IRT and GPR Techniques for Moisture Detection and Characterisation in Buildings

Abstract

The integrity, comfort, and energy demand of a building can be negatively affected by the presence of moisture in its walls. Therefore, it is essential to identify and characterise this building pathology with the most appropriate technologies to perform the required prevention and maintenance tasks. This paper proposes the joint application of InfraRed Thermography (IRT) and Ground-Penetrating Radar (GPR) for the detection and classification of moisture in interior walls of a building according to its severity level. The IRT method is based on the study of the temperature distribution of the thermal images acquired without an application of artificial thermal excitation for the detection of superficial moisture (less than 15 mm deep in plaster with passive IRT). Additionally, in order to characterise the level of moisture severity, the Evaporative Thermal Index (ETI) was obtained for each of the moisture areas. As for GPR, with measuring capacity from 10 mm up to 30 cm depth with a 2300 MHz antenna, several algorithms were developed based on the amplitude and spectrum of the received signals for the detection and classification of moisture through the inner layers of the wall. In this work, the complementarity of both methods has proven to be an effective approach to investigate both superficial and internal moisture and their severity. Specifically, IRT allowed estimating superficial water movement, whereas GPR allowed detecting points of internal water accumulation. Thus, through the combination of both techniques, it was possible to provide an interpretation of the water displacement from the exterior surface to the interior surface of the wall, and to give a relative depth of water inside the wall. Therefore, it was concluded that more information and greater reliability can be gained by using complementary IRT-GPR, showing the benefits of combining both techniques in the building sector.

Introduction of Deep Learning in Thermographic Monitoring of Cultural Heritage and Improvement by Automatic Thermogram Pre-Processing Algorithms

“…It should be noted that a process of erosion and dilation [ 9 ] was applied automatically after finding the respective intersection points in each overlapping histogram and before obtaining the definitive segmenting in each next_image (i.e., before obtaining Figure 15 ). The erosion process is applied to eliminate small-size segmented areas, considered as noise, while the subsequent dilation process is applied to group the closest segmented areas into one single segmented area.…”

“…The erosion process is applied to eliminate small-size segmented areas, considered as noise, while the subsequent dilation process is applied to group the closest segmented areas into one single segmented area. In addition, each segmented area is labelled with a different index by applying a connecting method [ 9 ]. In this way, the smallest segmented areas that were not eliminated by the erosion process are automatically eliminated by counting the number of pixels in each segmented area.…”

“…IRT presents the advantageous features that correspond to a Non-Destructive Testing (NDT) technique, i.e., (i) non-intrusion and non-damage to the integrity of the object as opposed to destructive techniques, and (ii) higher objectivity and speed compared to traditional methods [ 5 ]. In addition, IRT presents added advantageous features such as: (i) The non-contact with the heritage object, (ii) the real time operation, very important for cultural heritage monitoring, (iii) the ability to analyze any surface regardless of the type of object, (iv) the possibility to monitor many points of an object at the same time, (v) the capacity to perform large-scale studies of objects, (vi) the interpretation of the results in two and three dimensions [ 6 , 7 ], and (vii) the possibility of a qualitative and quantitative analysis [ 8 , 9 ].…”

Analysis of the Applicability of Non-Destructive Techniques to Determine In Situ Thermal Transmittance in Passive House Façades

“…In fact, Tejedor et al [35] highlighted that most studies were qualitative, to discover heterogeneities due to anomalies (moisture, thermal bridges, cracks, air leakages, etc.) below the plaster [36][37][38][39][40] and to define the geometry of a masonry, among other purposes [41]. Besides this, international standards (i.e., ISO 6781:1983 [42]), UNE EN 13187:1998 [43], ASTM E1311 [44], ASTM E1862 [45], and guidelines (i.e., RESNET [32]) only recommend boundary conditions for the use of qualitative IRT tests to carry out energy audits in buildings [33,46,47].…”

Special Issue on “Infrared Thermography and Additional Non-Destructive Testing for Building, Structure and Material Inspections”

“…Thus, through the combination of both techniques, it was possible to provide an interpretation of the water displacement, from the exterior surface to the interior surface of the wall, and to provide a relative depth of water inside the wall. It was concluded that more information and greater reliability can be gained by using complementary IRT-GPR, showing the benefits of combining both techniques in the building sector [ 8 ].…”