General enquiries on this form should be made to:Defra, Science Directorate, Management Support and Finance Team,Telephone No. 020 7238 1612E-mail: research.competitions@defra.gsi.gov.uk

SID 5 Research Project Final Report

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NoteIn line with the Freedom of Information Act 2000, Defra aims to place the results of its completed research projects in the public domain wherever possible. The SID 5 (Research Project Final Report) is designed to capture the information on the results and outputs of Defra-funded research in a format that is easily publishable through the Defra website. A SID 5 must be completed for all projects.

A SID 5A form must be completed where a project is paid on a monthly basis or against quarterly invoices. No SID 5A is required where payments are made at milestone points. When a SID 5A is required, no SID 5 form will be accepted without the accompanying SID 5A.

This form is in Word format and the boxes may be expanded or reduced, as appropriate.

ACCESS TO INFORMATIONThe information collected on this form will be stored electronically and may be sent to any part of Defra, or to individual researchers or organisations outside Defra for the purposes of reviewing the project. Defra may also disclose the information to any outside organisation acting as an agent authorised by Defra to process final research reports on its behalf. Defra intends to publish this form on its website, unless there are strong reasons not to, which fully comply with exemptions under the Environmental Information Regulations or the Freedom of Information Act 2000.Defra may be required to release information, including personal data and commercial information, on request under the Environmental Information Regulations or the Freedom of Information Act 2000. However, Defra will not permit any unwarranted breach of confidentiality or act in contravention of its obligations under the Data Protection Act 1998. Defra or its appointed agents may use the name, address or other details on your form to contact you in connection with occasional customer research aimed at improving the processes through which Defra works with its contractors.

Project identification

1. Defra Project code NF0605

2. Project title

Impovement of accoustic and fire performance of flax and hem thermal insulation

3. Contractororganisation(s)

The BioComposites Centre                         

54. Total Defra project costs £ 123,453

5. Project: start date................ 01 November 2004

end date................. 31 March 2006

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6. It is Defra’s intention to publish this form. Please confirm your agreement to do so...................................................................................YES NO (a) When preparing SID 5s contractors should bear in mind that Defra intends that they be made public. They

should be written in a clear and concise manner and represent a full account of the research project which someone not closely associated with the project can follow.Defra recognises that in a small minority of cases there may be information, such as intellectual property or commercially confidential data, used in or generated by the research project, which should not be disclosed. In these cases, such information should be detailed in a separate annex (not to be published) so that the SID 5 can be placed in the public domain. Where it is impossible to complete the Final Report without including references to any sensitive or confidential data, the information should be included and section (b) completed. NB: only in exceptional circumstances will Defra expect contractors to give a "No" answer.In all cases, reasons for withholding information must be fully in line with exemptions under the Environmental Information Regulations or the Freedom of Information Act 2000.

(b) If you have answered NO, please explain why the Final report should not be released into public domain

Executive Summary7. The executive summary must not exceed 2 sides in total of A4 and should be understandable to the

intelligent non-scientist. It should cover the main objectives, methods and findings of the research, together with any other significant events and options for new work.

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Improvement of Acoustic and Fire Performance of hemp and flax Thermal Insulation

1.0 Executive SummaryThe overriding purpose of this project was to expand the opportunity for natural fibre insulation and thereby increase the demand for UK grown hemp and flax fibres. This project has successfully addressed key market barriers relating to the fire and acoustic properties of natural fibre insulation. A significant increase in market opportunity for natural fibre insulation is anticipated. A further rapid acceleration of demand is expected if a UK production centre can be established.

This project has successfully delivered the specific objectives as set out in the proposal, which were to:

Identify the key fire and acoustic performance requirements of insulation materials and assessing market significance of UK construction codes, recommendations and regulations.

Optimise the hemp and flax fibre insulation to meet acoustic and fire performance requirements. Disseminate the results to end users, specifiers and the wider public.

These objectives were met through an extensive programme of research and development activities.

Literature reviews on acoustics and fire in construction. Consultation with external experts on the regulatory framework with respect to acoustic and fire

performance in construction. Fire and acoustic performance tests on existing Isonat product. Lab based development programme to optimise performance characteristics. Wide dissemination of the results and the development of case studies.

