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Textiles & Fabrics inFacadesNEW BUILDING MATERIALS & SPECIFICATIONS

AISWARYA SREEKUMAR

BEM/ 547 15-03-2013

BUILDING ENGINEERING

AND MANAGEMENT



AISWARYA SREEKUMAR - BEM/547, DEPT OF BEM, SPA-D | 15-03-2013

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ContentsList of Figures .......................................................................................................................................... 5

1 INTRODUCTION ............................................................................................................................... 7

1.1 Brief History of Textiles in Building Construction ................................................................... 7

1.2 Technical Textiles .................................................................................................................. 11

1.3 Making of Textiles and Fabrics .............................................................................................. 12

1.3.1 Woven Structures and Weaving ................................................................................... 13

1.3.2 Knitted Structures and Knitting ..................................................................................... 13

1.3.3 Nonwoven Structures and Nonwovens ........................................................................ 14

1.3.4 Fabric Finishing, Coating and Lamination ..................................................................... 15

1.4 Types of Fabric Façade Materials .......................................................................................... 16

2 MATERIAL STUDY- PVC coated PES ............................................................................................... 18

2.1 Introduction .......................................................................................................................... 18

2.2 Chemical Composition .......................................................................................................... 19

2.3 Method of Manufacture ....................................................................................................... 19

2.4 Characteristic Properties....................................................................................................... 22

2.4.1 Physical .......................................................................................................................... 22

2.4.2 Durability ....................................................................................................................... 22

2.4.3 Performance Properties ................................................................................................ 23

2.5 Testing and Acceptance Criteria ........................................................................................... 24

2.5.1 Non-Wicking .................................................................................................................. 24

2.5.2 Ultraviolet Light and Weathering Resistance ............................................................... 24

2.5.3 Fungus and Mildew Resistance ..................................................................................... 25

2.5.4 Flame Resistance ........................................................................................................... 25

2.5.5 Performance Properties for Architectural Fabrics ........................................................ 26

2.5.6 Summary ....................................................................................................................... 302.6 Applications ........................................................................................................................... 30

2.7 Advantages ............................................................................................................................ 31

2.8 Limitations............................................................................................................................. 31

2.9 Installation systems............................................................................................................... 32

2.10 Cost Analysis ......................................................................................................................... 32

2.11 Maintainability Aspects ......................................................................................................... 33

2.11.1 Material pollution: ........................................................................................................ 33

2.11.2 Cleaning: ........................................................................................................................ 33



TEXTILES & FABRICS IN FACADES | NEW BUILDING MATERIALS & SPECIFICATIONS

3 Textiles & Fabrics in Facades

2.11.3 Maintenance: ................................................................................................................ 33

2.11.4 Environmental compatibility: ........................................................................................ 33

2.12 Commercial Catalogues/ Brochures ..................................................................................... 33

2.13 Case Study ............................................................................................................................. 34

2.13.1 COPENHAGEN CONCERT CENTRE [DR KONCERTHUSET (DRK)] .................................... 34

2.13.2 BMW MOTORSHOW IAA FRANKFURT .......................................................................... 37

2.14 Performance Specification .................................................................................................... 39

2.14.1 PVC (Poly Vinyl-Chloride) COATED PES (POLYESTER) .................................................... 39

3 MATERIAL STUDY- ETFE ................................................................................................................ 41

3.1 Introduction .......................................................................................................................... 41

3.2 Chemical Composition .......................................................................................................... 42

3.3 Method of Manufacture ....................................................................................................... 42

3.4 Manufacturing of the ETFE granulate: .................................................................................. 43

3.4.1 Raw materials and monomers ...................................................................................... 44

3.4.2 Polymerization .............................................................................................................. 44

3.4.3 Granulation ................................................................................................................... 44

3.4.4 Refining ......................................................................................................................... 44

3.4.5 Extruding ....................................................................................................................... 45

3.4.6 Finishing the foil cushions: ............................................................................................ 46

3.4.7 Types of ETFE structure ................................................................................................. 46

3.5 Characteristic Properties....................................................................................................... 47

3.5.1 Material Strength .......................................................................................................... 47

3.5.2 Weight ........................................................................................................................... 48

3.5.3 Cushion Size .................................................................................................................. 48

3.5.4 Insulation....................................................................................................................... 48

3.5.5 Transparency and Translucency .................................................................................... 483.5.6 Solar Control ................................................................................................................. 49

3.5.7 G Value .......................................................................................................................... 50

3.5.8 Life Expectancy .............................................................................................................. 50

3.5.9 Fire ................................................................................................................................ 51

3.5.10 Acoustics ....................................................................................................................... 51

3.5.11 Environmental ............................................................................................................... 52

3.6 Applications ........................................................................................................................... 52

3.7 Advantages ............................................................................................................................ 53




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3.8 Limitations............................................................................................................................. 53

3.9 Handling, Installation and Storage ........................................................................................ 54

3.9.1 Fragility .......................................................................................................................... 54

3.9.2 Inflation Units ................................................................................................................ 55

3.9.3 Power Failure ................................................................................................................ 55

3.9.4 Safety/Explosion & Other Risk ...................................................................................... 55

3.9.5 Repair and Replacement ............................................................................................... 56

3.9.6 Transportation .............................................................................................................. 56

3.9.7 Framing ......................................................................................................................... 56

3.9.8 Typical Section of an ETFE Cushion ............................................................................... 57

3.10 Cost Analysis ......................................................................................................................... 57

3.11 Maintainability Aspects ......................................................................................................... 57

3.11.1 Rainwater & Drainage ................................................................................................... 57

3.11.2 Cleaning ......................................................................................................................... 58

3.11.3 Maintenance ................................................................................................................. 58

3.12 Commercial Catalogues/ Brochures ..................................................................................... 58

3.13 Case Study ............................................................................................................................. 59

3.13.1 GLASS CUBE - NATIONAL AQUATICS CENTRE BEIJING .................................................. 59

3.13.2 ALLIANZ ARENA, MUNICH, GERMANY .......................................................................... 63

3.14 Performance Specification .................................................................................................... 65

3.14.1 ETFE (Ethylene Tetra Fluoro Ethylene) .......................................................................... 65

4 References .................................................................................................................................... 66





List of Figures

Figure 1: Example of primordial tent construction using animal skin

Figure 2: American Indian Tepee

Figure 3: The Bedouin Tent

Figure 4a: Velaria over Roman Colloseum

Figure 4c: Royal Court Tents

Figure 4b: Circus Tents

Figure 5: German Pavilion for Expo ‘67, Montreal

Figure 5a: Fuji Company Pavilion Air-in filled Structure, Osaka

Figure 5b: American Pavilion Air-supported Structure, Osaka

Figure 6: British pavilion for expo’ 92, Seville

Figure 7: Constituents of Technical Textiles

Figure 8: Most common man-made façade fabric materials

Figure 9: Making of Textiles and Fabrics

Figure 10: Warp and Weft

Figure 11: Knitted fabricFigure 12: Fabric bond and showing the various layers and coats

Figure 13: Façade of Cogeneration Plant, Chinaham, United Kingdom with PVC coated PESmesh panels

Figure 14: Manufacturing Process of PVC coated PES

Figure 15: Façade Fabric of Deichmann Flagship Store, Germany

Figure 16: Typical substructure for textile architecture using PVC coated PES

Figure 17: Section showing the layers of the Stamisol system

Figure 18: Copenhagen Concert Centre at night displaying the cobalt blue PVC coated PESmesh facade

Figure 19: BMW motor show canopy made of PVC coated PES opaque structure fabric asroofing

Figure 20: ETFE tension layer on a facade

Figure 21: Flow chart of the ETFE granulate production

Figure22: ETFE granulate unpacked and packed




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Figure 23: ET-foils production line (1: extruder, 2: shaping, 3: casting, 4: winder, 5:automation)

Figure 24: Typical ETFE section

Figure 25: ETFE installation on the Beijing Water Cube

Figure 26: Conceptual drawing of ETFE skin of Water Cube

Figure 27: ETFE skin from the swimming pool inside of the Aquatics Centre

Figure 28: ETFE skin back lit with colour changing LED lights on the Allianz Arena

Figure 29: ETFE skin on installation during construction of the Allianz Arena





1 INTRODUCTION

1.1 Brief History of Textiles in Building Construction

Tensile architecture is probably one of the oldest methods used to provide protection from

adverse climatic conditions and against predator attack. The humble conic’ tent is the

simplest form of tensile structure, and excelled where two conditions prevailed: a shortage of

building material and a need for mobility. Evidence has been found which confirms that

humans have been making tents for at least 15.000 years, initially using animal skins, and

only 3000 years later, incorporating woven fabrics.

Figure 1: Example of primordial tent construction using animal skin

Differing forms depended on different materials available at the time — for example the

American Indian Tepee, the Bedouin tents or the Mongolian Yurt.

Figure 2: American Indian Tepee Figure 3: The Bedouin Tent




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Figure 4: The Mongolian Yurt

One of the first applications of tensile technology came at the very beginning by transferring

sailing principles, the spectators at Roman amphitheatres (e.g. the Coliseum) were protected

against the sun by retractable sheets and fabrics roofs, supported by timber masts and cotton

fibre ropes as operated by sailors.

Figure 4a: Velaria over Roman Colloseum

Figure 4c: Royal Court Tents Figure 4b: Circus Tents





FABRIC MEMBRANE AND CABLENET STRUCTURES

Figure 5: German Pavilion for Expo ‘67, Montreal

Modern fabric materials in modern architecture can shape space, enabling architects to sculpt

3-dimensional areas in a manner that is not possible with any other type of material. This kind

of architecture is offering much more: the designer is able to play with light and use this for

natural illumination of the space, softening it, fusing it, sharpening it or shaping it. This

creates mood and ambience to reflect architectural intent, resulting in an energy saving

covering system, by approaching the elementary need of being in touch with nature. The

dynamic shape and form of membranes allow new possibilities to become reality.

LARGE SPAN GRID SHELL AND AIR-STRUCTURES

Figure 5a: Fuji Company Pavilion Air-in filled Structure, Osaka

Figure 5b: American Pavilion Air-supported Structure, Osaka




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The light weight tensile membrane structures developed strongly after the World War II. Later

this was followed the pneumatic structures. Textile and fabric were also used in structures

where they had no load-bearing role.

