All building materials emit infrared radiation; and the primary source of infrared radiation is heat or thermal radiation. The warmer an object, the more infrared radiation is emitted.
A thermal camera detects this radiation, records its varying intensity, and processes the results through software. According to FLIR “Infrared thermography is the art of transforming an infrared image into a radiometric one, which allows temperature values to be read from the image”.
Most people are familiar with pixels in a digital image. The more pixels, the higher the quality of the final image. For thermal cameras, each pixel is best understood as a single thermometer. A thermal camera with a resolution of 320 x 240px can therefore record 76,800 temperatures (one per pixel). A thermal image could prosaically be described as a cleverly coloured spreadsheet of data illustrating the distribution of surface temperatures in a scene.
Thermal images reveal few of their secrets (such as air leakage) straight from the camera: they need to be processed through desktop software and analysed by an ABBE-qualified building thermographer. A thermogram not only allows us to see heat, but it also gives us 76,800 bits of data which we can be further analysed (if we use the example resolution above). In this way thermographers can get at the figures behind the image, run scripts and mathematically analyse inspection results.
The technology is exciting; however, to create a credible survey it is not enough simply to be comfortable with the tech. A building survey should be carried out by a practitioner who understands both the physics behind the thermal patterns he sees and the construction of the buildings he inspects.