Isonat was found to easily surpass the acoustic requirements of Part E of the Building Regulations. It was determined that there were no regulatory requirements to improve the acoustic performance of the product. Acoustic performance could be improved by increasing the density of Isonat. However, increasing the density would not improve thermal performance, and would have a detrimental effect on embodied energy. It was therefore concluded that aiming to improve acoustic performance is unnecessary and would increase the manufacturing cost.

Isonat achieved Euroclass E classification for fire performance that is sufficient for the product to be used in most applications. It was not found possible to achieve a higher classification through the fire treatment of the fibres alone. Lab based work was focused on finding low cost and/or more environmentally friendly chemicals that would improve fire performance.

Results from this project are being disseminated through trade shows (such as Ecobuild 2006 – www.ecobuild.co.uk), presentations, trade literature and web sites. It is also intended that The BioComposites Centre will publish some of the research findings in a peer-reviewed journal.

It is considered that the main benefit of this project is in providing quality technical information enabling Plant Fibre Technology to effectively communicate the performance of natural fibre insulation. It is believed that this knowledge base will ultimately lead to increased confidence amongst end-users and specifiers.

This report concludes that whilst improvements can be made to the fire and acoustic performance of natural fibre insulation, there is no legislative pressure and little market advantage to be gained from doing so at this time. It is considered that the key market barrier to the rapid expansion of natural fibre insulation is now related to the establishment of a UK production facility. The key technical barrier to the establishment of a UK production facility is related to the supply of fire retardant treated fibres.

Project Report to Defra8. As a guide this report should be no longer than 20 sides of A4. This report is to provide Defra with

details of the outputs of the research project for internal purposes; to meet the terms of the contract; and to allow Defra to publish details of the outputs to meet Environmental Information Regulation or Freedom of Information obligations. This short report to Defra does not preclude contractors from also seeking to publish a full, formal scientific report/paper in an appropriate scientific or other journal/publication. Indeed, Defra actively encourages such publications as part of the contract terms.

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The report to Defra should include: the scientific objectives as set out in the contract; the extent to which the objectives set out in the contract have been met; details of methods used and the results obtained, including statistical analysis (if appropriate); a discussion of the results and their reliability; the main implications of the findings; possible future work; and any action resulting from the research (e.g. IP, Knowledge Transfer).

2.0 Introduction and BackgroundThis project was designed to address two key technical issues associated with the specification and use of hemp and flax fibre insulation, namely acoustic and fire performance. Ultimately by improving the properties and knowledge base with respect to fire and acoustics this project aims to help increase the opportunity for natural fibre insulation products. Previous experience of the project partners in marketing natural fibre insulation indicated that the main concerns of architects and specifiers was the ability of flax and hemp insulation to meet the new regulatory requirements in terms of acoustic (Part E of Building Regulations) and fire performance (EN13501-1).

Although thermal performance is the primary functional requirement for insulation it was not considered in this research due to the fact that the thermal conductivity (λ) of plant fibre insulation is well known and is equivalent to that of mineral fibre. However, during this project the complex issue of the hygrothermal properties of natural materials when used in construction has been highlighted and it is considered that this property should become the subject of further research work.

An increase in the market for flax and hemp based insulation will create market opportunities for UK fibre producers. Lack of UK markets for products has been seen as a weak link in the chain of developing the industrial fibre crop industry in the UK. In Germany the market for flax and hemp insulation is approximately 1200 tonnes, equivalent to about 0.19% of the insulation market.

Increasing the use of flax and hemp fibre insulation has a number of important secondary benefits.

Reduced waste from manufacturing and disposal. Biodiversity is encouraged if flax and hemp fibre crops are grown as part of a crop rotation system. Increased insulation of buildings helps to reduce heat loss and thus reduce global warming. The embodied energy of natural insulation is lower than other, mineral based insulation products

(although we believe that an independent LCA needs to be undertaken). The use of renewable fibre crops reduces reliance on mined mineral resources. With reference to the above benefits, the overall sustainability of housing is improved.

To achieve these secondary benefits the project needed to help deliver an increased market opportunity for natural fibre insulation. This was delivered by developing a better understanding of the performance of natural fibre insulation with respect to the regulatory requirements and market opportunities and to effectively communicate this knowledge to the market.

2.1 Acoustic performanceAcoustic performance is an increasingly important consideration in the design of houses. Noise is now recognized as a factor that can have a detrimental effect on the health and well being of occupants and as such the government has brought about changes to The Building Regulations to take this into account (Approved Document E, Resistance to the passage of sound. 2003 edition). Consequently it is a market necessity to understand the acoustic performance of natural fibre insulation and to effectively communicate this information.

