A review of the use of infrared thermography in building envelope thermal property characterization studies

Innovations in Building Diagnostics and Condition Monitoring: A Comprehensive Review of Infrared Thermography Applications

“…In 1800, Sir William Herschel discovered infrared radiation and the recording of the first thermal image was performed by his son John Herschel, which added new dimensions to the temperature measurement, quality equipment, and technical knowhow [48]. In thermal radiation theory, the blackbody is considered as a hypothetical object which absorbs all incident radiation and radiates a continuous spectrum according to Planck's law and can be expressed by Equation (1) as follows [49][50][51][52].…”

“…where λ is the wavelength of the radiation (µm), L λ is the power radiated by the blackbody per unit surface and per unit solid angle for a particular wavelength (W m −2 µm −1 sr −1 ), T is the temperature in absolute scale (K), and C 1 and C 2 are the first and second radiations constants, respectively. On integrating Planck's law over all frequencies, Stefan-Boltzmann's law is derived and can be expressed by Equation ( 2) [48,50,53].…”