On the use of infrared thermography to assess air infiltration in building envelopes

Infrared thermography is an interesting technique that is often used for qualitative assessment of the building envelope. The method allows to detect construction deficiencies e.g. thermal bridges, moisture problems, incomplete blown-in retrofit insulation of cavity walls, wind washing in insulation layers etc. in a very fast way. Another application is the use of infrared thermography in combination with pressurization tests  in order to detect air leakages through the building envelope. As the airtightness plays a major role in reducing heat losses in well-insulated buildings, this is an interesting method as it allows for a quick qualitative evaluation of possible air infiltration/exfiltration locations. This paper offers a first attempt to analyse the important parameters (e.g. pressure difference, temperature difference between inside and outside) for a thermographic airtightness survey by means of simulations and in situ measurements. Furthermore an overview of the currently existing literature on thermographic surveys of the building envelope is given. Simulations show that the pressure difference does not play a significant role for the execution of a thermographic survey, while the indoor-outdoor temperature difference changes the outcome of the survey significantly. Without taking into account the environmental conditions, the survey can be either executed from the inside or along the outside. Solar radiation, wind and rain can although have a negative influence on the measurement results taken from the outside.