Long-term durability of External Thermal Insulation Composite Systems (ETICS): comparing the impact of natural exposure and accelerated climate aging

Abstract

The use of External Thermal Insulation Composite Systems (ETICS) has been consistently growing over the last decade. However, these systems are frequently exposed to weathering and anthropic factors affecting their long-term durability. This study intends to evaluate and compare the durability of four commercially available and certified ETICS after one year of natural aging (at urban and maritime zones in Portugal) and after accelerated climate aging (hygrothermal cycles). The systems were selected in order to have different composition, i.e., thermal insulation (EPS, ICB, or MW), base coat (with cementitious or hydraulic lime binders), and finishing coat (acrylic, silicate, or lime-based). Physical and aesthetic properties of non-aged, naturally and artificially aged systems were experimentally assessed. The biosusceptibility of ETICS rendering systems was also investigated. Results showed a significant loss of surface hydrophobicity after accelerated aging and traces of mold growth on the surface of the systems. The durability of the ETICS was significantly more affected after accelerated climate aging. Even though the amount of water for the accelerated and natural aging was quite similar, the moisture load happened in a much shorter timespan considering the hygrothermal artificial aging, leading to different impacts on the systems. These results, linked with the expected increase of extreme raining events derived from climate change, point out that ETICS could be more prone to premature failure and significant anomalies in the future. Furthermore, considerable color change for all systems was observed after aging, confirming aesthetic alteration. Results contribute toward the development of ETICS with enhanced durability.