Fire test of ventilated and unventilated wooden façades

Fire test of ventilated and unventilated wooden façades Lars Boström, Charlotta Skarin, Mathieu Duny, Robert McNamee SP Technical Research Institute of Sweden SP Report 216:16

Fire test of ventilated and unventilated wooden façades Fire test of ventilated and unventilated wooden façadesfire test of ventilated and unventilated wooden façades Lars Boström, Charlotta Skarin, Mathieu Duny, Robert McNamee

3 Abstract Fire test of ventilated and unventilated wooden façades Three large scale façade tests in accordance with SP Fire 15 as well as an ad hoc SBI test have been carried out. The façade tests included an inert façade made of lightweight concrete, one façade with a plywood cladding and finally a façade with plywood cladding with a fully ventilated cavity behind the cladding. The SBI test was made with plywood without ventilation cavity. The aim of the tests was to perform well controlled tests with numerous of measurements including heat release rate, heat from the combustion chamber, temperature on the façade surface, heat flux, plume temperatures and temperatures in the ventilation cavity. The results from the tests will be used for validation of simulation techniques as well as input for further development of the façade test methodology. Conclusions from the study were that the surface temperature for charring of the plywood cladding in this configuration was in the region of C and that the energy release originated from the façade during the test was almost twice as high when there was a 2 mm wide cavity behind the plywood cladding. Key words: fire test, facade, wood, ventilation cavity SP Sveriges Tekniska Forskningsinstitut SP Technical Research Institute of Sweden SP Report 216:16 ISBN 978-91-88349-2- ISSN 284-5172 Borås 216

4 Contents Abstract 3 Contents 4 Preface 5 Summary 6 1 Introduction 7 1.1 Background 7 1.2 Limitations 7 2 Experimental setup SP Fire 15 9 2.1 Test method 9 2.2 Test specimens 11 2.3 Instrumentation and measurements 11 3 Experimental setup SBI 14 4 Test results 16 4.1 General observations 16 4.2 Fire source 2 4.3 Heat release rate 23 4.4 Thermal exposure on the façade above the combustion chamber 24 4.5 Thermal exposure and heat flux one storey above the combustion chamber 25 4.6 Thermal exposure two storeys above the combustion chamber 27 4.7 Surface temperature 28 4.7.1 Temperature 1 mm above the combustion chamber 28 4.7.2 Temperature 27 mm above the combustion chamber 31 4.7.3 Temperature 345 mm above the combustion chamber 34 4.7.4 Temperature 4 mm above the combustion chamber 37 4.7.5 Temperature 5 mm above the combustion chamber 4 4.8 Plume temperature at different heights 43 4.8.1 Plume temperature 1 mm above the combustion chamber 43 4.8.2 Air temperature 27 mm above the combustion chamber 47 4.8.3 Air temperature 345 mm above fuel source 51 4.8.4 Air temperature 4 mm above combustion chamber 55 4.8.5 Air temperature 5 mm above combustion chamber 59 4.9 Temperature below the eave 63 4.1 Results from SBI test 65 5 Analysis and discussion 7 5.1 Fire source 7 5.2 Fire spread on the surface 71 5.2.1 Position of measurements 71 5.2.2 Measurement of fire spread on a material 71 5.3 Effect of ventilation cavity 76 6 Conclusions 78 7 References 79

5 Preface The façade is an important part of a building. It forms the envelope of the building, and has several functions. When combustible materials are used, or there are other risks in case of fire, i.e. large parts of the façade may fall down, it is necessary to evaluate the behavior of the façade when exposed to fire. The present project has mainly been an experimental study, involving large test specimens. We would like to thank the eminent group of technicians who have taken care of all practical details within a very pressed time schedule, no one named, no one forgotten. We would also like to thank Mr. Pär Johansson for valuable discussions on what, how and where to do all the different measurements and what the results might represent. The project is part of a collaboration between Centre Scientifique et Technique de Bâtiment (CSTB) in Paris, France, and SP Fire Research in Borås, Sweden, who both have financially supported the study.

6 Summary Three well documented façade fire tests in accordance with SP Fire 15 have been carried out. The tests consisted of one inert façade, one façade with a plywood cladding and finally one façade with a plywood cladding with a fully ventilated cavity behind the cladding. In all three tests numerous of measurements were made such as heat release rate, heat from the combustion chamber, surface temperatures, plume temperatures, heat flux, and temperatures in the ventilation cavity. In addition to the full scale façade tests, a SBI test was made in order to evaluate how flame spread on the surface can be determined by temperature measurements. There are some different aims with the study. Firstly, the experiments should be well documented and measurements should be done so the results can be used for validation of different simulation techniques, such as CFD (Computational Fluid Dynamics) modelling. Another aim was to assemble good data for the ongoing development of the next generation façade test methodology. Currently there are many different façade test methods, often national methods, which makes it difficult for industry. There is thus a demand for a harmonized test method. In the present study techniques for measurement of flame spread on a surface as well as how to measure or determine the heat exposure to the test specimen has been investigated. The present report is mainly an assembly of test results and a description of the tests carried out. The analysis of the results is limited, and more extended analysis will be published elsewhere. Furthermore, the tests made are limited to one type of combustible material, i.e. plywood, and thus more data will be needed for validation of the technique to measure fire spread on the surface and in cavities. Conclusions from the study were that the surface temperature for charring of the plywood cladding in this configuration was in the region of C and that the energy release originated from the façade during the test was almost twice as high when there was a 2 mm wide cavity behind the plywood cladding.

