Thermal imaging is a unique way of finding problems within the fabric of a building that are invisible to the human eye.
The higher an object's temperature, the more infrared radiation is emitted as black-body radiation. A thermal imaging camera can detect this radiation in a way similar to the way an ordinary camera detects visible light. It works even in total darkness because ambient light level does not matter.
This means that damp and timber problems can be diagnosed by finding where the cold spots in the building are located and correlating that with the visible issues on the internal walls.
It works best in the winter months where there is a big temperature difference between the internal and external wall surfaces.
The above picture shows a poor installation of cavity wall insulation. The mineral wool insulation had been injected into a wall that was known to have damp issues and it had clumped together as wet blocks of insulation within the cavity.