Assessing the fitness for purpose of products contributing to energy efficiency in housing: A case history with examples of assessed performance
C Smith Isofoam (South Africa) (Pty) Limited
K Bramwell and J van Wamelen Agrément South Africa
Paper presented at the International conference: Domestic use of energy: Cape Town, April 2001
ABSTRACT
Clark (1998) and Van Wamelen (2000) have pointed to the need for reassurance to buyers and specifiers, in South Africa, of products which contribute to energy efficiency in housing [1] and [2].
Isofoam (South Africa) (Pty) Ltd, has taken the lead in having its product evaluated for various applications by Agrément South Africa, the South African technical assessment organisation.
This paper gives an overview of the assessment process which leads to Agrément certification and summarises various aspects of performance, as assessed by Agrément South Africa.
INTRODUCTION
Isoboard® insulation is manufactured by Isofoam (South Africa) (Pty) Limited in their factory in Atlantis Industria, Cape Town.
Isoboard® thermal insulation is an extruded polystyrene rigid foam board, manufactured in a fully automated extrusion process. Boards have a closed cell structure and are white or blue in colour. Boards are 600 mm wide, and 30 mm, 40 mm or 50 mm thick, and 1250 mm or 2500 mm long. Longer lengths of board, as well as thicknesses of 60 mm and 70 mm can be made available on request. Edges of board are profiled to suit applications and may be square cut, shiplapped or tongue and grooved.
Isofoam (South Africa) (Pty) Limited distributes Isoboard® throughout South Africa through sales offices in Cape Town, Pretoria, Johannesburg and Durban. These offices provide technical support which includes guidance in the selection of the correct thickness of board to achieve specified thermal conditions or energy usage inside buildings.
Isofoam (South Africa) (Pty) Limited was established in South Africa in 1995. Isoboard® is therefore relatively new to South Africa but similar insulation materials are well known overseas.
Although extruded polystyrene (XPS) foam board is used extensively to insulate buildings in Europe, the USA and Persian Gulf countries, the product was not known in SA at the time of establishing the plant.
Early on it was clear that the specifying bodies required peace of mind when specifying XPS in the various applications.
Some of these applications are unique to South Africa and required thorough evaluation to prove fitness for purpose. The only recognised body in South Africa in a position to provide the industry with such a service is Agrément South Africa.
WHAT ARE AGRÉMENT SOUTH AFRICA, THE ASSESSMENT PROCESS AND AGRÉMENT CERTIFICATION?
The Board of Agrément South Africa was established in terms of a Ministerial Delegation of Authority by the Minister of Public Works in 1969. Members of the Board are appointed by the Minister and are drawn from all sectors of society, both technical and non-technical.
The mandate of the Board is to evaluate the fitness for purpose of non-standard construction systems or products and, where performance is acceptable, to certify such systems or products. Non-standard products are defined as those products for which there are no SABS standards or codes of practice. Products covered by SABS standards are not eligible for Agrément certification.
The Board is assisted in carrying out its mandate by the Agency of Agrément South Africa which is staffed by the CSIR and which is based at CSIR: Building and Construction Technology in Pretoria.
In order to carry out assessments the Agency draws on the necessary expertise within the CSIR, SABS, universities or elsewhere as is appropriate. Agrément South Africa is also a member of the World Federation of Technical Assessment Organizations which enables it to draw on the knowledge and experience of peer organisations internationally.
Fitness for purpose is established through an assessment process which entails a technical appraisal of the performance of the system or product based on:
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known behaviour of the materials involved
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documentation provided by the applicant (relevant test reports, that is, relevant to the intended use and South African conditions, from accredited organisations covering various aspects of performance are taken into account and often obviate the need for retesting)
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an inspection of the applicant`s factory and, if applicable, installations where the subject has been installed
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an assessment of the applicant`s quality management system.
It must be noted that a subject is not evaluated in isolation but as part of a whole, that is, conventional aspects of an installation or system affected by the subject or conversely which affect the subject must be considered.
