The Effect of Moisture Content of Insulation Boards on the Adhesion Strength of ETICS

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1 The Effect of Moisture Content of Insulation Boards on the Adhesion Strength of ETICS ENELI LIISMA, LEMBI-MERIKE RAADO, SILVER LUMI, IRENE LILL, VIRGO SULAKATKO Department of Building Production Tallinn University of Technology Ehitajate tee 5, Tallinn ESTONIA Abstract: - According to the requirements of the energy efficiency of buildings, old storey house façade renovation installing new external thermal insulation composition system (ETICS) has been the primary focus in Northern and East Europe in the past 10 years. This paper will compare different contemporary insulation materials with different moisture content on adhesive strength. The moisture content appears to have a slight effect on the adhesion between the insulation material and the reinforcement layer. Polystyrene materials kept at 95 % RH formed a slightly stronger bond with the reinforcement layer, than specimens kept at dry conditions. Too much extra moisture in the insulation material weakened the adhesion notably, specimens covered with thin layer of ice proved to reduce adhesion greatly. This paper is focused on the moisture content of the insulation board during installation process and the adhesive strength of ETICS. Keywords: - ETICS, installation process, moisture, adhesive strength, façade, wind-driven rain 1 Introduction External Thermal Insulation Composite Systems ETICS are used in Europe since the 70 due to its simple installation technique, reliability and low cost advantages. These several years of experience of using ETICS have been enabled to evaluate this system in different environments and to understand that there are a great number of potential problems related to materials, installation technique and climate. As the façade renovation need due to contemporary energy efficiency policies is considerably growing, there are considerable amount of research done in the field of ETICS performance. The main causes of ETICS wall façade damages are related to humidity - rain and especially wind-driven rain (WDR) are considered as one of the most important sources affecting the hydrothermal performance of building façades [1]. When high values of surface moisture in present with organic material close to façade walls, biological growth on ETICS is probable to happen however according to Barreira et al. [2] no changes occur in thermal performance of the system. This is mostly visual and unpleasant defect on façade walls. Researches on rainwater runoff from building facades were profoundly reviewed by Blocken et al. [3]. Porous and hygroscopic rendering materials with WDR in present will lead to potential problems with water ingress and rain penetration. In addition to in situ and laboratory tests simulation programs are constructed to understand ETICS and hygrothermal performance according to Zillig et al. [4] simulation program WUFI submitted that west facades have higher risk of condensation problems than followed by north, south and east facades. However Johansson et al. [5] presented that colour is the most important factor for the surface humidity levels on a south-facing façade (in the northern hemisphere), while on a north-facing façade, the thermal inertia is most important. Durability considerations of ETICS are studied by Hradil et al. [6]. Hygrothermal performance and durability of building facades with ETICS in cold climate where temperature is above zero are related to frost damages and structural cracking. When the moisture has a direct leakage into the building through the micro-cracks, serious negative consequences will start accelerated deterioration, dimensional changes, delaminating processes and possible internal structure damages are just few to mention. Addition to chemical and physical degradation processes there are human factor nuances during ETICS installation that should be taken into account. Main problems with human factor are preparing correct water-binder ratio of the rendering materials in situ, workability with the allowable open time and following the working temperatures and humidity of the weather. ISBN:

According to ETAG 004 (European Technical Approval Guideline) - External Thermal Insulation Composite Systems with Rendering [7] proven performance of service life is at least 25 years.

In North and East Europe the climate conditions are approximately 50% of the year below zero degrees of Celsius and yet the façade renovation works are in process.

