Introduction natural fibre (Autosaved)12 (2)

Application of Natural fibres in Construction

ABSTRACT

The objective of this project is to discuss and encourage the use of natural fibre in construction. Since the environment we live in is suffering from climate change caused by the use of fossil fuel which leads to emission poisonous gases like CO2, SO2 etc into the atmosphere. An alternative way of reducing the emission of these gases in to the air is by using materials that uses no fossil fuel or less fossil fuel during production. Since construction occurs every day, it has a big impact on our environment. For example, Fossil fuel is used during the production of cement. The paints used involve use of fossil fuel during production. Also a lot of transportation takes place during construction. All these affect our environment and everything that lives in it. Natural fibres have a great possibility to help reduce the environmental impact of construction, by having a better air quality, natural management of moisture levels and reductions in allergic reactions. Also it will improve and encourage more farmers in the UK and worldwide to invest in natural fibre.

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ACKNOWLEDGEMENTS

I want to appreciate everyone that has helped in the preparation and completion of this project. I will like to say thank you to University of Brighton for giving me the opportunity and the right training to become a Graduate Civil Engineer in their university.

I will also like to say a big thank you to my supervisor, Dr. Kevin Stone, for his advice and time during the preparation of this dissertation. My appreciation also goes to my lovely parents Prince Yomi Oyesola Adeleye and Chief Mrs Olutola Adeleye for their moral and financial support during my studies.

I will have to mention the likes of brothers, sister, cousins and friends (Adeyinka Adeleye, Adesewa Adeleye, Adejuwon Adeleye, Pekun Sobodu, Tominiyi Ajayi and many more).

Great thank you to GOD for his Guidance through out time in university.

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CONTENT

ABSTRACT.......................................................................................................2

ACKNOWLEDGEMENTS...............................................................................3

TABLE OF CONTENTS.....................................................................................4

LIST OF FIGURES..............................................................................................6

LIST OF TABLES...............................................................................................8

LIST OF NOTATION..........................................................................................9

INTRODUCTION.......................................................................................................10

CHAPTER 1

PLANT FIBRE

INTRODUCTION..........................................................................................................12

APPLICATION OF PLANT FIBRE IN CONSTRUCTION

INSULATION................................................................................................................12

FLOOR COVERING......................................................................................................17

LIGHT STRUCTURAL WALL MATERIALS.............................................................22

THATCH.........................................................................................................................26

PAINTS AND FINISHES..............................................................................................29

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CHAPTER 2

MINERAL FIBRE

INTRODUCTION....................................................................................................34

MINERAL WOOL...................................................................................................34

USES OF MINERAL WOOL..................................................................................35

INSULATION........................................................................................................35

ENVIRONMENTAL FRIENDLY.............................................................................37

ASBESTOS....................................................................................................................38

USES OF ASBESTOS...................................................................................................39

HEALTH ISSUES.........................................................................................................39

CARBON FIBRE..........................................................................................................40

FIBRE GLASS................................................................................................................43

APPLICATION OF FIBRE GLASS............................................................................43

CHAPTER 3

ANIMAL FIBRE

INTRODUCTION...........................................................................................................49

APPLICATION OF ANIMAL FIBRE IN CONSTRUCTION.......................................49

CHAPTER 4

CONCLUSION.....................................................................................................57

REFERENCES......................................................................................................59

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LIST OF FIGURES

Figure 1: Coconut fibre insulation...........................................................................................14

Figure 2:Reed ceiling...............................................................................................................15

Figure 3: Linoleum...................................................................................................................16

Figure 4: Coconut fibre insulation...........................................................................................17

Figure 5: Coir fibre rug...........................................................................................................17

Figure 6: Bamboo floor covering...........................................................................................18

Figure 7: Jute rug....................................................................................................................19

Figure 8: Seagrass floor..........................................................................................................19

Figure 9: Hemplime blocks......................................................................................................23

Figure 10: Strawbale wall.......................................................................................................24

Figure 11: Thatch straw..........................................................................................................26

Figure 12: Thatched roof building...........................................................................................26

Figure 13: Natural paints colour..............................................................................................28

Figure 14: Mineral wool insulation.........................................................................................35

Figure 15: Asbestos roof..........................................................................................................37

Figure 16: Density of different fibres.......................................................................................39

Figure 17: Young’s modulus (transverse) of different fibres...................................................39

Figure 18: Young’s modulus (longitudinal) of different fibres...............................................40

Figure 19: Tensile strength of different fibres ........................................................................40

Figure 20: Installation of carbon fibre reinforcement on a beam............................................41

Figure 21: Water pipes made from GRC..................................................................................42

Figure 22: Building built using GRC.......................................................................................43

Figure 23: Roof made from GRC.............................................................................................43

Figure 24: Glass fibre tank......................................................................................................44

Figure 25: GRC footbridge......................................................................................................45

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Figure 26: GRC staircase.........................................................................................................46

Figure 27: Termite nest reinforced by their natural secretion.............................................48.

Figure 28: Sheep wool insulation.....................................................................................49

Figure 29: Hand weaving mohair.........................................................................................51.

Figure 30: Coral reef system...............................................................................................52

Figure 31: Preparation of beeswax.......................................................................................53

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LIST OF TABLES

Table 1: Categories of plant fibres.................................................................................11

Table 2: Thermal performance data of different insulation............................................13

Table 3: Mechanical properties of coconut fibre...........................................................14

Table 4: Manufacturing process of bamboo flooring.....................................................19

Table 5: Comparing Rock wool with other insulating materials.....................................34

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List of Units and Notations

KN Kilo Newton

m meter

Kg kilograms

N Newton

Mm millimetres

MPa Mega Pascal

GPa Gega pascals

°C degree centigrade

M mass

SFR steel fibre reinforced concrete

GFC Glass reinforced concrete

J Joules

Db decibel

M mega

CAT centre alternative technology

RFC refractory ceramic fibre

BBA British board agreement

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INTRODUCTION

Egypt was the first country to make use of composite materials which was made with straw and clay around three thousand years ago to build walls(www.binaitimes.com). Natural fibre has provided us with all the raw materials we need for making different products like cloth, clothes, cordage and buildings. Most of the ancient plant fibres are no more in use. Some fibres like jute, kapok and coir just started getting imported into Europe in the 19th century.

Also during this time interest in synthetic fibres started developing because of its bogus dimension and properties. This slowly replaced the natural fibre in different application. Recently the uses of natural fibre started to rise because the use of synthetic fibres involves a lot of quantum energy during production and recycling. This process is expensive and it also affects the environment at the same time.

Every year about 30 million tonnes of natural fibre are produced worldwide (IYFN 2009). Encouraging the use of natural fibre in construction will help the environment in different ways such as better air quality, natural management of moisture level, reduction in allergic reaction and also help improve some developing countries where there main source of income is from natural fibres like Bangladesh produces juke and Tanzania produces sisal.

The use of natural fibres is driven by the key factors like:

Material performance Their sustainability Cost in use Politics Climate change The green movement

Natural fibres can be classified into natural and man-made or synthetic fibres. Natural are made from animals, plants and minerals sources.

