## 4 Discussion and Conclusions  
The integration of humidity, sonic velocity, and thermal maps provided complementary information that enabled the estimation of various critical factors such as detachments, rising damp, percolation, humidity, and other inhomogeneities, which represent typical decay phenomena in wall paintings. This comprehensive analysis allowed for the identification of potential critical areas, emphasizing the need for targeted conservation and restoration procedures for the wall paintings of St. Panfilo's Church. In particular, the SPV is useful to diagnose masonry in a non-destructive way and deepen the knowledge of the construction characteristics, evaluate the state of conservation, and provide important information for effective restoration interventions of masonry. The maps in SPV and HT enabled conservation problems (e.g. surface warping, painting layer detachments, and humidity distribution) to be evidenced and provided indications about different properties of the infill wall. These investigations aimed at assessing the consistency of the plaster coating and locating the possible presence of detachments, discontinuities, and voids. The SPV and HT tests highlighted how both microclimatic factors and the different exposure of the masonry to solar radiation have a significant influence on the conservation state of the frescoes. Thermal stress can be decisive in generating detachments and fractures in the painted plaster, as evident from Figure 3a,b. This area near the window is characterized by humidity inhomogeneities, which also affect the plaster, as indicated by the highly variable SPV values. On the other hand, the areas whose external walls are less exposed to sunlight (Figure 3c,d) show higher and relatively homogeneous humidity values. Regarding passive and active IRT, these techniques give information that can complement the SPV and HT maps. By comparing the passive IRT and SPV images, a certain degree of correlation between hot areas and slow areas in the presence of possible detachments is noticed (see Figures 3 and 5). In particular, in subplots \"e\" and \"g\", the hottest areas correspond to low-sound velocity areas in SPV images where possible detachments can be found. In many IRT images, the wall texture is visible, and in such areas, the presence of relevant detachments can be excluded. The PuCT active IRT, combined with virtual wave processing, can give detailed information about the plaster thickness and a better resolution than the well-known passive IRT approach (see Figure 6). All these advantages may help the restoration tangibly because the thermal imprints are read like a sort of tomography. Based on the integrated use of SPV, HT, PIRT, and PuCT techniques, several observations can be made regarding the conservation status of the frescoes:  
* plaster cohesion: several detached areas or damaged plaster resulting from fractures were evidenced;
* moisture distribution: the HT tests reveal variations in humidity levels across different areas. The moisture values are generally higher and more homogeneous in those regions potentially influenced by the position of the area relative to the sun exposure. Detached portions of plaster exhibit lower moisture values;
* temperature variations: the passive IRT analysis shows temperature discontinuities between different sections of the apse, indicating potential variations in wall texture and masonry structure. These differences may be attributed to factors such as materials, construction techniques, or later interventions;
* structural integrity of frescoes: the presence of fractures, discontinuities, and infill of the underlying masonry is evident from the SPV and PuCT results. These structural elements can affect the overall stability and conservation of the frescoes.