Effect of plaster thickness on performance of external thermal insulation cladding systems (ETICS) in buildings

Construction and Building Materials 122 (2016) 496–504

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Effect of plaster thickness on performance of external thermal insulation cladding systems (ETICS) in buildings Tayfun Uygunog˘lu a,⇑, Sevcan Özgüven a, Metehan Çalıs¸ b a b

Afyon Kocatepe University, Engineering Faculty, Civil Engineering Department, 03200 Afyonkarahisar, Turkey Turkish Standards Institution, Construction Materials Fire and Acustics Laboratory, Istanbul, Turkey

h i g h l i g h t s
Performance of different type of insulation boards was investigated.
Combustion of insulation boards were performed with plaster thicknesses from 2 to 8 mm.
Adhesion of insulation boards with plaster were also determined.
Insulation boards must be used with at least 4 mm plaster for the lowest combustion.

a r t i c l e

i n f o

Article history: Received 9 March 2016 Received in revised form 26 June 2016 Accepted 27 June 2016 Available online 9 July 2016 Keywords: Insulation boards Plaster thickness Fire resistance

a b s t r a c t In a properly designed and constructed building, insulating material contributes enormously to energy savings for the heating and cooling of buildings (about 60%). On the other hand, there is always the possibility of fire in buildings. Insulation materials mostly used in Turkey are expanded polystyrene foam (EPS), extruded polystyrene (XPS) and rock-wool (RW). RW is the best durable materials to fire, however it is expensive. EPS and XPS start to soften at low temperatures (about 80 °C). This is not only financial losses but also a contribution to CO2 and global warming. For the study, tests conducted to determine combustion characteristics of insulation boards with different plaster thicknesses of 2, 4, 6 and 8 mm. They were exposed to ignition by a single flame test setup on the front surface. Moreover, the ignition time on the insulation boards was gradually increased from 0.5 min to 25 min. At the end of tests, burnt length and burnt volume of EPS boards behind plaster on the specimen surface were measured. Results showed that in practical engineering, all types of boards except for RW, must be used as insulating materials with at least 4 mm plaster for the lowest combustion and hazard. The optimum thickness is measured as 6 mm for all the coatings. Ó 2016 Elsevier Ltd. All rights reserved.

1. Introduction In order to improve the thermal resistance of buildings and reduce heating loads, some new construction materials such as insulation boards, hollow bricks with different types of thermal insulation cores and hollow shapes and aerated concretes are used in construction. If buildings are properly designed and operated, significant energy savings can be achieved. Hence, building designers can play a major part in solving the energy problem by at an early stage making the appropriate design decisions when it comes to the selection and integration of building components [1]. Thermal insulation materials have an important role and their use is a logical first step to reducing the energy required to keep a good ⇑ Corresponding author. E-mail address: [email protected] (T. Uygunog˘lu). http://dx.doi.org/10.1016/j.conbuildmat.2016.06.128 0950-0618/Ó 2016 Elsevier Ltd. All rights reserved.

interior temperature and therefore achieve energy efficiency [2]. Heat losses in buildings may vary according to the architecture and state of the building project. Generally, heat losses of a multi-storey building is due 40% to the exterior walls, 30% to the windows, 7% to the roof, 6% to basement slab and 17% to air leaks. For a building to be retrofitted, interventions usually involve; roof, windows, walls and over cladding systems with insulation materials. Thermal insulation materials are specific products with high heat resistance, which are designed to provide only the minimum insulation thickness and used to reduce heat losses and gains [3]. Higher energy efficiency drives our demands for much thicker thermal insulation materials. However, this does not mean ‘‘the thicker the better”, especially considering various requirements and properties, such as the mechanical strength of the material, aging durability, water resistance, construction difficulty and even fire safety performance [4,5]. Commonly used thermal insulation