1) Animal Fibres – These types of fibre contain protein. For example silk, wool, spider silk, yak, mohair. Animal fibres can be subdivided into animal hair (wool or hairs), silk fibre and avian fibres.

2) Plant fibres – This type of fibre consist of cellulose (C6H10O5). Examples are flax, abaca, wood, bamboo and hemp. Vegetable fibres can subdivided in leaf, bast, fruit, seed and stalk fibres.

3) Mineral fibres – These are inorganic substance made from rock, slag, glass or clay.

They can be classified into three classes namely:

1) Fibre glass (glass wool and glass filament)2) Refractory ceramics fibres (RFC)3) Mineral wool (rock wool and slag wool)

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CHAPTER 1

PLANT FIBRE

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1.1 Plant fibre

Plant fibre is the most common type of natural fibre used in construction. Plant fibre can be sub divived into Seed fibre, leaf fibre, bast or skin fibres and stalk fibre.

Seed fibres Leaf fibres Skin fibres Stalk fibres

Cotton Abaca Flax Bamboo

Kapok Agave Jute Straw of wheat

Coir Banana Hemp rice

Sisal Kenaf grass

TABLE 1 Categories of plant fibre and examples of each categories (www.binaitimes.com).

1.2Applications of Plant Natural Fibre in construction

Insulation

The types of natural fibres used as an insulator in buildings are Coconut fibre,Hemp/flax boards, straw boards, wool, Etc.

Insulation materials are materials that prevent sound or heat from getting in or out of a structure. The use of natural fibre as an insulation material was not considered important until the 1970s (CIRIA 2004). In buildings, insulation materials are used in carrying the following parts.

During winter the heat is kept inside. During summer the inside is kept cool. Less noise is transferred from outside. Less noise is transferred from inside to outside.

Also insulation can be applied to

Absorb moisture from air Store heat energy Carry less dead/live load (particularly under floors) Protect fire from spreading

Thermal performance

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http://en.wikipedia.org/wiki/Banana


Heat transfer – A good thermal insulation material means that the material is poor in transferring heat. A material with 0.1w/mk or less can be considered as a thermal insulation material.

Material Conductivity W/mk U value of 150mmW/mK

Density Kg/m3

Flax 0.037-0.042 0.25-0.28 20-30Hemp 0.038 0.26 15-60Sheep’s wool 0.037-0.039 0.25-0.26 16-25Rock wool 0.033-0.047 0.23-0.31 23-200

Table 2 Thermal performance data for different insulation materials (CIBSE, 1999. Environmental Design Guide A, CIBSE, London).

The way most insulation work is by trapping air inside the material. And since air conducts heat at a very low rate this means the convection of heat is largely reduced. Moisture has an effect on insulation because water conducts heat. If an insulation material is moist heat will pass through it easily. This shows that when moisture content is increased the resistance of the material to heat movement is reduced. The effect is greater if the temperature is higher because the moist is free to move faster when it is warm which means it is transferred faster.

Heat storage capacity- To determine the amount of heat a material can store we need to know the specific heat capacity and the density of the material. The specific heat capacity and the density of the material is then multiplied, this result will then give us the capacity of heat the material can store.

Mineral based materials has a Specific Heat Capacity of 1.0kJ/kg.K while plant derived material has Specific Heat Capacity of around 2.0KJ/kg.K(Andrew cripps, R. H. (2004). This means that mineral based material will only store half the heat a plant derived material will store. This is applied for roof space and prefabricated timber construction.

Flax fibre Flax fibre are mostly used has thermal insulator in buildings. They are used between wall and roof timbers. This product contains about 20% of synthetic fibre and it has a primary embodied energy of about 70-90kWh/m3. The production process involves living it to rot, pressing into bales, breaking, stripping, treating with mineral salt and then formed into batts by a mechanical process (Andrew cripps, R. H. (2004)..

Advantages of Flax fibre

They are made from renewable material and it uses low energy during manufacture It is reusable

Disadvantages of flax fibre

The herbicides used during its growth may have an impact on the environment.

Acoustic Performance – Sound transfer

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Acoustic insulation materials are materials that absorb sound wave or energy. The softer, flexible and denser the material is the better its acoustic performance. Acoustic performance is an important part in construction to protect the inside from external noise such as traffic, and also the outside from internal noise such as load speakers.

There are three types of acoustic performance. Air borne sound, impact (structure- borne) sound and room acoustics.

Air borne sound- flow resistance

Air borne sound is sound energy transferred through air. A way of knowing if a material is a good sound insulator is by its specific flow resistance. The bigger the flow resistance of the material better its performance. A really good insulation material will improve the acoustic performance of a wall by 10 – 15db(CIRIA 2009). The materials used for acoustic performance must be flexible, dense and thick to get a good performance. Crop based material used for an acoustic performance include insulation batts made from sheep’s wool, hemp and flax.

Impact sound- dynamic stiffness

This is a sound energy that occurs by an impact with an element of a building. A way of improving impact sound performance is by getting a resilient layer. This layer will isolate the floating layer. The use of this kind of layer under a floating layer must have a low dynamic stiffness. Dynamic stiffness is used for describing the ability of a resilient material to transfer vibration (CIRIA 2009). A suitable crop based material for Acoustic performance is coconut fibre.

Coconut fibre product

Properties ValuesThermal conductivity 0.045W/mKFire classification B2Bulk density 50 -140 kg/m3Dynamic rigidity 23MN/m3

This fibre is mostly used as an acoustic insulation underneath screeds. It can be used as isolation strips for timber partition and timber flooring. Also as sealing strip building components, like door and windows.

Coconut fibre data properties

Table 3 Mechanical properties of Coconut fibre

(Andrew cripps, R. H. (2004). Crops in construction handbook. London: CIRIA.)

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FIG 1 Coconut fibre insulation (www.jebens-architecture.eu)

1. This type of fibre is obtained from the coconut shell. The production process involves picking fibre, skinning, roasting, washing, drying, sorted and compression. Its primary embodied energy is between 85-95kWh/m3 (wooley T and Kimmins, s. (2002). Green building handbook. london: spon).

.Advantages of using coconut fibre

It has great acoustic properties when used between wall and on the floor. There are no toxic emissions or bad smell during and after installation. It is a good resistance to insect attack. Also it has a good form of stability.

Fire performance

Insulation materials can also work as a fire resistance in construction. Mineral wool insulation products are really good when it comes to this aspect because they are not combustible but natural fibre insulation materials should not be considered as a fire resistance because they are combustible unless it is tested and indicated that they perform as required. Most crop based insulation material with inorganic fire retardants will reduce combustion. The most common fire retardants used in crop materials are flax, wool, coconut fibre, hemp, etc. Materials like compressed straw, reed, cork do not need additional fire retarding additives Etc. Most of the non mineral products are made up of additives that help their fire performance. The figure below is a reed insulation used in the ceilings because of its good fire resistance.

