This expert opinion was commissioned by EUMEPS. Published by the FIW in November 2021.
Background and scope of the project
ETIC-system is a well-known efficient system that offers peculiar properties thanks to the cooperation and interaction of its components that make it an optimal system for improving the thermal performance of the building envelope. However, the performance of ETICS and its suitability for special applications cannot be derived only from product testing according to the identification/specification standard. The tests described by the standard, indeed, do not provide information about the sensitivity of variations of single properties, nor do they provide a full set of possible relevant properties and statements about interactions under particular conditions. The practical interactions are not described by the standards, only a set of mainly descriptive single characteristics based on a defined laboratory framework is given.
Furthermore, over the last 50 years, most of the products were further developed changing their composition, thermal conductivity, water vapour transmission properties, mechanical properties and above all increased thickness to keep up with the increase of energy requirements. New products based on other thermal insulations were brought to the market as well. Therefore, the need to find a set of characteristics behind the optimal performance of ETICS and to understand the impact of the system component parameters on the system’s performance has arisen. These properties need to assess the hygrothermal and mechanical performance since they are dominant for the performance of ETICS. The study focuses on the thermal insulation component (EPS and mineral wool) due to the range extension of the task.
The project was carried out during the intensive work performed by TC88/WG18 on the development of the new harmonised standard (prEN 17237). Therefore, it is raised the need to create insight into the current status and development of the knowledge on the ETICS-topic to raise questions on the validity of the available declarations on the product characteristics and on the validity of the used models and test methods. In case of ETICS, the whole system is the product that is CE marked according to the harmonised standard. Therefore, the DoP is drawn up for ETICS by the system holder who is responsible for the conformity of the system.
Furthermore, declared values only partly represent the real values of the single products since they are given in spans of values and classes in the DoP and for each test, a specific product is tested and therefore there is no certainty that the product delivered on the building site has the same product properties as the set of declared values given by the manufacturer. Furthermore, the producers have also the possibility to declare the performance of the product in a conservative way. This means that the declared values could be (much) smaller than the test results and - as a consequence – the system performance might be different from expectations.
Indeed, the main purpose of the declared value is to allow identification of a product to provide unique description for the European market and not for evaluation design purposes. The set of relevant characteristics can be called the “fingerprint” of an ETICS (detailed definition in chapter 2.4 of the SoA report). The Fingerprint stands for unique identification and its concept can assume different shades. On the material level, the relevant set of characteristics is based on declared values for the product identification based on technical regulation. In addition, the Fingerprint can represent the specific performance of a specific product determined by a full set of tests on one batch. These are product properties that identify the product and allow regulations for sale and application. However, this identification does not necessarily give sufficient information to describe the building physics behaviour of the system. Therefore, additional parameters are needed. As an extension of the Fingerprint idea, the building physics fingerprint of a system deals with material properties that are based
on chemical and physical structure of the components and their interaction in the system, considering typical impositions.
Besides the role of describing the components and the system, the Fingerprint can be considered as the relation between the material properties or layer properties and the system performance. This means that by identifying the Fingerprint of an ETICS, it is possible to evaluate the tolerances of the products in relation to the performance of the system. Therefore, the evaluation of this set of interlocking product and layer performances show themechanisms behind the success and failure of an ETIC-system.The general aim of the research project is to identify relevant characteristics in terms of material properties that are suitable for modelling the performance of an ETIC system and can give information behind its key factors.
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