External Thermal Insulation Research Articles

Onsite monitoring of a wall retrofitted with an external vacuum insulation composite system

As it becomes more and more relevant to renovate existing buildings with energy efficiency as top priority towards a nearly Zero Energy Building (nZEB) stock, the need for new super-insulation materials to penetrate the construction market increases. A promising option is to incorporate vacuum insulation panels (VIPs) into an External Thermal Insulation Composite System (ETICS) - one of the most popular coating solutions used for insulating building walls. However, the widespread commercialization of VIP solutions for buildings still faces some uncertainties, such as regarding the long-term performance of the panels or the significance of the edge thermal bridging effects. In this context, studying onsite wall applications is of major importance in order to evaluate the actual performance of this innovative multilayer coating system under real exposure conditions.In this paper, the thermal behaviour of an ETICS façade incorporating a VIP insulation is studied. The building being retrofitted is located in Warsaw, Poland. Measurements of temperature, absolute humidity and heat flux are presented and discussed. Data is simultaneously recorded for a VIP ETICS wall and an adjacent conventional polystyrene-based ETICS wall. The VIP edge thermal bridging effect is also analysed. The thermal transmittance of both walls is estimated based on the experimental measurements. Furthermore, a computational algorithm for determining the thermal transmittance coefficient of the existing and the retrofitted wall based on temperature measurements is proposed. Additionally, a periodic infrared thermographic inspection is carried out during the 24-month monitoring period to identify anomalies.It was found that the VIP thermal resistance contribution is significantly higher than conventional expanded polystyrene-based solutions, even at the joint area between panels. No panels with vacuum loss or other anomalies were found during the monitoring period. The computational algorithm results based on the measurements were found to be accurate when compared with the predicted theoretical U-values.

Out-of-Plane Flexure of Masonry Panels with External Thermal Insulation

The combined seismic and energy retrofit of existing aged buildings represents a topic of importance for the building stock. The current study investigates the out-of-plane performance of a specific type of thermo-insulation scheme with panels attached on the external facades of multistory buildings. The investigation was carried out through flexure tests of prototype masonry specimens. From the comparison of their flexural performance, with or without thermo-insulating attachments, the influence of thermal insulation on the out-of-plane behavior of clay brick masonry is demonstrated. It was found that when the thermo-insulating attachment is in tension from such out-of-plane flexure of the masonry facade it performs in a satisfactory way and gives an increased flexural capacity for the assembly. The thermal insulating panels, although partially debonded from the masonry substrate at a limit-state, do not collapse, even when the masonry panel develops large flexural cracks. This is due to the presence of the used plastic anchors. When the thermo-insulating panel is subjected to compression during such an out-of-plane flexure the resulting increase in the out-of-plane load bearing capacity is relatively small. Based on these observations it can be concluded that such thermo-insulating panels may also lead to a less vulnerable seismic performance than that of the same masonry panel without this type of thermo-insulating attachment. This was also confirmed when the in-plane behavior was considered from a separate investigation already published. The employed numerical modeling was successful in simulating the most important aspects of the out-of-plane response of the tested masonry wallets with or without thermo-insulating attachments. The good agreement with observed performance as well as the general nature of this numerical simulation confirms its validity for further use.

Effects of hygrothermal, UV and SO2 accelerated ageing on the durability of ETICS in urban environments

External Thermal Insulation Composite Systems (ETICS) have been extensively used for either new constructions or building facades retrofitting in the last decades. These systems can provide improved thermal performance to the building envelope. However, their long-term durability remains a pervasive concern, with some systems presenting relevant anomalies after few years from their application. The durability assessment of ETICS is defined by the EAD 040083-00-0404 guideline, which stated an accelerated ageing procedure based on the hygrothermal and freeze-thaw behaviour. Nevertheless, further important environmental urban conditions, such as UV radiation and atmospheric pollutants, as well as bio-susceptibility, are not envisaged in the guideline. This paper presents the results of an experimental campaign with the aim of evaluating the durability of the rendering system of several commercially available ETICS exposed to an innovative accelerated ageing procedure, which consists of hygrothermal cycles, UV radiation and air pollutants (SO2) exposure. Physical and chemical-morphological tests were carried out prior and after each ageing cycle in order to evaluate the durability of ETICS. Biological susceptibility to moulds was also assessed. The experimental results showed that both surface hardness and surface gloss decreased after the combined effect of the hygrothermal, UV, and SO2 ageing cycles, whereas an increase of surface roughness was observed. Substantial colour change for all systems after the ageing procedure was observed, confirming aesthetic alteration. Traces of biological growth were detected on the systems after ageing and the contact angle decreased after the hygrothermal cycles, indicating a lower surface hydrophobicity of the systems.

