They say that people in glass houses should not throw stones. By the same token, people in poorly insulated homes should not take thermal images of other poorly insulated building, lest they should find themselves with egg on their faces.

The thermal imaging paparazzi have been out in force recently. It all began on 22 January 2014, when NPower issued a press release with the heading "Britain’s poshest postcodes top of the list for wasting energy." The Telegraph ran the story the same day with a cropped thermal image of the Houses of Parliament as shown below.

Not to be outdone, the Daily Mail then ran its story about NPower boss's poorly insulated home on 27 January with a thermal image borrowed from The Sun (see below) showing heat escaping from his 16th Century country property in Oxfordshire.

Subsequently on 31 January, the Daily Mail went to town with a story containing several thermal images of offending buildings, including some NPower buildings.

The upshot of all this is that thermal imaging, or thermography, is the easiest and quickest means of detecting moisture and energy waste in buildings. The main principle driving the technology behind thermal imaging is infrared (IR), part of the light spectrum which is normally completely invisible to human eyes. A thermal camera is able to pick up IR radiation and convert it into a visible image that showcases the detected heat differences as different colours on the image.

In the case of buildings, the versatility of IR cameras, combined with innovations in the technology which have reduced the price of owning a unit, have resulted in a boom in these devices being adopted in the building sector. Many manufacturers, particularly FLIR, have started developing thermal imaging systems built specifically for use in building applications.

By scanning outside a property with a thermal imaging system a building surveyor can spot hot and cold spots in the exterior brickwork of the property, detecting problems that may be caused by moisture, cracks in the building materials or more complex damage from insects or plants.