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Fig 2 Reed ceiling

The reasons why natural fibre insulation should be considered in construction

It has a low embodied energy. This is the energy consumed over the lifecycle of a building material i.e. during its manufacturing, processing, transportation, application and demolition. Compare to other competing materials the performance is better. The initial cost is expensive but it last longer than other competing materials, making the overall cost a lot cheaper.

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1.3 Floor covering

Crop based products also plays an important role in floor covering industry.

Floor covering serve as different objectives in a building:

For improving the thermal insulation of the floor. For improving the acoustic performance of a room. For improving the grip, for safety. For covering rough and raw surface.

Main floor coverings using crop based materials

1.4 LINOLEUM

Linoleum was discovered in the United Kingdom in 1864 (Andrew cripps, R. H. (2004). It was widely used in the around Europe until after the second world war due to the increase of vinyl tiles and other petrochemical-based floor covering. This is made up of twenty three per cent of linseed oil. This oil is boiled with a dry agent, oxidised and then mixed with other constituents like wood flour, softwood resin, cork flour, limestone powder, pigments, juke backing and zinc (drying agent). The constituents are all made from renewable resources which mean they are biodegradable. It is easy to maintain and also remains very environmental friendly. There are three types of linoleum; which are Tile, sheet and rug. The cheapest one out of the three types is tile linoleum and it is the least durable one while the rug types is the oldest type and now it is out of fashion.

FIG 3 Linoleum flooring (www.sierraclubgreenhome.com)

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http://homeimprovement.lovetoknow.com/Image:Linoleum_Flooring.jpg


1.5 COIR/COCONUT FIBRE

Coconut – This fibre is highly resilient, anti-bacterial and non rotting and makes a good, fully breathing component in mattresses and upholstery. It is also a good acoustic insulator. It is mainly produced in Asia, in countries such as India and Sri Lanka.

FIG 4 Coconut fibre flooring (www.cormatex.it, 2010)

Coir- Coir is hygroscopic. This will help maintain comfy indoor climate by absorbing changes in humidity. The disadvantage of this fibre is that its dimensions changes when it gets wet, when dried out it shrink unevenly. Also when its under direct sunlight it starts to fade out.

FIG 5 Coir fibre (www. greenrcompany.com , 2010)

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http://www.greenrcompany.com/

http://www.cormatex.it/

BAMBOO SIZING KNOT REMOVING SLICING

DRYING CARBONIZATION PLANKING

MOULDINGPLANKING

LAMINATION

COATINGSANDING


1.6 BAMBOO- This type of fibre is widely used in Asia, as a structural building material, flooring and other smaller products. Phyllostachys pubescence is a species of bamboo used to produce a hard wearing floor material. This is processed by cutting strips of bamboo and laminating them to flat boards just like that of timber floor. The bamboo is harder than other competing materials and they are suitable for home and office use and also public spaces like clubs, pubs and cinemas.

Manufacturing process of bamboo flooring

(www.jebcustomconstruction.com)

FIG 6 Bamboo floor covering(www.jebcustomconstruction.com)

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1.7 JUTE

This is produced from a plant called Genus corchorus. They are only grown in hot areas of Asia like India and Bangladesh (wooley T and Kimmins, s. (2002). The production involves labour intensive process. In some areas it is the main source of income in the world’s poorest places. Jute is a type of plant fibre used as the backing for linoleum. Soft, fine jute can also be used as carpet for light domestic use. Traditionally jute was used as backing for woollen rugs and still in use for backing other natural floor covering such as coir and sisal.

FIG 7 Jute rug (wwww.baltimorestyle.com)

1.8 Sea grass

Sea grass is produced from china. It is tough and attractive making it a reliable material for floor covering. It is a grass woven into yarn for weaving. It is suitable for light to medium contract use like restaurants, library, cinemas, night club, Etc. It is mostly kept in it’s natural colour which beige/yellow mix. ( Andrew cripps, R. H. (2004).

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Fig 8 Sea grass floor (www.sustainablelifestyles.com)

WHY CONSIDER CROP BASE FIBRE FLOOR COVERINGS

HEALTH ISSUES- Almost 1/3 of all 13 and 14 years old in UK (The guardian 2004) are affected by asthma which means UK is the third highest incidence of teenage asthma in the world. It is believed that 80% of asthma cases are caused by dust mites. Carpets are home for dust mites even after vacuum cleaning. Since most of us spends a lot of time on carpets and especially our kids. This means we are exposed to dust mites all the time and the chance of us having asthma is very high. Unlike linoleum and timber floor which are dust mites free.1

GREAT COMFORT- Artificial fibres do not absorb moisture. This makes it a bad material for indoor use where the humidity level changes. But crop based material are able to work indoor alongside other breathing elements in the room by absorbing change in humidity and also temperature.

MINIMISING USE OF NON RENEWABLE RAW MATERIALS AND ENERGY

Fibres like polyamide, polyacryl etc are all non renewable oil and uses a lot of energy during production. But crop based materials are renewable and uses less energy during production.

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1.9Light structural wall materials

These materials serve as two functions in a building. First it serves as thermal insulation and second as a structural part of a wall. Even though it serves as structural part of a wall it does not carry major structural loads but its self loads and wind loads. A good material for light structural wall is straw bales.

Concrete reinforcement

In the 1990’s the use of hemp as a building construction had been present in France.

Fibres are added to concrete when a large amount of energy needs to be absorbed, also where a high tensile strength and cracking reduction are needed.

Mixing fibre reinforced concrete

Mix proportions: Fibre reinforced concrete requires higher cement content to provide enough paste to coat the fibres. Using pozzolanas is a way of increasing the paste content without increasing the cement content. High ratio of fine to coarse aggregates should be used and the maximum aggregates size should be 10mm. (Concrete technology handout, 2009, university of Brighton)

Methods of mixing fibre reinforced concrete

Spraying up process method – This method is mostly used for glass fibres. A special pump and spray gun are used, chopped glass fibres and cement slurry are sprayed simultaneously on to the forming surface to produce the sheet. Up tp 10% of fibres by volume is used in the fibres reinforced concrete.

Premix process method – This method involves combining fibres with the cementation matrix in a mixer. In the method “balling up” can be a problem especially with steel. To avoid this, all the ingredients are mixed first then the fibres are added later. About 2% fibre by volume is used because fibres reduces the workability of the mix by this method.

Pulp types process –This technique is used when asbestos cement is replaced by cellulose fibres. The fibres are dissloved in cement slurry then dewatered to produce thin sheet materials. Between 10% - 20% by volume of fibre are employed.

Hand lay-up method – this method involves using the moulding of layer of fibres in form of mats or fabrics embedded within cement slurry and the vibrated or compressed to produced dense material with very high fibre content. . (Concrete technology handout, 2009, university of Brighton)

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Hemp

Hemp is a common natural fibre materials used in concrete reinforcement. This was first introduced in France in the early 1990’s (Evrard,2006).

Hemp lime composite is formed by adding hemp shiv and lime-based binder together. The lime binds the hemp aggregates together giving the material structural strength and stiffness.