7 1 Introduction 1.1 Background Façades are important from several perspectives for a building. It forms the envelope of the building and shall thus be the protection towards the outdoor climate, it is an important part controlling the energy demand of the building and it is also the face of the building and has thus architectural requirements. The façade has thus a number of functions for the building. During the last decades the use of combustible materials in buildings has increased, partly as a consequence of higher demands on energy efficient buildings. In order to determine the fire risks for different types of façade systems a good and reliable test methodology is needed. There are presently a large number of different test methods used around the world [1] which all have certain advantages but also disadvantages. In Sweden the test method SP Fire 15 [2] is currently used, but it is currently under a major revision. The Swedish test method was originally developed in the middle of the 198-ties as a part of a large study including burning of 14 façades with a fully developed room fire as a heat source [3]. The fire exposure was optimised in the SP Fire 15 test to correspond to the large test. In the large scale tests the fire load density was 11 MJ/m 2 of total surface area of the enclosure. The enclosure dimensions were 4 x 2.2 x 2.6 m 3 with the opening factor.6 m 1/2. During the tests approximately 5% of the fuel was burning outside the chamber. This factor is dependent on the geometry of the enclosure and on fuel parameters such as composition and geometry. In the SP Fire 15 test the fire source is 6 litres of heptane burning in trays with attached flame suppressors. The present study has the aim to give input data for the revision of SP Fire 15 as well as contribute with valuable data for validation of CFD modelling (Computational Fluid Dynamics). Another part of the study is to measure the difference in flame spread of combustible façade claddings with and without a ventilation cavity. One important aspect is how the flame spread on the surface, and in the cavity shall be determined. Presently the flame spread is determined by visual observations after the fire test in SP Fire 15, i.e. by visual observation of what type of damage has occurred, and how high up on the façade. This is a blunt tool, which in some cases is dependent on the persons doing the observation especially when much soot, tar and char is mixed in the area where the flame front is. In other methods measurements or estimations are done in different ways. In the British method BS 8414-1 [4] temperature is measured a distance of 5 mm from the surface at different heights. In the international standard ISO 13785-2 [5] a surface temperature as well as a temperature 1 mm from the surface are measured, in addition to heat flux measurements at different heights. 1.2 Limitations Only one test has been performed on each type of test setup. Even if the tests have been performed under controlled conditions, the fire behaviour in the combustion chamber and how it is evolving and protrude out of the combustion chamber might slightly change from test to test since it is a free burning test, i.e. it is not possible to control how the burning takes place and evolves in the combustion chamber. The aim of the present study was mainly to collect data for future analysis. The content of this report is therefore primarily a presentation of all measurements done, and a short

8 discussion on trends observed. Only a limited analysis of the results is included in the present report. These data will be used in other projects aiming for more thorough analysis.

9 2 Experimental setup SP Fire 15 2.1 Test method The experiments has been based on the Swedish test method SP Fire 15 [2]. In the present tests the façade cladding has been mounted on a lightweight concrete backing with the maximum density of kg/m 3. Openings for two fictitious windows have been used in the tests. The total area of the façade was 4 x 6 m (width x height). A principle drawing of the façade rig is presented in Figure 1. Fictitious window A Lightweight concrete wall Steel frame Eave Storey 1 Storey 2 Storey 3 27 27 Heat flux meter Fire Room 15 59 71 1 1 1 1 671 A Fire Source 1245 151 1245 Section A-A mm Figure 1. Test rig used in SP Fire 15 [2]. The fire source was two trays with the dimensions x mm filled with 3 litres of heptane each, placed so the total size of the fire source was x mm. On top of the tray a flame suppressor was installed, see figure 2.

1 Flame suppressor Heptane Water Tray of steel sheet x x mm Water to raise the surface of the heptane fuel to the lower edge of the flame suppressor at the start of the fire test. Fire Source - Heptane mm 2 Flame suppressor of perforated steel sheet, hole Ø=25 mm, center distance 4 mm. mm Figure 2. Principle drawing of the fire source. There is an air intake directly behind the fuel source with the dimensions 314 x mm, centrally placed 5 mm from the back wall of the fire room, see figure 3. Figure 3. Drawing of the fire room. The test rig was placed in the large fire hall at SP Fire Research in Borås, Sweden. The fuel trays as well as the heptane and water used were conditioned to the room temperature before any tests were performed. When filling the fuel into the trays first the right amount of heptane was filled. Thereafter water was added until the liquid surface reached the bottom surface of the flame suppressor.

11 Even when the test is carried out indoors, in the large test hall, the ventilation in the hall creates a wind. Some measurements have been done showing that the wind is in the order of.1-.5 m/s, and in the direction parallel to the face of the façade rig, going from right to left side of the façade. 2.2 Test specimens Three different tests were carried out. The first test was made without any cladding on the lightweight concrete, i.e. an inert façade. In the second test a cladding of 24 mm thick plywood was mounted directly onto the lightweight concrete, i.e. no ventilation cavity behind the plywood. In the third test plywood was mounted with a ventilation cavity of approximately 2 mm between the lightweight concrete and the plywood. The plywood was bought at a local store for building materials, and it was a standard product for the Swedish market, with the dimensions 1 x 2 mm 2. Samples were taken from the plywood for measurement of moisture content and density. These measurements were made approximately at the time of the tests. The plywood had a moisture content of 6.5 % and the density at that moisture content was determined to 489 kg/m 3. The plywood was mounted on the whole front surface of the test rig, except at the fictitious windows. In order to get an air cavity behind the plywood for Test 3, strips of mineral wool, with density of 18 kg/m 3, was used. These strips had a thickness of 2 mm (giving an air gap of 2 mm) and a width of approximately 3 mm. The mineral wool strips where mounted along all vertical edges of the plywood boards, i.e. they were not acting as fire stops in the vertical direction, although they were acting as fire stops in horizontal direction in the cavity. 2.3 Instrumentation and measurements The tests were performed with a lot of extra instrumentation in addition to the required instrumentation in accordance with SP Fire 15. Figure 4 shows the placement of different measuring devices on the surface of the test specimens. Devices C1-C19 are.5 mm wire diameter thermocouples, type K. The measuring point of the thermocouples were made with Quick-Tips, i.e. a small metal ring, diameter 3 mm and length 2 mm, that clamps the two wires together. The weight of a this size Quick-Tip is.1 g. In all tests the tip of the thermocouple (the Quick-Tip) was pressed into the surface of the exposed surface of the façade, i.e. the measurement represents approximately the surface temperature of the façade. In Test 3, plywood with a cavity, thermocouples were also mounted in the plywood surface on the cavity side at the same positions as on the front surface. Devices PT1-PT6 are conventional x mm plate thermometers, i.e. the same devices as used in fire resistance furnaces, see for example EN 1363-1 [6]. PT1-PT3 were placed on a distance mm from the combustion chamber and pointing towards the fire, see also Figure 7. PT4-PT6 were mounted on the surface of the façade and pointing outwards. Plate thermometers have an time constant of between 1 and 2 minutes [7].

