The Quality of ETICS in the Context of Energy and Social Changes (Case Study)

Abstract

The paper focuses on the quality of external composite ETICS (External Technical Insulation Composite System) façade systems from a long-term perspective in the context of energy and social changes and subsequent paths of housing construction, including reconstructions and renovations of prefabricated housing developments. These changes follow mainly from the EU energy concept and strategy in relation to housing and have an impact potential well beyond 2030. The aim of the paper is to show, based on field research and laboratory diagnostics on a selected reference sample of housing affected by biodegradation, to what extent the quality of ETICS façades is affected by technological aspects during the application of ETICS exterior plasters and during the implementation of photocatalytic coatings. The investigation shows that the influence of the human factor is one of the main aspects of negative impacts.

1. Introduction

Impacts of the energy crisis are leading to changes in society, and to a change in thinking. This is reflected, among other things, in the construction sector, including new housing construction and renovations. The pressures to reduce the energy demands of buildings bring not only new technologies and new materials, but also give rise to specific problems. In Central Europe, the application of external contact thermal insulation systems, known as ETICS (External Technical Insulation Composite System) [1], has become an affordable and widespread technology when it comes to reconstructions that include the building envelope. The ETICS system has been known in Europe since the 1950s. In the Czech Republic, the application of ETICS has seen a great expansion since the 1990s, mainly due to increasing pressures to save energy. According to publications [2,3,4], ETICS inarguably has many advantages. It improves the energy balance of the building, significantly contributes to savings, is an environmentally friendly material, is recyclable, is part of the circular economy and, last but not least, significantly improves the aesthetic appearance of renovated buildings, thus achieving the aesthetic improvement of urban areas, especially prefabricated panel housing developments. Available data show that, for example, in the Czech Republic, one of the most widespread insulating materials is expanded polystyrene, whose annual consumption in construction is close to 4 million cubic meters [5].

However, many years of experience have shown that it is a mistake to think that ETICS is a maintenance-free material. ETICS requires regular and systematic maintenance. A façade, that is fitted with ETICS without ensuring the provision of systematic care and maintenance will, in approximately 5 years, be affected by biodegradation—especially if it is a facade that is located in an exposed position (such as in proximity to greenery, water areas, northern orientation of the façade without sunlight, etc.). We currently define biodegradation as a modern problem occurring on façades with ETICS. The application of ETICS to perimeter claddings is therefore often associated with a higher risk of biodegradation compared to other façade solutions, such as double façade systems with a ventilated air gap, cladding panels, etc.

To a certain extent, the ever-increasing thickness of the thermal insulation contributes to the biodegradation damage of facades with ETICS. On the one hand, we achieve better thermal and energy properties in accordance with the EU strategy [6,7,8,9,10]; on the other hand, due to generally known building and physical links [11,12], a suitable basis for the colonization of the facade by biodegrading microorganisms is created [13,14].

The impacted, biodegraded façade raises the question, both with the lay and professional public, as to whether the biodegradation of the façade is not harmful to health. The scientific and professional literature and other scientific sources show that the predominant microorganisms in the affected façade are Chlorophycae, Alternaria, Aspergillus, and Cladosporium spores [15,16,17]. It has not yet been found or published that the spores of these microorganisms settling on the outer surfaces of the ETICS perimeter cladding cause serious health problems. In general, it can only be stated that, for example, molds, algae, fungi, and typhus can cause allergenic reactions in particularly sensitive individuals or allergy sufferers [18]. These people may be more sensitive to infections. However, the inhalation of these allergens from biodegraded areas on the ETICS surface, by an individual who is indoors, and this causing an allergic reaction, is very unlikely. An individual’s exposure to allergens is limited by the duration of exposure and the concentration of possible allergens. For residential buildings, we do not expect a large migration of allergens from the external environment from the ETICS surface to the interior. Most apartment buildings, built in the latter half of the last century in the Czech Republic, especially apartment buildings built using prefabricated panel technologies, have ventilation of living rooms by direct ventilation or micro-ventilation [19,20,21]; the concentration of the aforementioned allergens, in a longer period of time, is not expected.

One of the variants for protecting the outer perimeter cladding with ETICS from biodegradation is the application of a photocatalytic coating as part of the systematic care and maintenance of apartment buildings. Materials using photocatalytic active oxide (TiO₂) appear to be promising [22]. Photocatalytically active coatings in the form of paints can, thanks to their oxidizing potential, prevent the growth of mold and algae on house facades. A prerequisite, however, is that the surface of the facade is properly clean and free of all impurities and dust before applying the photocatalytic coating, and will not be wet, because these components offer the potential for the settlement and viability of microorganisms. Another is that the application will be performed correctly with respect to the technology.

