Thermographic 2D U-value map for quantifying thermal bridges in building façades

Abstract

Thermal bridges accounted for 30% of the impact on the energy performance of European residential building stock. Nevertheless, European countries and their standards do not take into account the influences of this type of anomaly. Furthermore, current methods for quantifying thermal bridges have three main drawbacks. Firstly, most of approaches consist of complex models based on fluid dynamics or finite elements as calculation procedure. Secondly, the disturbances of a thermal bridge can’t be assessed along the vertical and horizontal axis of a wall surface area, since the current methods only allow to perform local measurements. Thirdly, the stratigraphy and morphology of wall is unknown in most cases. Hence, this research proposes the implementation of a 2D U-value map to quantify the influence of thermal bridges in three heavy walls by internal quantitative infrared thermography (QIRT). The measurement campaigns were conducted on a walk-in climatic chamber to monitor and evaluate full-scale building elements. The results demonstrated that the use of 2D U-value maps could help to delimit the geometry of a thermal bridge as well as its area of greater influence, to quantify the U-value in any point of an entire wall with acceptable reliability and, to provide real information about the thermal behaviour of air voids inside opaque façades. Indeed, the U-value results measured by HFM and QIRT were similar in the inhomogeneous wall areas (from 0.08 to 8.55% of difference in most cases). In this way, the operational life of a building could be enhanced with specific refurbishment procedures.