A practical guide to infra-red thermography for building surveys.

This BRE Report gives a guide to the use of infra-red thermography as a means to investigate the thermal properties and hidden constructional details of building envelopes. An introduction is given to infra-red thermography, the operation of the camera and the difference between photography and electronic thermography. The guide describes the aims and requirements for carrying out an infra-red survey and discusses thermal analysis and application of the results. Also included is a section on sources of interference which can occur during thermography and may lead to misinterpretation of the results. Examples are shown of the qualitative and quantitative analysis of infra-red data used to study insulation defects, air infiltration, the heat loss from windows and many other qualitative building applications. For lightweight responsive components such as windows, U-values have been calculated from quantified thermograms to enable comparisons to be made between forms of window insulation. In heavy weight non-responsive components, the technique has been extended to combine the visual thermal image with that of U-value measurement using a heat flux meter. In the appendices, an introduction is given to the physics of thermal radiation and the derivation of emissivity and its importance in the infra-red technique. Also included is the derivation of the basic analysis formulae and their practical application to the AGEMA infra-red thermal imaging camera.