Active thermography is well suited for the detection of delaminations and cracks in façade elements like plaster and tiles. Not only artificial heating but also solar heating can be used if the adjustment of the façade and the weather conditions are suitable. Optical methods like laser scanners, photogrammetric methods and crack tracking sensors are providing geometrical 3D data which can be used for a 3D mapping of thermograms and for providing data with higher geometrical resolution. Thus, by the combination and fusion of these data, a comprehensive mapping and monitoring of damages of façade systems is possible.
For assessing building façades using active thermography, in case of direct solar exposure the sun itself can be used as heat source. It is shown that active thermography can be applied to large areas successfully, if a shadow cast occurs. After performing a sequence reconstruction in order to correct the temporal behaviour of shadow movement, the data could be analysed by pulse phase thermography (PPT). Compared to raw thermograms, the obtained phase images display an improved image quality with a lot of details. The frequency of the phase images is related to the probing depth. The presented case study describes the thermographic investigation of an historical building façade, where an area of 17 m x 13 m has been investigated.