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Study of experimental parameters for IRT applications in building elements using multi-layered analytical solutions

This paper compares experimental and heat transfer modeling results for thermography applications in building elements. Over the years most building envelope inspections using infrared thermography (IRT) have been focused on qualitative analysis using mostly passive thermography techniques. However, increased need for the monitorization and assessment of the energy performance and thermal behavior of buildings, along with ongoing structural safety concerns, has raised interest in quantitative studies and active IRT applications in buildings. Numerous other fields have benefited from developments in defect detection studies and from countless non-destructive testing applications. Pulse phase thermography, in which phase images are studied (instead of temperature images) using a long heating pulse have been proposed to be the most effective for Civil Engineering applications. However, the particular characteristics of building elements and materials, along with the complex nature of heat transfer phenomena, demand specific experimental procedures and processing techniques. In this paper, analytical solutions to simulate heat transfer in the frequency domain in multi-layered media are used to compute thermal wave phase results. These are compared to experimental IRT phase analysis results of experiments performed on test specimens simulating building elements with embedded defects. Crucial test parameters such as test duration and defect characteristics are changed and their influence is studied. In this way, this paper contributes to the understanding of building envelope thermal patterns using active IRT in defect detection studies and to the definition of test parameters.