Infrared thermography has been used for different aspects of building diagnostics to help with performance evaluation. I have read recently about the use of infrared thermography to determine other materials properties such as u-value especially for existing building. is this an effective and accurate process?
Thermography is good for detecting thermal bridges and defects in the structure. So as to determine U-value, apart from the surface temperatures that you get with an infrared camera, you need a heat flux sensor. All measuring equipment that boast that they can find U-value without a heat flux sensor are not trustworth. Keep in mind the relationship: Q=U*A*ΔΤ [heat flux equals Uvalue, times the surface, times the temperature difference]. You can get information on temperature difference with the infrared camera, but you also need to measure the heat flux, so as to determine U value. Maybe you find interesting this article: Conference Paper The Importance of Energy Audit in the Energy Certification o...
As is known to all materials above absolute zero gives infrared radiation infrared camera gives high optical resolution due to variation in temperature of the material
In recent years, several researchers highlighted the use of quantitative infrared thermography for building diagnostics. In fact, the combination of qualitative and quantitative IRT in the same inspection allows an in-depth evaluation of the building envelope, instead of providing a local measurement.
Maybe you find interesting my article (Tejedor et al., 2017). Quantitative internal IRT provides a high accuracy for heavy walls (1-4%). In terms of execution time, it only takes 2-3 h. These two aspects are considerably importants, since HFM method requires a minimum of 72h and its accuracy ranges from 14-28% according to ISO 9869-1:2014.
As regards "absorptivity" and "reflectivity", they can be determined following EN 13187:1998 (ISO 6781:1983 modified), the RESNET Interim Guideline for Thermographic Inspections of Buildings (RESNET, 2010) and so on. The body's absorptivity coincides with its emission capacity. In accordance with the standardized procedure, wall surface emissivity can be determined by a IR camera, a reflector (a piece of a crinkled aluminium foil) and a blackbody (black tape). The reflectivity is the difference between 1 and the emissivity, taking into account that the majority of bodies are opaques.
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