On site measurement and hygrothermal modelling of degraded ETICS facade with EPS and mineral wool fire breaks

Abstract

External Thermal Insulation Composite System (ETICS) facades are widespread and cost-effective building solutions in many climates. However, they are frequently found to deteriorate prematurely. In addition to other possible defects, several buildings were found with horizontal cracks on the facade between every floor level. Because of the fire safety requirements of multi-storey buildings, EPS insulation has been divided by mineral wool fire breaks at each floor level. The service life of the system usually ends up with horizontal cracks appearing at the lower level of the wool belt. This study aimed to determine the damage mechanism. One deteriorated facade was opened to explore possible construction technology errors and specimen were analysed in the laboratory. Temperature and RH were measured in situ inside the walls at different positions. It turned out that built in moisture of concrete was still drying out after three and a half years. Moisture content of concrete was found to be between 0.046 to 0.063 m3/m3 behind EPS insulation and 0.047 to 0.074 m3/m3 behind MW insulation - slightly higher than hygrothemal model was predicting. A possible solution was proposed to alleviate the similar problem in the future with application of waterproofing membrane behind mineral wool.