3.embodied energy in building materials

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CHAPTER 1

INTRODUCTION

Although the Indian economy uses both commercial and non-commercial energy

sources, the share of these fuels in the primary energy supply has declined from over 70% in

the early 50's to a little over 30% as of today. The traditional fuels are gradually getting

replaced by the commercial fuels such as coal, lignite, petroleum products, natural gas and

electricity . The ominous outcry for energy crisis in various sectors like agriculture,

transportation, land use and built environment are widely recognized during the past couple

of decades as a threat for the future generation. Building Industry is one of the fastest

growing and a major energy consuming sector in India. Needless to say, the buildings too

form a link in the energy-spatial structure relationship. Apart from the structural and

functional efficiencies, building infrastructure also needs to emphasize on the energy

conservation issues. The energy in buildings may be looked from two different perspectives.

Firstly the energy that goes into the construction of the building using a variety of materials.

Secondly the energy that is required to create a comfortable environment within the building

during its lifetime . Quite a few studies regarding the energy consumed during the

maintenance of the building (heating, cooling and lighting) are being considered. However

the assessment of the embodied energy in buildings is still in its nascent stage in India and

requires serious research.


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CHAPTER 2

NEED FOR ENERGY EFFICIENT BUILDINGS

The International Energy Report (IER) 1987 points out Investment in energy

conservation at a margin provides a better return than investment in energy supply (Trilok

Singh, 1999). The concept of green buildings is still at an emerging stage in India. The

concept of sustainable buildings and use of environmentally friendly construction materials

like stones, timber, thatch, mud etc have been practiced since ancient times. But the

perception of people about strong and durable buildings have changed with the advent and

lavish use of the present modern materials like steel, cement, aluminium, glass etc. A large

amount of fuel energy gets consumed in producing such materials. These materials being

industrial products further need to be transported to large distances before getting consumed

in the buildings thus making them energy intensive. An estimate of the energy consumed in

buildings using different permutations of materials and techniques will facilitate their

appropriate selection and reduce the embodied energy consumption . Apart from this a

building with greater embodied energy is not stable, it easily falls on small impacts.


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CHAPTER 3

ENERGY IN A BUILDINGEnergy in a building can be viewed from two different perspectives.

1. Energy that goes into the construction of the building.

2. Energy required for the proper working and maintenance of the building.

In this paper I would like to discuss about the first category, that is the energy that goes into

the construction of the building, which could also be called as the embodied energy. According to

WORLD ENERGY COUNCIL [WEC], embodied energy is defined as the sum of all energy inputs

into a product system , from all stages of life cycle. In simpler words it could be said that embodied

energy is the total energy required for the making of a building (excluding human labour).

For the formation of a building, the raw materials have to be made first. The making of raw

materials is not that easy and includes various processes which could be listed as

1. EXTRACTION2. PROCESSING3. MANUFACTURE4. TRANSPORTATION


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Chapter 4

ASSESSMENT OF EMBODIED ENERGY

The embodied energy in a building could be assessed in two different ways,

1. Gross energy requirement

2. Process energy requirement

-Gross energy requirement [GER]:-

Gross energy requirement is also called as the True embodied energy .It is impractical to measure

and therefore it is difficult to assess. Here the precise amount of energy utilised in each process should

be considered which makes it impractical to measure. Actually only a rough assessment of energy

utilised in each process could only be made.

-Process energy requirement [PER]:-

Here a rough amount of energy utilised for each process is calculated and measurement is done

directly along with the manufacture. It is much simpler to quantify and the main consideration here is

that the transportation energy required for the transportation of the transportation of raw materials to

the manufacture site is considered while the transportation energy required for the transportation of

finished raw material to the building site is not considered.It was also observed that the PER accounts

for 50-80% of the total GER.