As the subject of the assessment is non-standard there are no existing standards against which performance can be gauged. Agrément South Africa, therefore, bases its assessments, where possible, on the performance concept.
The elements of the performance concept are as follows:
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establishment of performance criteria appropriate to the use of the product;
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development of suitable test methods or methods of assessment which may be applied in the measurement of performance;
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measurement of the actual performance of the product according to the established methods;
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judgement of acceptability in the light of the measured or assessed performance of the product against the appropriate performance criteria.
Following a successful assessment, a system or product is certified fit-for-purpose. A certificate is a technical document which apart from listing general conditions of Agrément certification includes a description of the subject, summarises the results of the assessment and gives conditions that must be met for the subject to perform satisfactorily.
THE ASSESSMENT OF ISOBOARD® FOR CAVITY WALL, INVERTED ROOF AND OVER PURLIN APPLICATIONS
ISOBOARD® APPLICATIONS
Isoboard® has been evaluated for use in the following applications:
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as cavity wall insulation when installed during construction for use as a complete or partial fill board to reduce thermal transmittance through cavity walls with masonry inner and outer leaves
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as a thermally insulating layer, overlaid with water-permeable fabric and ballast, when applied on suitably designed and waterproofed flat concrete roofs to which there is limited access, in inverted roof (protected membrane) systems
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as a thermally insulating layer, installed between roof sheeting and purlins or between side cladding and girts in buildings.
To date (February 2001) the first two product evaluations have been finalized and certificates granted. The third product evaluation has been concluded and a draft certificate will be submitted to the Board of Agrément South Africa shortly for approval.
ASSESSMENT
Aspects of performance common to the three Isoboard® applications are set out below.
(a) Physical properties
The following physical properties had been determined by CSIR Building and Construction Technology just prior to assessment and were therefore not re-determined:
(b) Properties in relation to fire
Isoboard® is considered a combustible material in terms of SABS 0177: Part V and as such care must be exercised during storage to ensure no contact with naked flame or other heat sources, for example, naked light bulbs. Boards should also not be stored near materials such as packaging paper, waste and flammable liquids.
(c) Durability
Isoboard® is stable, rot-proof and offers no food value to vermin and will not support mould or fungal growth. However, it is affected by exposure to direct sunlight and exposure to solvents and under certain circumstances, heat. Boards are delivered to site in packs wrapped in translucent packaging material. IsoBoard must be stored in covered areas away from direct sunlight and ultra- violet light. Isoboard® must not be stored under black plastic sheets as excessive temperature build up when exposed to sunlight could result in warping of boards. Board must also not be stored in contact with volatile organic components.
(d) Thermal performance
Building regulations in South Africa do not currently specify minimum thermal performance requirements for various elements of buildings. For the purpose of this assessment Agrément South Africa did not set minimum thermal performance criteria. However, thermal performance aspects were assessed and are discussed below.
As is the case with similar foam board material, the thermal conductivity of Isoboard® will increase with age. This increase in conductivity results from:
In the case of XPS foam boards Agrément South Africa recommends that for design purposes in South African summer and winter conditions the test value of thermal conductivity be increased by 23%.
The position of Isoboard® relative to the thermal mass distribution in a structure can have a significant effect on the thermal performance of the building and as such steady-state calculations are insufficient for predicting indoor conditions and energy consumption.
Air to air thermal transmission (U) values for various combinations of materials have been included in the certificate and may be used in transient calculation methods like the Transfer Function Method developed by ASHRAE or other similar methods.
(e) Compliance with the National Building Regulations
In the opinion of Agrément South Africa, Isoboard® when used as specified, meets the requirements of Regulation A13(1)(a) of Part A: Administration, of the National Building Regulations.
(f) Quality Assurance
The quality management adopted by Isofoam (South Africa (Pty) Limited is based on the SABS ISO 9000 series and will ensure that acceptable manufacturing standards are consistently maintained.
