Quantification of air leaks through the building envelope using infrared thermography

A laboratory experimental procedure has been developed for the acquisition of thermograms of surface temperature distributions due to air leaks through the building envelope. Air leaks through a sample single layer building envelope assembly with a crack of variable width have been reproduced in an environmental chamber inside which conditions met during building envelope thermography surveys were reproduced. The reference emitter technique has been used for the improvement of the accuracy of the absolute temperature measurements with infrared thermography. A qualitative study of the thermograms obtained is presented highlighting the differences between temperature patterns due air leaks through the assembly under different conditions. Also, quantitative relationships between assembly surface temperature distributions due to air leaks and crack dimensions are established. Two methods are presented and discussed, the first based on image segmentation technique and the second on tomography, for building envelope cracks sizing using infrared thermography.