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CHAPTER 5

MATERIALS USED

The paper considers main materials used for the construction of the building. The main materials

used for construction of a building are

1. CEMENT2. STEEL3. BRICKS4. GLASS5. TIMBER

5.1CEMENTThe principal methods for the manufacture of the Portland cement are 1) Wet

process, 2) Dry process, 3) Semi dry process. The dry process is preferred on account

of very significant fuel economy. The dry process is adopted in most of the cement

industries. The heat energy required per Kg of the clinker in dry process is 1.572.35

MJ/Kg while in wet process it is about 2.64.2 (MJ/Kg). The highest value is of 4.2

MJ/Kg .Cement manufacture uses kilns. About 90% of the total energy consumption

for manufacture goes in kilns. Transportation uses very low amount of energy on

comparison with its manufacture and hence it is neglected. The rest of the energy goes

for processing of raw materials and grinding of the final product. This shows that

cement is a high energy intensive material.

5.2STEELThemaking of steelrequires a large number of raw materials a large number of

processes. The embodied energy includes the transportation of various raw materials like

Iron ore lumps, sinters and pellets, coke and fluxes such as limestone, dolomite and

includes various processes like Melting, Refining, Casting and Rolling all which requires

large amount of heat energy. Total energy estimate is about 36 MJ/Kg, including

transportation which makes steel a high energy intensive material.


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5.3BRICKSBricks are the main materials used for masonry work. Stones are also used for this

purpose. Manual process of making bricks include the following,

i. Soil preparationii. Moulding

iii. Dryingiv. Firing

Most of the energy consumed in bricks is due to firing. For firing process coal is

used.Thy quantity of coal varies from 18-22 tonnes depending upon the quality of coal usedand the climatic conditions. Coal releases an energy of about 12.3MJ-13.3MJ per tonne,

depending upon its quality. The embodied energy of a single brick is estimated to be about

5MJ inclusive of its transportation.

Energy comparison for different types of masonry materials used are given below,

Table 5.1

From the above table we could see that stone has the least embodied energy as it does not

require any manufacturing process. Both Burnt clay brick and Steam cured block requires a

great deal of energy as both of them requires burning. The materials with lower embodied

energy are Soil-Cement block and Hollow cement block, so its increased usage reduces the

overall embodied energy of the building.

TYPE OF UNIT SIZE (mm) ENERGY IN 1

BLOCK OFBRICK (MJ)

ENERGY PER

BRICKEQUIVALENT

(MJ)Stone 180x180x180 0 0

Burnt clay brick 230x105x70 4.25 4.25(100%)

Soil-Cement block 230x190x100 3.50 1.35(31.7%)

Hollow Cement

block

400x200x200 15.00 1.62(38.1%)

Steam cured block 230x190x100 6.70 2.58(60.6%)


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5.4GLASSThe use of glass in a building are for windows and for mirrors. The raw materials used for

the making of glass are

i. Glass sandii. Soda ash

iii. Salt cakeiv. Limestonev. Lead oxide, Pearl ash, Boric acid etc.

Processes involved in the making of glass are

i. Meltingii. Shaping or Forming

iii. Annealingiv. Finishing

Melting is the process of mixing all the raw materials and burning it at a very high

temperature. The energy required for melting is estimated to be about 15.9 MJ/Kg.

Due to this process of melting the embodied energy of glass is considered to be very

high. The second process is shaping or forming where the molten material is made

into the desired shape and size. The next step is annealing where the shaped material

is cooled to get hard solid material. The last one is the finishing process where works

like colouring and etching are done to increase the aesthetic appearance of the

material. But the main energy consumption is only for melting process while other

processes does not require much energy.

The alternatives that could be done are the use of Argon filled glass for windows

and use of Reflec Tech mirrors and use of modified window panes.

5.4.1 ARGON FILLED GLASSThis glass is prepared by filling argon gas in between two glass layers and using this

for windows. The advantage of using this is that, argon is a non-toxic gas with low

embodied energy and it is season sensitive. Season sensitive means that, it does not allow


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mirrors, while its embodied energy is 19% less than usual mirrors. Hence it is energy

saving.