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materials for walls are glass wool, mineral wool, EPS, XPS and polyurethane. Rossi et al. [6] investigated the characterization of smoke in EPS with and without fire retardant combustion. They reported that the charred particles are essentially composed of carbon rich structures with negligible oxidation having occurred. The fire retardant somewhat modifies the characteristics of the combustion of expanded polystyrene and the composition of the smoke. Pargana et al. [7] evaluated the environmental impacts and the consumption of renewable and non-renewable primary energy on the production of conventional thermal insulation materials. Extruded (XPS) and expanded polystyrene (EPS), polyurethane (PUR), expanded cork agglomerate (ICB) and expanded clay lightweight aggregates (LWA) were investigated in the study. The results showed that EPS, PUR and ICB makes a low contribution to all impact categories while the XPS and LWA makes the biggest contribution to six out of eight environmental impact categories. Jiang et al. [8] investigated the fire safety of organic thermal insulation, polyurethane foam (PUF) and extruded polystyrene (XPS) to carry out a series of lab-scale tests over a wide range of widths. They observed that both materials of gas phase temperature showed independent first-increasing and then-decreasing variations caused by wall-fire. In solid phase, XPS showed a constant melting stage, while PUF did not have for its unmelted and charring property. Hidalgo et al. [9] investigated the design criteria for the fire safe use of thermal insulation in buildings. The different hazards from insulation materials in fire were identified and a set of criteria were defined to identify likely failure modes by authors. Consequently, it was reported that all the fire hazards related to the use of insulation materials, the onset of pyrolysis and pyrolysis gases. Schiavoni et al. [10] performed a comparative study on different typical configurations of external walls in order to examine in depth the thermal performance of the assessed insulating materials used in the building sector, considering both commercial and unconventional materials. Among organic materials, PUF and polyisocyanurate are the only ones in B Euroclass; however some researchers showed that these materials release hazardous gases under fire conditions. An et al. [11] investigated the flammability and safety design of thermal insulation materials comprising polystyrene foams and fire barrier materials. Polystyrene foams flammability characteristics (flame heat flux, mass loss rate and flame height) and scale characteristics were measured and modeled. A model was proposed by which to predict whether a fire barrier zone could prevent flames from spreading upwards. HamdaniDevarennes et al. [12] applied to water-based fire retardant material on surface of EPS. The influence of suspension viscosity, coatings number, impregnation time and drying method was studied to monitor the amount of coating deposited and the coating thickness. EPS without hexabromocyclododecane (HBCD) is upgraded from F to E rating according to the EN ISO 11925-2 standard when the penetration of coating suspension into the core is high enough. Mandilaras et al. [13] carried out a comparative assessment of conventional and vacuum insulation panels (VIP) based ETICS utilizing both experimental and theoretical/numerical techniques. Analyses results showed that field measurements of thermal resistance were significantly lower than expected. Besides, hygrothermal monitoring indicated periods of high humidity values and the presence of condensates on the surfaces of the VIPs. Mahlia et al. [14] has studied the correlation between thermal conductivity and the width of thermal insulation materials. Özkan et al. [10] carried out a study on effect of insulation material thickness on thermal insulation. They proposed optimum insulation thickness for different insulation materials depending on four different regions of Turkey. In Turkey, due to economical reasons, the most preferred insulation materials in buildings are EPS and XPS without fire retardant. However, both materials are highly combustible [8,9] and