2.2 Fire PerformanceMineral fibre insulation does not burn. Natural fibre insulations are made from ligno-cellulosic compounds, which by their very nature are readily combustible. The lack of knowledge and understanding, of the issues involved with fire performance throughout the supply chain has perhaps contributed to a cautious adoption of natural fibre insulation products in this country. It is perhaps significant that the barriers to market expansion of natural fibre insulation in France are not caused by concerns over fire performance as 900m3 (equivalent to approximately 150 dwellings) of non fire retardant treated Isonat are sold every week. In contrast, in Germany, all natural insulation products are required to achieve a known level of fire performance.

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3.0 Summary of Scientific ObjectivesThe objectives of this research project were set out in the project proposal. These objectives and the extent to which they have been met are detailed in Section 4.

4.0 Extent to which objectives set out in the contract have been metThe tasks and objectives as set out in the project proposal have been met in full.

Objective 1: Identify the most appropriate fire and acoustic testing standards and establish test protocols.The most appropriate fire and acoustic testing standards were determined by conducting a literature review. The conclusions were then validated through consultation with industry experts and discussions with test houses. (See Section 5 for outcomes).

Objective 2: Determine the current acoustic and fire performance of ISONAT. To test regimes identified in Objective 1.Isonat natural fibre insulation was then tested to the fire and acoustic performance standards identified in Objective 1. (See Section 5 for outcomes)

Objective 3: Determine the regulatory implications of the acoustic and fire performance (determined in Objective 2) and recommend and justify targets for improved performance.The regulatory implications of the results from the fire and acoustic tests were considered and the results guided the remaining research activity. Acoustic performance was so good that there appeared to be no reason to attempt to improve on this property, as doing so would require increasing density. This would have an adverse effect on embodied energy and environmental profile of the material without improving market potential. With respect to fire performance it was concluded that the scope for improving fire performance (to the extent that a higher performance classification could be achieved) was limited. Work was therefore focused on identifying suitable low cost environmentally friendly fire retardants and on gaining a better understanding of the fire performance of natural fibre insulation.

Objective 4: Determine the technology options for improving the acoustic and fire performance in line with the recommendations made in Objective 3.As it was concluded that there was little commercial benefit in improving the acoustic performance of natural fibre insulation, the ongoing work was focused on fire performance. The performance of a number of different fire retardants has been assessed using a number of different techniques. However, it has been concluded that to move natural fibre insulation into a higher performance classification a surface coating would be required. Surface coating technology was outside the scope of this project. Also, surface coating would most likely have an adverse effect on the environmental profile of natural fibre insulation, would require new production technology and would not, at this stage in the development of the market, lead to a significant increase in market opportunity.

Objective 5: Manufacture of modified insulation samples in accordance with the technology options proposed in Objective 4, and report on the production implications.Full-scale production trials of Isonat were undertaken to produce samples of Isonat treated to three levels. Also, lab-based samples were produced and tested using a range of alternative fire retardant chemicals.

Objective 6: Determine the acoustic and fire performance of modified samples and optimise performance.The fire performance of the modified samples was determined. It was significant that although improved fire performance can be achieved by increasing the level of treatment, in terms of the performance standards, a higher classification could not be achieved. No fire performance classification could be achieved for the untreated sample. This issue is discussed further in Section 6. It was not possible to compare the performance of Isonat natural fibre insulation with other insulation products, as the data is either not available or not presented in an appropriate format to allow comparison.

Objective 7: Determine the regulatory implications of the improved fire and acoustic performance and analyse the market implications and opportunities.Isonat was found to easily surpass the acoustic requirements of Part E of the Building Regulations. It was considered that there were no regulatory requirements to improve the product and it is likely that the costs associated with improving acoustic performance (such as increasing product density) would far out-weigh any commercial benefits. Isonat achieved a Euroclass E classification for fire performance. It was not found possible to achieve a higher classification through the fire treatment of the fibres. However, a Euroclass E classification is sufficient for most applications. Improving performance beyond this classification may be of benefit when in competition with other natural insulation products, but it is not considered possible to achieve a performance level that could enable parity with mineral insulation products that achieve a Euroclass A classification.

