The absolute reduction in the consumption of fossil fuels and the increase in energy efficiency is the necessity of an effective transformation to a zero-carbon global economy, which will allow us to stop and ultimately mitigate climate changes that threaten our civilization. A circular economy, resources, affordability, and energy efficiency, decarbonizing the economy are priority issues for future sustainable development in the EU [1]. The European Commission, recognizing the importance of the problem in its ambitious European Green Deal strategy, decided to make Europe the world leader in the circular economy and the first climate-neutral continent [2]. Additionally, to help Member States recover from the crisis following the COVID-19 pandemic to the Multiannual Financial Framework (MFF) for 2021–2027, the EU added the recovery plan (NextGenerationEU). The EU constructed the MFF and NextGenerationEU in order not only to rebuild the EU economy but also to drive the green transformation. EUR 373.9 billion has been allocated to natural and environmental resources, including EUR 356.4 billion under the MFF [3].

In 1957, the world’s first external thermal insulation composite system (ETICS) was installed on a residential building in Berlin. Following the Germans, this solution was introduced by the Swiss and the Austrians. The beginning of the 1970s was a breakthrough in gaining European markets for ETICS when many countries were shaken by the first fuel crisis of such magnitude. The resulting increase in energy prices became an impulse to reflect on the need to minimize heat losses in the building—the development of the industry accelerated, and the awareness of the benefits of external insulating walls was growing [4]. Another critical stage in the development of ETICS in Europe was the admission of new member states from Central and Eastern Europe to the EU. Until the end of the 1990s, the construction of prefabricated residential housing was standard in these countries, the number of buildings requiring insulation was enormous [5]. From the beginning of this century, the EU, implementing the provisions of the Kyoto Protocol and the EU’s policy, defined increased energy efficiency as a strategic goal. The expression of EU activities in this area was the adoption of three key directives that cover the reduction and optimization of energy consumption in building over the past twenty years, followed by the adoption in 2002 of Directive 2002/91/EC [6], and in 2010 of Directives 2010/31/EU [7] and 2018/844 [8]. All this and the fact that the years of using ETICS have proven in practice their durability and long-term performance [9] resulted in the development of ETICS, making this method the most widely used method today in the EU [4]. It was and is not without significance in the success of the ETICS that the installation itself is relatively quick and does not require the use of too complicated methods. ETICS is used to insulate both new and renovated buildings. In 2017, more than 234 million square meters of external walls of buildings were insulated using ETICS [10]. According to the latest data of the European Association for ETICS, in 2020, 332.0 million square meters of external walls with an average insulation thickness of 125 mm were insulated in Europe [11]. On the European market, ETICS are offered by big international companies and many small and medium-sized enterprises.

2. ETICS from Academia Perspective

Before analyzing the issues related to the sustainability of ETICS from a scientific perspective, it is essential to recall one more important fact about ETICS. Namely: ETICS is the set of components specified by one base coat and one type of thermal insulation product ^[12][13][17,19]. Of course, in scientific research, the goal is to achieve the progress of knowledge by striving to discover so far unknown, new dependencies, by questioning what exists. A scientist who wants to achieve his goal can freely model his research. However, when examining a thermal insulation system consisting, for example, of two different thermal insulation materials, it should not be called ETICS, which is common, but rather the thermal insulation system of external walls.

The second important issue is the need to consider ETICS as a whole in testing and assessing the constancy of performance. It is evident for the producer, and this is the foundation of AVCP. Such a definition of ETICS in EAD 040083-00-0404 ^[13][19] and earlier in ETAG 004 ^[12][17] is associated with a necessary consequence: changing at least one ETICS component requires re-evaluation. From the scientific point of view, this is a limitation, which is also apparent.

The third important issue that needs to be addressed before starting the analysis of the works on sustainability and ETICS in this chapter, is that it is necessary to consider ETICS only in a holistic way from the producer’s perspective. From this perspective, the statement that possible synergetic effects among different agents are often neglected by the technical documents on the evaluation of ETICS ^[14][79] is unfounded. The nature of standardization documents is, among other things, to ensure that unnecessary diversity is reduced in the production. However, it does not mean that the manufacturer does not perform multi-aspect analysis and does not perform additional tests, which, however, he does not communicate due to the requirements of AVCP and CE marking. Another dimension is the assessment of the construction product by market surveillance authorities ^[15][80]. Each responsible producer must consider his ETICS being a construction product in a comprehensive manner, remembering that in a problem situation, he will be, next to the contractor, the addressee of the customer’s complaint.