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could generate large quantities of toxic gases as well. Once ignited, the fire could develop rapidly. Eventually, released heat and toxic gases cause deaths. EPS and XPS start to soften at a temperature of about 80 °C. Although fire hazard groups of all materials used in the insulation/coating applications for energy savings are indicated by manufacturer/vendor companies, the behavior of the composite materials formed using plaster mesh, plaster and decorative coatings is uncertain. In this study, the physical, mechanical, thermal and fire performances of ETICS with EPS, XPS and rock wool insulation materials were compared depending on the plaster thickness. 2. Experimental program 2.1. Materials used Four types of insulation materials were used; gray-EPS (graphite added EPS), white-EPS, XPS and rock-wool. All materials were of standard quality. Also, the EPS and rock-wool boards were selected in a length of 1.0 m and width of 0.5 m. XPS was 1.2 m in length and 0.60 m in width. The thickness of all the insulation materials was 50 mm. Characteristic properties of insulation materials are presented in Table 1. A plaster process with different thicknesses was applied to the insulation boards. Cement-based insulation plaster mortar containing mineral fibers (0.5%), and natural sand (SiO2) was used as plaster mortar. Constant mix proportion (water to cement: 0.30) was used to prepare the plaster mortar. The plaster mesh made of high-strength fiber glass was used as a reinforcement element in the preparation of the insulation samples. The plaster mesh weighed 50 g/m2 and was 4  4 mm2 in mesh size and white in color. The white plaster mortar, which was used in the applications for decorative purposes, and contains quartz sand, the largest grain size of which is 3 mm, was mixed with water pursuant to the technical specifications provided by respective company. 2.2. Preparation of insulation boards Fire experiments were performed on the insulation board samples. Their upper surfaces were covered by mineral fiber reinforced cement-based plaster in the thickness of 2, 4, 6, 8 and 10 mm. Plaster thickness was adjusted by the placing of gauge elements on the edges of the boards. EPS and XPS insulation boards are in the size of 1000  500 mm and 1200  600 mm, respectively. Decorative plaster which are used in applications was also covered on the boards after 24 h. Plastered insulation boards were cured for 28 days at room temperature about 23 °C with 65% humidity. After curing period, insulation boards were cut in the size of 100  300 mm from the same plate, in order to obtain a large number of ETICS samples (Fig. 1). 2.3. Adhesion test The adhesion strength of the plaster performed on the boards was measured using pull-off method. The metal boards glued to the plaster surface were pulled upward and maximum breaking load was measured at the moment of deformation (Fig. 2). Prior to the tests, the glue around the metal boards stuck to the board surfaces was cleaned off. The plaster was cut to the insulation boards and a certain area was formed under the metal boards. The load values were determined using the pull-off method and the adhesion strength was obtained in proportion to these values. 2.4. Thermal conductivity measurement The thermal conductivity coefficient of the insulated wall was measured using the wall-mounted thermal conductivity device (guarded hot box) EN 8990 [16] shown in Fig. 3a. A 19 cm-wide brick wall was built in the middle section of the

Table 1 Charactersitic properties of EPS and XPS. Properties

GreyEPS

WhiteEPS

XPS

RockWool

Thermal conductivity, W/m K Density, kg/m3 Compressive strength, kPa Water vapor diffusion resistance, l Water absorption, % Building material class (EU)

0.035 16 60 40 5.0 B1

0.035 16 60 40 5.0 B1

0.034 25 200 100 3.0 B1

0.040 15 1.0 1.0 12.0 A

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Fig. 1. Preparation of plastered insulation boards.

After one month, using different kinds of insulation boards, insulation was applied on the cold-room side of the wall representing the external environment. Plaster with a constant thickness of 4 mm was applied on the insulation. The ETICS was waited to constant weight for at least 28 days at room temperature. Afterwards, 0.5 m2 of wall framing was carried out on the 1.5  1.5 m square-sectioned wall and thermocouples were affixed to these regions (Fig. 3b). Hot and cold environments were set to be 40 °C and 0 °C, respectively. Temperatures on both sides of the wall were measured for three days and the data was transferred to a computer using an interface program. Coefficient of thermal conductivity (U) was determined with the data using the software in the interface program. In addition, in order to compare data with the standard, the thermal resistance (R) and the coefficient of thermal conductivity (U) values were calculated and recorded by Eqs. (1) and (2) given below based on the calculation method provided by TS 825 [17].

R ¼ Ri þ R n þ R e

ð1Þ

U ¼ 1=R

ð2Þ

In the equations, R represents the total thermal resistance of the wall (m2 K/W); Ri the surface thermal resistance of the inner surface (m2 K/W); Re the surface thermal resistance of the outer surface (m2 K/W); Rn the thermal resistance of the elements that constitute the wall (m2 K/W); U the total thermal transmittance coefficient of the wall (W/m2 K). 2.5. Fire test

Fig. 2. Adhesion test setup on ETICS sample.

testing device. Rough plaster with a thickness of 2.0 cm. was applied on the hotroom side of the wall and as a representation of the external environment, rough plaster with a thickness of 2.5 cm was applied on the cold-room side of the wall.