Installation of the product will not be the responsibility of Isofoam (South Africa) (Pty) Limited but the responsibility of the installing contractor who must ensure that the product is installed in accordance with specifications and guidelines.
Aspects of performance specific to the Isoboard® Cavity Wall Insulation application
(a) Resistance to water penetration and ground moisture of insulated walls
Isoboard® does not absorb water by capillary action and may therefore be used in situations where it bridges the damp-proof membrane of the inner or outer leaf.
However, because of the nature of joints between adjacent boards, Isoboard® cavity wall insulation must not be counted upon to prevent the passage of moisture through walling.
In areas of the country where cavity wall construction is a requirement, provision must be made for a minimum residual cavity of 50 mm. This assessment assumes that the Isoboard® is firmly attached to the inside skin of the cavity wall and that:
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this cavity is clear of mortar droppings
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the cavity ties incorporate effective drips
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damp-proof membranes are installed in accordance with the recommendations of SABS 021.
In areas of the country where cavity wall construction is not required, a residual cavity is similarly not required. The use of Isoboard® does not preclude the need to apply an external render coat or other suitable finish should such a coat or finish normally be required.
Where the outer leaf of a wall is of face brick construction, attention must be paid to the proper filling and finishing of mortar joints as would be the case with all face brick construction.
(b) Properties in relation to fire
Although considered to be combustible material in terms of SABS 0177: Part V, Isoboard® is unlikely to become ignited within the cavity. In order to prevent the movement of hot gases and toxic fumes between defined fire rated compartments, cavities are to be bricked closed around the perimeters of the defined compartments, both horizontally and/or vertically, and around window, door, vent or any other service openings.
The use of Isoboard® cavity wall insulation will not prejudice the fire resistance properties of walls when installed as specified.
(c) Structural strength of insulated walls
Isoboard® does not serve a structural function in walls. For structural purposes the width of the cavity is taken as the width of the board and any residual cavity.
Specified wall tie spacings do not meet the requirements of the National Home Builders Registration Council mainly because of increased vertical tie centres to accommodate the 600 mm width of Isoboard® cavity insulation. It is, however, assessed that adequate tie densities per square metre would be achieved by reducing horizontal tie centres accordingly.
Cavity walls not complying with the deemed-to-satisfy rules of the National Building Regulations must be the subject of rational design carried out by a competent person in accordance with the requirements of SABS 0164 Part I.
(d) Durability of insulation
Isoboard® cavity wall insulation boards will remain effective as insulation for the life of the building in which it is installed.
Aspects of performance specific to the Isoboard® Inverted Roof Insulation application
(a) Effect of Isoboard® on waterproofing membranes
Isoboard® will not improve the watertightness of waterproofing membranes nor will it cure membrane failure on existing roofs. However, if installed properly, Isoboard® will extend the life of new and existing waterproofing membranes by protecting them from:
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high temperatures caused by solar radiation
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temperature cycling
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degradation caused by ultra-violet light
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mechanical damage
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damage caused by interstitial condensation
Isoboard® can readily be lifted to facilitate membrane inspection and maintenance.
(b) Condensation
Warm water trapped under boards is likely to be replaced by colder water during periods of rain. During heavy or continuous rainfall roof waterproofing and the concrete roof slab will be cooled. Should condensation occur on the underside of roofs as a result of this cooling it would be short term, disappearing when rain stops.
Interstitial condensation will not be a problem with insulated concrete roof slabs.
(c) Durability of Isoboard®
The low water absorption of Isoboard® ensures that the insulation offers freeze-thaw resistance with durability unaffected by rain, snow, frost or water vapour.
Isoboard® is affected by ultra-violet light and should not be left exposed prior to installation. Isoboard® must be covered with gravel ballast or concrete paving slabs as soon as possible as work proceeds, and care must be taken to ensure that exposed edges of Isoboard® are protected by suitable cover flashings.