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Objective 8: Deliver wide and generic dissemination of the results (including installation of the insulation in at least one building to generate a real case-study).The results of this research are being disseminated at two trade shows (Ecobuild in London and Homes for Good in Taunton), through the preparation of marketing literature, through presentations to the public (Homes for Good and Uttlesford District Council) and through the publication of the research results on a number of web sites. A number of case studies of Isonat in use have been generated.

The main outstanding dissemination deliverable is the publication of a technical paper in a peer-reviewed journal. At the close of the project The BioComposites Centre intends to be in a position to have available sufficient data of a suitable quality to be compiled into a paper for submission to a journal (possibly Industrial Crops and Products).

5.0 Details of methods used and the results obtainedThis section highlights the approach adopted to achieving the project objectives.

5.1 Acoustic performanceAdvice from testing laboratories and consultants confirmed that the most appropriate lab-based way to demonstrate compliance with Part E of The Building Regulations was to carry out performance tests to BS EN ISO 140-3-1995 (described below) which requires the testing of complete building elements (such as partition wall) rather than the material. The limitation with this test is that it is costly and time consuming. The test has the advantage that it is relatively well known and understood within the industry. One of the key drawbacks of this test is that there are an almost infinite number of different construction details. A number of standard details were chosen to give a broad coverage of the main standard details for walls. (see Figures 1 to 6)

Due to the limitations of this test, an acoustic absorption test was also used to provide some fundamental data on the acoustic properties of the insulation. Whilst this data allows acousticians and designers to predict how the insulation may perform in-situ, it has no relevance with respect to meeting the acoustic performance requirements of the Building Regulations.

5.1.1 Airborne Sound TransmissionTests were carried out in accordance to BS EN ISO 140-3: 1995 (Laboratory measurement of airborne sound insulation of building elements) and BS EN / ISO 717-1:1997. (Rating of sound insulation in buildings and of building elements. Airborne sound Insulation). Tests were carried out by Sound Research Laboratories (SRL) to UKAS accredited standards.

This test consists of adjoining rooms, one containing a sound source – generating sounds over a range of frequencies and the other room containing equipment to measure the sound coming through the connecting wall. The connecting wall has a window / hole measuring 2.92m by 3.845m, into this hole are constructed various ‘wall’ build-ups to mimic building practices on site (see Figures 1 – 6).

Figure 1. Party wall timber stud Figure 2. Partition wall, double layer timber stud

Figure 3. Partition wall, single layer with timber stud.

Figure 4. Partition wall, double layer with metal stud.

Figure 5. Partition wall, single layer with metal stud.

Figure 6. Empty Cavity with metal stud

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The more effective the construction detail (wall build up) at stopping sound travelling from one room to another the higher the Rw (weighted sound reduction index) see Table 2 for results.

Table 2: Results of airborne sound transmission testTest Number Description Test

performanceRw (C;Ctr)

Regulatory requirement

RW1 2 x plasterboard each side of twin

timber stud, with insulation59 (-1;-6) 45 New

43 Rebuild2 2 x plasterboard each side of single

timber stud, with insulation48 (-1;-5) 40

3 1 x plasterboard each side of single timber stud, with insulation

45 (-3;-10) 40

4 2 x plasterboard each side of metal studwork, with insulation

52 (-2;-7) 40

5 1 x plasterboard each side of metal studwork, with insulation

46 (-3;-10) 40

6 1 x plasterboard each side of metal studwork.

37 (-2;-6) 40

C and Ctr are correction factors used for predicting the performance on site as apposed to in laboratory build ups.

5.1.2 Acoustic absorption Determination of the random incidence sound absorption coefficient was carried out in accordance with BS EN ISO 354:2003. Tests were carried out by Sound Research Laboratories to UKAS accredited standards.

For this test specimens are laid directly onto the floor of the test chamber (in this case a chamber with a total volume of 300m3). The samples are edged with wooden battens, to prevent edge effect adversely effecting the results. A sample thickness of 100mm and a total sample area of 10.69m2 was used for this trial. Once the samples were in place sound was then generated in the room over a range of frequencies and the amount of sound absorbed by the product recorded over that range of frequencies. Results are expressed as a single figure, the better the material is at absorbing sound the nearer the figure of random incidence sound absorption to 1 (one).

The random Incidence Sound Absorption (αω) of ISONAT is 1.00This is Class A calculated to ENISO 11654:1997

5.2 Fire performanceA thorough review of fire performance issues was conducted. A number of meetings were held with industry experts and test houses to establish the regulatory requirements and the most appropriate performance tests.