2 According to ETAG 004 (European Technical Approval Guideline) - External Thermal Insulation Composite Systems with Rendering [7] proven performance of service life is at least 25 years. However, the actual durability of the ETICS tends to remain below the outlined. In North and East Europe the climate conditions are approximately 50% of the year below zero degrees of Celsius and yet the façade renovation works are in process. For years façade renovation process with ETICS was performed on scaffolds without rain protecting tent, therefore WDR with water freezing was involved and rain accumulation in the insulation boards during installation process (Fig. 1). Likewise the stored material was uncovered near scaffolds and direct rain on surface in present (Fig.2). Prompted by this technical problem, this paper is focused on the moisture content of the insulation board during installation process and the adhesive strength of ETICS. 2.1 Methods and experimental setup All specimens were cut from thermal insulation boards with nominal dimensions and prepared with dimensions of 200 mm x 200 mm x 50 mm. 5 sides of the specimen were covered with waterproof material (bottom EKOBIT, bitumen based; sides aluminum tape) one side of the 200 mm x 200 mm was left open. According to experimental research program, specimens were kept in different laboratory conditions: a) 1 week in dry environment (+20 C, 40% RH); b) 1 week in moist environment (+20 C, 90% ± 5% RH); c) dry specimen covered with artificial rain (40 mm/min); d) dry specimen covered with artificial rain (40 mm/min) and kept 10 hours in -20 C to freeze the absorbed water. Specimens were covered with reinforcement mortar Sakret BAK and reinforced with a mesh for outdoors (4 mm x 4 mm) and kept in laboratory conditions (+20 C, 65% ± 5% RH), a) b) Fig.1. ETICS installation process a) no rain protecting tent on scaffolds 2 Experimental procedures 2.1 Materials The compounds of ETICS used in this experimental research program (Table 1, Table 2) are from the Estonian market production of Estonian, Finnish and Latvian factory. Selected thermal insulation materials are commonly used in façade renovations. The purpose of using rendering mortar Sakret SBP is suitability both to mineral wool and to thermoplastic thermal insulation boards. Fig.2. ETICS installation process b) uncovered material storage on construction site covered with decorative mortar (2 mm Sakret SBP) after 96 hours. The mortar mixture procedures were performed according to ETAG 004 and technical instructions of the manufacturer. Adhesive strength of the thermal insulation material and the mortar was tested after 144 hours (6 days) and 672 hours (28 days). 2.3 Test apparatus Artificial rain apparatus The artificial rain (AR) apparatus was constructed considering the principles that the diameter of the raindrop will be nearby to real life. According to [7] the diameter of the actual raindrop is between mm. Based on this the diameter of an ISBN:

a) b) c) Fig. 3. Artificial rain apparatus average artificial raindrop was chosen 4 mm tested in oil layer (Fig. 3.c). Therefore the kinetic energy of an average artificial raindrop is approximately 0.

One side of the sheet is covered with small pits with diameter of 1 mm after every 22 mm in a channel. Neighbor channel pits are shifted 11 mm from each other (Fig. 3.b).

On the basis of low flow rates of the water there is a constant pressure in polycarbonate sheet channels and pressure loss with friction loss are considered marginal. KKKK = 1/2 mmvv 2 (1) 2.3.

