ACCOUNTING FOR THE NONSTATIONARITY OF HEAT TRANSFER DURING THERMAL IMAGING OF INERTIAL BUILDING ENVELOPES
Thermal imaging inspection is the main method of non-destructive testing of the quality of enclosing structures thermal insulation and its installation. According to GOST for conducting a thermal imaging survey, the error caused by the non-stationarity of heat transfer through the design should not exceed 15%. During a thermal imaging survey of modern insulated and inertia enclosing structures, the main cause of the nonstationarity of heat transfer, which leads to significant errors in processing the results, is the variation of the average daily outdoor temperature. It is necessary that for about 10 days the average outside air temperature should change by no more than 0.2-0.5 ° C to achieve stationary heat transfer. This situation is practically not observed during the heating period. The paper proposes a method for taking into account the nonstationarity of heat transfer through the building envelope by averaging the outdoor air temperature with weighting factors. These weighting factors are calculated on the basis of the thermal inertia of individual layers of the building envelope. This method allows to reduce the error of thermal imaging due to the variation of the average daily outdoor temperature to 1-2% and meet the requirements to the error caused by the nonstationary heat transfer.