New fibres were invented and several new polymers, synthetic rubbers and adhesives for

coating and lamination of textiles were developed. These man-made materials were

developed to surpass the properties of natural fibres. Examples of textile and fabric

architecture that are horizontal coverings, either roofs or enclosing structures reached their

maturity in the 1970’s and 1980’s.

FABRIC FACADES

Figure 6: British pavilion for expo’ 92, Seville

THE FACADES were covered with textile and fabric fairly late, in the 1990’s. End-use

requirements impose demands on the design and also on the selection of fabric for façadetreatment. In no other sector of architecture do form and load distribution depend on each

other as greatly as they do in membrane construction. Hence, these represent the perfect

marriage between architecture and engineering. As in nature, the course of forces that are

shown in the form and shape can fascinate not only architects and engineers, but also the

wider public as well, especially those who can appreciate the equilibrium between aesthetics

and functionality.





1.2 Technical Textiles

TECHNICAL TEXTILES are replacing traditional textile materials as well as other materials,

metals and construction materials. Common to the manufacturing and use of all the

mentioned materials is the manipulation of fibres, fabrics and finishing and the

understanding of the properties of flexible materials. Technical textiles can be divided into

many categories, depending on their end use.

Figure 7: Constituents of Technical Textiles

BUILDTECH- These are the Construction Textiles, also known as Buildtex, used for concrete

reinforcement, facade foundation, interior construction, insulation, air conditioning, noiseprevention, visual protection, protection against sun light, building safety etc. Such fabrics as

PVC coated high tenacity PES, Teflon coated glass fibre fabrics or silicone coated PES are

used extensively in football stadia, airports and hotels.




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1.3 Making of Textiles and Fabrics

Figure 8: Most common man-made façade fabric materials

Figure 9: Making of Textiles and Fabrics





1.3.1 Woven Structures and Weaving

Weaving is the most common technique to produce textiles. Woven fabrics can obtain higher

strengths and stabilities than any other structures in textile manufacture. The two different

yarn directions in woven fabrics are the weave and the weft. Weaves are the ones running

along the length of the fabric and forming the warp. The weft crosses the warp from one side

to the other.

Figure 10: Warp and Weft

1.3.2 Knitted Structures and Knitting

It is less used in technical textile applications compared to the use of woven and nonwoven

fabrics. In knitting, one or several yarns are inter-looped to form a continuous structure &

compared to other production techniques, knitting has an advantage, which is its versatility

and rapidity. Possible structures are endless and knitted constructions can easily be designed

to meet exact end-use requirements such as flat structures, shapes, meshes and nets or three

dimensional products. The yarn encounters less stress than in weaving. Thus delicate fibres,

such as aramid, carbon and glass can be used.

Figure 11: Knitted fabric




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1.3.3 Nonwoven Structures and Nonwovens

Nonwoven fabric is a flat structure in which the chosen material is bonded chemically,

mechanically or thermally. The main difference with the traditional textile techniques is that

there is no need to convert the chosen material into yarn, nor is it woven or knitted to form a

binding structure. The production of nonwovens involves three stages:

web (or batt) forming,

web bonding and/or manipulation and

Finishing.

These operations can be performed one after another – separately or overlapping each other.

1 3 3 1 Web Forming Phase

The technique to form a web can be

a dry-laid technique that derives its origins from textile industry;

a wet-laid technique with roots in paper making or

a spun-laid or polymer-laid techniques that have their machinery developed for

polymer extrusion.

1 3 3 2 WEB BONDING PHASE

The technique to bond a web can be

chemical,

mechanical or

thermal and a combination of processes can be used.

In web formation, the manufacture width and weight are chosen. The composition of fibre

orientations affects the fabric’s tensile strength. In the web bonding stage, density, flexibility,

porosity, softness and strength are determined by the degree of bonding

1 3 3 3 FINISHING PHASE

The end-use application determines the processes chosen. Finishing can modify or add to

the existing properties of the nonwoven fabric. The finishing methods are traditionally

divided into dry and wet finishing. Chemical substances can be used before and after





binding, whereas mechanical finishing processes are applied after the web (batt) is reinforced

in the binding stage. After finishing, the nonwoven fabric is rolled and can be further

converted closer to its final form

1.3.4 Fabric Finishing, Coating and Lamination

Figure 12: Fabric bond and showing the various layers and coats

Irrespective of the techniques used in technical fabric production viz. woven, knitted or

nonwoven, the fabric is the finished, coated and laminated to obtain the desirable end use

properties.

1 3 4 1 Fabric Finishing

The purpose of FINISHING is to improve the fabric’s functionality and its aesthetic values.

Four main subgroups of finishing exist.

mechanical finishing processes,

heat setting processes,

chemical finishing processes and

finishing processes related to coating processes.

1 3 4 2 Fabric Coating

COATING processes differ from finishing processes. A coating process closes the holes of a

fabric to some degree, whereas finishing forms a cover only on the yarns. Coating is done by

applying a direct thermoplastic polymer spreading on the fabric. Here, the fabric acts as the




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substrate for the coating. After the spreading, the coating is dried or cured into a deposit

layer on top of the fabric. Coating materials worth mentioning are:

PVC (polyvinyl chloride),

PVCD (polyvinylidene chloride),

PTFE (polytetrafluoroethylene),

natural and synthetic rubbers,

polychloroprene (neoprene),

chlorosulphonated polyethylene (Hypalon),

silicone rubbers and polyurethanes.

1 3 4 3 Fabric Lamination

Polymer materials are applied to fabrics by a separate LAMINATION PROCESS. The used

adhesives are solvent or water-based films, granules, jellies, powders and webs. Machinery

and manufacturing methods are chosen according to the substrate material; flat and uniform

or stretchy and structurally uneven.

Lamination shortens the time of production, lowers the production costs and ensures even

quality. It can also prevent the need of sewing when the final product is prepared for its end-use purpose. The substrate fabric affects the physical properties, whereas coating or

lamination affects the chemical properties of the fabric. In addition to the properties of the

substrate and the polymer layer, many of the properties of the finished fabric result from the

combination of the layers. The layers are carefully designed to act together for the desired

purposes

1.4 Types of Fabric Façade Materials

a. COATED FABRICS, meshes, sheets or films.

b. UNCOATED FABRICS are cotton and polyester, metal and fluoro-polymer fabrics.

c. COTTON AND POLYESTER MIXES are impregnated against weathering and used mostly

in small to medium structures.

d. METAL FABRICS are chosen for facades, protection or sun shading purposes.

e. FLUORO-POLYMERS LIKE PTFE is suitable for kinetic structures.

f. Most of the architectural fabrics are coated or laminated fabrics with a closed or an open

textile matrix base.





1. PVC coated polyester and PTFE coated fibreglass – most common

2. Silicone coated fibreglass -newcomer.

3. Also popular materials are coated fluoro-polymer fabrics (PTFE, ETFE, PVDF etc.),

4. PVC coated glass fibres and aramide fabrics.5. ETFE sheeting replaces coated fabrics more often now.




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2 MATERIAL STUDY- PVC coated PES

Figure 13: Façade of Cogeneration Plant, Chinaham, United Kingdom with PVC coated

PES mesh panels

2.1 Introduction

PVC coated polyester is one of the most common architectural fabrics. Its advantages are its

tensile and tear strength and high elasticity. The material is considered inexpensive with a

life-span of approximately 15-20 years. It is suitable for example for long spans and

temporary structures. This high-tenacity membrane material has been used for more than 30

years for roofing and facades as well as for temporary structures and exhibition buildings.

The substrate fabric is polyester. The coating is PVC. The variety of different types available in

many different tensile strengths and colours allows a wide range of application. The high

tensile strength available allow wide span membrane structures to be built. In addition to its

suitability for permanent structures, the high flexibility of the fabric makes it ideal for

retractable systems. This is an economical membrane material that has become very popular

in all types of application. There is a wide range of strengths, weaving and coating types

available, from standard materials up to high quality, highly engineered membrane.





2.2 Chemical Composition

A coated structural fabric usually consists of a woven base cloth stabilized and protected by a

coating on both sides. The base cloth consists of warp threads running the length of the roll

and weft threads running across the width. A mesh fabric is a coated cloth with spacing

between the thread bundles. Sometimes mesh fabric can also refer to a woven shade cloth

where pre-coated threads are woven into cloth.

For the engineering of tension structures, the most common choices are PVC coated Polyester

cloth materials. Vinyl-coated polyester is the most frequently used material for flexible fabric

structures.

It is made up of a polyester scrim, a bonding or adhesive agent, and exterior PVC coatings.

The scrim supports the coating (which is initially applied in liquid form) and provides the

tensile strength, elongation, tear strength, and dimensional stability of the resulting fabric.

Vinyl-coated polyester is manufactured in large panels by heat-sealing an over-lap seam with

either a radio-frequency welder or a hot-air sealer. A proper seam will be able to carry the

load requirements for the structure. The seam area should be stronger than the original

coated fabric when testing for tensile strength.

The adhesive agent acts as a chemical bond between the polyester fibres and the exterior

coating and also prevents wicking, or fibres absorbing water, which could result in freeze-

thaw damage in the fabric.

2.3 Method of Manufacture

Polyester is produced by CP (continuous polymerisation) process using PTA

(purified Terephthalic Acid) and MEG. The old process is called Batch process

using DMT ( Dimethy Terephthalate) and MEG( Mono Ethylene Glycol). Catalysts like

5b3O3 (ANTIMONY TRIOXIDE) are used to start and control the reaction. TiO2

(Titanium di oxide) is added to make the polyester fibre / filament dull.

Firstly, PTA which is a white powder is fed by a screw conveyor into hot MEG to dissolve it.

Then catalysts and TiO2 are added. After that Esterification takes place at high temperature.

Then monomer is formed.




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Figure 14: Manufacturing Process of PVC coated PES





Secondly, Polymerisation is carried out at high temperature (290 to 300 degree centigrade)

and in almost total vacuum. Monomer gets polymerised into the final product, PET (Poly

ethylene Terephthalate).

Thirdly, PET is in the form of thick viscous liquid- them pumped to melt spinning machines –

a metering pump- discharges an accurate quantity of polymer per revolution (to control the

denier of the fibre) through a pack which has sand or stainless steel particles as filter

media and a spinnerette which could be circular or rectangular and will have a specific

number of holes depending on the technology used and the final denier being produced.