(a)

After 28 days, the samples covered with plaster mortars were subjected to flame testing using a single flame source test device with commercial propane of 95% minimum purity according to surface exposure method of TS EN ISO 119252 [18] standard. The flame height was set to 20 mm. and the flame was applied to the outer surface covered with plaster for 0.5, 4, 9, 16 and 25 min. The test was performed using a small-flame ignition source test device. The flame source was 40 mm above the lower edge of the coating sample (Fig. 4). Afterwards, the coating samples were removed from the device, cooled to room temperature. Firstly, the largest crack width on decorative plaster surface of each coating was measured with optical crack microscopy in X400 magnification at the fired region and then cut from the middle section along the longitudinal direction using a decoupage tool in order to observe the state of the coatings inside the samples. The combustion lengths on insulation boards behind the plaster and the total

(b)

hotroom

coolroom

thermocupl

Insulated wall

Fig. 3. Thermal conductivity measurement on insulated wall (a: thermal conductivity device; b: insulated wall).

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Plaster-board adherence, kPa

180 160 140 120 100 80 60

Grey-EPS White-EPS XPS

40 20 0 2.0

4.0

6.0

8.0

Plaster thickness, mm Fig. 5. Adherence of plaster on the insulation board.

Fig. 4. Fire test on ETICS sample.

volume of combustion were measured. The total volume of combustion was determined by adding water to the burning sections and measuring the weight of the water filling the combustion space. 2.6. High temperature on plaster High temperature tests were performed on cement-based insulation plaster mortar samples containing mineral fibers. The water-cement ratio of the plaster mortar was 0.30. The plaster mortar sample was placed in 4  4  16 cm prism molds. It was kept for 24 h in the molds to set and was then removed. The samples were placed in a curing pool and cured for 28 days. Afterwards, the samples were kept in a high-temperature furnace at 200 °C, 400 °C and 600 °C for 1 h. After the test, the samples were kept in the furnace until they cooled to room temperature. Following the high temperature, compression and bending tests (mid-points) were performed on the samples.

3. Results and discussions 3.1. Adhesion test results Fig. 5 shows the adhesion strength of the plaster mortar on different types of insulation boards depending on plaster thickness. The adhesion strength of the plaster on all the insulation boards increased with the increase of the plaster thickness, up to 6 mm. However, there was a slight decrease in the adhesion strength of the plaster at a thickness of 8 mm. The highest adhesion strength values for all the insulation boards were observed at 6 mm. The adhesion strength of thermal insulation board adhesive on EPS boards and application surfaces should be at least 80 kPa according to EN 13494 [19]. Given this lower limit, the desired strength was obtained from a 4–6 mm plaster thickness for gray-EPS, while adhesion strength values over 80 kPa were achieved for whiteEPS and XPS between the thicknesses of 4 and 8 mm. Therefore, it is proposed that at least 4 mm plaster thickness must be used in the ETICS applications. However, optimum plaster thickness is 6 mm for all the ETICS that given in this study. The optimum plaster cost will be higher than minimum thickness of plaster. But, in case of fire, ETICS with the minimum plaster will have higher damage when compared to with optimum thickness of plaster. Consequently, reconstruction cost of ETICS with the minimum plaster thickness will be higher than new construction cost of optimum plaster thickness. Comparing the adhesion strength values for a constant plaster thickness revealed that the highest adhesion strength value was obtained from XPS, while the lowest adhesion strength value was obtained from the white-EPS insulation boards. The adherence between the plaster and the XPS insulation board was higher compared to those of the other boards, because XPS had a denser structure.

Adherence strength, kPa

160 136.5

140 120 100

108.7 84.0

80 60 40

18.7

20 0 Grey-EPS

White-EPS

XPS

Rock-wool

Insulation board Fig. 6. Comparison of adherence strength of insulation boards.