Construction Technology and Measures of Building External Wall Thermal Insulation

Construction Technology and Measures of Building External Wall Thermal Insulation

Condition-Based Maintenance Strategies to Enhance the Durability of ETICS

The increase of awareness with sustainability and the desire of reducing the energy consumption in the construction sector haved increased the application of External Thermal Insulation Composite Systems (ETICS) across Europe in the last decades. Nevertheless, the implementation of appropriate maintenance strategies is still neglected. The aim of this study is to analyse the impact of different maintenance strategies. For that purpose, a condition-based maintenance model, based on Petri nets, is used to evaluate three maintenance strategies: MS1—total replacement only; MS2—combination of minor intervention and total replacement; and MS3—combination of cleaning operations, minor intervention, and total replacement. In the end, a multi-criteria analysis is used to discuss the impact of the three maintenance strategies proposed, evaluating the remaining service life, the global costs over time, the ETICS’ degradation condition, and the number of replacements (end of service life) over the time horizon. For this purpose, a sample of 378 ETICS was analysed, based on in situ visual inspections, carried out in Portugal. The results from this study reveal that maintenance plays an important role to increase the durability of ETICS, and therefore their sustainability. Regular maintenance can promote the extension of the ETICS’s service life between 88% and 159% (between 15 to 27 years), improve the global degradation condition of the ETICS, and reduce the impact on users by reducing the number of deeper interventions. Further research is essential to optimise the maintenance strategies (time interval between inspections, stakeholders’ performance criteria, and environmental exposure).

Analysis of newborn thermal comfort in a textile incubator

Data published by European and World Health Organizations show that since 1990 the number of births has been steadily decreasing, which poses the risk of lack of generational replacement. According to WHO report, every year, 2.6 millions of newborns in the world die in the first month of their life. One million of them in the first 24 h so they require special care and medical supervision, so for the first days or even months of their lives they remain in incubators. The purpose of the research was to develop the construction and build a prototype of a textile incubator, whose most important function is to keep the baby warm, with the possibility of cooling it during therapeutic hypothermia. The incubator model was built in three variants of material packages, and each of them consisted of five material layers. An innovative solution is using for the external thermal insulation layer a composite connecting a knitted fabric with aerogel. The total thermal conductivity resistance for the developed material packages of the incubator was measured using a thermally insulated sweating hot plate known as the ‘skin model’. The obtained values of thermal resistance coefficient R ct are within 2.07–2.83 clo, and in case of the package with an additional insulation layer R ct = 3.68 clo. It turned out that when the infant was placed in a textile incubator without a functional heating and cooling mat its heat balance for the adopted ambient temperatures from −5 to 24 °C was negative and ranged from −0.04 up to −50.50 W. In cases of positive heat balance, especially for all ambient temperatures, which took place for the second package where ΔQ = 0.10 ÷ 6.51 W, there is a risk of overheating the baby. The analysis of the heat balance components shows that convection and radiation have the greatest impact on the total heat loss, as on average they constitute 85.6% of the heat lost by a baby in a textile incubator.