Fourthly, Polymer which comes out of each hole of the spinneret is instantly solidified by the

flow of cool dry air. This process is called quenching.

Next, the filaments from each spinneret are collected together to form a small ribbon,

passed over a wheel which rotates in a bath of spin finish: and this ribbon is then mixed with

ribbon coming from other spinning positions, this combined ribbon is a tow and is coiled in

cans. The material is called undrawn TOW and has no textile properties.

At the next machine (the draw machine), undrawn tows from several cans are collected in

the form of a sheet and passed through a trough of hot water to raise the temperature of

polymer to 70 degrees C which is the glass transition temperature of this polymer so that the

polymer can be drawn. The polymer is drawn approximately 4 times and the actual draw or

the pull takes place either in a steam chamber or in a hot water trough.

After the drawing is complete, each filament has the required denier, and has all its submicroscopic chains aligned parallel to the fibre axis, thereby improving the crystallinity of the

fibre structure and imparting certain strength.

Next step is to set the strength by annealing the filaments by passing them under tension

on several steam heated cylinders at temperatures 180 to 220 degrees C.

Next the fibre is quenched in a hot water bath, then passed through a steam chest to again

heat up the tow to 100 degree C so that the crimping process which takes place in the stuffer

box proceeds smoothly and the crimps have a good stability.

Textile spin finish is applied either before crimping or after crimping by a bank of hollow cone

sprays mounted on both sides of the tow.

The last step is to set the crimps and dry the tow fully which is carried out by laying the

tow on a lattice which passes through a hot air chamber at 85 degrees centigrade or so.

Finally, the tow is guided to a cutter and the cut fibres are baled for despatch. The bale is

transported to a ware house where it is "matured" for a minimum of 8/10 days before it is

permitted to be despatched to the spinning mill.

Following the manufacture, the bale is then spun by weaving, or non-woven methods. Thesubstrate fibre is then finished, coated using PVC and then finally laminated




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2.4 Characteristic Properties

2.4.1 Physical

The base fabric's tensile strength is determined by the size (denier) and strength (tenacity) of

the yarns and the number of yarns per linear inch or meter. The larger the yarn and the more

yarns per inch, the greater the finished product's tensile strength.

Polyester fibres are available in 4 tenacity levels viz.:

Low pill fibres- 3.0 to 3.5 gpd [grams per denier (linear mass density of fibres)]

Medium Tenacity - 4.8 to 5.0 gpd

High tenacity 6.0 to 6.4 gpd range and

Super high tenacity 7.0 gpd and above

Currently most fibre producers offer only high tenacity fibres.

Depending on the material characteristics, translucency varies between about 5 and 35 %.

The material is available in a range of different colours and, dependant on the quantity

needed, can have different colours on the two sides. With the addition of an intermediate

layer, light transmission can be reduced to zero.

The PVC coating liquid (vinyl Organisol or Plastisol) contains chemicals to achieve the desired

properties of colour, water and mildew resistance, and flame retarding properties. Fabric can

also be manufactured that contains high levels of light transmission or can be made

completely opaque. After the coating has been applied to the scrim, the fabric is put through

a heating chamber that dries the liquid coating. PVC coatings are available in a range of

colours, although non-standard colours can be pricey. Colours may be subject to minimum

order runs that allow the coating machine to clear out traces of any previous colour

2.4.2 Durability

High quality low—wick treated PVC-Polyester fabrics generally have a structural lifespan in

excess of 20 years. On ordinary materials the plasticizers in the PVC migrate towards the

surface over a period of time making the surface harder to clean. The PVC coating contains

additives that include UV stabilisers, fire retardants, colouring and fungicidal agents.





2.4.3 Performance Properties

The type of yarn selected and the weave design of the base fabric will provide the following

performance properties:

High tensile strength

High tear strength

Uniaxial and biaxial stretch characteristics

Resistance to tear propagation

Puncture resistance

Dimensional stability of base fabric under changes in temperature and humidity

Resistance to chemical attack

Resistance to UV light degradation

Retention of these properties in years of outdoor exposure

The proper compounding of the vinyl coating and the appropriate coating processes will

impart the following characteristics to the architectural fabric:

Protection of the base fabric

Quality adhesion to the base fabric

High-temperature, dead-load performance

Non-wicking

Abrasion resistance

Flame resistance

Colour capability

Non-fading colours

Flexibility in cold weather

Flexibility in years of outdoor exposure

Weldability

Repairability in the field

Chemical resistance

Maintenance of these properties after years of outdoor exposure




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2.5 Testing and Acceptance Criteria

2.5.1 Non-Wicking

The ability of a material to resist moisture from wicking into the polyester yarns is important

for both structural and aesthetic reasons. Continuous filament polyester yarn can pull water

into the space between the filaments by capillary action. If allowed to do so, this moisture

can affect the adhesion properties of the material, causing seam problems or delamination of

the coating compound. Even small amounts of moisture present in the base fabric can be a

source of fungal growth, causing the material to discolour. This creates an aesthetic problem

when viewed from the inside of the building.

Non-wicking properties are achieved by the selection of polyester yarns, the adhesive coat,

and the coating procedure. In recent years, the use of anti-wick polyester yarns has greatly

reduced the problems associated with wicking. The yarns are treated with a finish by the yarn

producer to reduce wicking. In addition, the application of an adhesive coating compound

that fully saturates the base fabric is another effective way to eliminate wicking.

A wicking test is performed by immersing a one-inch strip of PVC-coated polyester fabric

into a dye-water solution. The sample is exposed on one end for a period of 24 hours, then

removed from the solution, and examined for wicking.

2.5.2 Ultraviolet Light and Weathering Resistance

The principle in extending the life of a structure is to maintain the tensile strength of the base

fabric. To do this, it is necessary to protect the base fabric from UV light and other factors.

With PVC-coated polyester fabric, it is the top exterior coating compound that provides

protection from UV light. The PVC compound must be formulated to either reflect UV light

or absorb the light, so that the UV light cannot affect the base fabric or the PVC compound

itself. This is normally accomplished with the proper selection of pigments, the use of UV

absorbers, or a combination of both. The formulating process gets further complicated when

considering the desire for different colour structures or light transmission into the structures.

Ultraviolet light testing of PVC-coated polyester fabrics can be performed by either ASTM G-

26 Xenon-Arc testing or ASTM G-53 Fluorescent UV testing. These accelerated weatheringmachines combine high concentrations of UV light with water spray and high temperatures.





These machines can simulate years of outdoor exposure in a matter of months, and have a

very good correlation to actual field exposure.

2.5.3 Fungus and Mildew Resistance

Architectural fabric structures are frequently used in hot and humid environments, which are

susceptible to fungus and mildew growth. Fungus growth on a PVC-coated polyester fabric

can be not only an aesthetic problem but can lead to structural problems with the material.

Frequently, fungus growth on a structure begins with a collection of dirt on the surface of the

material.

To minimize the potential problems of a fungal attack on the material, manufacturers will

incorporate a fungicide into the adhesive coat and the exterior coating compound. In

addition, the use of a top-coating system to reduce dirt collection on the material will help

reduce fungal attacks. While not a routine test, laboratory testing is done when a material is

developed to assure that the material does not support the growth of fungus or mildew.

2.5.4 Flame Resistance

The best way to describe the flame resistant characteristics of a PVC-coated polyester fabric

is to refer to it as a “limited combustible” material. The material will burn when in the

presence of a flame source, but will be self-extinguishing once the flame is removed. This

property can actually be an advantage when considering what happens during a fire inside

an architectural fabric building.

The fire-resistance properties of PVC-coated polyester fabric are related to the exterior-

coating compound. The PVC compound must be formulated with the proper types and

amounts of flame-retardant additives to impart the self-extinguishing properties that are

required for a safe building material. Since these additives are incorporated into the PVC

compound and are not extractable, the material will remain flame retardant for the life of the

coated fabric.

There are a variety of flame resistance testing procedures that are used for building materials,

but many of these do not apply to a PVC-coated polyester fabric. The primary test that is

used in the United States for coated fabric is the NFPA 701 Vertical Flame Test. In this test, asample of the PVC-coated polyester fabric is held in a vertical position and a flame is




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exposed to the bottom of the material for 12 seconds, then removed. The material must self-

extinguish within 2 seconds after the flame is removed, and cannot have an excessive char

length.

A second common flame test used with PVC coated polyester fabrics is the ASTM E-84

Tunnel Test. In this test, a 7.62m (25-ft.) sample of material is held in a horizontal position

and ignited from one end. The test then rates flame spread and smoke development of the

material as compared to a control material. PVC-coated materials have relatively low flame-

spread ratings due to their self-extinguishing properties, and the smoke-development

ratings are relatively low due to the materials light-weight nature.

2.5.5 Performance Properties for Architectural Fabrics

Architectural Fabrics are made up of four components: base fabric (greige goods), adhesive or

primer coat, exterior coatings (plasticized PVC), top coating systems.

Each of these components contributes to the different performance properties, with some of

the components having an effect on several properties. Our review of the different critical

performance properties of the architectural fabrics will continue to refer to the four different

components that make up the coated fabric.

2 5 5 1 Tensile Strength

The first and most important performance property that needs to be considered is the tensile

strength of the material. Because the tensile strength of the architectural fabric depends on

the base fabric and the polyester yarns, the useful life of a structure is then dependent on

keeping the yarns from deteriorating. If the yarns start to break down, then the structural

integrity of the entire building system is in question. Protecting the yarns from damage is one

of the main functions of the exterior coating compounds.

Testing the tensile strength of a material can be done by either the “Cut Strip Test Method” or

the “Grab Test Method” as outlined in ASTM D-751. Samples of a material are tested in both

the warp and fill directions and three to five samples are taken across the width of the

material.





2 5 5 2 Uniaxial And Biaxial Elongation

As a load is applied to PVC-coated polyester fabric, the material will stretch and ultimately

break at its breaking strength. This property is similar to conventional building materials such

as steel or glass. However, the length of elongation will be significantly greater for PVC coated

materials. Typical elongation at break values for PVC coated materials will range from 20

percent to 50 percent.

Testing the uniaxial elongation properties of a material can be done per ASTM D-751 Cut

Strip Test Method, or testing under a static load can be done by ASTM D-4851. Biaxial testing

is done by various test methods as developed by the material manufacturers or structure

fabricators.