3 a) b) c) Fig. 3. Artificial rain apparatus average artificial raindrop was chosen 4 mm tested in oil layer (Fig. 3.c). Therefore the kinetic energy of an average artificial raindrop is approximately 0.7 mj. The kinetic energy of the raindrop was calculated using formula (1). The artificial rain apparatus was constructed using Makrolon polycarbonate sheet with thickness of 8 mm. One side of the sheet is covered with small pits with diameter of 1 mm after every 22 mm in a channel. Neighbor channel pits are shifted 11 mm from each other (Fig. 3.b). Every 6 mm x 8 mm channel of the Polycarbonate sheet will be filled with water that will make artificial rain. On the basis of low flow rates of the water there is a constant pressure in polycarbonate sheet channels and pressure loss with friction loss are considered marginal. KKKK = 1/2 mmvv 2 (1) Adhesive strength The adhesive strength tests were based on the direct pull-out test principle using compressive test machine while working the opposite direction with digital hanging scale attached. Accuracy of the measurement is 0.01 kg with testing speed 3 mm/min. Every insulation board was tested with a minimum of 5 results. In other principles the adhesive strength test was performed according to standard EN (9). 3 Results In Tables 3 and 4 all average of adhesive strengths according to experimental setup are presented. 3.1 Adhesive strength Fig. 4 shows the results of the adhesive strength after 6 days of hardened rendering mortar in 65% of relative humidity. There are three groups of adhesive strengths A) Between 8 20 kpa, B) in range of kpa and C) in range of kpa. In group A) thermal insulation boards 5 and 7 with adhesive force perpendicular to the mineral wool fiber have significantly lower adhesive strength below 20 kpa. Group B) is formed of mineral wool with adhesive strength along the fiber (thermal insulation boards 6 and 8) and extruded polystyrene board 4 with an average adhesive strength in range of kpa. Group C) is formed of expanded polystyrene boards Nr 1, 2 and 3 with considerably higher adhesive strength in range kpa. Fig. 5 shows the adhesive strength results after 28 days of hardened rendering mortar in 65% of relative humidity where the three group analogy is alike. According to the results the mineral wool insulation boards conditioned in 95% RH have lower adhesive strength than in 65% RH. Thermal insulation boards with adhesive force perpendicular to the mineral wool fiber have similar or slightly lower adhesive strength in 95% RH conditions. However expanded polystyrene boards have similar or considerably higher adhesive strength in 95% RH conditions than in 65% RH conditions. When artificial rain conditions in present, group A) with mineral wool boards have remarkably lower adhesive strengths than in 65% RH conditions and slightly lower adhesive strengths than in 95% RH conditions. In group B) adhesive strengths with artificial rain are similar or slightly higher adhesive strengths than in RH 65% or 95%. In group C) expanded polystyrene materials with lower density have considerably lower adhesive strengths in artificial rain conditions than in 65% or 95% RH. ISBN:

4 When extreme conditions involved artificial rain with freezing conditions gives lower adhesive strength results in general. Table 1 Insulation materials used in experiment Nr Thermal insulation Type Marking Standard Density (kg/m 3 ) Thermal conductivity (W/mK) 1 Estplast EPS Thermoplastic material EPS Estplast EPS100 Estplast EPS60 Silver EN XPS Finnfoam XPS300 EN Paroc FAS Stone wool 6 Paroc FAL Mineral wool EN Isover FS Glass wool 8 Isover FL Water absorption (%) W< 3 W p 1 W lp 3 Table 2 Mortar materials used in experiment Material Reinforcement mortar Rendering mortar (thin-bed plaster) Product/ Marking Standard Adhesive strength (kpa) Capillary water adsorption class Sakret BAK EN W2 Sakret SBP EN W2 Table 3 Adhesive strength after 6 days Polystyrene materials Mineral wool materials Condition Nr 1 Nr 2 Nr 3 Nr 4 Nr 5 Nr 6 Nr 7 Nr 8 65% RH % RH AF Rain AF Rain+Freezing Table 4 Adhesive strength after 28 days Polystyrene materials Mineral wool materials Condition Nr 1 Nr 2 Nr 3 Nr 4 Nr 5 Nr 6 Nr 7 Nr 8 65% RH % RH AF Rain AF Rain+Freezing ISBN:

5 Group A) Group B) % RH 95% RH AF RAIN AF RAIN+FREEZING 2 Group C) Insulation board conditioning 3 Fig. 4. Adhesive strength after 6 day mortar hardening % RH 95% RH AF RAIN AF RAIN+FREEZING Group A) Group B) Group C) Insulation board conditioning 3 Fig. 5. Adhesive strength after 6 day mortar hardening 4 Discussion According to the test results polystyrene materials with higher relative humidity conditions will increase adhesive strengths between thermal insulation board and reinforcement mortar supposedly due to polystyrene bubble joints on surface. Increase of the adhesive strength is 8 35% depending on the expanded polystyrene material - higher density materials have more surface joints that will cause the adhesive increase and the strength growth. While the extruded polystyrene has the foam structure and no united bubble structure, therefore no surface joints available and no adhesive strength changes due to relative humidity. Direct rain or frozen surface of the insulation board will decrease the adhesive strengths due to thin layer of the water and cement based mixture under reinforcement mortar. Comparing to 65% condition ISBN:

