External Thermal Insulation Composite Systems: Critical Parameters for Surface Hygrothermal Behaviour

Abstract

External Thermal Insulation Composite Systems (ETICS) are often used in Europe. Despite its thermal advantages, low cost, and ease of application, this system has serious problems of biological growth causing the cladding defacement. Recent studies pointed that biological growth is due to high values of surface moisture content, which mostly results from the combined effect of exterior surface condensation, wind-driven rain, and drying process. Based on numerical simulation, this paper points the most critical parameters involved in hygrothermal behaviour of ETICS, considering the influence of thermal and hygric properties of the external rendering, the effect of the characteristics of the façade, and the consequences of the exterior and interior climate on exterior surface condensation, wind-driven rain, and drying process. The model used was previously validated by comparison with the results of an “in situ” campaign. The results of the sensitivity analyses show that relative humidity and temperature of the exterior air, atmospheric radiation, and emissivity of the exterior rendering are the parameters that most influence exterior surface condensation. Wind-driven rain depends mostly on horizontal rain, building’s height, wind velocity, and orientation. The drying capacity is influenced by short-wave absorbance, incident solar radiation, and orientation.

Application of the Factor Method to the Service Life Prediction of Etics

“…These systems began to be used almost exclusively in commercial buildings, being gradually applied over the years as a cladding solution in residential buildings. Nowadays, this system is applied in external walls of new or refurbished buildings in order to improve their thermal performance, namely through: i) the reduction of external walls' thickness -the characteristics and configuration of the thermal insulation system of the building envelope should be defined according to the outside environmental conditions as well the indoor thermal comfort requirements (Ucar & Balo, 2010); a study performed by Theodosiou and Papadopoulos (2008), comparing different insulation solutions, reveals that the ETICS systems (with a solution composed by a single brick wall with a thickness of 21 cm) allows reducing the required heating power by around 21% when compared to the most common type of insulation configuration (double brick wall, with a thickness of 30 cm); ii) the correction of thermal bridges, also preventing the moisture condensation; ii) the active contribution to the conservation of natural resources by increasing the insulation of buildings, reducing the energy losses through the substantial reduction of heating and air conditioning costs (Kolaitis et al, 2013;Amaro, Saraiva, de Brito, & Flores-Colen, 2014;Barreira & Freitas, 2014;Fernandes, de Brito, & Cruz, 2016a).…”

“…These solutions should have a well-planned integration in the façades, fulfilling all the design and detailing requirements (Fernandes et al, 2016a). This cladding system comprises the following layers: the thermal insulation material (boards of expanded polystyrene -EPS, extruded polystyrene -XPS, mineral wool, among others) and the necessary components and specified reinforcements (glue and/or mechanical fastening devices) to ensure the adherence to the substrate; the thin plaster laid in several coats reinforced with a glass fibber mesh (additionally, a primer coat can be applied after this reinforced layer) and, finally, the finishing decorative layer (Collina & Lignola, 2010;EAE, 2011;Amaro, Saraiva, de Brito, & Flores-Colen, 2013;Barreira & Freitas, 2014;Fernandes, de Brito, & Cruz, 2016b).…”

Influence of Rendering Type on the Environmental Characteristics of Expanded Polystyrene-Based External Thermal Insulation Composite System

“…• influence operation durability, It helps to keep its operational performance and functionality after a long time. ETICS systems eliminate the possibility of water vapor condensation in the walls and prevent the growth of fungi and mold [22]. With no thermal insulation, a sudden temperature drop takes place in a wall structural material and-due to its low thermal resistance-puts it at risk of condensed moisture freezing.…”

Modelling the Technical–Economic Relevance of the ETICS Construction Process

“…The list of shortcomings was formulated from descriptive instructions, recommendations, harmonized standards and set requirements [9,[22][23][24][25][26], research regarding simulations or material studies conducted in laboratory conditions [12][13][14], field research [3][4][5]34,[52][53][54][55][56][57][58][59][60][61][62][63][64], and books on the topic [6,10,11]. The selected factors were verified by two experts, who had more than 12 years' experience with ETICS.…”