5.4.3 ULTREXUsually the materials used for window panes are Wood, Aluminium and Vinyl. Of the

three wood is commonly used and the embodied energy of wood is very low. Hence viewing

from the energy part use of wood is adaptable. But wood has various limitations like it does

not withstand harsh climatic conditions and that it deteriorates very fast. Aluminium and

Vinyl are materials of very high embodied energy, hence their use was also not possible. This

increased the need for developing a new material for this purpose and the material thusdeveloped was ULTREX. It is a clustered fibreglass material capped with a finishing. The

main advantage of using fibreglass is that it has low embodied energy. It has 80% less

embodied energy than aluminium and 30% less embodied energy than vinyl. The other

advantages of ultrex include, greater strength, durability, stability, long life, sound barrier

property, non corrosive characteristics, needs less maintenance, higher thermal efficiency and

is also environmental friendly.

Fig.5.3.1

Fibreglass before and after compression.


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Crossectional view of ULTREX.

Fig.5.3.2

5.5 TIMBER

The next main material used for building work is timber. The raw material of timber is

wood and is available in abundance. Its main energy source is the energy from sunlight and

later this is converted to timber by drying process, which uses a very low amount of energy of

1.5MJ/Kg. It is light in weight and therefore does not require much energy for transportation.

Due to these, the embodied energy quotient of wood is neglected.


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CHAPTER 6

ROOFING

We could see that a large number of types of roofing are used worldwide. But here we

are considering only main four types of roofing. They are

1. Mangalore tiled roofing2. Asbestos cement sheet roofing(AC roofing)3. Reinforced concrete roofing(RC roofing)4. Hourdi tiled roofing

6.1 MANGALORE TILED ROOFING

Mangalore tiled roofing was first introduced in India in Mangalore, by German

missinories. Mangalore tiles are made by burning clay in kilns which is highly energy

consumptive. It provides great ventilation and allows smoke to escape. They are best suited

for high rainfall regions. If the supporting material used is timber rafter, then there is no much

energy consumption. But if RC rafters are used, then it shows an increase in energy

consumption of about 27%. It has good aesthetic appearance and is widely used in south

India.

Fig.6.1.1

6.2 ASBESTOS CEMENT SHEET ROOFING


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It uses a combination of cement as well as asbestos fibres. It uses about 80% cement

and 20% asbestos fibres. For purlins if steel truss or ferrocement may be more energy

efficient instead of using angle sections. It does not have much load carrying capacity and is

not widely used. It is mostly used for the construction of sheds and as roofing for industries.

Its advantages are that it does not rot like wood, fire resistant, less expensive, stable,

corrosion resistant, greater electrical insulation quality, light in weight and requires less

maintenance.

Fig.6.2.1


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6.2.1ADVANTAGES OF AC ROOFING

i. Does not rot like woodii. Fire resistant

iii. Less expensiveiv. Corrosion resistantv. More stable

vi. Greater electrical insulation qualityvii. Light in weight

viii. Requires less maintenance

6.2.2 DISADVANTAGES OF AC ROOFING

i. Produces serious health riskThis is due to the presence of microscopic fibres present in the material which

produces serious health risks like Cancer and respiratory problems.

ii. Low life span of 50-80 years on comparison with Mangaloretiled roofing which has an average life span of 100 years.

iii. Unsuitable for tropical climatesiv. Gives poor aesthetic appearance due to moss and lichen

growth.

6.3 REINFORCED CONCRETE ROOFING

It is being widely used in our country now. It uses cement and steel, both of which are

highly energy intensive as we have seen earlier. Its embodied energy is about 548 MJ/Kg,

which is a great deal of energy and this compels its reduced usage.

6.4 HOURDI TILED ROOFING

Hourdi tiles are produced by imposing a great amount of compressive stress on clay,

called as AURAM PRESS. It has a very large load carrying capacity of 1325Kg/m2, which is

very high on comparison with others. They are hollow and create roofs which are more

comfortable in hot climates, as they allow a great deal of air passage. They can be placed on a

building in two ways. One is by placing it on T- beams and the other is by placing it on

ferrocement channels.


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6.4.1 PLACING OF HOURDI BLOCKS ON TBEAM

STEPS INVOLVED ARE:

i.

Placing of T- beams.

Fig.6.4.1.1

ii.

Adjusting the Hourdi blocks into position

Fig.6.4.1.2

Here the Hourdi blocks are placed in position intact between the Tbeams.


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iii. Concreting the roof with cementThis is done to keep the blocks in place intact, and it also prevents water

seepage in between the blocks.