Methodology to assess the circularity in building construction and refurbishment activities

This paper proposes a novel and innovative methodology to assess the degree of Circularity in one of the most resource-consuming and impactful economic activities: the building construction and/or renovation works. The proposed approach measures the ratio of circular flows in three aspects: energy, water and materials consumption; and combines them with the measure of social added value and economic value of the entire activity along its life cycle, regardless of being a new building construction or a major renovation work. The whole methodology has been developed under a life cycle perspective, incorporating into the analysis all material flows and social, environmental and economic impacts from cradle to grave, i.e., from resource acquisition to end of life treatment processes or disposal. The proposed Key Performance Indicators (KPIs) measure different and non-directly related parameters (energy, materials, social impact…) and they are both quantitative and qualitative metrics. Hence, the proposed methodology performs the indicators calculation procedure independently. The methodology has been tested with a conventional energy renovation process consisting of an installation of an External Thermal Insulation Composite System (ETICS) – one of the most prevailing façade energy retrofitting alternatives – combined with a rooftop solar PV system. In this way, a calculation example is shown and some lessons can be extracted regarding the degree circularity of current building construction and refurbishment practices. Results show that current building envelope solutions – even including an efficient rooftop PV system – are far from being considered circular: whereas a significant 51% of Energy Circularity is achieved, only a 29% and a 21% degree of Circularity is observed for the materials and social aspects, also with high payback periods – above 20 years – on the economic side. The methodology also succeeds in showing the potential for improvement and its location along the building life cycle. It is also shown that buildings behave significantly different in each of the addressed CE aspects: materials, energy and water use, social added value and life cycle cost; showing also different potential of improvement.

Impact of Incorporating NIR Reflective Pigments in Finishing Coatings of ETICS

Near-infrared (NIR) reflective materials are being developed for mitigating building cooling needs. Their use contributes to broadening the range of colours, responding to the urban aesthetic demand without compromising the building performance. Despite the increase in NIR reflective pigments investigation, there is still a knowledge gap in their applicability, impact, and durability in multilayer finishing coatings of External Thermal Insulation Composite Systems (ETICS). Hence, the main goal of this work consists of evaluating the impact of incorporating NIR reflective pigments (NRP) in the solar reflectance of the surface layer of ETICS, without affecting the colour perception, as well as their influence on the colour durability and surface temperature. As such, colour, solar reflectance, and surface temperature were monitored for 2 years in dark-coloured specimens of ETICS, with and without NRP and a primer layer. It was confirmed that the main contribution of NRP is the increase of solar reflectance and, consequently, the decrease in surface temperature, especially for high exterior temperatures (around 30 °C). Moreover, these pigments highly increase the NIR reflectance without affecting the visible colour. In addition, they contribute to maintaining the colour characteristics. The application of primer increased the surface temperature, especially for higher exterior temperatures. However, it contributes to a lower colour difference and solar reflectance variation, which is an important achievement for durability purposes.

Towards Improving the Durability and Overall Performance of PV-ETICS by Application of a PCM Layer

The main goal of the paper was to numerically analyse the risk of overheating of the Energy Activated External Thermal Insulation Composite System (En-ActivETICS) as an example of Building Integrated Photovoltaics (BIPV). The analyses were conducted with the coupled power flow method (thermal and electrical) for 20 European cities. All locations were analysed considering the local climate in the context of building performance simulation as well as electricity production. The obtained results allowed for the determination of the risk of overheating, which can influence system durability, accelerated thermal ageing, and overall performance. It was revealed that the risk of overheating above 80 °C is possible in almost all locations; however, the intensity considerably differs between southern and northern Europe. The effect of latent heat storage for better thermal stabilization and overall performance was determined numerically for all locations. Finally, the improved solution with a phase change material (PCM) layer beside the PV panel was proposed individually for specific climatic zones, considering the required heat capacity. The maximum panel temperature for improved En-ActivETICS does not exceed 85 °C for any location.