The three aspects mentioned above related to ETICS as a construction product, whose functioning on the market is regulated by CPR, are perceived differently from industry and academia. It is not that science sees them in the same way as the industry does. That is not the point. However, it is crucial to be aware of these different perspectives. It is also essential in the aspect of sustainability as science, where it is often necessary to redefine the role of the researcher ^[16][81].

The issues related to sustainability, understood as the use of environmentally friendly raw materials and secondary materials in ETICS quantified with a set of environmental indicators, are not the subject of too many publications in scientific journals. There are various reasons for this. It is probably the result of the fact that the environmental aspects of thermal insulation materials are well described in the scientific literature ^{[17][18][19][20][21]}[68,82,83,84,85]. The thermal insulation material is an ETICS component that has a significant impact (50–90%) on the entire system ^[22][23][66,67]. Therefore, determining the environmental impact of the ETICS seems to be a bit secondary issue.

Kraus et al., recognizing that ETICS is a very well-studied system in terms of technology, thermal insulation, and economics but much less known in the health and environmental aspects, performed analysis using Data Envelopment Analysis (DEA). In the seven thermal insulation materials analyses, the purchase price was an economic variable, and thermal resistance was the technical parameter. The author’s survey used a questionnaire to determine the social aspect, and six environmental indicators (GWP, AP, EP, ODP, POCP, PERT) represented the environmental dimension. Out of the seven analyzed thermal insulation materials, three—EPS, blown cellulose, and wood wool—were classified by the authors as effective. The remaining four (XPS, glass wool, stone wool, and polyurethane foam) were assessed as ineffective in the analysis ^[24][86]. The successful use of the DEA method to determine the most optimal ETICS solution taking into account various positive and negative aspects has been described previously ^[25][87]. The ETICS was also subject to another assessment, which includes integrating a system in a building on a building’s global performance (energy, environmental, economic, and social) by Rezai and coworkers ^[26][88]. The analysis of thermal insulation materials (rock wool, EPS, XPS, kenaf, sheep wool, cotton, recycled glass, recycled PET, and recycled textile) subjected to multi-criteria sustainability assessment using the TOPSIS method interval revealed that recycled glass and sheep wool are the most desirable options in the conducted research taking into account various scenarios ^[27][89]. At this point, however, it is worth emphasizing that the most commonly used thermal insulation material in the construction industry is EPS, whose share in the European ETICS market in 2020 was 70%. According to the same source, MW had a 26% market share and all other thermal insulation materials only 4% [11]. It is also worth adding that in ETICS, the use of new biodegradable insulation materials, such as straw-based insulation panels with casein glue, is still being considered ^[28][90].

Potrč et al., in their research, compared the environmental impact of three systems of ETICS with the same fixed thermal transmittance parameter value of 0.27 W/ m²K, which corresponded to the use of EPS 14 cm thick, MW 12 cm, and wood fiberboard of 16 cm thick. The analysis covered the following seven categories: GWP, AP, EP, ODP, POCP, ADP, and ADP fossil. The analysis results clearly showed the advantage of the ETICS with EPS for the majority of the studied categories of environmental impact. ETICS with wood fiberboard stands out in the GWP category because wood stores carbon dioxide and therefore contributes to reducing global warming ^[23][67]. Other environmental impact studies of ETICS with EPS and MW using real production data from 2017 (modules from A1 to A3) for an ETICS production corresponding to approximately 10 million square meters of insulated external walls showed that ETICS with MW has a more negative environmental impact than a system with EPS for all nine categories tested: GWP, AP, EP, ODP, POCP, ADP, ADP fossil, PERT, and PENRT ^[22][66].