2 5 5 3 Dimensional Stability

The dimensional stability properties of any building material are important. If a material

changes in size due to change in temperature or humidity, these changes need to be

considered when engineering the building. This is very important when designing a tension

membrane structure since patterns are cut to a given size to allow for a given pre-tension on

the building.

The dimensional stability of an architectural fabric is directly related to the base fabric and the

polyester yarns. Early architectural fabrics were made from nylon fibres, but these materials

were not dimensionally stable and were quickly replaced with polyester yarns. The

dimensional stability of a base fabric made from polyester yarns is so good that this

performance property is generally not specified or tested, other than to require a polyester

base fabric.

2 5 5 4 Tear Strength

The tear strength of an architectural fabric is an important performance property. The ability

of a material to resist a tear or tear propagation may be critical to the structural integrity of

the building. This can be particularly true in an air-supported structure where the loss of air

pressure inside the building can lead to a catastrophic failure.




28

Tear strength properties are related to a combination of factors involving the base fabric,

weave construction, and adhesion values. To obtain the highest possible tear properties, the

yarns need to be able to slide within the PVC coated fabric.

Testing for tear strength of a material can be done by either ASTM D-751 Tongue Tear

Method or ASTM D-4533 Trapezoid Tear Method. In many cases both methods are used to

better characterize the tear properties. In addition, tear testing is performed on material that

has been aged, either naturally or by accelerated weathering, to determine if there is a loss in

tear strength over time.

2 5 5 5 Coating Adhesion

Coating adhesion is the ability of the exterior coating compound to be adhered to the

polyester base fabric. Having the strongest base fabric and the best-formulated PVC

compound is of no value if the two cannot be properly bonded together. Good coating

adhesion is required to allow the material to be handled and welded. It is also important in

preventing the exterior coating compound from delaminating when the material is exposed

to the environment.

Developing good coating adhesion is the primary function of the adhesive coat. The adhesive

coating compound is formulated as a PVC plastisol with an adhesion promoter added to the

compound. When this compound is applied to the base fabric, a chemical bond forms

between the polyester yarns and the adhesive coat. This process is carefully monitored to

develop the right level of adhesion. Too little adhesion will cause problems with seam

strength or coating delamination, and too-high adhesion will adversely affect tear strength.

Coating adhesion is tested per ASTM D-751 Peel Adhesion test. Samples are prepared byeither welding or gluing two pieces of material together, then peeling the samples apart in a

constant-rate-of-separation testing machine. Results are reported as pounds-force per inch.

2 5 5 6 Weldability and Seam Strength

One of the most advantageous performance properties of PVC coated polyester fabrics is its

ability to be efficiently welded into large panels that can be incorporated into a structure.

Unlike conventional building materials such as wood, steel or bricks that require assembly at





the job site, PVC coated polyester fabrics can be pre-fabricated into large panels and then

brought to the job site for final assembly.

The PVC-coated polyester fabric uses a plasticized PVC exterior coating compound on both

the top and bottom of the material. This PVC compound is a thermoplastic material, meaning

that it can be heat bonded to itself. The heat bonding process can be accomplished with a

radio frequency welder or a hot air or hot wedge welder. Seams can be produced at speeds of

up to 6.1m (20 ft.) per minute.

Since the base fabric carries the loads on a building, the seams must be able to transfer these

loads from one piece of coated fabric to another. This creates a shear force on the seam. As a

result, it is important that the tensile performance properties of the finished seam be equal to

the strength of the fabric itself to ensure the integrity of the entire structure. Each seam must

be able to handle all of the load requirements on the building under the full range of

environmental conditions.

The strength of the seam is a function of the adhesive coat, exterior coat, and the welding

process. The adhesive coat must form a bond between the polyester base fabric and the

exterior coating compound such that it can handle the shear forces that are created under

loads. The exterior coating compound must be formulated and applied properly such that it

can be welded to itself and handle the shear forces. The welding process must be designed to

give the proper amount of overlap and the necessary amount of heat and time to form a

good weld. Typically, high tensile strength materials require a greater overlap at the seam to

carry the shear forces.

Seam strength testing involves a series of tests that include weld adhesion, seam shearstrength, and dead (static) load testing. The weld adhesion is done with the same ASTM D-

751Peel Adhesion Test previously described. This is a quick check to determine that the PVC

coating compound has been heat bonded to itself.

The seam shear test is a modification of ASTM D-751 Cut Strip Tensile test. In this test, a

2.54cm (1-in.) sample is cut perpendicular to the seam and a tensile test is performed across

the seam. The coated fabric should always break outside the seam area, with results




30

equivalent to the tensile strength of the PVC coated fabric, assuring that the fabricated seam

is at least as strong as the fabric itself.

While no current ASTM procedure exists for a dead load or static load test on a seam, this is

the most important test that can be performed. The test involves applying a load across the

seam on a 2.54cm (1-in.) sample for a period of four hours. The test is performed at both

room temperature and at high temperature, usually 71C (160 F). This test most closely

simulates actual field conditions in that there is a constant load on the seam when the

building is in service.

2.5.6 Summary

High performance properties in an architectural fabric are achieved by the proper selection

of the base fibre, the selected fabric weave, the appropriate formulated coating compounds

and the coating processes utilized to produce the fabric.

2.6 Applications

Figure 15: Façade Fabric of Deichmann Flagship Store, Germany

PVC Coated Polyester Meshes (open matrix): uses include shade panels, sunscreens,

facade systems and printed screens

PVC Coated Polyester Fabric (opaque fabric): uses include canopies/roofs, walls,

facades and printed screens





2.7 Advantages

The fabric with light transmission of approximately 8% is sufficient to provide a good level of

diffuse daylight. Whereas a PVC coated PES with openness factor of 28% will have 100

percent light transmission. The availability of PVC coated PES in both opaque and open frame

allows the choice in range of day light transmissions, diffused or full.

The flexibility of the material reduces the risk of damage due to folding and unfolding;

although care must still be taken not to damage the fabric during transportation or

installation. The low shear stiffness of PVC-polyester fabric enables the double curvature of

conic forms to be achieved with little risk of wrinkling.

Whereas in open matrix PVC coated PES, their extremely low shear stiffness enables them to

be stretched around substructure framing.

The PVC coating provides excellent water-resistance over the life of the fabric, which is

anticipated to be well in excess of 15 years. The performance of PVC-coated polyester fabric

when exposed to fire is well known: the material will retreat from a flame, allowing the

canopy to be self-venting. The material is Class A in terms of flame spread, and does not

produce flaming droplets.

When compared to other façade fabrics:

1. most cost effective

2. temporary and permanent structures

3. soft, pliable and easy to handle

4. less expensive than PTFE and ETFE5. variety of colors, weights, topcoats and textures

6. Fire resistant (Class C, NFPA 701)

7. life span of 20+ years

2.8 Limitations

Disadvantages of PVC-coated polyester fabric, compared to PTFE-coated glass fibre fabrics,

include relatively high levels of creep which can necessitate re-tensioning, lower resistance todirt build-up and a shorter lifespan.




32

Typical serviceability considerations include the potential for temporary de-stressing of the

membrane or inversion of the fabric surface.

2.9 Installation systems

Figure 16: Typical substructure for textile architecture using PVC coated PES

2.10 Cost Analysis

Fabric type Typical use Cost comparison

PTFE-coated fiberglass Largo scale permanent

structures Class A

ASTM E-108

$75- 100 per sq. ft.

Silicone-coated fiberglass Large scale permanent

structures Class AASTM E-108

$75- 100 per sq. ft.

Vinyl-coated polyester Temporary and permanent

structures

$50 -76 per sq. ft.

Woven PTFE (More pliable than standard

PTFE) Retractable roofs,

structures

$85- 125 per sq. ft.





ETFE High transparency (97%) Atria.

Indoor parks, biospheres,

skylight applications

$100— 125 per sq. ft.

HDPE (High Density

PolyethyIene)

Shade structures/systems $25-50 per sq. ft.

Laminates Tents, awnings & canopies $36-50 per sq. ft.

2.11 Maintainability Aspects

2.11.1 Material pollution:

The addition of anti-adhesive PVDF (Polyvinyl di-fluoride) coatings has meant that material

staining has been considerably reduced over the past 10 years, compared to the standard

materials (still available) with only an acrylic coating. One major advantage of the PVDF

coating is the considerable increase in cleaning intervals.

2.11.2 Cleaning:

Depending on the specific characteristics of the coating, the material is more or less dirt

resistant and the cleaning intervals vary according to the appearance required.

2.11.3 Maintenance:

The material is maintenance-free. However, inspections are still recommended in order to

find defects (for example damage caused by mechanical impacts of sharp objects) and to

identify and repair such damages as early as possible. It is also recommended that the

perimeter clamping system and the primary structure be regularly inspected. The inspections

should normally be carried out annually. However, the specific intervals need to be assessed

on a project-by-project basis.

2.11.4 Environmental compatibility:

The recycling of PVC based products is well established, and efficient. The PVC can be

separated from the polyester base cloth and re-used for many useful products. The clamp

details (mainly aluminium clamp plates) can be easily separated from the membrane and can

be 100% recycled.

2.12 Commercial Catalogues/ Brochures




34

FERRARI – Stamisol F 381 HighTEX – PVC coated PES

2.13 Case Study

2.13.1 COPENHAGEN CONCERT CENTRE [DR KONCERTHUSET (DRK)]

2 13 1 1 Project Data

Location : Copenhagen, Denmark

Architect : Jean Nouvel

Opened on : January 2009

Area : 26,000 sq. m

Height : 45 metres

Client : Denmark Radio

Architect : Ateliers Jean Nouvel

Exterior (steel) framing: Bladt Industries A/S

Fabric assemblies : Seijlmager A/S

Assembly installation : August Olsen Eftf. A/S; Bladt Industries A/S

Fabric : Stamisol® FT381, “Ice blue” from Serge Ferrari

(Stamisol Colour absent)

Material : PVC coated polyester open fabric





Figure 17: Section showing the layers of the Stamisol system

2 13 1 2 Description

It encloses a series of volumes that include the main 1,800-seat concert hall and three

smaller, more flexible performance spaces. It is the home of the Danish National Symphony

Orchestra.

From the exterior, the cube-like DR Koncerthuset (DRK) is a compelling structure that

changes under the light of day and night.