12 Device HF1 is a Schmidt Boelter heat flux meter. The device was mounted flush with the surface of the fictitious window which is specified in SP Fire 15 [2]. Figure 4. Placement of measuring devices on the test specimens. PT1-PT3 are placed mm outwards from the combustion chamber and directed towards the fire. In addition to these measurements temperature was also measured at a distance and mm from the façade with.5 mm type K thermocouples with a welded tip. These temperature measurements were performed at the same positions as thermocouples C2, C3, C6, C7, C13, C14, C17 and C18. The same positions were also used in Test 3 in the ventilation cavity where the thermocouples were mounted in the centre between the lightweight concrete and the plywood, that is 1 mm from the plywood surface. Furthermore, as specified in SP Fire 15, two.5 mm type K thermocouples with a welded tip were positioned mm below the eave at the top of the façade rig (see figure 1), at a distance mm and mm from the façade surface, and at the centre line of the specimen.

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14 3 Experimental setup SBI A complimentary test was performed with the Single Burning Item (SBI) method, EN 13823 [8]. The SBI test is not a suitable method for testing façades due to several reasons, but it can be used for evaluation of the temperature measurements used for determination of fire spread on the façade surface. In the test two panels are used, one large wing with the dimensions 1. x 1.5 m 2 (width x height), and a small wing with the dimensions.49 x 1.5 m 2. In the bottom corner between the two panels a sand burner is used, which is burning with a constant effect of 3 kw. In the present study a total of 4 thermocouples were mounted on the surface of the test specimen, 2 thermocouples on the large wing, and 2 thermocouples on the small wing, see figure 5. The thermocouples were positioned at different heights, as shown in figure 5, and at different distance from the corner (,, and mm). Figure 5. Position of temperature measurements and type of hot tip of the thermocouples. The thermocouples were all of the same type,.5 mm diameter wire and of type K. The hot tip of the thermocouples, i.e. the tip where the two wires are connected, where prepared in four different ways.

15 At a height of mm and 7 mm above the floor level the tip was made with a Quick- Tip, i.e. a cylinder with diameter 3 mm and length 2 mm and a weight of.1 g, is clamped around the two wires. The Quick-Tip is then pressed into the surface of the specimen so it will be flush with the surface. This is a robust method which enables the measuring point to be pressed into the surface. Although, the thermal inertia is higher due to the mass of the Quick-Tip, compared with welded wires, and thus the response time is slightly longer for this type of thermocouple. At the height mm and 9 mm the thermocouple was welded to a copper disc with diameter 1 mm, i.e. the same type used for measurement of surface temperature in fire resistance tests in accordance with EN 1363-1 [6], but without using the insulation pad. The thermocouple and the copper disc were attached to the surface by clamping and tape. With this type of thermocouple the measured temperature is in principle averaged over a larger area, i.e. the area of the highly conductive copper disc. Although, the copper disc protects the underlying material for radiation from the fire, but it may be possible to detect eventual fire spread on the surface around the copper disc. At the height mm and mm a welded tip of the thermocouples were used. The wire was attached to the test specimen by clamping and tape. This type of thermocouple tip has the lowest thermal inertia and thus it gives the fastest response time in this study. Although, it is more difficult to mount it flush to the surface for estimations of surface temperature. At the height 8 mm the thermocouples were welded to a horizontal steel wire, i.e. all thermocouples were fixed to the same steel wire. The steel wire was clamped to the test specimen. The idea with this type of mounting was mainly to have a method for easy mounting of thermocouples.