Michałowski et al. studied the impact of rendering type on the environmental characteristic of ETICS with EPS. The subject of the analysis were nine environmental categories (GWP, AP, EP, ODP, POCP, ADP, ADP fossil, PERT, and PENRT) for systems with four different plasters (mineral, acrylic, silicone, and silicone-silicate) calculated based on production data for modules from A1 to A3. When analyzing the values of the studied indicators, it was shown that the choice of raw materials used to produce ETICS components has the most significant impact. At the same time, the share of the production process and internal transport are secondary. Systems with mineral plaster were characterized by the lowest negative impact on the environment (seven out of nine analyzed environmental categories) among the studied rendering systems ^[29][64].

Librelotto et al. analyzed the final layer of ETICS being decorative mineral render with a higher amount of lime and lower cement content. This solution is more environmentally friendly than ETICS, with mineral renders based only on cement as a binder. In addition, ETICS with cork boards (ICB) was assessed, and the use of this natural product makes ETICS even more environmentally friendly ^[30][91].

The cementitious adhesives that are part of the ETICS were also subject to environmental impact studies. The subject of the analysis was cementitious adhesives for bonding insulation material and adhesives for a base coat used in ETICS with EPS and MW systems. Comparisons were made for nine environmental categories: GWP, AP, EP, ODP, POCP, ADP, ADP fossil, PERT, and PENRT. The tested cementitious adhesives are characterized by the relatively low impact on most studied environmental categories except ODP and PERT ^[31][92].

An important aspect when considering the environmental impact is the timing of the assessment. The constant development of civilization and the related development of production technology, changes in raw materials to more environmentally friendly ones, change the environmental impact of products, including, of course, ETICS and all its components. Sustainability-oriented assessment of ETICS with EPS over a five-year period showed that changes in individual environmental indicators (GWP, AP, EP, ODP, POCP, ADP, ADP fossil, PERT, and PENRT) are significant, i.e., from several to several dozen percent ^[32][70]. It is a crucial aspect of the environmental assessment of the ETICS that must be taken into account when establishing the assessment criteria in the future.

The growing interest in environmentally friendly materials has led to the evaluation of ETICS with panels of cork insulation (ICB). The study of the global performance of systems with the ICB and EPS by Malanho et al. has shown that ETICS with ICB that reduces the environmental footprint is characterized by satisfactory global performance, similar to ETICS with EPS global performance ^[33][93]. Matos et al. presented an overview of the LCA study of ETICS with ICB developed to obtain EPD according to EN 15804 and ISO 14025 ^[34][94]. Recently, Silvestre et al. considered ETICS with EPS and ICB in the energetic renovation of the building envelope during a fifty-year study period. The use of ICB instead of EPS is beneficial in terms of environmental load for GWP and consumption of non-renewable primary energy ^[35][95].

The above-discussed environmental impact of the ETICS was related, first of all, to the environmental burden caused by the production and installation of the ETICS presented under the EPD concept resulting from EN 15804. There is another aspect of the environmental impact being the subject of the publication related to the maintenance of ETICS. It applies in particular to the aspect of possible leaching of chemical compounds derived from the biocides used, which Minarovičová emphasizes in her works ^[36][37][38][96,97,98]. Recognizing the importance of maintenance of ETICS, it is worth noting that damages or degradation of ETICS do not occur more often than in the case of walls covered with traditional renders. Moreover, the costs and frequency of ETICS maintenance are comparable to those external walls covered with traditional renders [9].

3. Conclusions

3.1. General

The analysis of the European Technical Assessments for ETICS, which were valid on the day of the analysis, showed that the Czech technical assessment body (TAB) issued the most documents—230, followed by Polish—124, German—84, and Austrian—70. It is in line with the estimation of the ETICS market, according to which as many as 142 million square meters of external walls have been insulated with ETICS in Central European countries [11]. TABs from four of the Scandinavian countries (Denmark, Finland, Norway, and Sweden) issued only four ETAs, which is also not surprising when you compare this number with the northern European market estimated at only 2.1 million m² [11]. Only 20 ETAs for ETICS have been issued based on EAD 040083-00-0404, although this document is valid from the end of October 2020.