Most notable is its cobalt blue skin, A STAMISOL® FT 381 FABRIC BY SERGE FERRARI.

Named Ice Blue, the fabric has been stretched over a structure of steel beams, tension cables

and a glass facade and functions as a translucent veil revealing the armature and spaces

within.




36

Figure 18: Copenhagen Concert Centre at night displaying the cobalt blue PVC coated

PES mesh facade

A quality of mystery infuses the building, which has been lauded for its intimate performance

spaces. By day, the outlines of the interior performance hall and studios, and people moving

about on different levels can be seen through the blue skin. By night, the deep blue textile

façade serves as a giant screen for projected video montages. “The façades are diaphanous

filters permitting views of the city, the canal and neighbouring architecture,” states Nouvel.

“At night these façades become screens for projecting images.”

Nouvel’s design strategy was to create a dialogue with the unremarkable site and its bold

design and the Ferrari fabric’s unique qualities allowed it to do so. It evokes a sense of

restrained drama as the translucent blue textile merges the building’s interior and exterior

worlds. By day, passers-by can visually access the interior spaces, albeit opaquely, and by

night local residents and visitors become an audience for the projected video montages.

The strong, durable blue skin imparts the DRK with a sense of lightness and luminosity. To

create the skin, 16,000 m2 of the fabric were stretched over panels measuring 5m by 15m to

15m by 15m. The membrane is fully recyclable and comes with a warranty of 10 years.





2.13.2 BMW MOTORSHOW IAA FRANKFURT


Location : Frankfurt, Germany

Architect : Jean Nouvel

Opened on : 1995

Area of fabric : 5,200 m²

Height : 45 metres

Client : BMW AG, Munich, Germany

Architect : Sobek, Rieger & Partners,

Fabric : Hightex®

Material : PVC-coated polyester opaque fabric

2 13 2 2 Description

BMW chose a tensile tent structure to solve its exhibit difficulties. The construction at the

Frankfurt exhibition complex in Germany drove auto market BMW out of its usual hall for the

1995 IAA Cars. An open courtyard area was converted into a traffic-stopping exhibition space

through the use of a tensile tent structure. The membrane structure, which measured 97 by

57 meters, offered 4,000 m2 of display space. The textile design highlights the idea of

mobility, for the pavilion could be reassembled anywhere else at any time.




38

Figure 19: BMW motor show canopy made of PVC coated PES opaque structure fabric

as roofing

At one end, it is cut out in semi-circular form around an existing forecourt. All components

and details were standardised to facilitate quick assembly and disassembly of this temporary

structure. One condition of the brief was that the existing surface of the site was not to be

affected by subsequent construction work. The tops of foundations were, therefore, set

below the level of the paving. With the removal of a minimum number of paving stones, the

feet of the steel masts can be bolted to or removed from the foundations. About 5,200m² of

PVC-coated polyester fabrics were heat-sealed together to form the tent roof. Only 1.1 mm

thick, it is made of high-strength plastic fibres and has a self-cleaning surface. The

membrane roof is supported by five raking steel lattice masts up to 22 m high and is held in

position by peripheral ropes fixed in membrane sleeves.

The ropes convey the loads from the roof to fully flexible node points, where they are in turn

transmitted to tubular columns and guy ropes. The flexible connections allow the roof skin to

change form, particularly during the assembly stage.

The facade consists of a pneumatic cushion and a system of open able glass louver, which, inconjunction with the eye-like glass-louvered openings at the tips of the masts, provide a





natural means of ventilation. A tubular air cushion and intermediate panels close the gap

between the facade and the membrane roof.

2.14 Performance Specification

2.14.1 PVC (Poly Vinyl-Chloride) COATED PES (POLYESTER)

2 14 1 1 Material

Tensile Strength - “Cut Strip Test Method” or the “Grab Test Method” as outlined in ASTM D-

751.

Uniaxial Elongation Test - ASTM D-751 Cut Strip Test Method, or testing under a static load

can be done by ASTM D-4851.

Surface Burning Characteristics of Building Material – ASTM E 84-77a

Tear Strength Test- ASTM D-751 Tongue Tear Method or ASTM D-4533 Trapezoid Tear

Method

Coating Adhesion Test- ASTM D-751 Peel Adhesion test

Seam Shear Strength Test - modification of ASTM D-751 Cut Strip Tensile test

PVC coated polyester shall be water and chemical resistant and shall have very high transit

strength to weight ratio and high modulus of elasticity, good textile processing The laminate

shall have low coefficient of thermal expansion and a high thermal conductivity and high

dielectric constants. The PVC coating shall be dimensionally stable, shall have moisture and

corrosion resistance.

2 14 1 2 Dimension Tolerance

Tolerance of + 0.10 mm in overall size of PVC coated PES

2 14 1 3 Temperature Tolerance

Tolerance of -30 to +70 degrees permissible.

2 14 1 4 Openness of fabric matrix

0 % to 30 % range permissible




40

2 14 1 5 Finish

Coating over polyester with PVC.

(1) A very thin layer of acrylic solution which is a formulation of acrylic resin and possibly other

resins such as PVC or polyurethane, dissolved in solvents is applied to the surface of the

material, with the resulting thickness of 508 to 1016μm (0.5 to 1 mm) or

(2) A PVDF (poly-vinylidene fluoride) resin solution top-finish which blend PVDF resin and

acrylic resin is applied to the surface of the PVC-coated material in the same manner as

an acrylic topcoat, but it is usually applied at a thickness of 762 to 1524μm (0.7 to 1.5 mm)

or

(3) Tedlar® PVF film finish to the PVC coated material. The Tedlar PVF film is chemically

similar to Teflon® fluoro-polymer material, and therefore is a very chemically inert and

durable material. Tedlar PVF film is available in pigmented films ranging in thickness from

0.0254 to 0.0381mm

2 14 1 6 Tests

Frequency of tests as per direction of Engineer-in-Charge & tests to be conducted as per para

2.14.1.1

2 14 1 7 Measurement and Rate

The width and length to be measured in centimetres and area to be calculated as square metre

correct up to two places of decimal. The rate includes cost of all the materials, labour scaffolding,

and fittings & fixing up to all heights etc. involved in operations described above, but excludes the

cost of paint.





3 MATERIAL STUDY- ETFE

Figure 20: ETFE tension layer on a facade

3.1 Introduction

ETFE is a relatively new material successfully being implemented for use in cladding. ETFE has

95% light transmission of all frequencies but does not offer the clear visibility of glass. The

first projects utilizing this extremely lightweight, almost completely transparent material were

botanical gardens, zoo buildings, swimming pools and exhibitions. ETFE is finding its place in

more traditional buildings as roofing for courtyards, atria, shopping malls, and stores. The

attraction to ETFE is the considerable savings on material required to support the cladding.

This savings translates into a more efficient building structure and a low maintenance

cladding system. An ETFE cladding system offers a flexible alternative to traditional glass

cladding which is sensitive to slight movements of the building's primary structure. ETFE,

whether used as a single-layer membrane stretched between frameworks or as pneumatically

pre-stressed cushions, has the ability to adapt to deformations of a structure.

ETFE foil roofs can be supplied as a single layer membrane supported by a cable net system

or commonly as a series of pneumatic cushions made up of between two and five layers of a




42

modified copolymer called Ethylene Tetra Flouro Ethylene (ETFE). The ETFE copolymer is

extruded into thin films (or foils) which are used to form either a single layer membrane or

multi-layer cushions supported in an aluminium perimeter extrusion which, in turn, is

supported by the main building frame.

In the case of ETFE cushions, they are kept continually pressurised by a small inflation unit

which maintains the pressure at approx. 220 Pa and gives the foil a structural stability and the

roof some insulation properties

3.2 Chemical Composition

ETFE (ethylene tetra fluoro ethylene) is a relatively new material in the building industry

gaining popularity in cladding use for modem structures.

First developed by Dr. Plunkett in 1938 at Dupont, it is one of the seven fluoro polymers

generated from the invention of PTFE (poly tetra fluoro ethylene) or the plastic more

commonly known as Teflon®. Each of the fluoropolymer PTFE relatives have unique material

properties, ETFE is has the distinctive capability of being extruded. ETFE is a thermo-plastic

and can be heated and extruded through a die producing a thin film.

Fluoro polymers are a class of plastics that contain both carbon and fluorine. ETFE is a

copolymer of ethylene and tetra fluoro ethylene and is known as a "tough polymer." The

ETFE film manufactured by Dupont is Tefzel®. Many other plastics manufacturers produce

ETFE under different names such as 3M's Dyneon® and Nowofol's NOWOFLON®.

3.3 Method of Manufacture

Unlike many synthetic plastics, ETFE is not a derivative of a petrochemical.

ETFE starts as a combination of fluorspar (CaF2), hydrogen sulfate (HSO4), and

trichloromethane (CHCl3) called chlorodifluoromethane (CHF2CL).

Chlorodi-fluoro-methane is a raw material classified as a class II substance under the

Montreal Treaty on ozone depleting substances; it does not contribute to global warming.

No Class I materials or ozone depleting substances are used in the manufacturing process of

ETFE. The chlorodi-fluoro-methane is then manufactured into tetra fluoro ethylene (TFE) in

the process describedThe by-products formed are calcium sulphate (CaSO4), hydrogen





fluoride (HF) and hydrochloric acid (HCl). The calcium sulfate and hydrogen fluoride are

reused to produce more fluorspar which can be used again as an input into the

manufacturing process.

3.4 Manufacturing of the ETFE granulate:

Figure 21: Flow chart of the ETFE granulate production




44

3.4.1 Raw materials and monomers

Unlike many synthetic plastics, ETFE is not a derivative of a petrochemical. ETFE starts as a

combination of fluorspar (CaF2), hydrogen sulfate (HSO4), and trichloromethane (CHCl3)

called chlorodifluoromethane (CHF2CL). Chlorodifluoromethane is a raw material classified as

a class II substance under the Montreal Treaty on ozone depleting substances; it does not

contribute to global warming. No Class I materials or ozone depleting substances are used in

the manufacturing process of ETFE. The chlorodifluoromethane is then manufactured into

tetra fluoro ethylene (TFE) in the process described below. The by-products formed are

calcium sulphate (CaSO4), hydrogen fluoride (HF) and hydrochloric acid (HCl). The calcium

sulphate and hydrogen fluoride are reused to produce more fluorspar which can be used

again as an input into the manufacturing process.