16 4 Test results 4.1 General observations Three tests were performed indoors in the large test hall at SP. In Test 1 the backing material of the façade rig consisted of lightweight concrete and was used without any further cladding. In Test 2 the lightweight concrete was covered with the plywood cladding. In Test 3 the same type of plywood cladding was used, with a 2 mm air gap, cavity, between the lightweight concrete and the plywood. The lightweight concrete on the façade rig, i.e. the inert façade, was in equilibrium with approximately 5 % relative humidity, and had a density of 55 kg/m 3. The moisture content and the density of the plywood was measured at the time of testing. The moisture content was 6.5 % and the density at that moisture content was determined to 489 kg/m 3. Table 1 gives some general information regarding the three tests made. Table 1. General information on the tests Test 1 Test 2 Test 3 Test date 215-11-26 (morning) 215-11-26 (afternoon) 215-11-27 (morning) Initial air temperature 18.8 C 17.3 C 18. C Initial relative humidity 38 % 4 % 49 % Temperature of heptane and water 19.2 C 16.2 C 15.9 C In tables 2-4 the visual observations made during the test are presented. It shall be noted that the visual observations represent the observations made during the tests, and that the actual issue observed may have occurred earlier than the noted time. Table 2. Visual observations during Test 1 inert façade. Time min:s Observations : The fire source of heptane is ignited. The test starts. 3:3 Smoke emerges out from the fire room. 4: Dark smoke emerges out from the fire room. 4:1 Flames and dark smoke emerge out from the fire room. 4:35 Some flames reach up to the lower edge of the lower window opening. 5:3 Some flames reach up to the upper edge of the lower window opening. 7: Flames reach half the height of the façade. 8:2 Flames reach up to the lower edge of the upper window opening. 1:3 Flames reach half the height of the façade. 12:5 Some flames reach up to the lower edge of the upper window opening. 14: Some flames reach just above the lower edge of the upper window opening. 15:3 Some flames reach up to the lower edge of the upper window opening. 16:5 The flames cease. 17: Flames reach just out from the fire room. Dark smoke comes out from the fire room. 18: The test terminates. The fire source has become extinct. The test specimen is extinguished with water.

17 Table 3. Visual observations during Test 2 plywood without cavity. Time min:s Observations : The fire source of heptane is ignited. The test starts. 3: Smoke emerges out from the fire room. 4:1 Flames and dark smoke emerge out from the fire room. 4:3 Flames reach up to the lower edge of the lower window opening. 5: Flames reach above the upper edge of the lower window opening. 5:25 Flames reach the eave. 5:5 It burns along the upper edge of the lower window opening. The plywood panel between the window openings glows. 7: It burns in the lower left corner of the upper window opening. 9: Flames reach up to the lower edge of the upper window opening. 1: Flames cease and reach half the height of the façade. 11:45 Flames along the right side of the façade reach up to the upper edge of the upper window opening. 12:15 Flames reach the eave. It burns in the lower right corner of the upper window opening. 13: It burns along the left side of the upper window opening. 13:45 It burns in the plywood panel on the right side between the window openings. 14:3 Flames along the left side of the façade reach up to the lower edge of the upper window opening. 15:3 Flames reach half the height of the façade. Small glowing pieces from the plywood fall down in front of the façade. 16: Flames reach up to the upper edge of the lower window opening. 16:15 Flames reach up to the lower edge of the lower window opening. 16:3 Flames reach just out from the fire room. 17:15 The test terminates. The fire source has become extinct. The test specimen is extinguished with water.

18 Table 4. Visual observations during Test 3 plywood with cavity. Time min:s Observations : The fire source of heptane is ignited. The test starts. 3:- Smoke emerges out from the fire room. 4: 4:25 Flames and dark smoke emerge out from the fire room. 5: Flames reach up to the lower edge of the lower window opening. 5:45 Flames reach up to the upper edge of the upper window opening. 6: It burns along the upper edge of the lower window opening 6:3 It burns along the lower edge of the upper window opening along the left side. 7:3 Flames reach the eave. 9:4 It burns along the upper edge of the lower window opening and along the lower edge of the upper window opening. 1:3 Flames reach almost to the eave. 11: It burns along the left side of the upper window opening. 11:2 It burns in the upper left corner of the upper window opening. 11:4 It burns along the upper edge of the upper window opening. 12:1 The lower left panel is not attached to the wall on the right side. 12:4 Flames reach the eave. 13: Part from the lower left panel falls down in front of the façade. 13:4 Some small burning pieces on the floor in front of the façade. 14: Flames reach above the eave. 14:2 It glows in the air gap by the eave. 16: Flames above the eave. 17: Flames cease. Dark smoke. 17:45 The test terminates. The fire source has become extinct. The test specimen is extinguished with water. Photographs taken during the tests are presented in figure 6. It can be noted that visual observations on the flame spread can be difficult due the extensive smoke production during the tests.

19 Test 1. Time: 9: min:s Test 2. Time: 9: min:s Test 3. Time: 7: min:s Test 1. Time: 12: min:s Test 2. Time: 11: min:s Test 3. Time: 12: min:s Test 1. Time: 15: min:s Test 2. Time: 14: min:s Test 3. Time: 13: min:s Figure 6. Photos taken during the test, Test 1 to the left, Test 2 in the centre, and Test 3 to the right.

2 4.2 Fire source The temperature from the fire source was measured by three plate thermometers placed.5 m from the opening of the combustion chamber (measured from the inner side of the lightweight concrete). The plate thermometers were pointing towards the fire, and would thus measure the heat exposure mainly from the fire source, see figures 4 and 7. Air intake Fire source 71 59 PT (Plate thermometer) 1 Figure 7. Position of plate thermometers in front of the combustion chamber. The measured temperatures in front of the combustion chamber from each test are presented in figures 8 1. It is clearly shown in the growth phase in the figures that the flames from the combustion chamber is more intense on the left side compared with the right side in all tests, which also was noted visually during the tests. During the growth phase the buoyancy force in the plume is apparently not strong enough to create a vertical flow speed high enough to counteract the side winds in the laboratory. It can also be noted that it is generally hotter in the centre, but there are shorter periods during the tests where it is hotter on the left side.

21 8 Test 1 - inert facade 7 PT1 PT2 PT3 5 1 15 2 Figure 8. Temperature measured with plate thermometers.5 m from the combustion chamber in Test 1, inert façade. PT1 on left side, PT2 at the centre, and PT3 on the right side. 8 Test 2 - plywood without cavity 7 PT1 PT2 PT3 5 1 15 2 Figure 9. Temperature measured with plate thermometers.5 m from the combustion chamber in Test 2, plywood façade without ventilation gap. PT1 on left side, PT2 at the centre, and PT3 on the right side.

