3.6 Non-destructive testing – NDT methodologies

Although the diagnostics included in 3ENCULT mainly focus on energyrelated issues, reliable understanding of a building’s state of preservation also needs to be obtained, so as to undertake all subsequent interventions safely. For this reason, a full diagnosis of the building must be made before any other work is started. Diagnoses are usually conducted to understand the reasons for some damage that has occurred and/or to augment the knowledge of the building’s structure. The diagnostic process should always follow a logical path, starting from visual indications and aiming to understand the causes of damage so that remedies can be implemented. The diagnostic plan would usually respond to the necessity of taking samples from the object under examination, ranging from micro-sampling for chemical analysis to cutting out sections of a wall for structural examination in a laboratory. Such invasive, destructive procedures should be kept to a minimum, so it is highly important to manage the sampling phase: for this purpose, a long series of Non-Destructive Testing (NDT) techniques exists that requires neither sampling nor destruction. These allow the operator to select the areas more suitable for sampling and also to extrapolate local results to broader areas of the object. NDT techniques may also be used to visualise hidden structures and structural defects, characterise surfaces and in general allow the operator to obtain a complete view of the object’s state of preservation. However, it is very important to remember that NDT techniques are mainly qualitative and do not allow some important characteristics of materials and objects, such as strength or residual stress, to be evaluated directly; in such cases destructive testing is mandatory and national regulations are quite strict in this respect. Moreover, NDT techniques usually require specialised personnel who must be able to interpret the results, not , even briefly, all the NDT techniques commonly utilised for the diagnosis of cultural heritage monuments.So, we will restrict the focus of this chapter to some of the NDT techniques employed in evaluating the energy efficiency of historic buildings.