Indicative fire tests with combustible insulation materials protected with various coverings

Transcription

1 Indicative fire tests with combustible insulation materials protected with various coverings Date : August Project name : MAT Risk assessment of new materials Version : 1 Author : Anders Dragsted

2 Content 1 INTRODUCTION BACKGROUND SCOPE 3 2 TEST SPECIMENS 4 3 TEST PROCEDURE 7 4 RESULTS TEMPERATURE MEASUREMENTS VISUAL OBSERVATIONS EPS PUR PHENOLIC PAPER FIBRE WOOD FIBRE OVERVIEW OF VISUAL OBSERVATIONS (DAMAGE TO SUBSTRATE) 19 5 DISCUSSION 20 6 CONCLUSION 23 7 SUGGESTIONS FOR FUTURE WORK 24 8 REFERENCES 25 9 ACKNOWLEDGEMENTS 26 APPENDIX 1 - TEMPERATURE MEASUREMENTS BEHIND COVERINGS 27 APPENDIX 2 - IGNITION TEMPERATURES OF INSULATION MATERIALS 31 Page: 2 of 31

3 1 Introduction 1.1 Background In the recent years there has been a concern among the fire safety community about the fire risks associated with the use of increasing insulation thickness combined with an extended use of combustible insulation materials [1] [4]. Reported incidents comprising combustible façade insulation is often related to the construction phase were the insulation is unprotected but some there are also examples of façade fires involving finished buildings. In Denmark the guidelines on pre-accepted fire safety solutions recommend combustible 1 insulation materials 2 to be protected with at least a so-called cladding class K 1 10 (for buildings up to 9,6 meters). This is in contrast to most other European countries where requirements/guidelines on exterior building surfaces are related to the reaction-to-fire properties of the façade system as a whole [5]. The Danish approach may be considered to have some advantages [5] but it is often perceived as rather rigid and difficult to comply with. Moreover, the classification criteria are sometimes accused of being too far away from real fire risks. In order to push the development of safe façade systems with combustible insulation materials DBI performed a series of fire tests with multi-layer constructions. 1.2 Scope The scope of the fire tests was - to produce more public available knowledge on various combustible insulation materials behind a fire protecting covering system and - to evaluate the classification criteria of the K 1 10 covering and - to inspire manufacturers and consultants in their innovation process. 1 Defined as insulation materials classified lower than D-s2,d2 on material related level 2 Defined as materials with a density lower than 300 kg/m³ Page: 3 of 31

4 2 Test specimens Four different types of insulation were tested; EPS (polystyrene), PUR (polyurethane), phenolic and cellulose fibre (paper and wood). The tested combinations of insulation and covering are listed in the table below. Insulation material EPS (class F), PUR, Phenolic Coverings 20,0 mm bricks with mortar 12,0-16,0 mm concrete rendering 12,0 mm plaster system with reinforcing mesh 45,0 mm stone wool board (30 kg/m³)* 10,0 mm fibre cement planks mounted with overlap* 9,5 mm wind stopping gypsum board* 9,0 mm water proof plywood* 12,5 mm gypsum board* Paper fibre (loose fill) Wood fibre (loose fill) 25,0 mm cement bonded wood wool board* supplied with reinforced plaster system 25,0 mm cement bonded wood wool board* 12,5 mm gypsum board* 12,0 mm water proof plywood* 25,0 mm cement bonded wood wool board* supplied with reinforced plaster system 25,0 mm cement bonded wood wool board* 12,5 mm gypsum board* 60,0 mm rigid wood fibre insulation board* supplied with reinforced plaster system Table 1: Overview of test specimens. Coverings marked with * was assembled with at least one linear joint. Even though insulation materials from different manufacturers are called the same (e.g. EPS) and are based on the same core components their properties including the reaction-to-fire properties are different. For example, EPS boards can achieve a euro-class classification in a span of class F to class D. Therefore, the tested insulation materials do not represent generic insulation types and the observations may only be considered as indicative for the four insulation types. No reaction-to-fire tests were performed during this project. The PUR slabs had an aluminium foil facing while the phenolic had a glass fibre felt facing. The EPS slabs had no facing. The test specimens were quadratic with side lengths of mm. The specimens used in the first fire test (EPS) were produced without a frame. The following test specimens (cellulose, PUR and phenolic) were installed in a wooden frame in order to avoid fire spread between specimens. The protective covering was mounted on the exposed side (downward side) while the non-exposed side (upward side) was closed with a chip board. Page: 4 of 31