22 8 Test 3 - plywood with cavity 7 PT1 PT2 PT3 5 1 15 2 Figure 1. Temperature measured with plate thermometers.5 m from the combustion chamber in Test 3, plywood façade with a ventilation gap. PT1 on left side, PT2 at the centre, and PT3 on the right side. A mean temperature from the three plate thermometers in each test is shown in figure 11. The start of the third test was slower compared to the two first tests. Therefore a small time compensation of 3 seconds have been subtracted for the third test. The results show that the initial phase of the fire is very similar in all tests, and the duration of the tests is the same. Although there is a difference in the interval from 5 minutes up to 15 minutes, where the façade with plywood cladding had both the highest and lowest temperatures. The plywood façade with cavity gap showed the lowest temperatures in front of the combustion chamber.

23 8 Mean temperature from each test 7 Test 1 - inert facade Test 2 - plywood without ventilation Test 3 - plywood with ventilation 5 1 15 2 Figure 11. Mean temperature measured with plate thermometers.5 m from the combustion chamber. 4.3 Heat release rate The heat release rate was measured by collecting the exhaust gases in a hood above the façade test rig [9]. The measured heat release rate is presented in figure 12. It can be noted that the initial phase of the test, up to 5 minutes, is similar in all tests, i.e. no difference between a combustible surface and an inert façade. From 5 minutes up to 1 minutes, the behaviour of the two tests with plywood is similar, i.e. the ventilation cavity does not influence on the heat release rate. The heat release rate increases with approximately kw for the combustible façades compared with the inert one. After 1 minutes into the tests, the heat release rate start to increase again, and here a difference shows up between the unventilated plywood façade and the one with a ventilation cavity. After 15 minutes the peak is reached in Test 3, and the heat release rate is approximately kw higher compared to the peak value obtained with plywood façade without ventilation, and more than kw compared to the inert façade.

24 3 Heat release rate (kw) 2 1 Test 1 - Inert facade Test 2 - plywood without ventilation Test 3 - plywood with ventilation 5 1 15 2 Figure 12. Heat release rate measured during the fire tests. The total energy produced during the tests has been calculated as the area below the heat release curves. In Test 1 the total released energy was determined to 155 MJ, in Test 2 it was 187 MJ, and in Test 3 it was 214 MJ. Thus the additional energy from the plywood in Test 2 was 32 MJ, and in Test 3 the additional energy from the plywood was 59 MJ. This means that the additional energy from the plywood is almost doubled by the ventilation cavity. 4.4 Thermal exposure on the façade above the combustion chamber The thermal exposure was measured with a plate thermometer placed 75 mm above the upper edge of the combustion chamber, plate thermometer PT4 in figure 4. The plate thermometer was mounted on the façade surface pointing outwards. The measurement thus represent the heat exposure to the façade surface. The results from the three tests are presented in figure 13. It is clear that on the height 75 mm above the combustion chamber there is almost no difference in heat exposure towards the façade, i.e. if there is a contribution from the burning plywood to the thermal exposure 75 mm above the combustion chamber, it is minimal compared with the thermal exposure from the combustion chamber. Theoretically it is also possible that there is no contribution from combustion from the surface material originated in this zone as the diffusion flames from the combustion chamber has a very low oxygen content, i.e. release of pyrolysis gasses happens from the materials in this zone but the actual burning is higher up in the fire plume where more oxygen is blended in.

25 9 8 7 Test 1 - inert facade Test 2 - plywood without cavity Test 3 - plywood with cavity 5 1 15 2 Figure 13. Thermal exposure to the façade 75 mm above the combustion chamber as measured with a plate thermometers directed outwards. 4.5 Thermal exposure and heat flux one storey above the combustion chamber In the centre of the fictitious window one storey above the combustion chamber the thermal exposure towards the window was measured with a plate thermometer, i.e. 2.1 m above the upper edge of the opening to the combustion chamber, plate thermometer PT5 shown in figure 4. The measured temperatures are shown in figure 14. As expected the inert façade show the lowest temperature. Comparing the two plywood façades the temperature development is similar during the first 8 minutes, at that time the temperature is approximately 65 C. Thereafter the temperature in the window cavity during the test of the specimen without air cavity behind the plywood cladding starts to decrease slowly, whereas the temperature continues to increase for the specimen with a ventilation gap behind the plywood cladding and reaches a maximum of 75 C after 13 minutes. It is clear that a combustible façade cladding increases the heat exposure to the window one storey above the fire source, and that a ventilation gap behind the combustible cladding increases the heat exposure even further.

26 8 7 Test 1 - inert facade Test 2 - plywood without cavity test 3 - plywood with cavity 5 1 15 2 Figure 14. Thermal exposure one storey above the fire source measured with plate thermometer directed outwards. In addition to the temperature, the heat flux was measured with a Schmidt Boelter total heat flux meter at the centre of the fictitious window (gauge HF1 shown in figure 4). The measured heat fluxes are shown in figures 15 and 16. In figure 16, the mean heat flux for each minute is shown. Heat flux (kw/m 2 ) 9 8 7 6 5 4 3 2 1 Test 1 - inert facade Test 2 - plywood without cavity Test 3 - plywood with cavity 5 1 15 2 Figure 15. Heat flux measured one storey above the fire source.