Despite that sustainable use of natural resources is the content of BWR 7 from 1 July 2013, i.e., the day when CPR requirements were applied in the EU countries, not so much has happened in this respect in the case of ETICS. In contrast to the 798 issued ETAs, the number of EPDs developed and verified by EPDs program operators is much smaller. Only 15 EPDs for ETICS with EPS, XPS, and MW identified in the EPDs program operators databases were analyzed. This insignificant number of EPDs for ETICS compared to the issued ETAs corresponds to a real interest in environmental impact issues. In some EU countries, there are national systems for placing construction products on the market in addition to the CE marking system, which also means a certain number of technical assessments for ETICS on the national level in the Member States. Of course, this is also the result that BWR 7 (sustainability) is not mandatory when the manufacturer carries out AVCP for ETICS. In addition, such a small amount of EPDs for ETICS is the result of the fact that, quite commonly, ETICS in terms of sustainability is perceived only through the prism of thermal insulation material. In the case of thermal insulation materials, the number of EPDs is much greater. For comparison, it is worth mentioning the recently published EPDs review of various insulation materials, in which Grazieschi et al. identified and analyzed as many as 156 EPDs ^[18][82].

The analysis of the GWP value for ETICS based on the 15 EPDs considered in this article shows that the general trend for each tested thermal insulation material used (EPS, XPS, and MW) in ETICS and the interrelationships between the ETICS and the three thermal insulation materials tested are identified. In many cases, the discrepancies between the GWP values for the same systems are so significant that it would not be possible to determine a threshold value of GWP for AVCP arbitrarily. The same is for the other environmental indicators. An additional argument pointing to the difficulty of using environmental indicators values for AVCP is that environmental indicators are determined based on historical data, which change over time. It is an additional aspect that prevents the effective use of environmental indicators for AVCP for ETICS. At this point, it is necessary to emphasize that EPDs are extremely useful and essential documents, and their use as a benchmark even though EPDs often vary broadly in terms of reporting results is invaluable ^[39][74]. Additionally, from the producer’s perspective, knowledge of environmental impacts and their changes are crucial for the continuous improvement of production and procurement processes ^[40][99]. For these and other reasons, actions are advisable to increase the number of EPDs and thus make the databases more representative (e.g., the pre-verified EPD tool) are advisable ^[41][100].

The analysis of available EPDs in terms of one environmental indicator—GWP for the tested ETICS with EPS, XP, and MW—showed that, in the future in AVCP in the field of BWR 7, there is a need to define other requirements than those related to EPD resulting from EN 15804. It seems that it is justified to pay attention to the durability of ETICS and redefine the scope of the sustainability assessment using this feature.

The small number of scientific publications on the environmental impact of ETICS compared to the total amount of scientific papers on ETICS (more than 150) is due to various reasons. Among which should be mentioned: the identification of ETIICS when considering environmental issues only with the thermal insulation material and the fact that scientific publications mainly use data from EPDs for ETICS developed by manufacturers.

3.2. Featured Application from the Construction Products Industry Perspective

This work shows the status of sustainability criterion introduction/evaluation in the AVCP process of ETICS. The requirement resulting from BWR 7 is not mandatory, and therefore not so many manufacturers evaluate their construction products regarding BWR 7. One of the few tools to determine the environmental impact assessment of a construction product, the EPD developed following EN 15804, is used to a limited extent. The analysis of available EPDs for ETICS showed that many of the specified environmental impacts are inconsistent. In the present situation, it isn’t easy to imagine that they could be the basis for establishing values of evaluation criteria. Moreover, the environmental impact indicators specified in EPDs refer to an individual system at a given time. In addition, they are determined based on historical data, and production processes and technologies undergo constant changes, which significantly affect the value of these indicators. Despite the lapse of more than eight years from the entry into force of the CPR requirements and the appearance of BWR 7, the possible implementation of a mandatory assessment in this area is not possible. Due to the importance of sustainability and the urgency of actions that should prevent unfavorable environmental changes, it seems necessary to change the approach. A possible revision of the CPR may reorganize the basic requirements and change the rules for adopting technical specifications.

In the light of the above undoubtedly crisis state of the sustainability issue in AVCP, it should be emphasized that the EPD is an important educational instrument in various dimensions. EPD is a source of knowledge for the user/customer and the manufacturer himself, which, through periodic evaluations and publication of the EPD, can monitor its activities in sustainability.