5 Figure 1: General sketch of test specimen. Exposed side (covering) in the bottom. Figure 2: Example of test specimen with covering (plaster system) applied. Thermocouples were installed between covering and insulation material in order to measure the temperature development during the fire test. In all test specimens at two thermocouples were installed in the outer quarters along the diagonal. An additional thermocouple was installed in the middle in specimens where the covering was mounted with a linear joint. The additional thermocouple was placed directly behind the joint. Figure 3: Thermocouple position. Without joint in the covering (left) and with joint (right) The joints where done as simple butt joints without any sealing e.g. filling or tape. All test specimens were stored in controlled environment in the test laboratory for at least 4 weeks after assembling. Page: 5 of 31

6 Both PUR and phenolic insulation were tested with their original facing attached to the surface (aluminium foil and glass fibre felt respectively). The facings probably influenced the results by forming an extra barrier between the furnace and the insulation material. Though, this is not evaluated in the present report. Page: 6 of 31

7 3 Test procedure The test procedure was based on EN 14135:2004 Coverings. Determination of fire protection ability. Though, the physical dimensions of the test specimens were reduced in order to perform more tests with the limited economical resources. The test specimens were placed in batches of four on a steel/concrete test frame. Each specimen covered a 500 mm x 500 mm hole in the frame. Figure 4: The test frame with specimens seen from above (left) and from below (right) The test frame was placed as the top side of the test furnace. Figure 5: Furnace with test frame and specimens installed (photo taken during test) When the tests started the furnace was heated using gas burners to achieve a temperature rise according to the standard fire curve (ISO 834). The test duration was 10 minutes according to EN (for a K 1 10 covering). Page: 7 of 31

8 Figure 6: ISO 834 temperature curve After 10 minutes the gas burners were shut down, the frame was lifted from the furnace to the floor and the test specimens were sprayed with water to reduce further heat conduction and in some specimens to extinguish flames. As fast as possible, the test specimens were disassembled to allow for visual inspection of the insulation material. According to EN , the covering must meet the following criteria during the test to fulfil its purpose: The substrate must not be damaged 3 and The temperature rise between the covering and the substrate must not exceed 250 C on average and 270 C as a maximum. 3 Damage is defined as any deformation, shrinkage, melting or charring. Page: 8 of 31

9 4 Results Only selected observations are included in this report. The reader is referred to the test reports [9] [12] for further detail. Please note that each combination of insulation/covering was only tested with one single test specimen. Therefore, observations during and after the fire tests are subject to a high degree of uncertainty. Hence, the results may only be considered as indicative. 4.1 Temperature measurements The following figures illustrate the temperature measurements behind the coverings for each of the tested insulation products. The values are mean temperatures measured in the thermocouples including thermocouples behind joints. Separate graphs for each covering are included in Appendix 1. Figure 7: Temperature measurements behind coverings with EPS insulation Page: 9 of 31

10 Figure 8: Temperature measurements behind coverings with PUR insulation Figure 9: Temperature measurements behind coverings with phenolic insulation Page: 10 of 31

11 Figure 10: Temperature measurements behind coverings with paper fibre insulation Figure 11: Temperature measurements behind coverings with wood fibre insulation Page: 11 of 31

12 Page: 12 of 31

13 4.2 Visual observations EPS Figure 12: EPS with brick covering Figure 13: EPS with concrete covering Figure 14: EPS with plaster system covering Figure 15: EPS with stone wool covering Figure 16: EPS with fibre cement covering Figure 17: EPS with 9,5 mm gypsum covering Page: 13 of 31

14 Figure 18: EPS with plywood covering Figure 19: EPS with 12,5 mm gypsum covering PUR Figure 20: PUR with brick covering Figure 21: PUR with plaster system covering Figure 22: PUR with concrete covering Figure 23: PUR with stone wool covering Figure 24: PUR with fibre cement covering Figure 25: PUR with plywood covering Page: 14 of 31