2. Method of Study

The aim of the paper is to compare, based on diagnostics and their results, whether there are obvious differences in manifestations of biodegradation on facades with ETICS that have a photocatalytic coating and the facades with ETICS without a photocatalytic coating. The basic starting point is field and laboratory analysis and surveying. The facades of selected apartment buildings with the ETICS application (see Appendix A) serve as the background material for the laboratory analysis; samples were taken from the façade surface for diagnosis and subsequent laboratory analysis, followed by a comparison and evaluation. The procedure is divided into three steps and is shown in Figure 1. The number of samples taken and the composition of the cladding are given in

Table 1. Evaluation of apartment buildings.

Number of Houses	Perimeter Cladding	Photocatalytic Coating
1 Number of samples: 3	Facade material solution: Gas silicate block panel th. 300 mm + 150 mm ETICS	Yes
2 Number of samples: 3	Facade material solution: Reinforced concrete panel th. 300 mm + 150 mm ETICS	No

. Samples were always taken from the north or northwest side of the building, in places where biodegradation was more than 0.50 m². Three samples were taken from each apartment building; a total of six samples were taken for diagnostics and laboratory analysis.

Characterization of individual steps according to Figure 1:

• Selection of urbanized area with housing development and selection of the building (field survey);
• Visual inspection of selected objects and diagnostics including examination of the influence of external factors on the growth of microorganisms (field survey);
• Sampling and microscopic survey of the surface of external plasters (diagnostics);
• Laboratory analysis of collected samples, definition of the type of microorganisms (diagnostics);
• Comparison and evaluation.

3. Theoretical Basis

The theoretical basis of the issue lies in structural architectural work for both new buildings and reconstructed buildings. When applying the principles of reducing the energy ratings of buildings, it is necessary to pay attention to the complexity of interaction links “buildings-materials and technology-environmental contexts”.

To investigate the essence of the biodegradation of facades, in addition to environmental contexts (for example, proximity to water and greenery and the direction of prevailing winds, the direction the building faces, dust concentration, industrial environment, etc.), we must look at the theoretical foundations of thermal processes in building structures and the technical properties of building materials and products, including their technological processes.

The theoretical basis of biodegradation is based on the fact that microorganisms need moisture, nutrients, light, and oxygen for life. ETICS external plasters are more stressed by moisture than plasters of single-layer perimeter structures (for example, a panel concrete wall or a masonry wall). Water from the surface of the outer external plasters on the substrate, which is not provided with ETICS, migrates by capillary conductivity towards the dry surface, and thus the occurrence of a water emulsion compared to ETICS facades is significantly short term. In contrast, the polystyrene used in ETICS is insoluble in water and has a closed microscopic structure, so that closed pores in their structure absorb almost no water, and water is concentrated at the surface [23,24]. In contrast to buildings without ETICS, the surface layer of buildings with ETICS is not heated, especially in the autumn and spring months, by the heat that escapes from the interior of the buildings. On the contrary, the greater the thickness of the insulation, the greater the theoretical prediction of moisture on the outer surface and the impact on the facade by biodegradation—the facade is wet. The outer plasters are strongly cooled, particularly on clear nights, when the surface temperature of ETICS decreases faster than the ambient air temperature. If the temperature drops below the dew point, moisture is precipitated on the cold surface of the facade. As a result of cooling, there is condensation and moisture, which is kept on the facade surface, especially on the northern sides of the building or sides that are more shaded. Thus, the conditions for the growth of microorganisms become favorable, as microorganisms have a sufficient nutrient supply. In masonry without thermal insulation, the risk of night condensation last for approximately 2 months of the calendar year. In masonry with thermal insulation, there is a risk of water vapor condensation on the I surface under night conditions for up to 6 months [25].

The assessment of ETICS durability is defined by legislative documents and EAD Directive 040083-00-0404 [26,27]. The Directive lists a number of technical aspects that relate to the durability and aging of ETICS. However, environmental aspects arising from the built-up area environment are not taken into account, such as impacts from industrial areas and air quality (airborne dust concentrations), the proximity to greenery and water, the impact of prevailing winds, technological aspects of ETICS execution relating to the quality exterior plasters, etc. They are not appropriately taken into account in the structural physical context and physical processes that compare environmental environments, the buildings, the materials, and the technologies (see above).

3.1. Analysis and Evaluation of Apartment Building Number 1

The apartment building is located in an urbanized residential area. The apartment building was built in the 1970s. There is park greenery near the apartment building and there are no water areas near the apartment building that would predict the possibility of the facade being attacked by biodegradation agents such as algae, fungi, and hypha. The exterior perimeter cladding of Apartment building number 1 is comprised according to Table 1. (number of samples, 1). The perimeter cladding is provided with a photocatalytic coating, and the façade of the apartment building is not regularly cleaned (approximately in a five-year cycle). The age of the photocatalytic coating is more than 5 years.