The lime based cementations binder used in hemp concrete consist of hydrated lime, Hydraulic lime and cement. Lime is made from limestone and other sources like chalk, coral rocks or shells etc. The formula for limestone is CaCO3. When heated it gives out CO2 and CaO (quicklime). When CaO is added to water Ca(OH)2 is formed known as hydrated lime.

Hydraulic limes are made from limestone that contains fine clay materials. When fired in kiln it combines with lime to form active compound. Cement are formed from different compounds such as calcium oxide, silica, aluminium and ferric oxide. The advantage cement has over lime is that it sets quicker and changes chemically while hardening. Rich lime is still believed to be the appropriate binder for hemp concrete than cement. The reason for this is that slow carbonation process of the lime is more compatible with fast water uptake of the hempshives compared with the reaction of a hydraulic binder such as cement. Limes high PH protects the hempshives from mould and bacteria for a long time.

This composite material combines fast growing renewable and carbon sequestrating plant based aggregates (hemp shiv) with a lime base binder to form a less weight material that will suit different types of construction application, including solid walls, roof insulation and under floor insulation.( Bruijin, P. d. (2008). Hemp Concrete- Mechanical properties using both Shives. Sweden: Alnarp.)

Material properties

Hemp concrete has a mechanical, thermal and acoustic property that differs from those of conventional concrete. Experiments show that hemp lime has a good thermal and acoustic performance. Also it has the ability to regulate internal relative humidity through hygroscopic material behaviour. This makes it a healthier building and providing effective thermal mass, but it is not load bearing.

Compressive strength

The compressive strength of hemp concrete varies depending on the exact mix and age of the materials. Compressive strength values for hemp concrete is between 0.02 to 1.22Mpa (Arnaud and Cerezo, 2001). This compressive strength is not enough for the material to be load bearing, additional structure is needed.

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Tensile strength

The tensile strength of hemp concrete varies between 0.12 to 0.23Mpa. When the hemp shives to lime ratio is 3:1 by volume, a tensile strength of 0.15Mpa was obtained (O’Dowd and Quinn 2005).

Thermal Insulation

Hemp concrete is a lot more of a better insulation than plain concrete. Hemp concrete has a thermal conductivity value ranging between 0.07 to 0.11W/mK (O’Dowd and Quinn 2005).

.

The potential benefit from using hemp and lime:

Lower embodied energy construction Great synergy with timber frame building Reduce heating energy use Great quality internal environment Buffering of indoor moisture

Ecological properties

Advantages: when growing hemp the use of herbicides, fertilizers or pesticides.

Disadvantages: Requires shuttering which can be labour intensive.

FIG 9 HEMP LIME BLOCKS (www.bath.ac.uk)

Application

Durability – Hemp houses durability is equal to that of traditional construction

Removal – Easy to remove and break up at end of the building life

Disposal – Hemp lime aggregate can be used as a soil condition

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Straw bales

The use of straw bales in construction can be divided into two; structural (load bearing) or non Structural (in fill). They are mostly used when constructing walls but can be used as conventional cavity insulation in floor, roof, reinforcement for concrete in floor slabs etc.

For both load bearing and in fill construction, bales must be kept clean and dry during straw gathering, transportation and construction process. To minimise the risk of bacterial and fungal attack, optimum moisture level should be less than 15% (wet weight basis) (King Bruce, M. A. (2006).

Design guidance

Protection against insect and rodent should be done to prevent degrading strength and quality of the structure. This is done by application of lime or other coating.

Fire protection is an issue to be aware about. So the structure must be sheathed with conventional plaster board or plaster render.

Electric cables should be encased in conduits to reduce any risk due to overheating of cable. Water pipe should be placed within internal walls because leakage can lead to significant effect.(CIRIA 2009)

FIG 10 STRAW BALE WALL (www.gcbl.org/.../straw-bale-construction)

Application

Typical interior with straw visible in one area at the centre for alternative technology (CAT)

A small straw bale building at (CAT) Completed interior Straw being installed in a smoke shed

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http://www.gcbl.org/building/green-building/straw-bale-construction


1.10 THATCH

Thatch is moisture permeable and involves use of grasses or straw as a building material. When constructed in a traditional way, it provides weather resistant, breathable and highly durable roofing material.

The use of thatch in construction goes at least as far as the Bronze Age. Over 50,000 houses in England and Wales has thatch roofs, most at the South west in Devon, Cornwall and Dorset.

Materials like oats, marsh reed, broom, bracken. Etc. Are used for thatching but the main materials used at the moment are long straw, combed wheat reed and water reed.

Long straw – Its short life makes it uneconomic for thatching. The materials used now for straw thatching has to be specially grown crop, strains such as Huntsman, Little joss or square head master to give 900mm stems. To protect the stem from getting damaged, it is cut with reaper and threshed with machine (CIRIA, 2009).

Combed wheat reed – This is grown in a special way but bunched from the threshing tackle fitted with a special combing drum, transported and stacked on site, combed through to remove bent or broken stems. It is laid the same way as long straw but only the cut end of the stems show, giving it a neater and trimmer look than the long straw. This is similar to long straw except that the surface is worked over on completion to trim any loose stems (CIRIA, 2009).

Water reed – This type is cut during the winter season by special cutting machine. They stacked and covered until the time it is needed for construction. Most of the material is imported from Central Europe. It is laid on battens (or reed flecking), laid across the rafters, fixed and detailed but beaten up tightly to expose only the cut ends of the reeds.

RECOMMENDATIONS

Smoke alarm should be placed at the highest point of the roof void. Avoid recessed lighting in ceiling and external floodlights below the thatch Avoid use of blowtorch for metal plumbing in the roof space Chimney should be well above the height of the ridge for fire precautions.

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FIG 11 THATCH STRAW (Andrew cripps, R. H. (2004)

FIG 12 THATCHED ROOF BUILDING IN LONDON (Andrew cripps, R. H. 2004)

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ECOLOGICAL ASSESSMENT

Composition: Biologically regenerative.

Durability: Needs protection from fire, insects and rodents. Life span from 15-50 years.

Disposal: No disposal issue.

Source: UK and Europe

Cost: Between £600 - £800 (10ft by 10ft) (CIRIA, 2009).

ADVANTAGES

Flexibility Lightweight (35-45kg/m2) (CIRIA, 2009). Good thermal insulation Renewable resource Gutters and downpipes not usually required

DISADVANTAGES

Traditionally it is a fire hazard It is bulky in storage space during construction It is expensive in first cost at £30 - £50/m2 for water reed Open to damaged by bird

(Andrew cripps, R. H. (2004). Crops in construction handbook)

1.11 PAINTS AND FINISHES

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Paints and finishes takes a big role in construction by changing the appearance and creating a comfortable living and working environment of a building. It also takes the following role in construction:

It protects the structure from dust, moisture, dust etc. It enhances the artistic value of building interior and exterior.