27 8 7 Test 1 - inert facade Test 2 - plywood without cavity Test 3 - plywood with cavity 6 Heat flux (kw/m 2 ) 5 4 3 2 1 5 1 15 2 Figure 16. Heat flux (mean valued over one minute) measured one storey above the fire source. 4.6 Thermal exposure two storeys above the combustion chamber In the centre of the fictitious window two storeys above the combustion chamber the temperature exposure towards the window was measured with a plate thermometer, i.e. 4,8 m above the upper edge of the opening to the combustion chamber, plate thermometer PT6 shown in figure 4. The measured temperatures are shown in figure 17. At this height there is a clear difference between the tests. The ventilation cavity used in Test 3 has a significant effect on the heat exposure to the fictitious window two stories above the fire room. After 15 minutes the temperature is over C in Test 3. When comparing Test 1 and Test 2, i.e. the inert façade and the plywood cladding without cavity, the difference between these tests is relatively small. The façade with plywood cladding have a faster temperature rise between 5 and 7 minutes, after which the temperature stabilizes between -25 C. The inert façade has a slower temperature rise, but it reaches almost as high in temperature.

28 7 Test 1 - inert facade Test 2 - plywood without cavity Test 3 - plywood with cavity 5 1 15 2 Figure 17. Thermal exposure two storeys above the fire source measured with plate thermometer directed outwards. 4.7 Surface temperature The surface temperature was measured by.5 mm wire diameter thermocouples type K with a Quick-Tip as described above. The Quick-Tip of the thermocouple was forced into the surface, measuring the temperature of the surface during the test. A total of 19 thermocouples, C1-C19, was used on the fire exposed surface of the façade. In the third test, with a cavity behind the plywood cladding, an additional 19 thermocouples, C21- C39, were positioned on the cavity side of the plywood, opposite C1-C19. Thermocouple C21 is positioned opposite C1, thermocouple C22 opposed to C2, and so on. The positions of thermocouple C1-C19 are shown in figure 4. 4.7.1 Temperature 1 mm above the combustion chamber The measured temperatures on the surface at a level 1 mm above the edge of the opening of the combustion chamber are presented in figures 18 2, one figure for each test. The results clearly show that the fire was more severe on the left side.

29 7 Test 1 - inert facade C1 C2 C3 C4 5 1 15 2 Figure 18. Temperature on the surface during Test 1, 1 mm above the combustion chamber. 9 8 7 C1 C2 C3 C4 Test 2 - plywood without cavity 5 1 15 2 Figure 19. Temperature on the surface during Test 2, 1 mm above the combustion chamber.

3 9 8 Test 3 - plywood with cavity 7 C1 C2 C3 C4 5 1 15 2 Figure 2. Temperature on the surface during Test 3, 1 mm above the combustion chamber. 45 35 25 15 Test 3 - plywood with cavity Surface temperature in the cavity C21 C22 C23 C24 5 5 1 15 2 Figure 21. Temperature on the surface of the plywood in the cavity 1 mm above the combustion chamber. The temperature was measured on the surface of the plywood in the cavity during Test 3. The results from these measurements are shown in figure 21 above. Unlike the temperatures measured on the outward surface, which decreases at the end of the tests, the temperature increases rapidly.

31 Figure 22 display the mean temperature of all thermocouples at this level presented for each test, as well as the mean surface temperature on the plywood surface in the cavity. As the figure shows there is a substantial difference on the temperature level between the combustible cladding and the inert façade. 8 Mean surface temperature in each test 7 Mean test 1 Mean test 2 Mean test 3 Mean test 3 - cavity 5 1 15 2 Figure 22. Mean surface temperature at a level 1 mm above the upper edge of the combustion chamber. 4.7.2 Temperature 27 mm above the combustion chamber The measured temperatures on the surface at a level 27 mm above the edge of the opening of the combustion chamber are presented in figures 23 25, one figure for each test. The results clearly show that the fire was more severe on the left side.

32 45 Test 1 - inert facade 35 25 15 C5 C6 C7 C8 5 5 1 15 2 Figure 23. Temperature on the surface during Test 1, 27 mm above the combustion chamber. 8 Test 2 - plywood without cavity 7 C5 C6 C7 C8 5 1 15 2 Figure 24. Temperature on the surface during Test 2, 27 mm above the combustion chamber.

33 8 Test 3 - plywood with cavity 7 C5 C6 C7 C8 5 1 15 2 Figure 25. Temperature on the surface during Test 3, 27 mm above the combustion chamber. The temperature was measured on the surface of the plywood in the cavity during Test 3. The results from these measurements are shown in figure 26. Unlike the temperatures measured on the outward surface, which decreases at the end of the tests, the temperature increases rapidly. 18 16 14 12 8 6 Test 3 - plywood with cavity Surface temperature of plywood in cavity C25 C26 C27 C28 4 2 5 1 15 2 Figure 26. Temperature on the surface of the plywood in the cavity 27 mm above the combustion chamber.

34 In figure 27 the mean temperature of all thermocouples at this level presented for each test, as well as the mean surface temperature on the plywood surface in the cavity. As the figure shows there is a substantial difference on the temperature level between the combustible cladding and the inert façade. 7 Mean surface temperature in each test Mean test 1 Mean test 2 Mean test 3 Mean test 3 - cavity 5 1 15 2 Figure 27. Mean surface temperature at a level 27 mm above the upper edge of the combustion chamber. 4.7.3 Temperature 345 mm above the combustion chamber The measured temperatures on the surface at a level 345 mm above the edge of the opening of the combustion chamber are presented in figures 28 3, one figure for each test. The results clearly show that the fire was more severe on the left side.

35 35 Test 1 - inert facade 25 15 C9 C1 C11 5 5 1 15 2 Figure 28. Temperature on the surface during Test 1, 345 mm above the combustion chamber. 8 Test 2 - plywood without cavity 7 C9 C1 C11 5 1 15 2 Figure 29. Temperature on the surface during Test 2, 345 mm above the combustion chamber.