3.4.2 Polymerization

The process takes place at 125 degrees Celsius. The TFE is then polymerized with ethylene to

produce ETFE (25% ethylene and 75% TFE). Polymerization is a chemical reaction that

constructs a long molecular chain using small basic molecules each with a double bond. The

entire ETFE manufacturing process is water based and does not include use of any solvents

or additives. The result of the process is an ETFE powder.

3.4.3 Granulation

The next step is granulation: heating up the powder to 265-285 degrees and forming ETFE

granules. ETFE producers sell the material in granules which can be formed into many

different products including a sheet, rod, and film. The ETFE product used in the building

industry for cladding is ETFE film, also referred to as ETFE foil.

3.4.4 Refining

The degassed thermoplastic dispersion is precipitated and the resulting powder is dried.

Since the powder is difficult to process due to its low pourability, it is melt granulated before

dispatch. After this, quality control determines whether the product meets the customer

requirements. It is dispatched only after a positive result.





Figure22: ETFE granulate unpacked and packed

3.4.5 Extruding

The dehumidified granules are placed in an extruder then melted by the friction created by

metal screw as well as external heating: the process occurs at 250 degrees Celsius. The ETFE

is dehumidified again under a vacuum and filtered through a sieve. Lastly, the material is

pushed out through a nozzle. The ETFE film is extruded through a die at a thickness of 30-

200 microns.

Figure 23: ET-foils production line (1: extruder, 2: shaping, 3: casting, 4: winder, 5:

automation)

The typical width of extruded sheet of ETFE foil is 1.2-1.55 m. ETFE film can be manufactured

in three product types: transparent film, translucent film, and film printed with a graphical

design. Additionally, colored foil can be produced by adding pigments to the material during

the manufacturing process. The fabrication of ETFE is still quite specialized, most of the

manufacturers are found in Germany. ETFE manufacturers often provide the entire cladding




46

system and oversee the film production, pillow fabrication, and erection of the pillows onto

the support structure.

3.4.6 Finishing the foil cushions:

In accordance with the construction requirements, the sheets delivered with a width of 1550

mm and – depending on the foil thickness – approximately 200 m linear length, are cut to

length. The individual units for the cushions are tailored on a cutting plotter. At the same

time, the relevant positions of all further components to be assembled, for example valves,

are drawn in. Then, the individual sheets are welded into larger surfaces (surface welding)

and the valves are installed. Two or more layers of the welded foil units are laid exactly one

on top of the other and are fixed by means of a manual welding tools. Subsequently, in theborder area of the cushions, the keder are welded and the cushions are thereby closed (edge

welding). The tailoring is thus completed and the large cushion can be packed for dispatch:

the large cushion is folded into a sheet with approximately 30 cm width and 2.5 m length,

and wrapped in a polyethylene protective film. Together with three to six other cushions, the

foil package is prepared for dispatch in a wooden box. The remaining components for the

overall project (aluminium profiles, keder, seal and screws) are sorted and packed for

dispatch.

3.4.7 Types of ETFE structure





3.5 Characteristic Properties

ETFE polymer films are replacing textile fabrics more and more often. They are not textiles

but plastic foils and so commonly used that the material deserves to be studied along the

coated fabrics. ETFE has high mechanical properties and a high fire resistance factor. ETFE can

be coloured and printed onto. The lifespan of ETFE is up to 25-35 years and it is an

inexpensive material.

It is often chosen for pneumatic structures, greenhouses, swimming pool buildings etc.. Its

maximum spans are smaller than those of PVC coated polyester and it is not used in large

span load bearing structures.

3.5.1 Material Strength

Based on 250 micron ETFE Foil

ETFE film is an extremely flexible plastic membrane that can support high short term loading.

ETFE foil experiences large deflections under extreme loading conditions. The tear




48

propagation strength of ETFE film is 180 N/mm. The breaking strength of ETFE is 50 N/mm2.

However, the fracture strength of ETFE is less valuable than the yield strength. ETFE cushions

are not designed for failure in the plastic rang because of the large deformations of up to

800% at fracture strength. The yield point for ETFE film is 21 N/mm2 or 23 N/mm2.[17] Theyield strength is a function of temperature, loading rate, load history, and stress state. ETFE is

very ductile material and demonstrates good failure behaviour: the large deformations

before breaking point visually indicate yielding and future failure.

3.5.2 Weight

ETFE Foil cushions are extremely light weight weighing only 2 - 3.5 kg/m².

3.5.3 Cushion Size

ETFE foil cushions can be manufactured to any size and to fit any shape. Size is limited by the

wind and snow loading allowed for within the design and by the orientation of the cushions

i.e. whether they are installed horizontally or vertically.

As a general design guideline, rectangular cushions can span up to 3.5m in one direction and

as long as required in the other direction. For triangular cushions, the size can be greater

than this. If design dictates that larger cushions are required, these can be created by

reinforcing the internal and external layers of the cushion by cable restraints.

3.5.4 Insulation

While a single ply ETFE membrane has an approximate U value of 5.6 w/m² K, a standard

three layer cushion can achieve a U value of 1.96 w/m² K – a better insulation value than

triple glazing when used horizontally (glazing manufacturers figures are for vertical glazing

which considerably enhances the figures). The insulative qualities of ETFE cushions can also

be improved by the addition of more layers of foil (up to five in total) or by treating the foil

with specialist coatings to enhance the thermal properties.

3.5.5 Transparency and Translucency

ETFE Foil is naturally a very transparent material and transmits light across the entire visible

light region (380- 780nm). A single layer of medium weight ETFE has an approximate 85%

light transmission, although multiple layers will lead to a small reduction. Transmission across

the ultraviolet range (320- 380nm) is also very good (approx 83-88%) and therefore allows





plants and vegetation underneath to thrive. It is also important to note that the film absorbs

a large proportion of infra-red light transmitted, a quality which can be exploited to improve

buildings energy consumption

Translucency of the ETFE membrane is about 95 % within the range of 400 - 600 Nm, with

scattered light at a proportion of 12 % and direct light at a proportion of 88 %. For a three-

layered module (upper layer 200μm, middle layer 100μm, inner layer 200μm), the degree of

light transmission for vertical incidence is = 0.7. This range represents the translucency

characteristics important for life (of humans, animals and plants).

Compared to open air environment the dangerous UV-B and UV-C radiation (which causes

burning and is carcinogenic) is considerably reduced by filtration.

U-values are as follows:

(1) for one-layered membranes ≈ 5.1 W/m²K

(2) for two-layered membranes ≈ 3.5 W/m²K

(3) for three-layered membranes ≈ 2.0 W/m²K

(4) for four-layered membranes ≈ 1.5 W/m²K

Depending on test procedures these values may vary considerably.

3.5.6 Solar Control

As described above, the base material of an ETFE installation is very transparent, however, the

ETFE Foil can be treated in a number of different ways to manipulate its light transmission

properties. These include:

1. Printing: Also known as fritting, the surface of the foil is covered with a variety of

patterns to reduce solar gain while retaining translucency. By varying the percentage

of coverage and density of the ink, the energy transmission can be altered.

Alternatively, the foil can be over printed with a number of treatments to affect

transmission. A range of over 20 standard fritting patterns is available in the market

to achieve this variety of light transmissions, however, bespoke patterns are available

at an extra cost.




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2. Tinting: A selection of coloured foils are also available, although less readily than the

standard clear foil. Coloured foils can be used alongside clear foil to incorporate

branding and large scale imagery. White ETFE foil can be used to reduce glare but

maintain some light transmission and insulation properties.3. Surface treatments: Surface treatments undertaken during the manufacturing process

can vary the properties of the fabric and allow us to manipulate light transmission.

These treatments render the foil matt in appearance and therefore provide an excellent

projection surface for light shows and images.

4. Radiation: The foil be conditioned with a range of radiation treatments which can

reduce the levels of IR and UV rays transmitting through the membrane skin. Adding

additional layers of ETFE foil to a cushion also allows light transmission and solar gainto be controlled. Multi-layer cushions can be constructed to incorporate movable

layers and intelligent (offset) printing. By alternatively pressurising individual

chambers within the cushion, maximum shading or reduced shading as and when

required is achievable. Essentially this means that it is possible to create a building

skin which is reactive to the environment through changes in climate.

3.5.7 G Value

The G value of an installation reflects the fraction of solar energy transmittance through

glazing. This is usually expressed as a percentage or a value between 0 & 1; the higher the

number, the more energy is being transmitted through the glazing and the more the building

will heat up. The G value of an ETFE roof can be reduced to as little as 0.48 for a 2 layer

system with a fritted top surface and to around 0.35 by using a 3 layer system. For

comparison, standard glass is approx 0.88 whereas some specially treated glass may be as

low as 0.46.

It must be noted that the G value of any ETFE installation is very dependent on aspect and

location and should be calculated on a project by project basis taking these elements into

account.

3.5.8 Life Expectancy

ETFE Foil has an excellent life expectancy as it is unaffected by UV light, atmospheric

pollution and other forms of environmental weathering. While no ETFE structures have been





in place for long enough to gain a true understanding of the life cycle of the foil, the material

has been extensively researched and tested in a laboratory environment and out in the field.

These tests have concluded that no degradation or loss of strength has occurred and there is

no sign that the material will become brittle or discolour over time. As a result, it isanticipated that the material has a life expectancy in excess of 50 years.

3.5.9 Fire

ETFE Foil as a material has low flammability (270C) and is considered self-extinguishing. In

the event of a fire, hot smoke will cause the foil to soften, fail and then shrink away from the

fire source to create natural ventilation. The quantity of material used in the roof is not

important in this situation – the foil will not create molten drips or any fumes. ETFE foil hasbeen comprehensively tested. This is a selection of the fire results:

DIN 4102 Class B1

EN 13501-1 Class B-s1,d0

NFP 92-505 M2

NFPA 701 Pass

In some cases, it is not possible to guarantee that smoke will reach the ETFE at a temperature

which will cause the cushions to fail, therefore, it is worth considering the installation of

automatic actuators in order to ventilate the space of smoke. It has a working temperature

range of 89 K to 423 K (-185 °C to 150 °C or -300 °F to 300 °F)

3.5.10 Acoustics

ETFE foil cushions are a relatively transparent form of roofing which means that there are

minimal acoustic benefits in its natural state. Rain noise can be suppressed using a rain

attenuation layer added to the top surface of the cushions. This acts as a dampener, stopping

the sound reverberating around the space below. In general, the installation of a rain

attenuation layer is only necessary in exceptional circumstances. This can be retro-fitted to

the ETFE foil cushion system and therefore is recommended that rain noise is assessed prior

to making a decision to install.




