Abstract
This chapter provides technical information and physics background to the use of thermographic cameras in the field of preservation and restoration of architectural cultural heritage. After an overview on how IR cameras work, both applications and common cases will be presented so that the operator may easily deal and recognize building pathologies and masonry anomalies. These, described in detail, range from water moist problems to structural gaps. As moisture and humidity related problems represent the majority of IR surveying cases in the field of architecture, they will be handled in a comprehensive way so that both the operator and the scholar are well prepared to understand and treat the pathologies these may cause. The operator is instructed on how to perform a project survey on a step by step layout based on the UNI 9252, the UNI EN 13187 and the ISO 9712:2005 regarding the methodologies of IR survey and the procedures of non destructive tests.
TopBackground
Thermography is a method that measures the flow of electromagnetic radiation that are emitted by each body with temperature higher than the absolute zero (-273,15 °C or 0 K). There are three units of temperature (T): kelvin, Celsius degrees and Fahrenheit degrees, respectively denoted by K, ° C and ° F. Each of these units are linked with the others by the following formulas:
Key Terms in this Chapter
Sulphate Reducing Bacteria: Sulphate reducing bacteria are those that can obtain energy by or molecular (H 2 ) while (SO2-4) to (H 2 S). In a sense, these organisms “breathe” sulfate rather than oxygen.
Infrared (IR): The electromagnetic radiation with a frequency band of the electromagnetic spectrum lower than that of visible light, but greater than that of radio waves. Its wavelength ranges between 700 nm and 1 mm. The term means “below red” (from the Latin infra, “below”), because red is the visible color with the lowest frequency.
Conduction: Thermal conduction refers to the transmission of heat that occurs in a solid, liquid or aeriform medium within a body from areas at a higher temperature toward those with lower temperature.
Emissivity: The emissivity is the ability of a body to first absorb heat and then to transmit and emit the thermal energy in the infrared range. It may have a value of e = 0,0 when all of the energy is reflected, or a value of e = 1,0 when all the energy is absorbed as in the case of the black body.
Convection: Thermal convection is the mechanism of thermal energy transfer that occurs between a solid surface and a fluid (liquid or gas) that are in contact with them at different temperatures.
Nitrifying Bacteria: Nitrifying bacteria convert the organic nitrogen contained in the waste and in the remains of animals and plants, to nitrite and nitrate, inorganic substances formed from nitrogen and oxygen.
Ente Nazionale Italiano di Unificazione (UNI): The Italian Organization for Standardization is a private non-profit organization recognized by the Italian State and by the European Union. It develops and publishes voluntary technical standards - UNI - in many areas such as industry, commerce and tertiary).
Irradiance: Irradiance is one of three ways in which the propagation of heat takes place. In particular, in contrast to conduction and convection, irradiation does not require a direct contact between the exchangers nor a medium to propagate. It is a phenomenon that affects every solid, liquid or aeriform aggregate, and it can take place even in a vacuum. This is justified by the fact that the transfer of heat by radiation comes in the form of electromagnetic waves.
Istantaneous Field of View (IFOV): This indicates the ability of the optics of the thermal camera to measure the temperature of a punctiform area within a thermal image. It also defines the spatial and geometrical resolution of the optics, that is the ability of a system to distinguish two adjacent punctiform areas; it is therefore always calculated as dimensional or angle value.