What is a thermographic survey?
A thermographic survey uses images taken with an infrared (thermal imaging) camera, in which surface temperatures are shown as colours. Warm areas usually appear yellow to red, cold areas blue to purple. In buildings, these images are used to trace heat loss, missing insulation, thermal bridges, air leaks and damp problems.
What can it reveal?
- Missing or slumped insulation in cavity walls, roofs or floors.
- Thermal bridges at lintels, floor edges, balcony slabs and window frame junctions.
- Air leaks around frames, eaves and service penetrations, especially clear when combined with a blower door test.
- Damp: wet areas cool down through evaporation and show up as colder patches.
- Pipes of underfloor heating and leaks in heating pipes.
How to get a useful image
- Temperature difference: make sure there is a large difference between inside and outside. A rule of thumb is at least 10 °C, so surveys are done in the heating season.
- No sun: outside, preferably take images in the evening or early morning, when the facade has not been warmed by the sun.
- Dry weather and little wind: rain and wind cool the facade and distort the picture.
- Inside and outside: images taken from inside often show cold spots more clearly than those taken from outside.
- Watch out for reflection: glass, metal and glazed tiles reflect heat from their surroundings, so the camera does not measure their real temperature.
Cost and practice
A survey by an energy assessor or building surveyor is a modest cost, depending on the size of the house and whether a written report is included. A clip-on camera for your phone is affordable, but interpreting the images takes experience: a colour difference is not automatically a defect.
Related terms
- Infrared photo
- Thermal bridge
- Thermal insulation
- Airtightness
- Blower door test
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