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3.5.11 Environmental

The raw material associated with ETFE is a class II substance admitted under the Montréal

treaty. Unlike its class I counterparts it causes minimal damage to the ozone layer, as is the

case for all materials used in the manufacturing process. The production of ETFE involves the

transformation of the monomer TFE in to the polymer ETFE using polymerisation; no solvents

are used in this water based procedure. The material is then extruded to varying thicknesses

depending on application; a process which uses minimal energy. Fabrication of the foil

involves welding large sheets of the ETFE; this is relatively quick and again a low energy

consumer.

ETFE can be recycled with ease, but due to its properties (does not degrade under UV light,

sunlight, weather, pollution) it has a very long life which is estimated between 50-100 years,

making the need for recycling small. Excess material from the cushion manufacturing process

can be recycled effectively by all ETFE suppliers. The aluminium frames do require a high

level of energy for production, but they also have a long life and are readily recycled when

they reach their end of life.

ETFE cushion systems offer both good insulation and translucency, due to the fact they trap alayer of air and can be adapted using dot matrix coatings to change the solar transmission.

The cleaning and maintenance of ETFE is also small, the majority of the time water will wash

off any dirt, and this is due to the smoothness and anti-adhesive properties of the material. If

cleaning is needed then only light PH neutral detergents are used making the environmental

impact minimal.

3.6 Applications

ETFE foil systems are mainly utilized for transparent roofs and facades in architecturally

challenging buildings. The transmittance of ultra-violet light also makes them ideal for

private and public swimming pools as well as in zoological and botanical gardens. The light

transmission can be intelligently controlled by printing patterns onto the foils or by adding

pigments to colour the foils. The combination of several layers of foil, staggered printing and

pneumatic controls allow shading to be adjusted in a selective manner.





3.7 Advantages

Compared to glass, ETFE:

1. Transmits more light2. Insulates better

3. Costs 24% to 70% less to install

4. Is only 1/100 the weight of glass. The system’s low weight (particularly advantageous

for refurbishment projects)

ETFE is often called a miracle construction material because:

1. ETFE is strong enough to bear 400 times its own weight

2. ETFE can be stretched to three times its length without loss of elasticity- Flexible 3D

shaping

3. ETFE can be repaired by welding patches over tears

4. ETFE has a non-stick surface that resists dirt

5. ETFE is expected to last as long as 50 years

6. Can be used in single and multi-layers which can produce desired spatial acoustics

with short reverberation times

7. ETFE cushions will not break or fall from the extrusion frames if damaged

8. Wider spans result in a larger transparent/translucent spaces

9. Deformation is not an issue and therefore ideally suited for cable structures

10. Large range of colouring and graphic printing available

11. Lower cleaning costs

12. Light weight supporting structure options possible

3.8 Limitations ETFE does have disadvantages, however.

1. ETFE has poor acoustic insulation transmits more sound than glass, and can be too

noisy for some places

2. ETFE is usually applied in several layers that must be inflated and require steady air

pressure

3. It can be punctured by excessive bird pecking and sharp edges




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4. Working with ETFE is too complex for small residential projects

5. Maintenance of the inflation units is challenging.

3.9 Handling, Installation and Storage

3.9.1 Fragility

ETFE foil cushion systems are certified as class C non fragile roof assembly in accordance with

ACR (M) 001:200 – test for fragility of roofing assemblies. Class C is the lowest class of non-

fragile assembly and, particularly if engineered to pass the test criteria, may be close to the

boundary between fragile and non-fragile. Its classification and use therefore requires the

following to be taken into account:

a) Normal industry-recommended best practice is that Class 'C' assemblies should never

intentionally be walked upon and appropriate temporary access equipment, such as crawling

boards, etc., should always be used. Note: Accidental damage to such assemblies might

render the classification void.

b) A Class C assembly must be treated like any other safety critical item, e.g., a safety net.

Therefore, any adverse occurrence that could affect its fitness for purpose should trigger an

inspection. If an assembly has been subjected to an impact load (such as a trip or stumble), it

can be treated as a fragile area and identified and protected accordingly, until it has been

replaced and the adjoining fitted panels inspected by a competent person and replaced if

necessary. Procedures to ensure this happens must be in place.

c) The workforce must be aware of these limitations, as required by Regulations 3 and 8 of

the Managing Health and Safety at Work Regulations [MHSWR].

d) Any person falling on a class C assembly may make it fragile for subsequent loads. While

persons may be capable of self-recovery from a fall or stumble, where they are unable to, the

additional weight of a rescuer may cause the assembly to fail. And, because all non-fragility

classifications depend on the fixings of assemblies, any adjoining assemblies may also have

become fragile. In such situations the incident panel and all adjoining panels must be treated

as fragile. This is a foreseeable risk of selecting Class C assemblies. Therefore, where class C

assemblies are being used, rescue plans must be developed in advance of work starting.





Again, in accordance with Reg. 5 and 8 of the MHSWR, the workforce needs to be aware of

the Rescue Procedures.

3.9.2 Inflation Units

ETFE cushion systems are continually inflated by air handling units from which air pipes run

to each individual cushion. As the cushions only need to maintain pressure and not generate

air flow, the energy consumption used by these units is minimal. An entire roof is generally

powered by a single air handling unit which contains 2 fans powered by electric motors. For

large installations there is sometimes a need for additional air handling units to be installed.

The fans run alternately to maintain pressure within the cushions, with only one fan running

at any given time. In the event of a cushion failure, adverse weather conditions or a drop incushion pressure, both fans will run simultaneously to maintain a steady pressure.

If required the inflation units are also fitted with dehumidifiers to dry the air being fed into

the cushions. A typical air inflation unit measures 1.2m x 1.2m x 0.9m and is located near to

the ETFE cushion system, internally or externally. The system requires a dedicated and secure

power supply consisting of two 240V 13 amp electrical connections – as the ETFE foil roof is a

live system the cushions are permanently linked to the air inflation unit to ensure the

pressure is maintained.

3.9.3 Power Failure

In the unlikely case of a power failure, the ETFE cushion system will maintain pressure for

between 3 and 6 hours before deflating (dependant on weather conditions). This is due to

the non-return values built into the air inflation units. After this time, there is a possibility

that, as pressure drops, the roof will become damaged. As a result it is recommended that

there is either a standby generator or alternatively a cable bracing system installed to

support the cushions should this situation arise.

3.9.4 Safety/Explosion Other Risk

As a flexible material, ETFE Foil can take very high loadings for a short period of time which

makes it an ideal material for use in locations where there is a risk of explosion. If vandalism

is a threat, ETFE foil is also an advantage as the cushions will not break or fall from the

extrusion frames if damaged.




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3 9 4 1 Birds

The most common threat of tearing or damage is from birds; excessive bird pecking can

cause small punctures in the ETFE cushions. In general this poses no threat to the stability of

the cushion as a whole as our system is supplied with built in active monitoring which will

automatically adjust to compensate for the slight drop in pressure.

3.9.5 Repair and Replacement

One of the outstanding characteristics of EFTE foil is its exceptional tear resistance, lack of

notch weakness and stress crack concentration. Any cuts and scratches initially propagate but

the material rapidly stretches and rounds out into a tough low radius area that dissipates the

loads and prevents further tearing.

Minor repairs to the foil, such as a puncture hole, can be carried out in situ and within a

relatively short timescale by using an adhesive ETFE foil patch. Fritted material would be used

to match existing fritted foil in order that repairs do not affect the aesthetics of the structure.

If an ETFE Foil cushion becomes more significantly damaged, an individual cushion can be

easily removed and replaced with minimal disruption to the installation as a whole. The

outside surface of the ETFE cushion can be accessed by technicians, using rope access

techniques, from the main structural steel support.

3.9.6 Transportation

The weight and size of the EFTE has added benefits making it much more energy efficient

than materials with the same desired architectural effect. For example, transportation of the

material is much easier as it can be rolled, taking up less space, hence the need for less

conveyance.

3.9.7 Framing

The ETFE foil pillows are normally installed with aluminum clips and supported by a steel,

timber, or cable grid net. Extruded aluminum framing is fastened to the primary structure

and clamps the pillows in place. The joint between the pillows and the aluminum framing

includes beading (EPDM gaskets) for waterproofing the connection. The aluminum framing is





attached to the primary structure by plates and bolts. Special care must be taken with

placement of the bolts hole so that screws do not pierce the pillows.

3.9.8 Typical Section of an ETFE Cushion

Figure 24: Typical ETFE section

3.10 Cost Analysis

Façade Fabric types Cost per square feet

Teflon coated fiberglass (PTFE) $75-125

Other “non-combustibles” $85-150

Ethylene Tetra fluoroethylene film (ETFE $100-150

Vinyl coated polyester (PVC/PVDF) $50-75

High density polyethylene (HDPE) $25-50

Laminates and Interior Fabrics $35-50

3.11 Maintainability Aspects

3.11.1 Rainwater Drainage

All ETFE structures are designed with curvature to ensure that rainwater does not ‘pond’ or

collate on the top of the membrane as this leads to deformation of the foil. Rainwater will be

channelled to the perimeter of the roof where it can be collected in the main gutter system.




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3.11.2 Cleaning

ETFE membrane is self-cleaning due to its chemical composition, and will therefore retain its

high translucency throughout its life. Any accumulated dirt is washed off by normal rain if the

shape and the connection details are designed correctly. In climates where rainfall is minimal,

or if special cleaning is required, cleaning is carried out using ecologically ‘green’ detergents.

3.11.3 Maintenance

The material is maintenance-free. However, inspections are still recommended in order to

find defects (for example damage caused by mechanical impacts of sharp objects) and to

identify and repair such damage as early as possible. It is also recommended that the

perimeter clamping system and the primary structure be regularly inspected. The inspections

should normally be carried out annually. However, the specific intervals need to be assessed

on a project-by-project basis. They can be carried out in conjunction with the cleaning, if the

client requests this.