To demonstrate compliance with UK regulations it was decided that the new European Reaction to Fire test standards should be used.

Standard DescriptionEN ISO 11925-2 Ignitability testEN 13823 (SBI) Heat release and smoke production test (Single

Burning Item)EN ISO 1716 Bomb calorimeter test (provides a calorific value)EN ISO 1182 Non combustibility testEN 13501-1 Classification standard (tells you how to use the

four test standards in order to obtain a classification)

One or combinations of the above tests are used to obtain a Euro-classification from “A1” (best) down to “F” (worst):

To enable lab-based screening of insulation samples two methods were selected – an in-house lab-based method and the cone calorimeter test (described in ISO 5660).

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5.2.1 Ignitability The ease of ignitability of the product was determined by EN ISO 11925-2. The test requires 16 samples measuring 250mm x 90mm to be exposed to a naked flame of given height. If the material burns the height of that burn is recorded and samples graded accordingly.

Relevance: This test is the first test that all samples must pass if they are to be graded according to EN 13501-1 and assigned an Euroclass for fire performance. This test is very relevant throughout Europe.

Table 3: Comparison of ISONAT treated with different levels of fire retardant.Sample Result CommentUntreated ISONAT Failed No fire retardant usedStandard ISONAT Passed Some directional effects were observedSuper treated ISONAT Passed Passed easily

5.2.2 Single Burning Item (SBI)The SBI or EN 13823 is a test to simulate a waste paper basket in a corner of a room and the contribution of heat and smoke made to that fire by materials in the corner of the wall where the basket / fire source is located.

The relevance of this test has been hotly debated throughout this project. However it is referred to in The Building Standards 2000 and so is very relevant to getting this product in the market place. The conditions do not mimic those in a loft situation (horizontal application of the material) or if used in a wall situation (vertical) when the material would never be used un-faced but would have a covering of plasterboard or similar. However this is the test that must be carried out to achieve a higher Euroclass than if just testing to EN ISO 11925-2. It is also the test used by competitors in the industry and as such is become something of a benchmark, if mistakenly so.

Samples of material are fixed to a backing material in a ‘L’ shape (as per the corner of a room. The length of one wall is 500mm and the length of the other is 1000mm the height of both walls is 1500mm. This construction is then exposed to a fire of known intensity and the reaction of the material to the fire recorded, rate of heat release, smoke production, production of flaming droplets, spread of flames etc. The performance of the material is then graded according to the various parameters.

Initial indicative tests (one sample rather than three for certification) were carried out only on standard ISONAT. The test house was unable to find a suitable method for attaching the material to a backing board – due to the tough fibrous nature of the product, conventional methods of attachment were unsuitable. A metal frame was therefore used to hold the sample in place; this was less than satisfactory and may have contributed to the poor performance of the product. Parts of the sample fell out of the frame and onto the burner, as such the test was deemed invalid.

5.2.3 Cone Calorimeter TestThe cone calorimeter test is described in ISO 5660.

This test can be used to predict how products will perform in the SBI test without the need for full-scale tests or more costly experiments. It is therefore a useful experimental tool to screen a large number of different treatments.

In the cone calorimeter test specimens with an area of 100mm x 100mm are exposed to a constant radiant heat flux. A spark plug positioned over the test specimen ignites any flammable gasses produced by the test specimens. Effluents from the test are then collected in a hood and transported through a duct where the smoke produced and temperature reached is measured. The weight loss of the sample is also recorded.

Table 4. Summary of Results for ISONAT (averaged for 3 specimens)Sample Time to

ignition (S)

Time to extinction

(S)

Total heat(kJ)

Rate of Heat Release (RHR)

peak

Mass Loss(%)

Untreated 14 440 369 209 87.1Standard 12 533 486 157 94Super Treated

12 559 199 94 65.7

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5.2.4 Laboratory based screening of fire retardantsStandard tests for fire performance (how much a material contributes to a fire) and fire resistance (how much a material/structure contains a fire) are unsuitable to developmental work. This is partly because they are expensive and partly because they require finished products. Manufacturing sufficient quantities of treated experimental fibre for production runs is not always possible. While the cone calorimeter method is considered to be an appropriate method for screening before full-scale production of samples, a simple low cost in-house method was also required.