Comparing the adhesion strength values of the insulation boards showed that the best adhesion result was obtained with the XPS insulation boards (Fig. 6). This is mainly because the XPS has a denser structure and therefore a higher tensile strength. The lowest adhesion strength was obtained with the rock wool, because rock wool is made of stone fibers melt and then cooled and pressed without the use of any binder. The adhesion strength values of the gray and white EPS were between those of the XPS and the rock wool. 3.2. Thermal conductivity of ETICS Coefficient of thermal conductivity is the quantity of heat that is transferred through a unit cube of two surfaces of perpendicular distance to each other in a given unit of time when the difference in temperature of the two surfaces is 1 °C and its unit is W/m K. According to IS0 and CEN Standards, materials which have lower coefficient of thermal conductivity values than 0065 W/m K are defined as thermal insulation materials, and this is the most important criteria in the selection of thermal insulation materials. Therefore, the lower the coefficient of thermal conductivity of a material, the higher its thermal insulation resistance [14,15]. Other materials are considered as general scope building materials. If a structural component or element is composed of materials of different thermal conductivity calculation values, the thermal transmittance value (U) of that structural component or element is calculated by taking into account the thickness and area/length values of each material. Table 2 shows the measurements carried out by the thermal testing device in the wall model for the uncoated wall, and for the wall coated with EPS, XPS and rock-wool insulation boards. U values were measured both experimentally, depending on the wall composite thickness, and calculated according to the TS 825 [17] calculation method. The standard deviation values between the

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500 Table 2 Thermal performance of insulated wall.

Uncoated White EPS Grey EPS XPS Rock-wool

Wall thickness, m

Thermal resistivity, R (m2 K/W)

Thermal transmittance (Exp.), U (W/m2 K)

Thermal transmittance (TS 825), U (W/m2 K)

0.19 0.25 0.25 0.25 0.25

0.485 2.06 2.12 2.31 2.10

2.06 0.48 0.471 0.43 0.476

2.11 0.542 0.52 0.497 0.531

Combustion length, mm

Wall-coating

250 200 150

2 mm 4 mm 6 mm 8 mm

100 50 0 0.5

16

25

Fig. 8. Combustion length of plastered white-EPS after fire.

250 200 150

2 mm 4 mm 6 mm 8 mm

100 50 0 0.5

4

9

16

25

Fire duration, min

3.3. Fire durability

Fig. 9. Combustion length of plastered gray-EPS after fire.

250

Combustion length, mm

Fig. 7 shows the temperature distribution values of the plaster coated materials exposed to flame from their outer surfaces. The values were measured using a thermal imaging camera at the end of the period of each exposure. The surface temperature of the coatings exposed to a 20 mm flame for 0.5 min in the test setting, was about 270 °C, while the surface temperature at the outer surface of the coatings exposed to a flame for 25 min, reached up to 470 °C in the regions near the flame source. The surface temperature of the sample decreased when moved upwards from the flame source and dropped to 50 °C at the peak. Figs. 8–10 show the combustion lengths of the white-EPS, the gray-EPS and XPS coating materials depending on the plaster thickness and the flame exposure time, respectively. The highest combustion length was observed at 2 mm behind the plaster in all the insulation boards. The combustion length values of all the insulation boards decreased with an increase in the plaster thickness. The time of transfer of the heat behind the plaster was extended by increasing the plaster thickness, and less burning deformation was observed with thicker plaster for the same period of time.

2 mm 4 mm 6 mm 8 mm

200 150 100 50 0 0.5

4

9

16

25

Fire duration, min Fig. 10. Combustion length of plastered XPS after fire.

450

Combustion volume, cm3

350

Surface line length, mm

9

Fire duration, min

Combustion length, mm

two coefficient values were also determined. The highest coefficient of thermal transmittance was observed in the uncoated wall, while the lowest coefficient of thermal transmittance was observed in the wall coated with XPS. The heat transfer in the white-EPS coated wall was 4.3 times lower than that in the uncoated wall, while the heat transfers in the walls coated with the gray-EPS, XPS and the rock-wool were 4.4, 4.8 and 4.33 times lower than the uncoated wall, respectively. When applied to the wall surface, the white-EPS, the gray-EPS, XPS and the rock-wool provided 76%, 77%, 79% and 77% energy savings compared to the uncoated wall. Other structural elements such as windows, beams and columns may lead to a decrease in these values. These heat transfer coefficient values could be determined experimentally with a maximum deviation of 5% compared to the values calculated using TS 825 [17].