The condition of the façade in the area of the silicone plaster, as derived from 3 samples, is shown in Figure 2; the biodegradation is visually perceptible.

3.2. Analysis and Assessment of Apartment Building Number 2

The apartment building is also located in an urbanized residential area and was built in the 1980s. There is a park with mature greenery near the apartment building and there are no water areas near the apartment building that would predict the possibility of the façade being attacked by biodegradation agents such as algae, fungi, and hypha. The exterior perimeter cladding of Apartment building number 2 is comprised according to Table 1. (number of samples, 2). The perimeter cladding was not provided with a photocatalytic coating, and the façade of the apartment building is not regularly cleaned (approximately in a five-year cycle). The issue of biodegradation in this type of apartment building, and others with the same constructional and material design, has been described in detail in the literature [4,28]. The state of the façade derived from 3 samples is shown in Figure 3; marked, surface-wide biodegradation damage greater than 0.50 m² is visually perceptible.

4. Results and Discussion

4.1. Results of the Apartment Building Number 1

The results of diagnostics and microscopic evaluation show that, at the site of biodegradation damage, the plaster is heavily degraded by lichens and also by black mold. A microscopic analysis (using an optical microscope) also shows that molds and lichens are located below the surface of the photocatalytic coating and grow out of small micro-fissures and cracks in the photocatalytic coating. The assumption that the roots of the biotic infestation are below the surface of the coating was supported by electron microscopy. The coating layer was found to be approximately 50 μm, which is a very weak protective layer, as a typical coating layer is usually 150 to 500 μm and is applied in 2 to 3 coats, see Figure 4a,b and Figure 5, in the side section of the paint. Figure 5 shows a top view and the photocatalytic coating at 100,000× magnification, showing the nanostructured character of the protective layer surface in the range of 30 to 150 nm, which corresponds to a photocatalytic coating with binders [29,30].

4.2. Results of the Apartment Building Number 2

From the diagnostic results and microscopy evaluation, it follows that the site of the biodegradation the façade has been degraded by cyanobacteria, algae, and lichens. These microorganisms were easily detectable by electron microscopy, confirming a group of green terrestrial algae-forming colonies, see Figure 6a,b.

4.3. Technological Aspects of Exterior ETICS Facades

Technological aspects are very important when applying ETICS external plasters, including the technology of applying protective photocatalytic coatings. Any non-compliance with strict technological procedures forms the basis for a biotic attack on the façade, even though the façade is treated with a photocatalytic coating. If the surface is not thoroughly diagnosed and the base is not cleaned in accordance with the prescribed regulations [30], undesirable phenomena in the form of the colonization of facades by microorganisms may occur. An example of a technological error can be seen in Figure 7a,b, where, upon microscopic examination, structural anomalies (of a technological nature) are apparent, which arose during the execution of exterior ETICS facades in the form of micro-fissures or micro-abrasions. These can eventually contribute to greater absorption and accumulation of water and moisture, thereby promoting or providing the basis for the growth of microorganisms. The surface quality of the external plaster must not show any structural anomalies, and the surface must maintain its integrity.

4.4. Remarks

The results of field research, diagnostics, and laboratory research show that the degradation of the external surface of ETICS occurs both in a façade that is not treated with a photocatalytic coating, as well as in a façade that is treated with photocatalytic coating, see

Table 2. Evaluation of field research, diagnostics, and laboratory analysis.

Locality	Number of Buildings (Total)	Number of Buildings with Photocatalytic Coating	Number of Samples from 1 Buildings	Ingrowth of ETICS Microorganisms	Number of Positive Samples: Microorganism	Genus
Ostrava	9	1	3	Yes	3	Chlorophycae Alternaria Aspergillus Cladodosporium spores
Havířov * Ostrava	33 9	0 0	0 3	Yes Yes	3	Chlorophycae Alternaria Aspergillus

Note: * Link to long-term monitored objects—see Appendix A.

.

The first negative phenomenon to be perceived is the color change of the facade, which reduces the quality of the aesthetic appearance when looking at the building. This can be characterized as a secondary phenomenon because, upon deeper examination, it was found that in selected samples the primary negative factor occurs in the phase of diagnostics of the base layer before the actual application of the photocatalytic coating or in inconsistent technological implementation. Technological error usually leads to stress in the pore system of the exterior plasters of ETICS, and the result of this reaction is an increase in the size of the pores in the plaster. Then, due to natural building and physical phenomena and regularities, there is a greater strain on the facade by water and moisture (data on diagnostics, implementation technology, etc., can be monitored on the basis of an entry in the construction diary; the construction diary is an integral part of the reconstruction work and is a key document in the construction and reconstruction process).