The use of minerals is common to both natural and synthetic paints. Natural paint manufacturers choose to use more crop based materials, even though it cost a lot. This is done so that they can produce products with great quality, with many long term advantages. Also to reduce damage to the environment and protect painters and people living in the building from potential health hazards of complex chemical present in synthetic paints. Environmental harm from paints and finishes can occur from obtaining the raw materials, from the manufacturing process and from eventual disposal.

FIG 13 Natural paints colour (Andrew cripps, R. H. (2004)

Ingredients present in paint have different functions:

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Pigments give the colour and it makes up about 30% of the paint content. Example of natural based crop pigment is Reseda or weld (Reseda inteola) gives yellow to olive green.

Binder carries the colour during application and makes it stays when dry. It makes up 34% of the paint content. Example of natural crop based binder is Linseed oil (Linum usitatissimum)– extracted from flax seeds.

Solvent and emulsifiers are added to paints to produce uniform paint work. It makes up 34% of the paint content. Example of natural crop based solvent is citrus peel oil (D-Limonene citrus terpene) extracted from orange peel by cold pressing and steam distillation.

Drying agent and additives makes the paint dry within a reasonable time and improve its performance. This makes up only 2% of the paint content. Example of natural crop based additives is rosemary oil. (Andrew cripps, R. H. (2004). Crops in construction handbook)

Examples of Natural paints and their properties

Casein wall paintThis is made from milk protein, mixed with clays and chalk. Casein wall paints does not attract and retain dirt particles. It ages more slowly than most paints, it is easy to apply on walls and they dry quicker. This type of paint is good for the environment because of the following properties;

No solvents are needed. It makes use of low energy during production. It is 100% biodegradable. It can be supplied in powder form, for easy transport.

Linseed oil and Linseed oil based finishesThis made from flax seeds. They have extremely small molecules, about 50 times smaller than those in synthetic resins. This binder is good for the environment because of the following properties

Renewable resources. Completely non toxic. Use waste products. Vapour permeable. 100% organic linseed oil.

Performance, Design and Selection issues

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Drying times – Natural paints and finishes take longer to dry compare to synthetic products. This is because the chemicals present in synthetic paints are present to help dry quicker. So when applying natural paints longer time for drying should be considered.

Colour range – An issue that occurs when using natural fibre based paints is that not every colour can be produced. Also natural material for some colour can be really expensive compare to the synthetic material.

Repeatability

Many natural raw materials vary in their evenness and colour, and paints made from them also show variation from batch to batch than products from a chemical production line. Sometimes these variations give a special quality and life to surface, but care is needed where completely consistency of hue is needed.

Applying the finishes

Natural paint and finish are applied the same way as conventional finishes. For a successful application of natural paint we need to understand the following differences such as

Number of coats to use. Thickness of each coat. Direction of application. Tools and equipment to use.

Reasons why ordinary paints should not be used:

Ordinary paints are made up of large range of ingredient synthesised from petro chemical.

They are non degradable and highly toxic waste. The ratio of product to waste is really poor (1:30) i.e. 1 tonnes of product to 30 tonnes

of waste. The industries where these paints are made produce as much atmospheric pollution as

vehicle exhaust. Aromatic solvent used in ordinary paints are derived from crude oil. These solvent

contains volatile compound which are harmful to our health.

Reasons why crop based paints should be considered:

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Crop based paints do not crack when the surface expands and contracts. It allows moisture to pass through it. It has a low or non toxic material. It reduces poor indoor air quality. It involves low energy during production Most of the ingredients used are part of the natural cycle, deriving energy from the

sun and having a little global impact.

(Andrew cripps, R. H. (2004). Crops in construction handbook)

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CHAPTER 2

MINERAL FIBRE

2.1 Mineral fibres

These are inorganic substance made from rock, slag, glass or clay.

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They can be classified into three classes namely:

Fibre glass (glass wool and glass filament) Refractory ceramics fibres (RFC) Mineral wool (rock wool and slag wool)

2.2 MINERAL WOOL

Mineral wool is made from naturally occurring inorganic mineral material found in the earth’s crust. Mineral wool has been used for over 100 years worldwide. They have a good thermal, acoustic, fire and environmental characteristic. Mineral wools are made from glass, rock or stone and they are always referred to as mineral wool , insulation wool, etc.

Rock wool

This is sometimes referred to as stone wool. They are wholly natural material spun into wool from rocks. They are formed from one of the earth’s most abundant material volcanic diabase rock over 200 million years ago.

These rocks are crushed and graded to perfect size, then mixed with coke and slag. It is then put in a furnace to melt at a temperature of 1500°c. The melted product is then put in a series of rotating wheel where it is turned into wool. Small quantities of resin binder and mineral oil are added to keep the strands together and to make it repellent to liquids (EURISOL, 2009).

Insulation

Like every other mineral fibre, rock wool is also used as an insulator in buildings. For example, it is used as thermal insulator to keep the heat from getting out or in of the building. Also used as an acoustic insulator to keep sound from getting inside or outside the buildings. Using rock wool as insulator in cavity walls, loft will help save money on fuel bills and also help the environment.

Table 5 Comparing Rockwool with other insulating materials

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(http://www.rockwool.co.uk/stockists/installers/cavity+wall+insulation)

2.3 Uses of mineral wool

1) Insulation – This is the main use of mineral wool in construction. Insulation can be sub divided into thermal, acoustic, fire resistance, moisture resistance and corrosion resistance. Each of these properties are explained further below.

Thermal performance – Mineral wool is good thermal insulation material which means it is poor in transferring heat. Mineral wool products have a thermal conductivity between the ranges of 0.032 to 0.040w/mk. This performance is achieved by entrapping air within the material. The thermal conductivity in mineral wool does not deprecate with time while foamed plastic insulate depreciates. Foamed plastic insulator are produced using gases such as HCFC which are not environmental friendly or some time produced with pentane which increases fire risk. Mineral wool knit easily and firm together reducing thermal bridge unlike foamed plastic insulator (Eurisol, UK mineral wool association).

Moisture resistance – When mineral wool is used for cavity wall insulating it contains additives that repel water. These with the orientation of the mineral wool will prevent wind from driving in rain to the external leaf.

The British Board Agrement (BBA) carried out a test showing that mineral wool cavity insulation will not transmit water into the inner leaf and will also not transmit moisture caused by capillary action. These was confirmed by independent research conducted for the Government Energy Efficiency Office.

Between 1993 and 1994 the Government’s Energy Efficiency Office studied over 30,000 homes, for rain penetration of fully filled and unfilled cavity walls. The main findings were the risk of rain penetration is very low.

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Fire – When a test was carried out to BS476: part 4: 1970 (1984), it showed that mineral wool product used in cavity wall insulation is not combustible.

This is different to petro chemical based insulator material like phenolic foam, polyurethane foam etc. Which are combustible and gives out toxic gases and smoke in a fire.

Acoustics – One of the main benefit mineral wool has over other insulating material is acoustic control. More rigid insulation material like foamed plastic transmit sound through the insulator to the cladding and into the surrounding environment but mineral wool has a spring effect which help to prevent transmitting sound into the environment.