Mechanical Properties of Polyurethane Adhesive Bonds in a Mineral Wool-Based External Thermal Insulation Composite System for Timber Frame Buildings

This paper aims to provide a preliminary assessment of polyurethane adhesive applicability as an alternative to conventional cement-based adhesives used to fix thermal insulation materials to substrates concerning mineral wool-based external thermal insulation composite systems. Currently, polyurethane adhesives are only used in expanded polystyrene-based ETICS. This study discusses the suitability of polyurethane adhesive for ETICS with lamella mineral-wool for timber frame buildings. Bond strength, shear strength and shear modulus tests were conducted. In addition, microstructure and apparent density were analysed. Mechanical properties were analysed in terms of the influence of substrate type and thermal and moisture conditions, taking into account solutions typical for sheathing on timber frame (oriented strand boards (OSB), fibre-reinforced gypsum boards (FGB) and cement-bonded particleboards (CPB)), as well as limit conditions for adhesive application. It was found that PU adhesive can achieve adhesion, both to MW and OSB, and FGB and CPB at ≥80 kPa, which is considered satisfactory for PU adhesives for EPS-based ETICS. Favourable shear properties were also obtained. There was no significant effect of sheathing type on the properties considered, but the influence of temperature and relative humidity, in which the bonds were made, was spotted. The results obtained can be considered promising in further assessing the usefulness of PU adhesives for MW-based ETICS.

Impact of Water-Repellent Products on the Moisture Transport Properties and Mould Susceptibility of External Thermal Insulation Composite Systems

External Thermal Insulation Composite Systems (ETICS) are constructive solutions widely used to increase the thermal insulation in new and retrofitted buildings. However, these systems can present several anomalies due to their constant exposure to weathering agents and anthropic factors. Water is generally the major cause of degradation. Thus, the application of water-repellent products can minimize the appearance of anomalies and increase the durability of the systems. In this paper, acrylic-based and siloxane-based hydrophobic products were applied to ETICS, with the aim of assessing the compatibility, effectiveness, and durability of these products. The moisture transport properties and mould susceptibility were assessed through laboratory tests on untreated and treated specimens. The durability of the hydrophobic treatments was also evaluated through artificial aging tests (heat-cold and freeze-thaw cycles). Results show that the protection products generally decreased water absorption, slightly decreased the drying rate, and presented adequate water vapor permeability. After aging, the products still had reasonable effectiveness and, with one exception, improved the water vapor diffusion of the systems. Additionally, ETICS underwent an alteration in the finishing coat (possible modification of the porosity) due to the aging cycles. No clear linear correlation was found between the contact angle values and water absorption results, evidencing the influence of other factors related to the composition of the water-repellent products.

Influence of Thermal Alternation on the Interface between Insulation Layer and Bonding Mortar

The safety of the external thermal insulation system has been widely concerned by people. In this paper, strain gauges and temperature sensor are preset at the interface of bonding layer/insulation layer, bonding layer/mortar layer. The interface stress variation rules of graphite polystyrene board, polystyrene board and homogeneous board were studied under 30 times of thermal alternating environment and the test results were analyzed in combination with physical properties of the materials. The results show that the strain at the interface of the samples composed of three kinds of thermal insulation materials increases with the increase of the number of thermal alternating cycles. The total interfacial strain of the sample composed of homogeneous board is the largest, and that of graphite polystyrene board is the smallest.

Performance and Durability of Rendering and Basecoat Mortars for ETICS with CSA and Portland Cement

The production of Portland cement (OP) is commonly associated to significant level of energy consumption and gas emissions. The use of calcium sulfoaluminate cement (CSA) can be a sustainable alternative binder, since its production releases about half of the CO2 emissions and its clinker requires 200 °C lower temperatures, when compared to OP. Furthermore, CSA has fast setting time and achieves higher strength in shorter periods, as well as reduced shrinkage. This paper discusses the incorporation of CSA in rendering mortars and basecoat mortars for ETICS (External Thermal Insulation Composite Systems). The physical-mechanical properties of mortars made with OP and CSA cements were experimental evaluated. The results showed that the introduction of CSA generally improves shrinkage, compressive strength, water absorption at low pressure, enhances the tensile bending strength and decreases the setting time. The amount of CSA introduced into the mixture significantly affected the properties of the cement matrix.