Although the reference sample is small, the results can be interpreted for similar types of housing construction (especially prefabricated housing construction), in the Czech Republic. This assumption can be pronounced on the basis of data and survey results for prefabricated housing constructions implemented in the Ostrava-Karvina region, in two selected locations. Prefabricated housing constructions were not equipped with ETICS after 2000. The results showed that defects and disorders were very similar, if not the same, independent of the locality where the panel housing construction was located.

Reconstruction work to improve thermal energy properties with ETICS applications has been used in the Czech Republic since the start or redevelopment, and it expanded with the introduction of state subsidies and financial support (See Appendix B, Figure A1 and Figure A2).

The application of ETICS to housing is widespread throughout Europe; it is also supported by the European Union, in terms of sustainability. Therefore, the issue needs to be further addressed in relation to new strategies [31,32].

Further research of the issue of biodegradation of ETICS must not be neglected. Future directions of research must especially focus on:

• Diagnostic aspects prior to the actual use of ETICS or before the application of protective photocatalytic coatings following the recommended standards and methodologies;
• Diagnostics and laboratory analyses of ETICS surfaces, which are affected by micro cracks, to determine whether these create the potential for the growth of carcinogenic fungi under external plaster, and to eliminate the possible potency of allergens;
• Environmental contexts in the given urbanized housing development zone.

5. Conclusions

A good standard of living is a basic component and necessity in people’s lives. The approach to housing quality assessment in the 21st century is multidisciplinary. Healthy and good quality housing must respect not only the technical and building principles of design and construction, but also the social, cultural, and environmental contexts.

In the 21st century, housing has taken a significantly different course of development than in previous centuries. The main role in its development is played by the energy aspect, which has an impact on all economic areas, including the construction of new flats and the reconstruction of existing housing developments. The innovation potential in construction has a dynamic character in the application of new materials and nanotechnologies. However, great attention must be paid to the quality of construction, the quality of reconstructions and, finally, the standard of the indoor environment. The application of ETICS spanning a monitored period of over 30 years shows great potential for further development. However, it is necessary to eliminate the influence of the human factor, which can negatively affect the resulting quality; this avoids the “trial and error” method. ETICS application must be understood as an efficient technology that leads to environmental protection, improves the energy performance of apartment buildings, and is efficient.

Emphasis needs to be placed on balancing the main pillars of construction in terms of energy efficiency, namely the sustainable structural and architectural design of buildings, efficient technologies, and the use of renewable resources. These pillars relate to new and renovated buildings. ETICS is an irreplaceable component of construction, especially for reconstructed buildings.

The results of the case study show that, in connection with the application of ETICS, all the risks occurring when implementing ETICS must be addressed, by ensuring the necessary quality in the implementation of ETICS. This can be achieved by minimizing or completely eliminating resources and risk factors that create the potential of possible biotic infestation. In particular, this involves a thorough diagnostic of the substrate before starting ETICS work (elimination of the organic infestation of the original substrate, cleaning of the substrate, elimination of moisture in the original substrate), the consistent technological procedure for performing all layers of ETICS, the choice of external plaster with less grain, and application of photocatalytic protective coatings regular and systematic maintenance in a five-year cycle. Excluding the potential of biotic infestation then leads to a quality result. This means that the possible emergence of disputes and molds in the ETICS is not only possible on the surface of the external plaster, but also under the plaster. It can be said that the building is “healthy” and does not create the potential for negative discussions regarding the harmfulness of biodegradation.

The essence of this case study is that it shows how the underestimation of the importance of diagnostic and technological work in the construction leads to a biotic attack on both external plasters without a photocatalytic coating and plasters with a photocatalytic coating.

In addition to high-quality technological processes in the field of ETICS, it is possible to apply new generation thermal insulation to the facade insulation, such as gray polystyrene, which is thinner and lighter than white expanded polystyrene while maintaining thermal insulation properties and has low thermal conductivity. It is an alternative solution where, with a smaller insulation thickness, we achieves a better value of the heat transfer coefficient.

Other variants include ventilated facades and ventilated tiles. It is always necessary to consider the long-term perspective, the options of the investor, and the set system care and maintenance system.

Reducing the energy performance of buildings is part of a long-term plan for Europe’s transformation into a climatic neutral continent by 2050 [33]. Buildings and their renovations play a key role in achieving the set goals. This is partly because buildings account for up to 40% of energy consumption and up to 36% of greenhouse gases in the EU. ETICS is an integral part of these strategic plans in the context of social and societal change.