15 Figure 26: PUR with 9,5 mm gypsum covering Figure 27: PUR with 12,5 mm gypsum covering Page: 15 of 31

16 4.2.3 Phenolic Figure 28: Phenolic with brick covering Figure 29: Phenolic with plaster system covering Figure 30: Phenolic with concrete covering Figure 31: Phenolic with stone wool covering Figure 32: Phenolic with fibre cement covering Figure 33: Phenolic with plywood covering Figure 34: Phenolic with 9,5 mm gypsum covering Figure 35: Phenolic with 12,5 mm gypsum covering Page: 16 of 31

17 4.2.4 Paper fibre Figure 36: Paper fibre with a covering of cement bonded wood wool and plaster system Figure 37: Paper fibre with a covering of cement bonded wood wool Figure 38: Paper fibre with 12,5 mm gypsum covering Figure 39: Paper fibre with plywood covering Page: 17 of 31

18 4.2.5 Wood fibre Figure 40: No insulation, only a covering of cement bonded wood wool and plaster system Figure 41: Wood fibre with a covering of cement bonded wood wool Figure 42: Wood fibre with 12,5 mm gypsum covering Figure 43: Wood fibre with a covering of rigid wood fibre board and plaster system Page: 18 of 31

19 4.2.6 Overview of visual observations (damage to substrate) Insulation material EPS PUR Phenolic Paper fibre Wood fibre Covering Damage to substrate (if any) 20,0 mm bricks with mortar EPS shrunken and melted in a large area 12,0-16,0 mm concrete rendering EPS completely burned away 12,0 mm plaster system with reinforcing mesh EPS melted in a large area 45,0 mm stone wool board (30 kg/m³) EPS partly shrunken and melted 10,0 mm fibre cement planks mounted with overlap Most of the EPS melted 9,5 mm wind stopping gypsum board Almost all EPS burned away 9,0 mm water proof plywood EPS completely burned away 12,5 mm gypsum board EPS melted along the joint 20,0 mm bricks with mortar No damage 12,0-16,0 mm concrete rendering PUR charred and shrunken approx. 20 mm 12,0 mm plaster system with reinforcing mesh PUR charred and shrunken approx mm 45,0 mm stone wool board (30 kg/m³) PUR charred and shrunken approx mm 10,0 mm fibre cement planks mounted with overlap PUR charred along joints. Shrunken approx mm 9,0 mm water proof plywood PUR charred and shrunken approx. 15 mm 9,5 mm wind stopping gypsum board No damage 12,5 mm gypsum board No damage 20,0 mm bricks with mortar Light discolouration in a thin layer 12,0-16,0 mm concrete rendering Phenolic insulation charred approx. 15 mm 12,0 mm plaster system with reinforcing mesh Phenolic insulation charred approx. 10 mm 45,0 mm stone wool board (30 kg/m³) Phenolic insulation charred approx. 15 mm 10,0 mm fibre cement planks mounted with overlap Phenolic insulation charred along the plank joints 9,0 mm water proof plywood Phenolic insulation charred approx. 10 mm 9,5 mm wind stopping gypsum board No damage 12,5 mm gypsum board No damage 25,0 mm cement bonded wood wool board supplied Light discolouration along the joint with reinforced plaster system 25,0 mm cement bonded wood wool board Charring along a crack line in the perimeter of the wood wool board. Light discolouration along the joint 12,5 mm gypsum board No damage 12,0 mm water proof plywood Discolouration 25,0 mm cement bonded wood wool board supplied No insulation in the specimen with reinforced plaster system 25,0 mm cement bonded wood wool board Charring along a crack line in the perimeter of the wood wool board. Light discolouration along the joint 12,5 mm gypsum board Very light discolouration 60,0 mm rigid wood fibre insulation board supplied No damage with reinforced plaster system Page: 19 of 31

