The Infrared Thermography is the ability of instrumentations (thermal imaging cameras) to turn an infrared image into a radiometric image allowing to read the temperature values of an image. The thermal energy (infrared) is located in  the not visible spectrum because its wavelength is too long to be seen by the human eye.
It is located in that part of the electromagnetic spectrum hat we perceive as heat. Any object that has a temperature above absolute zero emits infrared radiation, invisible to the human eye. More the temperature of an object it is high, more are the IR radiation which emits.
The images recorded with the Thermal Image camera consist of a map of colors which indicate the surface temperature of an object. Infrared cameras are thus invaluable diagnostic tools used in many areas, as they can detect components or areas prone to hot / cold.
Rovergamma has a Thermal Image Camera type FLIR series T 425 which covers a temperature range from -20 ° CC to + 1200 ° C.

In the infrared images you can swim very well where there are heat loss: Photo 1 are located between the junctions of the side boxes to the main wall, in Photo 2 the upper part is not to be perfectly insulated from the inner side as the bottom.