Usually, thermographic cameras detect radiation in the long-infrared range of the electromagnetic spectrum. They produce images of that radiation, called thermograms. Infrared radiation is emitted by all objects with a temperature above absolute zero according to the black body radiation law. According to this thermography it is possible to see the environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature; therefore, thermography allows one to see variations in temperature. Thermal images, or thermograms, are actually visual displays of the amount of infrared energy emitted, transmitted, and reflected by an object.
In the below article by A. Preda and I. C. Scurtu which was presented in the 5th International Scientific Conference SEA in 2019, thermal imaging of buildings is used as a powerful and non-invasive method for monitoring and diagnosing heat loss problems from buildings.
With a thermal imaging camera you can identify problems early and correct issues before becoming more serious and more costly. By this method, the heat loss through the surface of the building can be exemplified. Thermal imaging consists of scanning the building with infrared, using a special camera. The radiated heat leads to a temperature variation on the surface of the building element in which it is embedded. This method, corroborated with the calculation of heat loss, provides a technical and economical solution for the problem of thermal discomfort in the building. For more information on this method and reviewing the results of a thermographic study of an office space in Bucharest, as shown below, please read the original article from the below link.