20 5 Discussion A total of 32 different combinations of covering and substrate (insulation material) were tested leading to production of a large amount of data. Though, each combination was only tested once (one single test specimen). Therefore, it is not possible to draw solid conclusions for specific material combinations. Moreover, the size of test specimens was relatively small (exposed area of 500 mm x 500 mm) which induce a significant source of uncertainty when the results are related to real scale buildings, especially when considering mechanical behaviour. That is, results and conclusions in the present report may only be considered as indicative. The main purpose of a fire protecting covering is to avoid combustible substrates from contributing to the fire. The fire protection ability is defined be the evaluation criteria on temperature rise behind the covering and damage to the substrate. The fire tests described in the present report indicated that a covering may fail the standardised criteria without any sign of combustion in the substrate. That is, the covering failed the test but the substrate did not contribute to the fire. Regarding EPS insulation substrate, it seems obvious to claim that the covering test will always fail the damage criterion before failing the temperature criterion. This is due to the fact that EPS has a melting/shrinkage temperature in the area of C. Due to bound water and a porous structure, most mineral based coverings will reach a temperature of 100 C on the non-exposed side during the 10 minute covering test. The temperature might not exceed 100 C for the rest of the test period but the test is failed because the EPS is damaged. This illustrates that the damage criterion is not applicable to evaluate whether a covering is capable of avoiding the substrate from contributing to the fire. Since the visual inspection of damages to the insulation materials was only done after (and not during) the 10 minute fire test, it was not possible to identify the time at which the insulation materials were damaged. It may be claimed, that shrinkage of the insulation pose a risk since it leads to cavities occurring between covering and insulation where a fire may spread. Though, if the covering is capable of protecting the insulation from ignition there is no risk of fire spreading through the cavities. Moreover, cavities are often part of the initial façade design in order to ventilate the construction. The temperature criterion may be considered to be more appropriate than the damage criterion since combustion in the substrate is directly related to a certain critical temperature rise. Though, combustible insulation materials have different ignition temperatures, that is, in order to comply with the overall purpose of the covering (avoid the substrate from contributing to the fire), the temperature criterion should be based on the ignition temperature of the actual substrate. If the ignition temperature in not known it seems reasonable to use the 250/270 C temperature rise defined in the standard since most solid materials have ignition temperatures for short exposures above 300 C [13]. Though, the ignition temperature for EPS may be lower (see Appendix 2 - Ignition temperatures of insulation materials). Ignition temperatures for the specific insulation materials used in the fire tests are not known to the author but comparable generic insulation materials are reported to have ignition temperatures in the range C for piloted ignition and C for non-piloted ignition (self-ignition) (see Appendix 2 - Ignition temperatures of insulation materials). Page: 20 of 31

21 Considering performance based fire safety design, a 10 minute protection time may not be applicable. Instead, the level of fire protection applied to combustible insulation materials may be chosen based on the combustibility (including the ignition temperature) and the risk class of the building as illustrated in the figure below. Figure 44: Proposed concept for the relationship between insulation properties and choice of protection [5] Considering the temperature increase measured in the 32 test specimens during the present fire tests, the most distinct phenomenon is a flattening of the temperature curve when it reaches approximately 100 C. The phenomenon is seen in all specimens with coverings with a high content of chemically bound water (plaster, gypsum and fibre cement). The obvious explanation is that the energy infused by the test furnace is absorbed by the water when it changes phase from solid to gas. Until most of the water is boiled out the temperature in the covering is relatively constant. For a given type of covering material, the mass of bound water is directly proportional to the mass of the covering. Hence, if the thickness of the covering is increased, the duration of the water boiling period increases. Off course, the fraction of bound water (m water /m total ) differs from one material to another but this is not considered in the present study. The temperature increase behind the covering is not determined by the covering alone, it is also affected by the behaviour of the substrate. Energy passing through the covering may be diverted in the substrate by conduction and mass transport. The conductive energy transfer is determined by the thermal conductivity coefficient and the heat capacity of the substrate. The energy transfer by mass transport (primarily water vapour) to the substrate is determined by the porosity of the substrate including any facings which to some extent may be air tight. Mass transport may also take place in any cavities, joints or cracks. Energy transfer may also be caused by hot air flowing through the materials. The three cellular plastic insulation materials (EPS, PUR and phenolic) were tested with a 45 mm stone wool covering. Stone wool is usually considered to have reasonable fire protective properties, but after the tests, a significant damage to the insulation was observed. The damage was probably caused be hot air forced through the stone wool by the positive pressure in the furnace. The pressure may not be as high in a real façade fire, though the gas flow in a window plume impinging to the façade has the potential to create pressure differences and thereby force hot air through leakages. Therefore, an important property of a fire protecting covering is to be sufficiently air tight at least if the covering has to pass the covering test. Page: 21 of 31