Various different methods were tried but repeatability was found to be a problem. The most reliable method consisted simply of placing a 2 gram ball of fibre onto a radiant heat element and of observing the behaviour of the material. A scoring scheme was devised from which it was possible to estimate the addition level required to achieve a ‘Euroclass E’ performance level.

Table 5 shows how this method was able to distinguish between the different samples of commercially produced Isonat.

Table 5 Comparison of ISONAT treated to different levels with standard fire retardant.

Material description Assigned Score EuroclassUntreated 0 No

classificationStandard Treatment 2 ESuper Treated 7 E

(data provided by CSTB)

The laboratory based screening method described above was also used to test a variety of flame retardants. All the fire retardants used were liquids and had a suitable viscosity for allowing pumping and spray application methods. The fire retardants were applied at different levels of addition and from the results an estimate was made of the addition level required (solid on solid) to achieve an acceptable fire retardance. Table 6 summarise this, the lower the figure in the right hand column the more effective the retardant. An additional five other fire retardants were also tested but failed to achieve acceptable performance.

Table 6 Summary of the addition level of different fire retardants required to achieve an acceptable level of fire retardance.

Trade Name / Supplier Chemical base % addition level needed

Pekoflam PES / Clariant 6Amgard CT / Rhodia Complex phosphates 10TCPP / EcoChem Technologies

Tris (1-chloro-2-propyl) phosphate 10

TDCPP / EcoChem Technologies

Tris (1,3-Dichloro-2-propyl) phosphate

15

Flovan CGN / CIBA 6Fyrban / Stephenson Group Ltd

polyphosphate 6

Formulated in BC labs borax 5Formulated in BC labs ammonium phosphate 10Formulated in BC labs sodium bicarbonate 1Formulated in BC labs sodium carbonate 2

From this work it was concluded that the performance of commercially available products was disappointing, whilst simple and low cost sodium bicarbonate solution was found to perform very well.

6.0 Comments on the results and their reliability6.1 Acoustic performance

The acoustic performance of Isonat natural fibre insulation was found to surpass the requirements of Part E of the Building Regulations. The requirement of a party wall (between dwellings) is 45 and 43 Rw for new and renovation respectively, while the Building Regulations required that party walls be tested on site to meet the requirements of Part E the laboratory test indicated that this wall build up (Test reference number 1 – Table 2) would more than adequately meet the requirements with the correction factor applied. For the internal partitions

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(Tests reference numbers 2 to 6 – Table 2) no correction factor is required and all the wall build-ups pass the 40 RwdB required by Part E of the standard.

It is difficult to determine precisely how the performance of Isonat compares to other insulation products, as the construction details used in the available published data are always different. For example plasterboard thickness, plasterboard make, stud type and timber density, build quality etc will all have an effect on acoustic performance.

The acoustic test results, when considered alongside recommendations from consultants and the views of specifiers, indicated that the acoustic performance was so good that there appeared to be no reason to attempt to improve on this property, as doing so would require increasing density which would have an adverse effect on embodied energy and environmental profile of the material without improving market potential. It is now apparent that specifiers and end users are concerned solely with compliance with Part E of the Building Regulations.

6.2 Fire Performance

6.2.1 IgnitabilityThe performance of ISONAT in the ignitability tests (EN ISO 11925-2) was found to be dependant upon the level of fire retardant applied. Observation of the tests also indicated that even application of the fire retardant was essential for consistent results. This has implications for the development of fire treatment processes. Currently the only established method of treating hemp and flax fibres with a fire retardant is complete saturation with a fire retardant solution and subsequent drying. This process is considered to be energy intensive, creates a waste stream and would add to the cost.

6.2.2 Single Burning Item (SBI)The rate of heat release is a key feature in determining the performance of a product in the SBI test. Analysis of this property confirms that untreated ISONAT performs worse than standard or super treated ISONAT. However both the treated and super treated product achieved the same Euroclass classification – that is Euroclass E. It was concluded from these results that it would be difficult for a natural fibre insulation to achieve a higher classification without the application of a surface barrier. It should also be noted that this test only considers the surface reaction to fire of the insulation and not a products or assemblies resistance to fire. Therefore future work should look at the fire performance of construction assemblies containing natural fibre insulation to determine whether their fire performance would be compromised.

