What about thermal imaging?#
Thermal imaging is a popular idea and it is often possible to borrow a thermal imaging cameras from the local Council, the library, or a local tools library if your area has one. They can be useful, but we have some reservations about their use, and don’t include them in our programme. The pictures are a compelling way of changing hearts and minds, but without training, it’s hard to get useful technical results from them.
Thermal imagers sense the infrared radiation coming from a surface and translate that into surface temperatures. Those temperatures are then mapped onto a set of colours from “cold” to “hot” to make it easier to for people to understand the data. Not all thermal imaging cameras are useful for buildings.
(c)Tiia Monto, licensed under Creative Commons CC BY 3.0.
The first problem is simply that materials differ in how they emit, reflect, and transfer infrared radiation, so stone, metal, and glass could all be at exactly the same temperature, but they will show up as different ones to the camera. That’s fine if you point it at a uniform bit of wall, but less good for complex areas. Most building materials are similar, but you need to get the camera settings right and be aware that shiny or metallic surfaces won’t give accurate results and of how furnishings and corners affect readings.
The second problem is that the results depend on the ambient conditions - ideally, you want a 15C difference between indoors and outdoors, limiting what months you can usefully take images. Damp air or surfaces and wind both change the picture, and sun or air temperature swings can affect the readings for a surprisingly long time.
The third problem is just one of how the cameras tend to be used. By default, cameras will vary the colours they show based on the range of temperatures it reads. That means red doesn’t always mean the same thing. Understanding heat loss in a buildings takes good record-keeping and a well-thought out process.
This doesn’t make the cameras useless, but it’s not point and click. In some areas, there are trained volunteer groups willing to do heat loss surveys for you. It takes less skill to do things like find hidden pipe runs and check whether the insulation behind a uniform surface is patchy.
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