Assessment of Thermal Bridging Heat Loss by Means of the Infrared Thermography Technique

Thermal bridges influence the thermal standard of a building envelope. They are taken into account in the linear thermal transmittance or Ψ-value, and can be estimated from tabulated values for standard building details or from numerical modelling. However, these methods are not applicable for existing buildings with unknown structure. In these cases, in situ measurement of the Ψ-value is necessary. In this study, a methodology to measure the actual thermal bridging performance is developed. The methodology is based on a infrared thermography technique, which can be used on any existing thermal bridge. To ensure high accuracy, temperature-dependent surface heat transfer coefficients are calculated using the surface temperatures recorded by the infrared camera. The methodology has been validated under steady state conditions in a hot box apparatus with very good agreement.