Thermogramm of a traditional building in the background and a "passive house "in the foreground
Infrared thermography (IRT), thermal imaging, and thermal video are examples of infrared imaging science. Thermographic cameras detect radiation in the infrared range of the electromagnetic spectrum (roughly 9,000–14,000 nanometers or 9–14 µm) and produce images of that radiation, called thermograms. Since infrared radiation is emitted by all objects above absolute zero according to the black body radiation law, thermography makes it possible to see one's 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. When viewed through a thermal imaging camera, warm objects stand out well against cooler backgrounds; humans and other warm-blooded animals become easily visible against the environment, day or night. As a result, thermography is particularly useful to military and other users of surveillance cameras.
In the building industry thermal imaging is a very useful tool.
Building construction technicians can see thermal signatures that indicate heat leaks in faulty thermal insulation and can use the results to rectify the problems and so improve the efficiency of heating and air-conditioning units.
In passivhaus construction it is, together with the BlowerDoor test, another useful tool to find thermal breaches due to faulty insulation application or structural problems.