The British Board of Agrément has assessed the life of inverted roof systems using similar insulation material covered with gravel or concrete paving slabs to be at least 20 years.
Isoboard® is compatible with materials commonly used for waterproofing, such as bitumen, asphalt and many plastics. However, waterproofing membranes and other materials containing solvents or volatile organic components could adversely affect the polystyrene.
(d) Wind uplift on and flotation of Isoboard® once installed
Isoboard® must be covered with either gravel ballast or concrete paving slabs in order to prevent boards lifting during wind or floating should ponding occur during rainfall. The amount of loading required will depend on the thickness of the insulation board, the anticipated wind force and that part of the roof being considered. In many instances the loading required to overcome buoyancy will be greater than that required to resist wind uplift. Buoyancy and wind uplift need not be considered to act simultaneously.
(e) Effect of gravel ballast or concrete paving slabs as loading for Isoboard® on roof structures
The mass of gravel ballast or paving slabs required over Isoboard® insulation is important and new roofs must be designed accordingly. Existing roofs must be structurally assessed prior to installation and strengthened where necessary.
During installation care must be taken to ensure that local areas of roof are not overstressed with stockpiles of ballast or paving slabs.
(f) Properties in relation to fire
Once covered with gravel ballast or paving slabs, the fire performance will be satisfactory.
(g) Resistance of Isoboard® to foot traffic and to concentrated loads
Light concentrated loads associated with insulation installation and maintenance operations should not adversely affect ballasted Isoboard®. Gravel should preferably be 20-40 mm nominal size aggregate and must be placed on a water-permeable filter fabric.
Where regular foot traffic is envisaged, for example, access to lift motor rooms etc, walkways of concrete paving slabs must be provided. Where such traffic cannot be controlled, paving slabs should be used throughout. These paving slabs must be bedded on a 20 mm thick layer of 4-8 mm nominal sized gravel.
Concentrated loads on Isoboard® which would occur under the supports of machinery or equipment installed on roofs must be avoided and such items must be supported on properly designed plinths or brackets supported directly on the concrete roof slab.
Isoboard® Over Purlin Roof Insulation application
(a) Condensation
Improved thermal performance will reduce the occurrence of condensation in susceptible buildings.
However, varying degrees of interstitial condensation can be expected to occur in all over-purlin installations in all areas of South Africa. As a result of interstitial condensation, crevice corrosion could occur on the inner face of uncoated galvanized steel sheets. Agrément South Africa has therefore recommended that the interior surface of galvanized steel sheets be protected by a good quality bitumen paint prior to sheets being installed. Periodic examination of selected roof fasteners should also be carried out to monitor the extent of possible corrosion.
(b) Ability of Isoboard® to span between purlins
Short term laboratory tests and inspections of completed buildings, some up to two years old, indicate that the specified maximum spans for the different board thicknesses are sufficient to resist selfweight and likely wind suction conditions.
Under no circumstance during installation, must any attempt be made to walk on the insulation boards between purlins.
(c) Effects of roof sheet temperatures on Isoboard®
Maximum roof sheet temperatures exceed the maximum allowable working temperatures usually imposed on extruded polystyrene rigid foam; however, inspections of established Isoboard® over-purlin installations indicate only minor effects from heat. Minor indentations below roof sheet troughs, over short lengths along purlin supports, can be expected to occur. Despite slight sheet settlements, both serrated nail and screw fixings hold sheets in place without undue play and without permitting rain penetration at exposed fixing points.
Certain over-purlin insulation installations over pre-painted corrugated steel roof sheeting have been reported to be "noisy" (creaking and squeaking, triggered usually by small wind pressure variations). These noises have been attributed to differential thermal movements between roof sheets and insulation boards. Noise is found to be more severe when sheet fixings have not been installed in accordance with the sheet manufacturer`s recommendations.