3.12 Commercial Catalogues/ Brochures

There are many manufacturers of ETFE foil cushion systems, most of the companies are in

Germany. Vector Special Projects, Vector Foiltec, and Skyspan each have developed their own

cushion cladding system. The first application of an ETFE cushion system was in the

Netherlands for a building at the Burgers Zoo in Arnheim in 1982. Since then, Vector Foiltec

has manufactured ETFE cladding systems for three more buildings at the zoo. ETFE foil

cushions have experienced the most popularity for cladding use in UK and Germany





3.13 Case Study

3.13.1 GLASS CUBE - NATIONAL AQUATICS CENTRE BEIJING

"The Water Cube is largest ETFE structure in the world."


Location : China, Beijing

Architect : CSCEC & DESIGN, Arup Pty. Ltd, Peddle Thorp Walker Architects

Contractor : China State Construction Engineering Corporation (CSCEC),

Size : 100.000 m²

Date : 2007

Fabric : Vector Foiltec ®

Material : ETFE

Figure 25: ETFE installation on the Beijing Water Cube




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It comprises over 100,000sqm of ETFE foils making this the single largest ETFE structure in

the world to date. The Water Cube is essentially a structure made from an organic network of

steel tubular members and clad with translucent ETFE pillows. The huge complex is

177x177x31m.

The cube is comprised of a series of steel tubes welded to round steel nodes, which vary

according to the loads placed upon them. There is therefore a huge variety in sizes, with

around 22000 steel members and 12000 nodes in total. There are 4,000 bubbles making up

the Water Cube, with some as large as 7.5m wide. The roof comprises seven bubbles and the

walls 16 bubbles, which are repeated throughout.

Figure 26: Conceptual drawing of ETFE skin of Water Cube

Comprising a steel space frame, it is the largest ETFE clad structure in the world with over

100,000 m² of ETFE pillows that are only 0.2 mm (1/125 of an inch) in total thickness. The

ETFE cladding allows more light and heat penetration than traditional glass, resulting in a

30% decrease in energy costs.

The outer wall is based on the Weaire–Phelan structure, a structure devised from the natural

pattern of bubbles in soap lather. In the true Weaire-Phelan structure the edge of each cell is

curved in order to maintain 109.5 degree angles at each vertex (satisfying Plateau's rules),

but of course as a structural support system each beam was required to be straight so as to

better resist axial compression. The complex Weaire–Phelan pattern was developed by slicing





through bubbles in soap foam, resulting in more irregular, organic patterns than foam bubble

structures proposed earlier by the scientist Kelvin. Using the Weaire–Phelan geometry, the

Water Cube's exterior cladding is made of 4,000 ETFE bubbles, some as large as 9.14 metres

(30.0 ft) across, with seven different sizes for the roof and 15 for the walls.

Figure 27: ETFE skin from the swimming pool inside of the Aquatics Centre

3 13 1 2 Design details

There are two parts to the Water Cube's structural framework – internal and external. The

external structure forms the actual roof, ceiling and walls and comprises a flat web of

rectangular boxed sections. These sections are then clad with the inflatable material

transparent "teflon" material known as ethylene tetrafluoroethylene (ETFE).

The internal steel frame is based on the unique geometry of biological cells or soap bubbles.

Ove Arup and PTW based this "soap bubbles" structural concept on a solution from two Irish

professors of physics at Trinity College, Dublin, known as the Weaire-Phelan structure,

whereby a recurring pattern of polyhedrons is packed together to occupy a three

dimensional space in the most efficient way possible.

Over 22,000 stainless steel members form the sides of these "bubbles", which are welded at

the joints to more than 12,000 spherical steel nodes. The benefit of this frame design, as well




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as resembling water bubbles, is that it is ideally suited to the seismic conditions found in

Beijing.

One of the challenges encountered by the designers was convincing Chinese authorities of

the value of ETFE. There were a lot of myths about the use of ETFE, regarding the material

growing mould and being ineffective in muting external noise, which had to be dispelled.

PTW managing director John Bilmon and his team put the claims to bed by conducting

extensive tests and making some adjustments to the material that would reduce the acoustic

impact of outside noise. The material was also shown to be superior in terms of lighting and

thermal efficiency, and will protect the internal steel members from exposure to the harsh

chlorinated aquatic environment – preventing their corrosion.

The use of ETFE will help the building last for about 100 years. The transmission of light and

strength of the ETFE membrane deteriorates far less than other materials. The membrane is

resistant to fire and severe heat, and possesses ductility and crushing resistance. It is self-

cleaning in nature as the friction coefficient of the material prevents the dust from forming a

layer on the material and rain can easily clear away the dust.

The venue's design as an enclosed swimming gymnasium could have led to high humidity.

This was addressed by taking a new approach to the air conditioning system. A stringent

temperature and humidity control system, and a recycled hot water system were

incorporated into the design. These help to air-condition the public area and the swimming

pool. Indoor and outdoor air recycling systems, solar energy systems and deck ventilation

systems maintain a comfortable climate and humidity of 50%-60% in the venue.

The designers also had to prevent dewdrop from the ceiling, which could affect theswimmers in the pool or divers on the springboard. The ETFE and air conditioning systems

have partially helped to prevent dew dropping. Moreover, the building's air supply, return

inlets and exhaust outlets improve the ventilation in the upper spaces of the building.

3 13 1 3 Environmental considerations

The ETFE cladding lets in solar heat, reducing energy costs by up to 30%. The design of the

Water Cube allows 140,000t of recycled water to be saved a year.





The space between the air-pillow walls has been completely sealed off creating a layer of

insulation. During summer, a 1m-high vent regulates the indoor temperature of the building

through heat exchange by drawing out the inside warm air and letting in the outside cool air.

The vent is sealed off during winter maintaining the warm temperature inside the venue.

3.13.2 ALLIANZ ARENA, MUNICH, GERMANY


Location Munich, Germany

Opened 30 May 2005

Owner Allianz Arena München Stadion GmbH

Operator Allianz Arena München Stadion GmbH

Architect Herzog & de Meuron

Structural engineer Ove Arup & Partners

Capacity 66,000 (2005)

69,901 (2006–2012)

71,137 (2012–) (League Matches)

67,812 (International Matches)

Figure 28: ETFE skin back lit with colour changing LED lights on the Allianz Arena




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The football stadium in Munich, Germany is shared by two football clubs: FC Bayern and TSV

1860. Construction began in fall of 2002, the stadium is a curved shell designed by Swiss

architects Herzog & de Meuron. The roof is a double layered ETFE membrane pairing white

translucent and transparent foil layers. The stadium will highlight the ETFE fagade byprojecting colors on it during the night. The fagade of the shell is composed of printed foil

cushions that will be illuminated with different team colors at night.

Figure 29: ETFE skin on installation during construction of the Allianz Arena

There are 2,816 cushions that span up to 2 m by 4.25 m and are composed of foil layers of

0.22 mm thickness. The ETFE film pillows cover an approximately area of 65,000 m2. The ETFE

roof cushions are designed for snowfall up to 1.6m. The cushions are all unique rhomboid

shapes, the same cushion shape only occurs twice in the structure.





This variety of shapes and sizes would be difficult to achieve with traditional glazing but is

easily accomplished with ETFE cushions. The roof and some parts of the arena's facade are

transparent and the remaining portion of the cladding is composed of translucent white ETFE

film. The Allianz Arena cladding system also features opening panels to provide the stadium

with natural ventilation.

3.14 Performance Specification

3.14.1 ETFE (Ethylene Tetra Fluoro Ethylene)

3 14 1 1 General Description

Tefzel ® ETFE a fluorocarbon-based polymer. ETFE is an abbreviation for the chemical name

Ethylene TetrafluoroEthylene. and the Tefzel ® brand of ETFE manufactured only by DuPont.

This material is to provide with both corrosion resistance and mechanical strength over a

wide temperature range.

3 14 1 2 General Properties

Tefzel ® ETFE of high purity, excellent chemical resistance, good permeability resistance, and

excellent abrasion resistance over a temperature range of -300°F to +300°F (-185°C to

+150°C). Tefzel ® ETFE in sheet, rod and film forms. Or a fabric-backed sheet for construction

of dual laminate vessels or the lining of existing chemical vessels.

3 14 1 3 Material Properties:

Test Unit Value Test Method

Tensile Strength M Pa 50 DIN EN ISO 527-1Tensile Stress at 10% strain M Pa 21 DIN EN ISO 527-1Tensile Strain at Break % 600 DIN EN ISO 527-1Tear Resistance N/mm 500 DIN 53 363Opacity % 7.5 DIN 53 363

Tensile strength > 50 N/mm², Elongation at break > 350% according to DIN EN ISO 527-1,

Tearing resistance > 400 N/mm according to DIN 53363, Cold temperature resistance of -

160°C, High light transmission including UV radiation, UV stable and ageing/weathering

resistant, Anti-adhesive smooth surface (self-cleaning), Resistant to hail according to SlA V280



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and EN 13583, Young’s Modulus of approximately 700 N/mm², Fire class B1, non-burning drip

from 250°C, Suitable for welding

3 14 1 4 Tests

Frequency of tests as per direction of Engineer-in-Charge & tests should be as per 3.14..1.3

3 14 1 5 Measurement and Rate

The width and length to be measured in centimetres and area to be calculated as square

metre correct up to two places of decimal. The rate includes cost of all the materials, labour

scaffolding, and fittings & fixing up to all heights etc. involved in operations described above,

but excludes the cost of paint.

4 References

(1) http://fabricarchitecturemag.com/articles/0512_f2_copenhagen_concert.html

(2) http://fabricarchitecturemag.com/articles/0700_id_part1.html

(3) http://fabricarchitecturemag.com/articles/0900_id_part2.html

(4) Robinson-Gayle, S., Kolokotroni, M., Cripps, A., & Tanno, S., 2001. "ETFE foil cushions

in roofs and atria." Construction and Building Materials. Vol.15, Feb., pp.3 2 3 -32 7.

(5) Moritz, K. & Barthel, R. 2004. Building with ETFE sheeting. (In Kaltenbach, F. (ed.)

Translucent Materials: Glass Plastic Metals. Munich: Architecktur-DokumentationGmbH & Co.KG, pp.70-78.)

http://fabricarchitecturemag.com/articles/0512_f2_copenhagen_concert.html


http://fabricarchitecturemag.com/articles/0700_id_part1.html







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