It can also reduce noise levels from pipes used for transporting gases, fluids or solid particles at high speed. The performance varies depending on the thickness of the mineral wool. For example, 31dB reduction can be achieved with 100mm insulation thickness under a 20swg mild steel cover (Eurisol, UK mineral wool association).

Corrosion – Mineral wool pipe insulation is chemically inert and compatible with copper and steel pipe work. The mineral contain low level of chlorides and inherently high level of stress corrosion inhibitors in form of silicate ions and sodium ions. An aqueous extract of the pipe section is neutral or a bit alkaline which means that mineral wool, unlike other form of insulator, does not need and special coating to prevent chemical attack. (Eurisol, UK mineral wool association).

FIG 14 Mineral wool insulation (www.blue-bird.com)

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2.4 Environmentally friendly

Environmental impact of a material is becoming a big concern in the generation we are in due to climate change and health risk. Mineral wool insulation contains no CFC, HCFC or other harmful materials and it uses available material for its production.

The uses of mineral wool insulating product reduces distribution losses from H&V pipe work and ducting. Also the emission of major green house gas, carbon dioxide, is reduced

For example, As an example 50mm thick mineral wool pipe insulation on an industrial steel pipe with a diameter of 114mm, operating with a hot face at 350°c and a surface temperature on galvanised cladding of 55°c, can save 56,581Mj/m in an operating year of 4,500 hours. The insulating embodies energy of 48Mj/m and the operational time necessary to recoup the investment in embodies energy is only 3.5hrs (Eurisol, UK mineral wool association).

Advantages of rock wool

It will minimise thermal bridging. It is non combustible. It also improves the acoustic performance of the ceiling They don’t decay They are water repellent It helps the structure to breathe. It is cost effective. It saves energy

2.5 Asbestos

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This is a group of silicate minerals that occur naturally in the environment. Asbestos are commonly used for roofing and pipes. They have high abrasion and corrosion resistance.

FIG 15 Asbestos roof (www.asbestosaferoofing.com)

There are six types of asbestos but the three main types produced are:

1) Crocidolite – blue asbestos2) Amosite – brown asbestos3) Chrysotile – white asbestos.

2. Between the 1900s and mid 1970s, asbestos was widely used in building materials, insulation and household products. Until 1974, the application of sprayed asbestos was ceased and asbestos reinforced insulation board were phased out in 1980. From 1986, UK stopped the importation of the two most dangerous forms of asbestos which are amosite and crocidolite. Chrysotile is the only type of asbestos that might still be in use in the UK and some European Union countries. (wooley T and Kimmins, s. (2002). Green building handbook. london: spon).

2.6 Uses of Asbestos

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In buildings, asbestos are used as a reinforcing agent in asbestos cement sheeting which are usually used on walls and roofs. Asbestos cement building products, such as tiles, pipes and gutters. It is also used as an insulating board for wall partition, fire doors, ceiling tiles, etc. Also it can be used in yarns and textiles; in lagging and in sprayed coating for decoration purpose. (http://www.ihsti.com.ezproxy.brighton.ac.uk/tempimg/144CBED-CIS888614800251158.pdf)

2.7 Health issues

Asbestos particles are very small fibrous which can be easily breathed in. Some of it will disappear while some may stay in the deeper parts of the lungs. The reason for this is because the particles do not readily dissolve when inhaled. Inhaling high level of asbestos over long period of time may lead to lung cancer, asbestosis and mesothelioma.

2.8 Carbon Fibre

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http://www.ihsti.com.ezproxy.brighton.ac.uk/tempimg/144CBED-CIS888614800251158.pdf

http://www.ihsti.com.ezproxy.brighton.ac.uk/tempimg/144CBED-CIS888614800251158.pdf


Carbon fibre is one of the stiffest and strongest fibres used as reinforcement for polymer composites. They are made from pure carbon in form of graphite, it has a low density and a negative coefficient of longitudinal thermal expansion (Lars Hallvist ApS). When used in concrete it prevents corrosion and its weighs about one fifth less than similar amount of steel. This makes it easier to handle and also reduces the construction cost. It is said to be stronger than steel. The disadvantages it has are; it is about 10 times more expensive than steel and it has low shear strength but it has a good tensile strength (Carbon fibre reinforced polymer,2000). As you can see below carbon material properties are been compared with steel and other natural fibres. Additionally, carbon’s resistance against magnetism is great advantage.

HEMP

GLASS

CARBON

STEEL

0 1 2 3 4 5 6 7 8 9

DENSITY(g/mm3)

DENSITY(g/mm3)

Density for different fibres (Holmes, M. (. (1983). GRP in structural engineering. London: Applied science.)

hemp glass carbon steel0

50

100

150

200

250

YOUNG MODULUS (KN/mm2)Series2Series3

Fig 17 Young’s modulus (transversal) of different fibres (Holmes, M. (. (1983). GRP in structural engineering. London: Applied science.)

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HEMP GLASS CARBON STEEL0

50

100

150

200

250

YOUNG MODULUS(KN/mm2)#REF!Series3

Fig 18 Young’s modulus (longitudinal) of different fibre (Holmes, M. (. (1983). GRP in structural engineering. London: Applied science.)

HEMP GLASS CARBON STEEL0

0.5

1

1.5

2

2.5

3

TENSILE STRENGTH (KN/mm2)Series2Series3

Fig 19 Tensile strength of different fibres (Holmes, M. (. (1983). GRP in structural engineering. London: Applied science.

The use of steel plate reinforcement is used for strengthening structure to its original condition or to achieve higher performance. This was first introduced in France during the

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1960’s on Auto route du Sud Bridge to increase the capacity of the bridge. But due to problems like weight and corrosion, researcher introduced carbon fibre reinforcement. This was first used in USA and Japan for seismic retro fitting of structures. Now in Europe it is used by concrete repair and strengthening industries. They are applied like wallpaper; it can be easily cut with sharp scissors and pasted onto the surface of the element with epoxy resin. Then a roller is used to draw out all air pocket and to make sure the epoxy resin has saturated the individual fibres. They are mostly applied on slab, beam, floor, walls, column etc.

The advantage of carbon fibre is the impressive strength/weight ratio; also its tensile strength is greater than that of steel and its density is only one fifth. (Technical and Practice. (2000). The architect's jornal , 36-37).

Fig 20 Installation of Carbon Fibre reinforcement on a beam (www.zeraconstruction.com)

2.9 Fibre glass

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Glass reinforced concrete also known as glass reinforcement cement was developed to replace asbestos cladding sheets due to health hazard. It is similar to asbestos cement but the different is glass reinforced cement is reinforced by fairly long glass fibre instead of short finely separated asbestos fibre. Health issue is not the only advantage glass reinforced cement has over asbestos but also it is much less brittle than asbestos cement i.e. it has resistance to damage than asbestos cement.

2.10 Applications of Glass reinforced cement (GRC)

Water transport

The smooth, moulded and impermeable finish that GRC has makes it popular in the water industry. Also GRC’s light weight has given it additional site laying benefit.

