Thermal (or infrared) cameras are becoming more and more affordable, and their use in building surveys is becoming widespread to identify problems and areas for improvement. However, understanding the results involves more than just looking at pretty pictures.

Many applications but pitfalls

This sounds great, but thermal cameras are not a panacea for building inspections – in reality, they will complement other tools that building surveyors possess, not least their own knowledge of the built environment. It is crucial to remember that there is skill in both conducting a thermal survey and in interpreting the resultant thermal images.

The main pitfall for a user of a thermal camera is assuming that ‘seeing is believing’. There are many things that can result in temperature differences across a surface, and they may not be what the user is actually looking for.

Underlying principles

It is essential that users of infrared cameras are aware of the underlying principles of their use. All objects radiate energy, with the amount dependent on both the temperature of the object and its emissivity.

Emissivity is defined as the ratio of how much radiation an object can emit compared to some baseline measurement (known as a black body). In more simplistic terms, emissivity is the ability of a surface to emit thermal radiation.

It is very hard to see thermal patterns from low emissivity surfaces, for example, shiny metals. Fortunately, most building materials have a high emissivity, but it is not a constant, and different materials or finishes may change it. Where an infrared camera is used on a low emissivity surface, most of the image will actually be reflected radiation from other surfaces.

Experienced operator needed

The capability of the person using a thermal camera is just as important as the technical capability of the camera itself. It is recommended that practitioners should be working to a minimum of Level 2 (ASNT equivalent) certification and have experience of building surveys.