Hygrothermal performance of a new aerogel-based insulating render through weathering: Impact on building energy efficiency

Abstract

Highly efficient insulating systems help reduce heat losses and promote building energy efficiency due to their very low thermal conductivity. However, when applied to outdoor surfaces, climate conditions exposure might deteriorate the material's properties, compromising the building's energy performance over its lifetime. In the framework of a European research project (Horizon2020 - Wall-ACE), a novel aerogel-based insulating external render was developed, characterized, and submitted to a large-scale weathering test to assess its durability. The test rig was equipped with hygrothermal, impedance, and heat flux sensors, used as reference data to create and calibrate a 2D heat and moisture transfer (HMT) model that compared impedance readings and predicted water content. Before and after the test, thermal properties, e.g., U-Value, were measured to assess the weather impact on the exterior render performance, which were also investigated through building energy simulation (BES). In this article, both experimental and numerical procedures are described. Results show high water absorption in the analyzed render systems during weathering, especially at the innermost layer, demonstrated by both impedance and simulation outputs. An adjusted base coat and attention at the execution phase can avoid such intrusion of water. Nevertheless, a low thermal conductivity degradation was measured after the large-scale test, showing that the aerogel-based insulating system's effectiveness is not harshly compromised throughout its life-cycle.