6.2.3 Cone CalorimeterThe cone calorimeter method is a proven method for testing materials and from these results predictions can be made about how a product will perform in the SBI test. The cone calorimeter method has the advantage over the SBI that relatively small sample sizes are required allowing screening of a number of options, however to achieve an Euroclass fire classification then a full SBI test must be carried out. For screening purposes the cone calorimeter method was considered to be the most appropriate and reliable test available.

The cone calorimeter results did distinguish between the different treatments – the super treated sample performing better than the other two samples in almost all performance criteria measured (see Table 4).

6.2.4 Laboratory based screening of fire retardantsThe development of an in-house method for screening fire retardants and application levels proved to be challenging from the point of view of reliability and relevance to how the product performs in service. The in-house method eventually adopted, whilst serving the purpose of screening out a number of different fire retardants, relied solely on a visual assessment method. However, this in-house method made it possible to distinguish between various treatment levels and to distinguish between different treatment types. The results therefore provided some information as to the most appropriate treatment.

When issues such as performance are considered alongside cost and environmental impact the soda based treatment showed some promise (See Table 6 in Section 5.2.4). A soda-based treatment is currently used by the manufacturers of Thermohanf (the European market leading natural fibre insulation made from hemp).

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7.0 Main implications of the findings7.1 Acoustic Performance

The results from analysis of the acoustic performance of Isonat shows that natural fibre insulation was able to help specifiers and end-users demonstrate compliance with the requirements of Part E of the Building Regulations. This consideration along with the market knowledge gained through the dissemination indicates that there is little commercial benefit in pursuing improved acoustic performance. It is also widely understood that, if necessary, acoustic performance could be improved by increasing the density of the product. The main implications of the findings relating to the acoustic analysis can be summarised as follows:

Natural fibre insulation performs exceptionally well at reducing airborne sound transmission across walls. The negative environmental and cost implications of aiming to improve the acoustic performance of

natural fibre insulation outweigh any potential benefits.

7.2 Fire PerformanceThe results from the analysis from the fire performance of Isonat indicates that natural fibre insulation is able to achieve a Euroclass E performance rating which is sufficient to allow the product to be used in domestic and non-domestic buildings. However there are certain applications where a higher performance rating would be beneficial (such as non-domestic buildings over 15m high). It is considered that such an improvement in performance is not realistically achievable for insulation products made from natural fibres without adding a surface barrier. The main implications of the findings relating to the fire performance analysis can be summarised as follows:

Natural fibre insulation is fit for use in UK construction provided the fibres are treated with an appropriate fire retardant.

Fire performance requirements do not substantially limit the market opportunity for Isonat. In domestic situations the building regulations permit the use of Isonat in situations where the height of

buildings does not exceed 18m. Presently there is little benefit in aiming to improve the fire performance of Isonat beyond a Euroclass E. It is anticipated that to achieve a higher classification a surface barrier would be required. Although natural fibre insulation can satisfy regulatory requirements there is a need to alter market

perceptions regarding their fire performance. The manufacturing process requires fibres to be pre-treated with a fire retardant. However, the relatively

low levels required indicate that a more cost effective approach than the current method of complete immersion within a fire retardant solution should be developed.

As it is relatively simple to achieve the Euroclass E classification there is an opportunity to use lower cost and/or more environmentally friendly chemicals (such as Soda).

8.0 Future WorkThis section is divided into future work that has already been commissioned and future work for which the resources to undertake the research have yet to be sourced or allocated.

8.1.Scheduled Future WorkThis section details work relating to fire performance, the results of which have yet to be delivered to the project partners.

8.1.1 Fire resistance testingIt has been established that Isonat meets the acoustic and fire performance requirements of the Building Regulations. However, it has not been established whether the use of Isonat within a building element would enhance or reduce the performance of that building element in a fire. Therefore to analyse this issue indicative Fire Resistance tests (in line with BS 476 part 22) will be undertaken on a timber stud wall. Tests will be conducted using an empty cavity, a cavity filled with mineral wool and a cavity filled with Isonat natural fibre insulation. By monitoring the temperature rise on the side not exposed to the heat source it will be possible to make a direct comparison of performance.

8.1.2 Cone calorimeter screening of fire retardantsTo validate the results of the in-house screening method, the most favourable treatments will be applied to hemp fibres and then tested in the cone calorimeter using a holding frame specially constructed to allow the testing of loose fibres.