(d) Properties in relation to fire
Large-scale fire tests indicate that insulation installed over purlins in a roof with a three degree pitch did not support any flame spread, while no significant flame spread occurred in insulation installed vertically between girts and side cladding. This is attributed to the thermoplastic nature of the material which ensures that the material melts or softens and falls out of the hot zone prior to reaching ignition temperature. During testing, quantities of molten and softened material which had fallen to the ground did not ignite at any stage therefore posing minimal risk. The application of surface films to boards could radically alter fire properties of Isoboard® and such laminates have not been covered by this assessment.
The toxicity of the combustion products of polystyrene is less than that associated with, for instance, timber. Given the lack of significant flame spread in the event of fire, toxic gas emissions from Isoboard® are not considered to be significant.
Agrément South Africa is of the opinion that Isoboard® over purlin insulation will perform satisfactorily from a fire point of view. However, as is the case in any structure utilizing combustible insulation materials, fire safety must be addressed in a proper fire engineering design with consideration being given to occupancy, fire ventilation and contents of the proposed structure.
(e) Durability of Isoboard®
The water absorption characteristics of Isoboard® will ensure that during and after installation the durability of Isoboard® will be unaffected by rain, snow, frost or water vapour.
Isoboard® is affected by ultra-violet light and should not be left exposed outside prior to installation.
Care must be exercised during the cleaning of boards with high-pressure water jets in order to prevent pitting or other surface damage. Advice on recommended water pressures and the distance of the nozzle from the board and, if applicable, suitable cleaning agents and disinfectants should be obtained from the certificate holder.
In exposed areas, especially at lower levels of insulated side cladding, the surface of boards may become scuffed or cut by sharp objects or slightly damaged (dented) by soft body impacts.
Provided Isoboard® is protected from physical damage and provided it is installed as specified, it will remain durable for the life of the building in which it is installed.
CONCLUSION
The assessment of Isoboard® has resulted in the following Agrément certificates:
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Agrément certificate 2000/276: Isoboard® Cavity Wall Insulation [3]
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Agrément certificate 2000/277: Isoboard® Inverted Roof Insulation [4]
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The benefits of certification have been that the specifiers are now in a position to specify the product with assurance.
REFERENCES
[1] Clark, A: "Energy-efficient lighting in low-income households". Proceedings, International conference, Domestic use of electrical energy, Cape Town, April 1998.
[2] Van Wamelen, J: "Assessing the fitness for purpose of construction materials and products contributing to energy efficiency in housing". Proceedings, International conference, Domestic use of energy, Cape Town, April 2000.
[3] Agrément Certificate 2000/276: "Isoboard® Cavity Wall Insulation", published by Agrément South Africa.
[4] Agrément Certificate 2000/277: "Isoboard® Inverted Roof Insulation", published by Agrément South Africa
AUTHORS
Principal Author: Conrad Smith (Pr Eng.) (Civ. Eng) is the General Manager of Isofoam SA (Pty) Ltd, and has been involved in establishing IsoBoard into the South African market since inception.
His address is:
Co-author: Kevin Bramwell is a professional technologist (engineering). He works for Agrément South Africa as a technical evaluator. His main function is that of managing the assessment process of products or systems submitted for technical assessment and the preparation of draft certificates for submission to the Board for approval.
His address is:
Agrément South Africa
122 Caledon Street
6025 SHERWOOD
PORT ELIZABETH
Telephone and fax 041 371 2278
E-mail: kbramwel@csir.co.za
Co-author: Joop van Wamelen is a professional engineer with a passion for innovation and appropriate technology for development. He works for Agrément South Africa, with a brief to update and modernise Agrément`s assessment criteria and to broaden the scope of Agrément technical assessment and certification from mainly building systems and products to the full range of innovative construction products.
As regards his professional involvement, Joop is a member of the South African Institution of Civil Engineering. Furthermore he was the founder president of the Southern African Society for Trenchless Technology in 1992 and 1993. He was re-elected president for the year 2000.
His address is:
Presenter: The paper is presented by Conrad Smith
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