22 Based on the discussion above it may be concluded, that the present version of the covering classification standard does not meet its purpose when façade systems fail on the damage criterion alone. Take an imaginary façade system built up by polystyrene insulation and a covering. If the covering is sufficiently air tight and has a high amount of bound water it may be capable of protection the polystyrene insulation against ignition for a considerable period Moreover, it may be asserted that the test standard prescribes unrealistic conditions in terms of heat exposure (standard fire curve as opposed to an external window plume) and orientation (horizontally as opposed to vertically). Thus, the standard treats products designed merely for facades as if they were to be used for all applications in the built environment. In most European countries the prescriptive requirements for external surfaces on facades are based solely on reaction-to-fire on product level (end-use conditions). Often a class B, C or D is deemed to be sufficient, that is, the reaction-to-fire properties are evaluated using the Single Burning Item (SBI) test and the Small Flame test (with the SBI test being most crucial to the classification). The SBI test is not described in detail in this report but it should be noted that it is not at all comparable to the covering test. The two tests are very different in terms of important factors like heat/fire exposure, furnace/room pressure, specimen size, orientation, test duration, evaluation criteria etc. Therefore, it is not possible to predict the result of a covering test on the basis of SBI test results alone. A particular risk which is difficult to address in the current fire test system is the risk of failure of the covering joints. In several fire tests described in the present report, the joints turned out to be the weakest part of the covering. It should be noted, that joints in the test specimens were not done according to the manufacturer of the covering product, that is, no tape or filling was applied to the joints and there was no support along the back. This might be very different from the design used for fire classification testing where great care is taken when producing the test specimens. Though, it is questionable whether the same quality is achieved in real life construction sites. The risk of joint failure must be handled when using most board type coverings. Especially when the underlying insulation material has combustibility properties similar to EPS where just a minor opening in the covering may lead to severe fire spread in the insulation. The risk of joint failure is expected to be even more distinct when testing in larger scale since the mechanical behaviour gets more important. Page: 22 of 31

23 6 Conclusion This report describes 8 fire tests with a total of 32 specimens which were performed to demonstrate the performance of various combinations of combustible insulation materials protected with coverings. The test procedure was based on EN 14135:2004 Coverings. Determination of fire protection ability. Conclusions may only be considered as indicative since no tests were repeated. Based on the results from the fire tests it is claimed that the damage criterion used for evaluation of K 1 10 coverings may be inappropriate when an insulation material based on cellular plastic is used as substrate. Instead it may be more reasonable to use a substrate specific temperature defined by the critical temperature at which the substrate (insulation material) ignites and combust. Though, the critical temperature is very difficult to determine. Alternatively, the damage criterion should be moderated to allow for harmless damage and to consider only a defined critical damage. Considering the existing standards for classifying a K 1 10 covering, the following simple recommendations may be given when a designer has to choose or develop a covering for protection of a combustible insulation material: Choose a covering material with a high fraction of bound water unless the substrate is sensible to temperatures below 100 C Increase the thickness (and hence mass) of the covering Design the covering to be air tight and to stay air tight when heated Pay special attention to joints or avoid them Suggestions for future work are given in the following chapter. Page: 23 of 31

