If there is a temperature differential between the two sides of a structure (be it a wall, chimney, etc), thermal irregularities of the constituent materials that make up a that structure can be observed as thermal anomalies on its surface.
Thus, the temperature distribution on a surface that is under observation can be used to pinpoint isolation defects, areas with excess humidity, air infiltration (thru cracks, window and door joints, badly isolated wall panels). The collected temperatures become part of energy calculations that will help the energy efficiency assessment process.
The physical principles underlying this method are based on the fact that any object emits thermal radiation generated by transitions between vibrational and rotational quantum levels and by reflected radiation originating from other sources. The visualization technique of infrared images obtained from thermal radiation emission characteristics of objects is known as "thermovision" or "thermography technique".
The principle of operation of a measuring device is as follows: the optic system picks up the infrared radiation from the environment and filters it into one of two spectral bands (3-5 microns or 8-14 microns) and focuses the result onto an array of detectors. The radiation sensitive elements of the receiver convert the electromagnetic signal into a corresponding electrical signal that gets amplified and then reconstructed as an 8 bit per pixel image.The advantages of thermography:
Laboratory methods exist for evaluation of thermal insulation materials and components - calorimetric experiments to evaluate conductivity of materials (ISO and UNI) and the transmittance of homogeneous bodies (ASTM and ISO). The value of such a methodology is key when starting from the physical quantities measured at the constituent materials can reconstruct the behavior of entire structures. From this point of view the infrared method has the best chance as an assessment method based on the following specific characteristics
The very short time required for recording thermograms, the relatively low cost of processing and interpretation can make this method appear as the most viable one for investigating industrial and civil structures.
|device||Flir Thermacam E25|
|detector||Focal plane array (uncooled microbolometer)|
|spectral response||7.5 - 13 µm|
|temperature measuring range||-20°C - 250°C|
|accuracy||±2 °C or ±2% of absolute temperature in °C|
|field of view||12° x 9° (at 1.2m)|
|frame resolution||320 x 240 pixels|
|laser aiming system||yes|
|device||Raytek MI 105|
|spectral response||7.6 - 18 µm|
|temperature measuring range||0°C - 450°C|
|response time||120 ms|
|emissivity||0.20 to 1.00 adjustable|
|temperature measuring range||20 - 600°C|
|emissivity||0.1 - 1.0 adjustable|
|spatial resolution||2 mrad|
|laser aiming system||yes|
|device||AGA RS-10 (black body)|
|calibration range||16 - 100°C|
|infrared view of Ion Luca Caragiale National College, Ploieşti - north side roof, panoramic view|
|'Armata Poporului' subway station, AutoCAD rendering|
|Tarniţa dam, left bank|
|Cistiro Bistriţa, oven #3|