A Tool for the Evaluation of Energy-Environmental Retrofit Interventions on Opaque Walls Using ETICS

Buildings in Europe are the largest consumers of energy, since they are responsible for 40% of energy consumption and 36% of pollutant gas emissions. The energy efficiency, the consequential economic savings and the reduction of environmental impacts must necessarily consider the design of improvements that affect the opaque vertical envelope of a building. The vertical envelope generally constitutes the largest dispersing surface. In this paper, a comparative evaluation of different ETICS (External Thermal Insulation Composite System) solutions through the application of a multicriteria decision support method is proposed. The criteria at the basis of the procedure relate to the energy, environmental, indoor comfort, and economic aspects. Through the application to the case study, consisting of two types of vertical walls with reference to three different climate zones, the ETICS alternative that achieves the best compromise between the various evaluation criteria is highlighted and the solidity of the method itself is tested. The potential of the methodology in the analysis of the alternatives in adherence to individual subcriteria and the possibility of implementation with additional indicators as the needs change are also highlighted. The social impact is undoubtedly one of the expected effects of the application of the method, since a better performance of the building envelope leads to an increase in comfort and liveability of indoor spaces. Moreover, all studies aimed at increasing the performance of the building or parts of it, consequently, lead to greater accessibility by the most vulnerable members of society, in line with the principles of sustainability and inclusiveness of the United Nations 2030 Agenda.

Masonry panels with external thermal insulation subjected to in-plane diagonal compression

Partial collapse of masonry facades during past strong earthquakes is well documented together with the increased vulnerability due to the presence of thermo-insulation within double wythe masonry. The combined seismic and energy retrofit of existing aged buildings represents a topic of importance for the building stock. The current study investigates the in-plane performance of a specific thermo-insulation scheme with panels attached on the external facades of multistory buildings. Diagonal compression tests of prototype specimens are done to study the influence of thermal insulation on the in-plane behaviour of clay brick masonry panels with or without thermal insulation. It was found that the thermo insulating attachment of the tested type performs in a satisfactory way when subjected to the stress field that arises to these masonry panels when subjected to diagonal compression. The thermo insolating panels, although finally debonded from the masonry substrate, do not collapse, even when the masonry panel develops large diagonal cracks, due to the presence of the used plastic anchors. The presence of such thermo insulating attachments leads to an increase of the in-plane load capacity and to a less brittle behaviour than the one without this thermo-insulation. This may also lead to a less vulnerable seismic performance than that of the same masonry panel without this thermo insulating attachment, although further validation is needed considering also the out-of-plane performance. The employed numerical modeling was successful in simulating the most important aspects of the in-plane response of the tested masonry wallets with or without thermo-insulating attachments. The good agreement with observed performance as well as the general nature of this numerical simulation confirms its validity.

Impact of Environmental Exposure Conditions on the Maintenance of Facades’ Claddings

Façades, as the most external building envelope component, are subject to different ex-ternal environmental loads, such as: Temperature, precipitation, damp, and wind. Therefore, the contribution of environmental actions to the occurrence of defects in façades claddings is an important subject of study since these actions strongly affect the degradation process and natural ageing of these components during their service life. In this study, a methodology to support decision-makers in the process of selecting a façade cladding system and the maintenance strategy to implement is presented and discussed. This methodology covers the performance of four façade claddings (ceramic tiling systems (CTS), natural stone claddings (NSC), external thermal insulation composite systems (ETICS), and architectural concrete façades (ACF)) over time, according to three environmental exposure variables (exposure to damp, distance from the sea, and orientation). The databases were established based on the diagnosis of the degradation condition of these claddings in-service conditions, in Portugal. The results reveal that the environmental exposure variables have a significant impact on maintenance requirements and costs. For all the categories of the environmental exposure condition variables, under all scenarios, ETICS is the least favorable constructive solution while CTS is the most advantageous solution. Furthermore, the results show that properly implemented maintenance activities enhance the performance level of building components, which positively affects their degradation behavior over time.

