Infrared thermography is a method of capturing images based on the heat they emit. Infrared energy is light that is not visible to the naked eye due to the length of its wavelength. It is part of the electromagnetic spectrum that we perceive as heat. In the infrared world, everything with a temperature above absolute zero (-273°C) emits heat. The higher the objects temperature, the greater the infrared radiation emitted.
The special lens in an infrared camera will detect the infrared emitted from an object, transform the amount of infrared energy into temperature, and then display the object as an infrared or thermographic image.
Contrary to what you may see on TV or in movies, infrared cannot “see” through objects. The heat from an object can travel through another object and be seen by an infrared camera. Infrared light can pass through many materials which visible light cannot pass through. The reverse is also true – visible light can pass through some objects but infrared light cannot.
In the two pictures on the right, in visible light, you cannot see the arm inside the plastic garbage bag, but the heat from the arm and hand passes through the plastic and can be detected by an infrared camera. But the heat cannot pass through glass, so in the infrared picture, the man’s body heat cannot pass through his glasses, making them appear dark.
What the eye sees ...
What infrared "sees" ...
By proper use of an infrared camera and the proper interpretation of the results, under the correct conditions, a thermographer can identify missing insulation, air gaps and moisture behind walls or under floors. Infrared scanning can check in-floor or radiant heating. Infrared can help find missing elements in the house.
Moisture is the biggest enemy for a house. Left undetected, moisture can lead to mold and rot. Water typically appears as cold areas with an infrared camera. But not all cold areas mean that there is water present. All cold areas found should be further tested with a moisture meter - if "wet", then there is a moisture concern; if "dry", then there is something else causing the cold spot.
Below are some items that were readily seen with the use of an infrared camera.