Fig.6.4.1.3


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iv. The final view

Fig.6.4.1.4

6.4.2 PLACING OF HOURDI BLOCKS ON FERROCEMENT

CHANNELS

THE VARIOUS STEPS INVOLVED ARE:

i. Placing of ferrocement channels on the roof portion.ii. Adjusting the Hourdi blocks in between the ferrocement channels

Fig.6.4.2.1


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The ferrocemenet channels are properly placed at proper spacings and the Hourdi

blocks are placed in between them intact, without a gap.

v. Casting is done using cement, soil, earth and gravel.

Fig.6.4.2.2

vi. The final view.

Fig.6.4.2.3


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Of the two types, that is placing on T- beam and on Ferrocement channel, the second

one gives a better ventilation than the first.

6.5 LOAD CARRYING CAPACITY OF DIFFERENT TYPES OF

ROOFING

Table 6.1

TYPE OF LOAD LOAD IN Kg/m2

Mangalore tiled roofing 20

Asbestos Cement sheet roofing 90

Reinforced Concrete roofing 200

Hourdi tiled roofing 1325

From the above table we could see that Hourdi tiled roofing has the greater load

carrying capacity and than comes the Reinforced concrete roofing. Mangalore tiled roofing

has the least load carryi g load carrying capacity. Hourdi tiled roofing is the most adaptable

type.


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CHAPTER 7

ADVANTAGES OF ANALYSING EMBODIED ENERGY

a. The main advantage of analysing the embodied energy is the ECONOMICBENEFIT.

A material with greater embodied energy requires a large number of processes for its

manufacture and each process would be much energy consuming. Therefore by analysing the

embodied energy of materials used for construction, we could choose alternative materials

with a lower embodied energy and form a much stable building than that formed by using the

initial materials.

b. The second advantage of analysing embodied energy is ENERGYCONSERVATION.

A great deal of energy is being wasted by using materials with higher embodied

energy, and in todays developing world the need for energy is increasing day by day. So the

need for energy conservation must be given great importance. By lowering the embodied

energy of the building materials, a great amount of energy could be saved.

c. The other main advantage of analysing embodied energy is ECOLOGICALBALANCE.

Saving a large amount of energy means that the ecological balance is being conserved

and indirectly we are assisting our existence on Earth.


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CHAPTER 8

CONCLUSIONS

[1]The main building materials like Cement, Steel, Brick and Glass are highly energyintensive and try to reduce its usage wherever possible.

[2]Use of materials with less embodied energy must be appreciated.[3]If no alternatives could be used than try to reduce the operational energy of the

building, thereby reducing the overall energy in a building.

[4]Buildings with less number of storeys must be appreciated wherever possible. Abuilding with larger number of storeys means, need for greater amount of raw

materials which consequently increases the embodied energy of the building.

[5]Use of materials like stone and bricks from demolished structures must be appreciatedas it does not add up to the embodied energy of the building.


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CHAPTER 9

REFERENCES

[1] Sarma, E.A.S., Maggo, I.N., Sachdeva, A. S. India's energy scenario in 2020 WorldEnergy Council.

[2] Susan Owens (1986) Energy, Planning and Urban Form, Pion Limited.[3] K.S.Jagadish, Energy Efficient Building Materials and Technologies Lecture

Notes, ASTRA, IISc, Bangalore.

[4] Gartner E.M. and Smith M.A. (June 1976) Energy costs of house construction,Building Research Establishment, Watford.

[5]

Trilok Singh (1999) Energy Conservation : need of the hour, Indian Journal ofPower and River Valley development, pp. 12-13.

[6] S.S.Verma, (June 1999) An Approach towards Renewable Energy Education,Environment and People, pp. 47 -51.

[7] Mainstreaming Sustainable Buildings in India Sustainable Habitat Design Advisor,Issue 1, June 2005.

[8] B.V.V. Reddy (Oct 2004), Sustainable Building Technologies, Current Science,Vol 87, No7, pp 899907.

[9] Green Habitat, A news letter on Green Buildings from Indian Green BuildingCouncil, CII- Sohrabji Godrej

[10] Green Building centre.[11] Wikipedia.

3.embodied energy in building materials

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