Fig 21 Water pipes made from GRC (www. alterra.hu)

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2.11 General building

The use of GRC has made it possible to reduce the on-site labour content content, component such as simulated roof tiles and shingles; decorative sunscreen, complex architectural mouldings and features such as barrel-vault roofs; window surround; and light weight lintels.

Fig 22 Building built using GRC (www. strombergarchitectural.com)

Fig 23 Roof made from GRC (www. cybglassfibre.co.uk)

2.12 Canal lining

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GRC corrugated sheets can be used to line canal banks as a corrosion and rot proof, it is also capable of withstanding erosion and traffic damage. In soft soil, the sheets are vibration piled into the banks giving a rapid method of relining.

2.13 Tanks

Tanks made with GFC are water rigid, durable, resistance to fungi and algae, and unaffected by frost or sunshine. The combination of properties led to the use of GRC in many places such as swimming pool etc.

Fig 24 Glass Fibre Tank (www.tanksalesandrentals.com)

2.14 Highway Engineering

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Traffic noise is an increasing issue in urban areas. GFC has been used as noise barriers on railways and motorways. The density of GRC means that a single sheet of GRC 10mm thick can provide a noise attenuation in excess of 25dB. The mould ability of GRC allows a high standard of aesthetic design

Other application of Glass reinforced cement

Self supporting walls Floor units Load bearing internal wall Integral stair cases Small footbridge

Fig 25 GRC footbridge (www. composites.ugent.be)

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Fig 26 GRC staircase (www.fibrolux.com)

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CHAPTER 3

ANIMAL FIBRE

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3.1 ANIMAL FIBRES

Animal Fibres – These types of fibre contain protein. For example silk, wool, spider silk, yak, mohair. Animal fibres can be subdivided into animal hair (wool or hairs), silk fibre and avian fibres. Sheep are the main source of natural animal fibre and there are over 200 breeds of sheep worldwide. Britain has the largest number of breeds with a total number of 65.

The use of animal products such as hides and sinews for fastening and cladding has been used in the ancient constructions. The main uses of animal fibre in construction are reinforcement in concrete or clay and flooring (Rugs/carpets) and these two uses are discussed below. Apart from animal fur or hair, other parts of animal are used in construction. For example, the use of animal bone as a structural material for steppes was discovered in Eastern and Northern Europe. Also use of animal glue was common in Ancient construction. And this was the first type of glue known and was used in ancient Egypt. (www.binaitimes.com).

APPLICATION OF ANIMAL FIBRE IN CONSTRUCTION 3.2 Wool for reinforcement in soil Constructing with soil dates back to the earliest form of human dwellings and settlement. Building with earth is not only used by humans, it is also used by animals. Termite is an example of n animal that makes use of earth for building their nest. This is done by combining polymer from their natural secretions with soil. Below figure shows a termite nest.Recently there are renewed interests in building with earth among building professionals due to the climate change. Wool is part of the composite when building with earth. Wool is used to add reinforcement in the composite. This will be taken from sheep’s, untreated and straight from the animals fleece. This means that no artificial addictives will be introduced during usage.Other animal fibre materials used as composite are;Alginate: This is a natural polymer and rich in the cell walls of brown algaeLignum sulphate: This is extracted from tree bark. This is added to soil to improve its workability

Fig 27 Termites nest reinforced by their natural secretions (www. science.slashdot.org)

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3.3 Sheep wool insulator

Reducing fossil fuel energy use especially heating energy is a big challenge and it’s the most important environmental consideration. Since buildings are responsible for 45%-50% of all the energy used in developed countries, the use of natural fibre insulator is the best way to reduce the use of fossil fuel energy for heating houses. Sheep wool insulator is an example of a natural fibre insulator. Sheep wool insulator has a thermal perfoemance of 0.0037W/mK. When comparing with other equivalent insulation materials it performs as well as, or even better than polystyrene (0.34W/mK) and foamed glass (0.042W/mK). When comparing with glass fibre insulation, it is produced with a fraction of energy used for producing glass fibre insulation (14%). The production of sheep wool fibre helps poor rural areas in uk towards there economies. (Andrew cripps, R. H. (2004)

FIG 28 Sheep wool insulation(www.enviromaterials.co.uk)

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The advantages of using sheep’s wool insulation are as follows:

It is breathable and can absorb moisture with no loss of thermal efficiency. It has a condensation control, and generates heats when moisture from atmosphere is

absorbed. It is a natural fire resistance. Sheep’s wool is extremely durable and will last 50 years with no reduce performance. They are flexible and easy to use. They are completely harmless to human and animals.

Disadvantage of using sheep’s wool insulation

Unfortunately, sheep’s wool cannot be used in cavity foundation walls because, being a natural material it needs to have an air gap of at least 50mm (2”) to provide sufficient airflow for it to breathe. As far as conventional options go, rock wool is the next best option because it has low energy consumption relative to other insulation materials.

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3.4 Mohair rugs/carpets

Mohair has an elegant beauty and it has been long known for its great durability. The brilliant sheen and its room lighting enhances it attractiveness. The strength of cordage yarn which interlocks the weaving makes it incorporate very long stapled pile into carpets. This is an important property that makes it considerably for making rugs (the longer the staple the more secure the rug is going to be) (www.binhaitimes.com/mohair). Comparing mohair and wool, Mohair is much stronger than wool and its able to withstand the large pressure of human traffic. Mohair from young goats is used in knitwear, from intermediate age it is used in suiting materials but stronger fine hair types are used as rug in houses, cinemas, offices, restaurants etc.

The unique qualities of Mohair are;

Insulation Durability Comfort Strength Shrink resistance Elasticity Moisture transfer Luster Light weight Non flammability Easy to wash

Fig 29 Hand weaving mohair rug (www. weavinghands.com)

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http://www.binhaitimes.com/mohair


Other animal parts used for as building materials

3.5 Coral - Coral is a specie that can be used in construction. The part of coral used for construction is the mineral part. Coral is widely used in construction in the Maldives such as filler for concrete (www1.american.edu/TED/SRICORAL.HTM). Coral has other uses such as food supplies, medicinal purposes and protecting coastline from storms and erosion.

FIG 30 Coral reef system (www.geology.com/rocks)

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http://www1.american.edu/TED/SRICORAL.HTM


3.6 Beeswax

Beeswax is a common substance used for treating timber. They are produced by bees to form honeycombs. It basic use is for butcher block or wood salad bowls. Where polished used must not be poisonous because it’s used on food. In a double boiler add 40% beeswax to 60% food grade mineral oil like what you find at the pharmacy. If it is still not the right consistency for your application you can just reheat and add more mineral oil to make the paste smoother.It is has been used as wood polish for centuries. This is done by adding it to a odourless turpentine or it can be boiled with linseed oil. Beeswax can be used as a lubricant, for coating screws and nails so they can go in easier. It can be used also on window sills and drawers to make it slide smoothly.