24 7 Suggestions for future work Perform more tests using some of the combinations already tested. Purpose: To provide more data and thereby allow for more specific conclusions on selected combinations. Perform SBI tests, full scale covering tests and façade tests of selected combinations from the present tests. Purpose: To provide comparable data on the correlation/difference between the different scales. Thereby, it may be possible to assess to what extent fire testing in small scale may be used to predict the performance of a façade system exposed to a full scale façade test. Investigate the influence of various types of facings. Purpose: To assess whether the choice of facing should be taken into account when choosing the appropriate covering. Investigate the performance of various types of joints and sealing principles. Purpose: To provide the industry with knowledge on how to optimize the fire protection ability of a covering. Develop a method to quantify the energy contribution to the fire from insulation materials behind weak coverings, that is, combinations of covering and insulation material which do not fulfil the covering criteria. Purpose: To assess whether the covering criteria may be changed without compromising the purpose of the covering (does the substrate contribute to the fire?). Propose a change of the classification criteria for a covering (EN 14135). Preferably, the qualitative substrate damage criterion should be changed to a quantitative ignition and/or contribution to fire criterion. Purpose: To allow for fire classification of façade systems with more emphasis on the fire performance of the specific insulation material in use. Develop the concept illustrated in Figure 44 towards an operable tool. Purpose: To allow for a more risk based approach to fire safety assessment of façade designs. Page: 24 of 31

25 8 References [1] N. White and M. Delichatsios, Fire Hazards of Exterior Wall Assemblies Containing Combustible Components, CSIRO and FireSERT, University of Ulster, EP142293, Jun [2] B. Meacham, J. Echeverria, R. Cheng, and B. Poole, Fire Safety Challenges of Green Buildings, The Fire Protection Research Foundation, Quincy, MA, USA, Nov [3] U. Krause, W. Grosshandler, and L. Gritzo, The International FORUM of Fire Research Directors: A position paper on sustainability and fire safety, Fire Saf. J., vol. 2012, no. 49, pp , Feb [4] J. Tidwell and J. J. Murphy, Bridging the Gap Fire Safety and Green Buildings, National Association of State Fire Marshals, Aug [5] A. Dragsted and A. B. Vestergaard, A new approach to the Danish guidelines for fire protection of combustible insulation, presented at the 1st International Seminar for Fire Safety of Facades, Paris, 2013, vol [6] J. M. Davies, Lightweight Sandwich Construction. Blackwell Science Ltd., [7] V. Babrauskas, Ignition Handbook. Inter science Communications Ltd., [8] M. Pfundstein, R. Gellert, M. H. Spitzner, and A. Rudolphi, Insulating Materials: Principles, Materials, Applications, 1st edition. Birkhäuser - Publishers for Architecture, [9] T. D. Jensen and A. Dragsted, InnoBYG small scale demonstration tests - Part 1 (EPS), DBI - Danish Institute of Fire and Security Technology, Test report, Jan [10] T. D. Jensen and A. Dragsted, InnoBYG small scale demonstration tests - Part 2 (Wood/paper), DBI - Danish Institute of Fire and Security Technology, Test report, Jul [11] T. D. Jensen and A. Dragsted, InnoBYG small scale demonstration tests - Part 3 (PUR), DBI - Danish Institute of Fire and Security Technology, Test report, Jul [12] T. D. Jensen and A. Dragsted, InnoBYG small scale demonstration tests - Part 4 (phenolic), DBI - Danish Institute of Fire and Security Technology, Test report, Jul [13] V. Babrauskas, Ignition: A Century of Research and an Assessment of Our Current Status, J. FIRE Prot. Eng., vol. 2007, no. 17, pp , Aug Page: 25 of 31

26 9 Acknowledgements The fire tests (staff time) were funded by InnoBYG Innovation Network for Energy Efficient and Sustainable Construction. Material sponsors: - Sundolitt - Sto Denmark - Panelbyg ApS - Kingspan Danmark - Papiruld Danmark - Homatherm - Nordisk NHL Page: 26 of 31

27 Appendix 1 - Temperature measurements behind coverings Page: 27 of 31

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31 Appendix 2 - Ignition temperatures of insulation materials In relation to the temperature rise criterion, it should be noted that a significant variation of ignition temperatures for the different insulation materials are reported in the literature. Examples are listed in the table below. Material Ignition temperature Piloted ignition Self-ignition (spontaneous ignition) EPS C [6] 490 C [6] C [7] PUR C [6] C [6] C [7] PF 490 C [6] 450 C [6] Cellulose fibre C [7] 280 C [8] 4 Ignition temperatures of loose fill cellulose insulation are highly dependent on density and the use of fire retardants. Page: 31 of 31