Fellow home inspector Richard and myself are looking for signs of water leaks with our thermal camera.
The image you see in the mirror with the colored background is actually our heat reflecting off the glass! Pretty cool isn’t it!? What I hope to find when searching for water leaks is that the water will be a different temperature than the walls. When it is and it’s active, the water looks dark blue (if it’s cooler) and shows up as a contrast in colors much as the mirror is doing. In some cases the water may move the insulation so I can see a temperature difference without the water leak being active.
Again, the camera is only a sample tool in trying to find moisture, it also takes experience, building knowledge, visual, tactile senses, maybe a moisture meter and some common sense to complete the job