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8.2 Proposed Future WorkThe future work recommended in this section relates to that which is specific to the development of the fire and acoustic performance of natural fibre insulation and that which has come to light during the execution of this project and which would increase the market opportunity for natural fibre insulation.

8.2.1 Use of sodium bicarbonate (soda) as a fire retardantThe lab-based screening method demonstrated that soda has excellent properties when used as a fire retardant. Soda is low cost and is believed to have a low environmental impact. However, the low solubility levels indicate that higher drying energies may be required. Future work should focus on a detailed exploration of the performance properties and environmental profile of soda as a fire retardant treatment for natural fibres.

8.2.2 Replacement of thermoplastic binderAll natural fibre insulation products are bound together with thermoplastic polyester fibres at an addition level of between 15% and 20%. This fibre acts as a fuel to support combustion. Replacement of these fibres with an alternative ‘low combustibility’ binder would improve the fire performance. It would also be beneficial to remove the polyester binding fibres to reduce cost and improve the environmental performance. It is estimated that the polyester fibres account for in excess of 50% of the embodied energy of natural fibre insulation and cost 2.5 times that of the natural fibres such as hemp. Future work should therefore look at replacing the polyester fibres with a low cost ‘sprayable’ binder preferably produced from a renewable resource. The BioComposites Centre have recently filed a patent application on an air blending method combining hemp and flax fibres with a fire retardant and sprayable binder. This process has been proved at lab-bench scale. Funds are now being sought to scale-up the process.

8.2.3 Life Cycle AnalysisThe embodied energy of construction materials is one of the important future market battlegrounds. An in-house desk based study conducted by Plant Fibre Technology conflicts widely with a study commissioned by Rockwool. It is therefore recommended that a fully independent study be commissioned.

8.2.4 Hygrothermal propertiesThe ability of natural fibre insulation to absorb and release moisture has led to the view that the in-use thermal performance may be better than that of other fibre based insulation products which have a similar value of thermal conductivity. It is also postulated that the water sorption properties of natural fibres may help to reduce the risk of interstitial condensation and help to regulate internal humidity levels to create a more comfortable internal environment. Buildings that have been constructed in a manner that maximises the sorption property benefits of natural materials have been termed ‘breathing’ constructions. This construction method is being pioneered in the UK by Natural Building Technologies (www.natural-building.co.uk). The quantification of the benefits of the complex hygrothermal properties of natural fibres on the health of occupants and the performance of a building could lead to a rapid increase in demand for natural fibre products such as hemp and flax insulation and wood fibre construction boards. Such work would require a detailed understanding of building physics and would benefit from the development of modelling software and from the construction of demonstration houses.

8.2.5 DurabilityNatural fibre insulation products based on hemp and flax have been produced and sold in Europe since the mid 1990’s. There is therefore little knowledge available on the long-term performance. The key issues are settlement (it is well known that low density mineral fibres settle over time), the potential for mechanical damage from insects and rodents and the extent to which natural fibres could support the growth of moulds and fungi.

9.0 Action resulting from the research.The research project and the subsequent dissemination has led to a number of additional activities which are expected to increase the opportunity for natural fibre insulation in the UK.

The ability to present detailed fire and acoustic performance data and to back up this data with an in-depth knowledge of the issues has undoubtedly increased the credibility of natural fibre insulation together with that of Plant Fibre Technology. This is expected to have a significant impact on market opportunity.

The project has also increased the interest of manufacturers and potential fibre suppliers in developing a UK production base. Discussions have now commenced with a potential UK producer. However, it has

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become apparent that a key barrier to establishing UK production centre is the ability to supply fire retardant treated fibres.

The interest expressed by potential manufacturers is creating the focus to support the scale-up of fibre treatment technology developed by the BioComposites Centre in a separate Welsh Government funded research project.

The confidence gained in the technical performance of natural fibre insulation created in part as a result of this research project has led Plant Fibre Technology to seek additional investment to support the development of the UK market.

References to published material9. This section should be used to record links (hypertext links where possible) or references to other

published material generated by, or relating to this project.

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Performance datawww.naturalinsulation.co.uk (expected to go live by mid April 2006)www.natural-building.co.uk (expected to go live by end April 2006)

Case Studieswww.impetusconsult.co.uk/publications.htm (expected to go live by 31/03/06)www.est.org.uk/housingbuildings/funding/innovative/examples/ (expected to go live by end of April 2006)

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