Renovation and innovation using thermal insulation lining systems - Acoustic performance

Retrofit and design of thermal cladding systems provide an opportunity to improve the acoustic properties of a building. However, the complexity of the calculation process to predict sound insulation improvement may inhibit rather than encourage novelty and innovation. This paper investigates whether it is realistic to calculate the frequency dependant sound insulation improvement due to modern thermal insulation wall lining systems with just a few input parameters. The calculation procedure is tested using measured results for one external thermal insulation composite system (ETICS) and three curtain wall systems. The accuracy of the procedure is examined using three factors: (1) precision of the measurement, (2) variation of some of the basic parameters of the calculation procedure, and (3) an estimation of the standard error of the calculation. For the ETICS, agreement within <6.0 dB is achieved across much of the frequency range and the trend of the extended dip due to the spring-mass action of the panel is corroborated. The case for using this methodology on curtain wall systems is adequate, however, the trend of calculated results is mostly outside of the 95% confidence limits of the measured results. Possible reasons for this include lack of airtightness of all curtain wall systems and additional transmission due to radiation into and out of the cavity, neither of which are included in the model. The assumption of radiating points or lines, rather than a radiating surface involving the whole panel, gave better agreement at high frequencies for three of the four measured systems (f ≥ 2500 Hz).

Upward Fire Spread Rate Over Real-Scale EPS ETICS Façades

The expanded polystyrene (EPS) facade has been widely used to save building energy, but it has also caused many severe facade fire accidents worldwide. Especially for aged buildings, the naturally weathered exterior surface layer can further increase the facade fire risk and the fire spread rate (FSR). In this work, a series of real-scale EPS External Thermal Insulation Composite System (ETICS) facades are tested via the JIS A 1310 standard. The EPS thickness varies from 100 to 300 mm, density changes from 15 kg/m3 to 30 kg/m3, and heat release rate (HRR) of window spilled flame ranges from 600 kW to 1100 kW. Tests showed that the surface cement layer was quickly damaged by a spilled flame that provided negligible fire resistance for the internal flammable EPS panel. The measured upward FSR increases with the rising of HRR and with the decreasing EPS thickness like the thermally thin material. An empirical correlation of instantaneous upward FRS is proposed, FSR = 0.22Φ + 3.45 [cm/min], where Φ is a modified fire propagation index derived from the experimental temperature distribution. In addition, a simple prediction method for FSR is proposed for the facade fire and verified by the experimental data. This work provides a useful method to quantify the upward facade fire propagation, which also helps evaluate the fire risk and hazard of EPS ETICS facade prior to the costly large-scale tests and installation.

On the use of dynamic vibration absorbers to counteract the loss of sound insulation due to mass-spring-mass resonance effects in external thermal insulation composite systems

One of the common ways to increase the energy performance of existing buildings is to add a thermal insulation layer to their façade elements, which in turn is covered by a thin protecting cement plaster. Such an arrangement is commonly known as External Thermal Insulation Composite System (ETICS). This article studies the effect of an ETICS implementation induced mechanical resonance mechanism, which results in a loss of performance in the sound insulation spectrum. A mitigating approach is proposed, which is based on an array of dynamic vibration absorbers that were designed to counteract the decrease of the sound reduction index. Using a wavenumber domain approach combined with unit cell FEM-modelling employing Bloch-Floquet boundary conditions, numerical predictions are presented for the sound reduction index. A number of different dynamic vibration absorber designs were tested on a silicate cement brick wall in a transmission loss facility. The predictions are in good agreement with experimental data obtained by classical, microphone based acoustic isolation measurements and laser Doppler vibrometry.

Energy Performance Assessment of Innovative Building Solutions Coming from Construction and Demolition Waste Materials.

Prefabricated solutions incorporating thermal insulation are increasingly adopted as an energy conservation measure for building renovation. The InnoWEE European project developed three technologies from Construction and Demolition Waste (CDW) materials through a manufacturing process that supports the circular economy strategy of the European Union. Two of them consisted of geopolymer panels incorporated into an External Thermal Insulation Composite System (ETICS) and a ventilated façade. This study evaluates their thermal performance by means of monitoring data from three pilot case studies in Greece, Italy, and Romania, and calibrated building simulation models enabling the reliable prediction of energy savings in different climates and use scenarios. Results showed a reduction in energy demand for all demo buildings, with annual energy savings up to 25% after placing the novel insulation solutions. However, savings are highly dependent on weather conditions since the panels affect cooling and heating loads differently. Finally, a parametric assessment is performed to assess the impact of insulation thickness through an energy performance prediction and a cash flow analysis.