4

0.5 min 4 min 9 min 16 min 25 min

300 250 200 150 100 50 0 0

50

100

150

200

250

300

350

400

Surface temperature, oC Fig. 7. Surface temperature of ETICS after fire.

450

500

400 350 300 250

2 mm 4 mm 6 mm 8 mm

200 150 100 50 0 0.5

4

9

16

25

Fire duration, min Fig. 11. Combustion volume of plastered white-EPS after fire.

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Combustion volume, cm3

450 400 350 300 250

2 mm 4 mm 6 mm 8 mm

200 150 100 50 0 0.5

4

9

16

25

Fire duration, min Fig. 12. Combustion volume of plastered gray-EPS after fire.

Combustion volume, cm3

450 400 350 300

2 mm 4 mm 6 mm 8 mm

250 200 150 100 50 0 0.5

4

9

16

25

Fire duration, min Fig. 13. Combustion volume of plastered XPS after fire.

Overall, the combustion lengths observed with a plaster thickness of 8 mm and a flame exposure of 25 min were very close to the burning deformation observed with a plaster thickness of 2 mm and 4 min of flame exposure. Combustion length in the gray-EPS, the white-EPS and XPS insulations were 8, 11 and 10 times higher than the flame length. After 8 mm, plaster boards with the highest thickness were exposed to a flame for 25 min, and their

501

combustion heights were about 5 times higher than the flame length. The reason the combustion length in the insulation boards increase is because the temperature of the material surface increases with the plaster mortar being exposed to flame, and also because the plaster transmits the heat upwards and leads to the burning of the insulation board. On the other, increasing the thickness of the plaster will cause more load on the insulation board which has low tensile strength and therefore, make it difficult for the wall surface to bear the plaster. When the flame exposure time is increased for the fixed plaster thickness, the deformation in the material increases with an increase in the flame exposure time (see Fig. 10). The volume of combustion showed behavior which was similar to that of the combustion length. Figs. 11–13 show the combustion volumes of the white-EPS, the gray-EPS and XPS insulation boards, or in other words, the discharged volumes behind the plaster after burning. The highest combustion volume occurred in the lowest plaster thickness, while the lowest combustion volume was measured behind the boards which were coated with 8 mm plaster (the maximum thickness of plaster). The volume of combustion of the insulation boards with a 2 mm plaster thickness, varied between 300 and 400 cm3 after 25 min. This also means that about one-third of the insulation board in per unit area burned and the back of the plaster discharged. The amount of combustion per unit area decreased by half when the plaster thickness was increased up to 8 mm. The samples were subjected to tests for the determination of the combustion damage which occurred behind the plaster coatings with a 2 mm plaster thickness exposed to flame. These samples were cut lengthwise in the middle. Fig. 14a–d show the amount of damage in the EPS and XPS insulation boards for the white-EPS, gray-EPS, XPS and rock-wool, respectively. The amount of damage in all the insulation boards increased with an increase in the flame exposure time. When EPS and XPS are exposed to high temperatures, initially the cell-walls soften, the cellular structure collapses and the foam starts to shrink [20–25]. As a result of exposure to flame, the coating materials could not bear the plaster due to the gaps formed behind the plaster, and the plaster fell off during fire. No deformation due to burning was observed in the rockwool. No burning or deformation was observed in the plaster mesh after insulation materials were subjected to flame.

Fig. 14. Deformations on insulation boards after fire (a: white-EPS; b: gray-EPS; c: XPS; d: rock-wool).

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The experimental studies show that the use of materials such as EPS and XPS is not suitable as regards fire. As a solution to this problem, these materials are produced and marketed fire retardant. Due to economic reasons, normal EPS and XPS materials are used extensively in Turkey. On the other hand, mineral wools are also preferred as an alternative to polymeric materials such as EPS and XPS. However, these materials must also be very well insulated against water. Mineral wools can withstand very high temperatures (>600 °C). Time dependent burning length values indicate that in a plastered coating subjected to fixed flame height, deformation behind the plaster increases with time during the first 25-min-period. Accordingly, deformation with time can also be expected to increase with the increase in time. However, the plaster temperature will