6 to direct rain condition, the adhesive strength decreasing is approximately from 2% to 12%. Lower density expanded polystyrene materials have higher decrease due to higher water adsorption capacity that will vaporizes during hardening process of the reinforcement mortar. However, based on the test results with mineral wools, the outcome is on contrary higher relative humidity will cause considerable decrease of mineral wool with adhesive force perpendicular to the mineral wool fiber. Comparing adhesive strength in 65% and 95% relative humidity conditions, decreasing is up to 49%. When fiber is along to adhesive force, adhesive strength is notably decreasing up to 25%. Decreasing is probably caused by drying out process during hardening of the adhesive mortar. When direct rain or frozen surface of the thermal insulation in present, decreasing is notable comparing to 65% relative humidity condition. Comparing test results to normative then according to ETAG 004 [8] adhesive strength between expanded polystyrene and rendering mortar must be at least 80 kpa when breaking of the material takes place in the material surface. When breaking takes place inside the material, one result of five is allowed to be less than 80 kpa but at least 60 kpa. In addition to ETAG 004, Finnish normative BY 57 Eriste- ja levyrappaus [9] contains requirement for adhesive strength at least 15 kpa between mineral wool thermal insulation materials and rendering mortar. Therefore it is important to use rain protective tent with scaffolds while ETICS installation process is active and insulation material storage must be covered. Otherwise this can be the cause for important cladding failures, such as low adhesive strength between thermal insulation boards and rendering mortar during installation process which later appears in detachment. 5 Conclusion This test program proved that adhesive strength of the thermal insulation board and rendering mortar depends on the insulation board s hygrothermal condition during installation process. Polystyrene insulation materials of with higher relative humidity will increase the adhesive strength but when rain in present or frozen water on surface, adhesive strength will have decreasing effect. However with mineral wool thermal insulation board s higher relative humidity causes lower adhesive strengths. Winddriven rain and frozen water on mineral wools surface decreases adhesive strengths comparing to dry insulation materials Acknowledgements The research has been conducted as part of the IUT1-15 project Nearly-zero energy solutions and their implementations on deep renovation of buildings financed by Estonian Research Council. References: [1] B. Blocken, J. Carmeliet, On the accuracy of wind-driven rain measurements on buildings. Building Environement, No. 41(12), 2006, pp [2] E. Barreira, V. P de Freitas, Experimental study of the hygrothermal behavior of External Thermal Insulation Composite Systems (ETICS), Building and Environment, No. 63, 2013, pp [3] B. Blocken, D. Derome, J. Carmeliet, Rainwater runoff from building facades: A review, Building and Environment, No.60, 2013, pp [4] W. Zillig, K. Lenz, M. Krus, Condensation on facades influence of construction type and orientation, Research in Building Physics, Leuven, Belgium; K.U. Leuven, p [5] S. Johansson, L. Wadsö, K. Sandin, Estimation of mould growth levels on rendered facades based on surface relative humidity and surface temperature measurements, Building and Environment, No 45, 2010, pp [6] P. Hradil, T. Toratti, E. Vesikari, M. Ferreira, T. Häkkinen, Durability considerations of refurbished external walls, Construction and Building Materials, No 53, 2014, pp [7] Characteristics of Particles and Particle Dispersoids, Handbook of Chemistry and Physics, 62 nd Edition, New York: CRC, 1981 [8] ETAG 004, European Technical Approval Guideline, External Thermal Insulation Composite Systems with Rendering. [9] EN , Methods of test for mortar for masonry Part 12: Determination of adhesive strength of hardened rendering and plastering mortars on substrates. [10] BY 57, Eriste- ja levyrappaus, Suomen Rakennusmedia Oy, 2011 ISBN:

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