36 8 Test 3 - plywood with cavity 7 C9 C1 C11 5 1 15 2 Figure 3. Temperature on the surface during Test 3, 345 mm above the combustion chamber. The temperature was measured on the surface of the plywood in the cavity during Test 3. The results from these measurements are shown in figure 31. At this level the temperature in the surface of the plywood in the cavity do not show the same increasing temperatures at the end of the test. 9 8 7 Test 3 - plywood with cavity Surface temperature of plywood in cavity C29 C3 C31 5 1 15 2 Figure 31. Temperature on the surface of the plywood in the cavity 345 mm above the combustion chamber.

37 In figure 32 the mean temperature of all thermocouples at this level is presented for each test, as well as the mean surface temperature on the plywood surface in the cavity. As the figure shows there is a substantial difference on the temperature level between the combustible cladding and the inert façade. It can also be noted that the mean surface temperature in Test 3 is approximately the same on the outer surface as on the surface in the cavity at the end of the test. 8 7 Mean surface temperature in each test Mean test 1 Mean test 2 Mean test 3 Mean test 3 - cavity 5 1 15 2 Figure 32. Mean surface temperature at a level 345 mm above the upper edge of the combustion chamber. 4.7.4 Temperature 4 mm above the combustion chamber The measured temperatures on the surface at a level 4 mm above the edge of the opening of the combustion chamber are presented in figures 33 35, one figure for each test. The results clearly show that the fire was more severe on the left side in Test 2 and Test 3. In Test 1, however, the temperature readings show a more centrally exposure at this level.

38 18 16 14 12 8 6 4 C12 C13 C14 C15 Test 1 - inert facade 2 5 1 15 2 Figure 33. Temperature on the surface during Test 1, 4 mm above the combustion chamber. 7 Test 2 - plywood without cavity C12 C13 C14 C15 5 1 15 2 Figure 34. Temperature on the surface during Test 2, 4 mm above the combustion chamber.

39 7 Test 3 - plywood with cavity C12 C13 C14 C15 5 1 15 2 Figure 35. Temperature on the surface during Test 3, 4 mm above the combustion chamber. The temperature was measured on the surface of the plywood in the cavity during Test 3. The results from these measurements are shown in figure 36. At this level the temperature in the surface of the plywood in the cavity is continuously increasing, and accelerating at the end of the test. 12 8 6 4 Test 3 - plywood with cavity Surface temperature of plywood in cavity C32 C33 C34 C35 2 5 1 15 2 Figure 36. Temperature on the surface of the plywood in the cavity 4 mm above the combustion chamber.

4 In figure 37 the mean temperature of all thermocouples at this level is presented for each test, as well as the mean surface temperature on the plywood surface in the cavity. As the figure shows there is a substantial difference on the temperature level between the combustible cladding and the inert façade. Mean surface temperature in each test 35 25 15 Mean test 1 Mean test 2 Mean test 3 Mean test 3 - cavity 5 5 1 15 2 Figure 37. Mean surface temperature at a level 4 mm above the upper edge of the combustion chamber. 4.7.5 Temperature 5 mm above the combustion chamber The measured temperatures on the surface at a level 5 mm above the edge of the opening of the combustion chamber are presented in figures 38 4, one figure for each test. The results clearly show that the fire was more severe on the left side of the specimen in all three tests.

41 18 16 14 12 8 6 4 C16 C17 C18 C19 Test 1 - inert facade 2 5 1 15 2 Figure 38. Temperature on the surface during Test 1, 5 mm above the combustion chamber. Test 2 - plywood without cavity 35 25 15 C16 C17 C18 C19 5 5 1 15 2 Figure 39. Temperature on the surface during Test 2, 5 mm above the combustion chamber.

42 45 Test 3 - plywood with cavity 35 25 15 C16 C17 C18 C19 5 5 1 15 2 Figure 4. Temperature on the surface during Test 3, 5 mm above the combustion chamber. The temperature was measured on the surface of the plywood in the cavity during Test 3. The results from these measurements are shown in figure 41. At this level the temperature in the surface of the plywood in the cavity is continuously increasing, but decreasing at the end of the test. 16 14 12 8 6 Test 3 - plywood with cavity Surface temperature of plywood in cavity C36 C37 C38 C39 4 2 5 1 15 2 Figure 41. Temperature on the surface of the plywood in the cavity 5 mm above the combustion chamber.

43 In figure 42 the mean temperature of all thermocouples at this level is presented for each test, as well as the mean surface temperature on the plywood surface in the cavity. As the figure shows there is a substantial difference on the temperature level between the combustible cladding and the inert façade. Mean surface temperature in each test 25 15 Mean test 1 Mean test 2 Mean test 3 Mean test 3 - cavity 5 5 1 15 2 Figure 42. Mean surface temperature at a level 5 mm above the upper edge of the combustion chamber. 4.8 Plume temperature at different heights The temperature was also measured mm and mm from the surface, i.e. in the plume, with.5 mm thermocouples wires type K with welded tip. The thermocouples were fixed on long screws that were fixed to the façade surface. The gas temperature in the cavity in Test 3 was also measured with the same type of thermocouples, and the measurements were made in the centre of the cavity, i.e. 1 mm from the surface. Details about the positions are explained in the text following figure 4. 4.8.1 Plume temperature 1 mm above the combustion chamber 4.8.1.1 Measurements mm from the surface The measured temperature mm from the surface at a level 1 mm above the edge of the opening of the combustion chamber is presented in figures 43 45, one figure for each test. The results clearly show that the fire was more severe on the left side of the specimen in all three tests.

