Building thermography - Part 1: The basis

The global warning of global warming and the inevitable end of fossil fuels has made the energy performance of buildings a major issue. Unnecessarily excessive heating consumption represents a fabulous source of savings to be exploited, while improving and controlling the quality of construction, in line with increasingly pressing needs, is a new challenge that the building trades are committed to meeting. Two excellent tools stand out for contributing to performance and ensuring its expertise: infiltrometry and thermography. While the former is already well established and a regulatory requirement, the latter is on the road to formalization and professionalization.

Over the course of this article, we'll be constantly reminding you of what's so special about building thermography: the risk of misinterpretation. Of all the applications we've supported in over 30 years in this business, building thermography is the most captivating, and therefore the most... trapping. The technique is very simple to use, and thermal images are easy to interpret. However, the thermal camera does not provide temperature mapping in the common sense of the word, and buildings are complex thermal machines in an evolving environment: so, without exception, there are thermal images everywhere, which are so many pitfalls that beginners, amateurs and clients naturally run aground on. Then they give up and decry. Those who suffer from the pretentiousness of their diplomas, or who consider this technique to be self-evident, will learn here, often to their surprise, that modesty and careful thought are required at all times.

It's essential to understand radiation before venturing to speak in terms of heat flows or temperatures: the synthesis between thermography and thermodynamics can then be achieved. Thermography is exciting, combining the advantages of images with those of measurement, but it also combines the difficulties and limitations: what is explained too soon, in the heat of field action, may be contradicted when interpreted coldly and logically.

The thermographer starts the thermographic diagnosis at the right moment, revealing radiative losses from the envelope. The thermographer will know under what conditions he will also obtain convective losses. With this new concept, irregularities or defects can be quantified in terms of their impact on the building's energy consumption. The document is illustrated by a typology of such irregularities and defects, with comments, before concluding with suggestions for further formalization.

But this article is only a short summary of the subject: the reader won't come out a specialist in building thermography. In fact, learning to do so will present a certain degree of difficulty when it calls...