Thermal Cameras for Building Surveys

Prices of entry-level thermal cameras continue to fall, and with this, a number of companies are offering surveys with inadequate equipment. It is generally the rule that if someone will not pay for professional equipment, they will not have paid for professional training as well! See here for more information on training standards for building thermography.

Whilst there are various guidelines for the minimum standard of equipment to be used in thermal imaging surveys of buildings, these are almost never enforced.  So here is a summary of some international guidelines plus our own view.

The 3 basic specifications affecting camera performance are as follows:

• Detector size.  This defines the number of pixels in the image. The bigger the number the better.
  • 640×480 (professional – 300,000 pixels per image)
  • 320×240 (mid-range – 75,000 pixels per image)
  • < 320×240 (entry level/hobbyist)
  • An entry level camera can still be useful for basic tasks like finding a hot pipe, but is NOT suitable for whole building surveys
• Thermal sensitivity. This defines the minimum temperature difference the camera can detect and is extremely important in building surveys due to the small temperature differences we are often looking for. The smaller the number the better.
  • <30mK (0.03 degC) – high end professional
  • <40mK (0.04 degC) – professional
  • <50mK (0.05 degC) – mid-range
  • >60mK (0.06 degC) -not suitable for building surveys
• Lens angle. Like a normal visual camera, thermal imaging lenses from wide angle to telephoto are available.
  • 45deg wide angle.  Generally speaking, with a professional camera (640×480) a wide angle lens is useful for most building applications giving enough resolution and a whole view of walls or rooms
  • 35deg slightly wide angle – a good compromise on mid range cameras
  • 25deg standard lens – may be required with smaller detectors to provide enough resolution, but gives restricted view of buildings or rooms leading to a “itty bitty” report where it is hard to see what is going on.

So do check what type of camera is being used – there is a strong temptation by many companies to use a £1500 entry level camera with fixed focus rather than a mid range (typically £7000+) or professional camera (typically £15,000+).  Be careful of reports with images where the visual and thermal images are overlaid – this is usually done to give an impression of resolution which is not there and is impossible to analyse in thermal data. Adding visual information helps you see where the thermal image was taken (just like your eyes would) but it makes no difference to the missing thermal data. There is still not enough to use!

Finally do not lose sight of the operator who is always more important than the camera. A good thermographer with a mid-range camera is better than a bad thermographer with a professional camera.

We only used 640×480 cameras and these range from 35mK to our latest 20mK “best in industry” ultra sensitive camera. See our cameras here.