The influence of pressure on the accuracy of thermal imaging examination

Abstract

Thermal imaging examination in Ukraine is performed in accordance with DSTU B EN 13187: 2011 “Thermal characteristics of buildings. Qualitative detection of thermal failures in enclosing structures. Infrared method. It is completely identical to the European standard EN 13187: 1998.

This standard is used to identify the locations of heat failure sites and the location of air filtration areas through enclosure structures.

When conducting surveys, it is necessary to monitor and record information regarding outside air temperature, cloud cover, rainfall and humidity outside the building, along with wind parameters. The orientation of the building to the sides of the world should also be recorded.

To determine the anomaly of the thermal insulation properties of the observed deviations on the obtained thermograms, they are compared with the expected temperature distribution over the surface, determined by the design characteristics of the enclosure structure in the environmental conditions observed during the survey. The expected temperature distribution can be determined using "reference" thermograms, calculations or other studies.

If air filtration can affect the test results, a pressure difference on either side of the enclosure should be created, or the test should be performed under conditions where a pressure difference exists. If the primary purpose of the thermal imaging examination is to determine the air filtration, then the pressure difference must be not less than 5 Pa at the test site. Thermal imaging is performed with less pressure.

When defining air filtration locations, the operator is faced with uncertainty in the distribution of the pressure difference between the inner and outer parts of the structure. Such uncertainty arises from the influence of the following factors: temperature difference between indoor and outdoor air; building height; effect of wind on the structure; influence of mechanical ventilation.

A qualitative result can be obtained if, during the shooting, the wind is directed directly to the investigated part of the facade, or if excess pressure or dilution in comparison with the ambient pressure is created in the house. This can be implemented with the help of special equipment for determining the breathability of buildings, called the Blower Door Test.