become stable after a certain period of time because the flame height is constant and the burning of the insulation material will come to a halt. Fig. 15a–c show the graphical expression of this condition. Early on, the burning length behind the plaster layer subjected to flame increases rapidly, while as time passes, burning rate decreases sharply. In other words, the reason for this is in fact that the surface temperature of the plaster becomes stable and the heat deformation of the material behind the plaster comes to a halt [25]. Spalling or cracking of plaster during or after the fire which is a critical factor from durability standpoint. Therefore, the largest crack width measurements of decorative or finish plaster after fire test were performed on each external cladding composites and the results were given in Fig. 16 depending on plaster thickness and fire duration. It can be clearly seen that crack width increases with an increasing of fire duration because of shrinkage of finish plaster

140 120 100 80

y = 60.328x-1.292 R² = 0.9785 (2 mm)

y = 53.863x-1.313 R² = 0.9743 (4 mm)

2 mm

y = 39.282x-1.312 R² = 0.9676 (6 mm)

18.382x-1.029

6 mm

0.40

4 mm

y= R² = 0.9081 (8 mm)

8 mm

60 40 20 0 0

2

4

6

8

10

12

Plaster crack width, mm

Combustion velocity, mm/min

160

Time, min0.5

0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00

0.5

(a)

4

140 120 100 80 60

y = 81.52x-1.02 R² = 0.9832 (2 mm)

y = 45.586x-1.304 R² = 0.9911 (4 mm)

y = 45.05x-1.51 R² = 0.96 (6 mm)

y = 27.782x-1.35 R² = 0.9704 (8 mm)

2 mm

0.40

4 mm

0.35

2mm

0.30

4mm

0.25

6mm

0.20

8 mm

6 mm 8 mm

40 20 0

2

4

6

Time,

25

8

10

12

16

25

16

25

0.15 0.10 0.05 0.00

min0.5

0.5

4

(b)

9

Fire duration, min

(b)

160

60.648x-1.392

140 120 100 80

44.028x-1.469

y= R² = 0.9722 (2 mm)

y= R² = 0.9742 (4 mm)

y = 59.205x-1.648 R² = 0.9859 (6 mm)

y = 33.434x-1.431 R² = 0.9674 (8 mm)

2 mm

0.40

4 mm

0.35

Plaster crack width, mm

Combustion velocity, mm/min

16

(a)

160

0

9

Fire duration, min

Plaster crack width, mm

Combustion velocity, mm/min

2mm 4mm 6mm 8 mm

6 mm 8 mm

60 40 20 0 0

2

4

6

8

10

12

Time, min0.5

(c) Fig. 15. Consumption velocity of 2 mm plastered insulation boards during fire (a: white-EPS; b: gray-EPS; c: XPS).

0.30 0.25

2mm 4mm 6mm 8 mm

0.20 0.15 0.10 0.05 0.00 0.5

4

9

Fire duration, min

(c) Fig. 16. Crack width on plaster after fire (a: white-EPS; b: gray-EPS; c: XPS).

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Residual strength, %

120 Compressive str. Flexural Str.

100 80 60 40 20 0 0

200

400

600

800

Temperature, oC Fig. 17. Residual strength of plaster under high temperature.

