, t/m2

1 Conventional (RCC framed)

(burnt clay ? RCC roof)

0.300

2 Conventional (LBS) (burnt clay ? RCC roof) 0.240

3 Alternative 1 (LBS with

cement pozzolona mortar)

Total CO2 emissions, t/m2

FAB masonry ? FSR 0.150

HCB masonry ? FSR 0.146

SCB masonry ? FSR 0.135

ACB masonry ? FSR 0.142

FAB masonry ? RSR 0.167

HCB masonry ? RSR 0.161

SCB masonry ? RSR 0.151

ACB masonry ? RSR 0.158

FAB masonry ? PBR 0.160

HCB masonry ? PBR 0.154

SCB masonry ? PBR 0.144

ACB masonry ? PBR 0.151

FAB masonry ? PJR 0.168

HCB masonry ? PJR 0.163

SCB masonry ? PJR 0.152

ACB masonry ? PJR 0.159

4 Alternative 2 (RC framed structure

with cement pozzolona mortar)

Total CO2 emissions, t/m2

FAB masonry ? FSR 0.208

HCB masonry ? FSR 0.202

SCB masonry ? FSR 0.192

ACB masonry ? FSR 0.199

FAB masonry ? RSR 0.223

HCB masonry ? RSR 0.217

SCB masonry ? RSR 0.207

ACB masonry ? RSR 0.215

FAB masonry ? PBR 0.216

HCB masonry ? PBR 0.210

SCB masonry ? PBR 0.200

ACB masonry ? PBR 0.207

FAB masonry ? PJR 0.225

HCB masonry ? PJR 0.219

SCB masonry ? PJR 0.209

ACB masonry ? PJR 0.216


123

amount to 0.250 tonnes CO2/m2 of floor area. The study

shows that a conventional load bearing construction alone

can reduce the Embodied energy demand of the building by

about 22 % and its corresponding environmental impact by

20 %. When alternative materials are used the energy sav-

ings amount to between 50 and 60 % corresponding to a

44–55 % reduction in CO2 emissions for a load bearing

construction technique. Soil cement blocks ? filler slabs

(60 %) and aerated concrete blocks ? filler slabs (57 %)

have better energy performance and least environmental

impact (45–47 %) among the alternative materials using the

load bearing construction technique. The same alternative

materials give energy savings between 30 and 42 % and

reduction in CO2 emissions between 25 and 36 % for a RC

framed construction technique. Hence it is clear from the

study that a load bearing construction is certainly a better

option in lieu of an RC framed construction for single and

two storied residential structures, leading to reduced con-

struction costs as well as low environmental impacts.

Following are a summary of conclusions drawn from the

above study:

• A conventional two-storey load bearing structure is

22 % more energy efficient than a RC framed structure.

• Embodied energy savings are between 50 and 60 %

with use of alternative materials for LB structure.

• Embodied energy savings are between 30 and 42 %

with use of alternative materials for RC structure.

• Soil cement blocks and aerated concrete blocks with filler

slabs have least environmental impact. They give a CO2

reduction between 53 and 55 % over conventional

materials for a load bearing construction technique.

• Soil cement blocks and aerated concrete blocks with

filler slabs give reduction in CO2 emissions between 33

and 36 % for a RC framed construction technique.

Recommendations The study proposes various alternative

materials which can be used in day to day construction in

order to mitigate the environmental impact and climate

change due to construction activity in India. The results of

this study can be used to quantify and analyse the energy

requirements and environmental impacts for multistoreyed

residential buildings like apartments.

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