44 9 8 Test 1 - inert facade 7 A1 A2 5 1 15 2 Figure 43. Temperature in the plume mm from the surface during Test 1, 1 mm above the combustion chamber. 9 8 7 A1 A2 Test 2 - plywood without cavity 5 1 15 2 Figure 44. Temperature in the plume mm from the surface during Test 2, 1 mm above the combustion chamber.

45 9 Test 3 - plywood with cavity 8 7 A1 A2 5 1 15 2 Figure 45. Temperature in the plume mm from the surface during Test 3, 1 mm above the combustion chamber. In figure 46 is the mean temperature of the two thermocouples mm from the surface shown for each test. The results are similar to the temperatures measured on the surface at the same level, figure 22, i.e. the lowest temperatures in Test 1, and highest in Test 2. 9 8 7 Mean temperature mm from surface Mean test 1 Mean test 2 Mean test 3 5 1 15 2 Figure 46. Mean plume temperature mm from the surface at a level 1 mm above the upper edge of the combustion chamber.

46 4.8.1.2 Measurements mm from the surface The temperature was also measured mm from the surface, but only in Test 1, i.e. the inert façade. The measured temperature is shown in figure 47. A mean temperature (mean of two measurements) is presented in figure 48 for the measurement of temperature mm as well as mm from the surface. 8 7 Test 1 - inert facade B1 B2 5 1 15 2 Figure 47. Temperature in the air mm from the surface during Test 1, 1 mm above the combustion chamber. 8 7 Mean mm from surface Mean mm from surface Test 1 - inert facade 5 1 15 2 Figure 48. Mean temperature during Test 1, mm and mm from the surface, measured 1 mm above the fire source.

47 4.8.1.3 Measurements in the cavity The temperature was also measured in the cavity in Test 3, centrally between the lightweight concrete backing and the plywood. The test results at a level 1 mm above the fire source are shown in figure 49. D1 D2 Test 3 - plywood with cavity Temperature in cavity 5 1 15 2 Figure 49. Temperature in the cavity 1 mm above the fire source during Test 3. 4.8.2 Air temperature 27 mm above the combustion chamber 4.8.2.1 Measurements mm from the surface The measured temperature mm from the surface at a level 27 mm above the edge of the opening of the combustion chamber is presented in figures 5 52, one figure for each test. The results clearly show that the fire was more severe on the left side of the specimen in all three tests.

48 Test 1 - inert facade A3 A4 5 1 15 2 Figure 5. Temperature in the air mm from the surface during Test 1, 27 mm above the combustion chamber. 8 Test 2 - plywood without cavity 7 A3 A4 5 1 15 2 Figure 51. Temperature in the plume mm from the surface during Test 2, 27 mm above the combustion chamber.

49 9 8 Test 3 - plywood with cavity 7 A3 A4 5 1 15 2 Figure 52. Temperature in the air mm from the surface during Test 3, 27 mm above the combustion chamber. In figure 53 is the mean temperature of the two thermocouples mm from the surface shown for each test. The results are similar to the temperatures measured on the surface at the same level, figure 27, i.e. the lowest temperatures in Test 1, and highest in Test 2. 7 Mean temperature mm from surface Mean test 1 Mean test 2 Mean test 3 5 1 15 2 Figure 53. Mean plume temperature mm from the surface at a level 27 mm above the upper edge of the combustion chamber.

5 4.8.2.2 Measurements mm from the surface The temperature was also measured mm from the surface, but only in Test 1, i.e. the inert façade. The measured temperature is shown in figure 54. A mean temperature (mean of two measurements) is presented in figure 55 for the measurement of temperature mm as well as mm from the surface. 45 Test 1 - inert facade 35 B3 B4 25 15 5 5 1 15 2 Figure 54. Temperature in the plume mm from the surface during Test 1, 27 mm above the combustion chamber. 45 35 Mean mm from surface Mean mm from surface Test 1 - inert facade 25 15 5 5 1 15 2 Figure 55. Mean temperature during Test 1 mm and mm from the surface measured 27 mm above the fire source.

51 4.8.2.3 Measurements in the cavity The temperature was also measured in the cavity in Test 3, centrally between the lightweight concrete backing and the plywood. The test results at a level 27 mm above the fire source are shown in figure 56. 25 15 D3 D4 Test 3 - plywood with cavity Temperature in cavity 5 5 1 15 2 Figure 56. Temperature in the cavity 27 mm above the fire source during Test 3. 4.8.3 Air temperature 345 mm above fuel source 4.8.3.1 Measurements mm from the surface The measured temperature mm from the surface at a level 345 mm above the edge of the opening of the combustion chamber is presented in figures 57 59, one figure for each test. Also on this height the results show that the fire was more severe on the left side of the specimen in all three tests.

52 45 Test 1 - inert facade 35 25 15 A5 A6 5 5 1 15 2 Figure 57. Temperature in the air mm from the surface during Test 1, 345 mm above the combustion chamber. 8 Test 2 - plywood without cavity 7 A5 A6 5 1 15 2 Figure 58. Temperature in the air mm from the surface during Test 2, 345 mm above the combustion chamber.

53 9 8 Test 3 - plywood with cavity 7 A5 A6 5 1 15 2 Figure 59. Temperature in the air mm from the surface during Test 3, 345 mm above the combustion chamber. In figure 6 is the mean temperature of the two thermocouples mm from the surface shown for each test. The results are similar to the temperatures measured on the surface at the same level, figure 32, i.e. the lowest temperatures in Test 1, and approximately the same temperature in Test 2 and Test 3 except at the end of the test where Test 3 show higher temperature.. 7 Mean temperature mm from surface Mean test 1 Mean test 2 Mean test 3 5 1 15 2 Figure 6. Mean air temperature mm from the surface at a level 345 mm above the upper edge of the combustion chamber.