mortar with increasing the temperature. Even though increasing of temperature depending on fire duration, crack width decreased with thicker plaster. High temperature due to increasing of fire duration can easily reach to insulation boards that behind of plaster via cracks. Thus, ETICS with cracked plaster surfaces would be more damaged when compared to ETICS with un-cracked plaster surface. 3.4. High temperature effect on plaster Plaster mortars will also be affected by the high temperature when ETICSs are subjected to fire. Fig. 17 shows the remaining strengths of the compressive and flexural strength values in order to determine the degree of influence between 20 and 600 °C. The compressive strength values of the cement-based mortar (20 MPa at ambient temperature) decreased 32%, 55% and 58% at 200, 400 and 600 °C, respectively. For the same temperature values, the flexural strength values (originally 5 MPa) decreased 43%, 55% and 80%, respectively. It was probably due to the internal vapor stress in the hydrated cement matrix because of water that located in the porous structure of mortar. Decomposition of calcium silicate hydrate (C–S–H) gel resulted in an increase of CTE between 250 and 500 °C. After of the water evaporates from the specimen, the thermal expansion of mortar began to decrease due to shrinkage of mortar with increasing the temperature. Plaster mortar contains natural sand in size of 1–3 mm. Siliceous aggregates containing quartz, such as natural sand, may cause distress in concrete or mortar at about 573 °C since the transformation of quartz from a to b form is associated with a sudden expansion of concrete or mortar. Thus, the mortar strength may deteriorate under these conditions [26]. 4. Conclusions This study investigated the performance, under different conditions, of plaster-coated insulation boards, used in external insulation applications and the following results were drawn.
Comparing the adhesion strength values of the insulation boards shows that the best adhesion result was obtained with the XPS insulation boards. The lowest adhesion strength was obtained with the rock wool. The adhesion strength values of the gray and white EPS were between those of the XPS and the rock wool.
The lowest coefficient of thermal conductivity was observed in the wall coated with XPS. The heat transfer in the white-EPS coated wall was 4.3 times lower than that in the uncoated wall, while the heat transfers in the walls coated with the gray-EPS, XPS and the rock-wool were 4.4, 4.8 and 4.33 times lower than the uncoated wall, respectively.

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When flame at the height of 20 mm was applied to the plastered insulation boards, the temperature of the surface coating increased depending on the time of exposure and reached up to 475 °C at the end of 25 min.
An increase in the duration of exposure of the plastered insulation boards to flame, increased the amount of damage and the burn height behind the plaster.
Combustion heights in the gray-EPS, the white-EPS and XPS insulations were 8, 11 and 10 times higher than the flame height. The volume of combustion of the insulation materials subjected to flame at different time periods increased with an increase in the flame exposure time.
Early on, the burning height behind the plaster layer subjected to flame, increased rapidly, while as time passes, burning rate decreased sharply.
Compared to the compressive strength values of the mortars at ambient temperature, the compressive strength values of the cement-based mortar decreased 32%, 55% and 58% at 200, 400 and 600 °C, respectively. For the same temperature values, the flexural strength values (originally 5 MPa) decreased 43%, 55% and 80%, respectively. The results of this study indicate that large fire damages may occur in insulations subjected to fire. This study also reveals that it is necessary to investigate the fire performance of fire retardant coatings. 5. Recommendations Thermal insulation materials have an important role and their use is a logical first step to reducing the energy required to keep a good interior temperature and therefore achieve energy efficiency. In this study, the flammability characteristics and the construction characteristics of insulation materials are measured. Like practically all organic building materials EPS and XPS are combustible. It is therefore recommended that fire retardant insulation boards must be preferred in the applications, and installed insulation boards should always be covered by a protective facing, suitably fixed to prevent collapse in the event of fire. Protection of the surface of insulation boards with at least 4 mm (optimum is 6 mm) thick plaster has been shown to provide resistance to ignition and good adhesive strength. Moreover, plaster thickness can be increased to 8 mm if the protective facing is mechanically supported. Otherwise, insulation boards would be damaged in high ratio during the fire, and it can be resulted with casualties because of collapsing of plaster from the burned surface of insulation boards at facades. Moreover, at these situations, cost of reconstruction of ETICS will be higher than that of new. Acknowledgements The authors would like to thank Afyon Kocatepe Universtiy for the support of foundation with project number of AKU-BAP 14.FEN. BIL.11. References [1] S. Chirarattananon, V.D. Hien, P. Tummu, Thermal performance and cost effectiveness of wall insulation under Thai climate, Energy Build. 45 (2012) 82–90. [2] K. Comakli, B. Yuksel, Optimum insulation thickness of external walls for energy saving, Appl. Therm. Eng. 23 (2003) 473–479. [3] A. Uker, F. Balo, Determination of the energy savings and the optimum insulation thickness in the four different insulated exterior walls, Renew. Energy 35 (2010) 88–94. [4] O.A. Dombayci, M. Golcu, Y. Pancar, Optimization of insulation thickness for external walls using different energy sources, Appl. Energy 83 (2006) 921–928.

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