FIG 31 Preparation of beeswax

(www.hiveharvest.com/facts_about_beeswax)

3.7 Paint made from fish oilThe use of fish oil as a binder in paints was used in the UK dating back to the twelfth century, but there is evidence that the use of oil for coating was present for a longer time before. Cod - liver oil can use for making fish oil paint. They hardly smell and it dries up within couple of weeks, depending on the pigment.The paint is durable, weatherproof, and it has a good resistance to sea water. The drying time for this type of paint is about two weeks and it is mostly used on rough wood outdoors. It’s durability is about 10 years but after 5 years a coating of linseed must be done to maintain the good qualities.

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http://www.flypiedrahita.com/blog/wp-content/uploads/2009/03/draining-warre-honey.jpg


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CHAPTER 4

CONCLUSION AND REFERENCES

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CONCLUSION

Thinking about a more sustainable world is important, not just for meeting the needs of the present generation but also meeting the needs of the future generation. This is done by aiming to achieve a balance between environmental protection, social and economic growth, and also working in peace with earth’s ecosystem.

Since buildings are responsible for 50% of EU energy use, constructing in a greener way will help the environment, and also the health of people living in it (http://www.brufma.co.uk). This dissertation focuses on how this can be achieved by using natural fibre in construction.

Insulation plays a very important part in reducing the environmental impact in buildings. However,when natural fibre insulation is used the reduction in environmental impact is even more. Almost 35% of the total energy consumption in the United State of America accounts for heating and cooling of the buildings which leads to various disadvantages such as air, water pollution and health risks (www.naturalfibresinfo.com/why.php). Comparing natural fibre insulator (sheep wool, glass wool) with synthetic fibre insulator (polyurethane board, polystyrene), glass wool has a conductivity value of 0.033W/mK while polystyrene has a similar value of 0.032W/mK. They both have similar conductivity but the disadvantages of using synthetic fibre insulation (polystyrene) are that it releases toxic fumes when burnt and releases gases under UV light. It is also expanded using pentane which produces smog. They are not recyclable and take a long time to decompose. All of which are harmful to humans and the environment. Natural fibre like sheep wool or mineral wool does not have these disadvantages. They are recyclable and rot proof. They have a much lower embodied energy compare to polystyrene, the embodied enrgy for producing polystyrene is 12 times greater than that of mineral wool(www.livingrainforest.org). Comparing the price of polystyrene and mineral wool (glass wool), polystyrene cost £5 per m2 while glass wool cost £2 per m2.

Information from CDC (Centre for disease control) shows that blood lead level in toxic range is common in children between the age of one to two years which is about six per cent and black children between the age of one to five about eleven per cent. Lead affects people of any age but mostly children because of their rapid development of nervous system which is sensitive to the effect of lead. The common sources of lead are lead paint and lead contained in soil and water. Houses built before 1950 has high risks of containing lead based paint. This had a wide range of effects on children’s development and behaviour. When a small amount of lead level is exposed to children, they tend to be inattentive, hyperactive and irritable. In addition, children with high levels of lead may have learning and reading problems. Also delayed growth and hearing loss has been experienced in children due to lead. But when the level is incredibly high it may lead to brain damage or even death. This can be prevented by using paints produced with natural fibre such as linseed oil and paints produced from milk protein. They are non toxic and 100% biodegradable. They are also vapour permeable i.e. the health of the people living in the building will not be affected because the building can breathe. Ordinarily, concrete contains numerous micro cracks due to low tensile strength of the material. But addition of closely spaced fibres will increase the tensile and flexural strength of the concrete. Increasing the fibre volume also affects the behaviour of the

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http://www.naturalfibresinfo.com/why.php


concrete. When fibre volume is less than 1%, are used for reducing shrinkage. When fibre volume is increased between 1% and 2% the modulus of rupture, fracture, toughness and impact resistance increases. When fibre volume is > 2% the fibre at this level leads to strain hardening of composites because of this improved behaviour these composite are often referred as high performance fibre reinforced composite (concrete, microstructure, properties and materials, third edition, P.Kumar, Mehta, Paul J.M).

Out of all the natural fibre, carbon fibre is the only one that has similar or even higher tensile strength than steel with a value 2.5KN/mm2 and it is one of the natural fibre used as load bearing. As most of the natural fibre like hemp, sisal, jute cannot be used as a load bearing, they need a load bearing structure to withstand the tensile strength and compressive strength. Fibres like hemp, jute, sisal, rock wool are also used as insulator.

Out of all the natural fibre, Asbestos is the only one with a major concern to human health. Asbestos particles have very small fibrous which can be easily inhaled. Some of it will disappear while some may stay in the deeper parts of the lungs. This is because that the particles do not readily dissolve when inhaled. Inhaling high level of asbestos over long period of time may lead to lung cancer, asbestosis and mesothelioma. But it has been replaced by glass wool which as similar properties but does not harm humans.

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REFERENCE

1. Allen, H. (1975). Glass-fibre reinforced cement-strength and stiffness. london: Construction Industry Research and information Association.

2. Andrew cripps, R. H. (2004). Crops in construction handbook. London: CIRIA.

3. Bruijin, P. d. (2008). Hemp Concrete- Mechanical properties using both Shives. Sweden: Alnarp.

4. Halliwell, S. (2000). Polymer composites in construction. London: CRC Ltd.

5. Holmes, M. (. (1983). GRP in structural engineering. London: Applied science.

6. institution, B. s. (1996). Thermal insulation- Determination of steady-state thermal transmission properties. London: BSI.

7. J. Petric-Gray, C. G.-M.-G.-G. (2009). SOIL STABILIZATION WITH ALGINATE AND WOOL FOR CONSTRUCTION INDUSTRY. Glasgow.

8. J. Petric-Gray1, C. G.-M.-G.-G. (2009). SOIL STABILIZATION WITH ALGINATE AND WOOL FOR CONSTRUCTION INDUSTRY. Bath.

9. King Bruce, M. A. (2006). Design of Straw bale building. London: Green Building press.

10. Limited, E. U. (2006). The benefits of mineral wool. Herts: Owens Corning .

11. Natural fibres. (n.d.). Retrieved December 3, 2009, from Natural Plant and Animal Fibres : www.binhaitmies.com/history

12. Ngowi, A. B. (1996). Improving the traditional earth construction. Gaborone: Elsevier science.

13. Priscilla Chew and Colin MacDougall, P. (2008). Hemp Fibres for Building Construction. Kingston: Quen's University, Kingston.

14. Romildo Dias Tolêdo Filho, K. J. (1999). THE USE OF SISAL FIBRE AS REINFORCEMENT IN CEMENT BASED COMPOSITES. Campina Grande.

15. S. Elfordy, F. L. (2006). Mechanical and thermal properties of lime and hemp concrete. France: Elsevier.

16. strawbale future. (n.d.). Retrieved 2010, from www.strawbalefuture.org.uk

17. Technical and Practice. (2000). The architect's jornal , 36-37.

18. wooley T and Kimmins, s. (2002). Green building handbook. london: spon.

19. Burchell Jim, Design and build in timber frame / J. Burchell, F.W. Sunter, Harlow (1st Edition Longman Scientific & Technical, 1987).

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Introduction natural fibre (Autosaved)12 (2)

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