Thermal balance of a building as a tool for evaluating infiltration rate

Theoretically if the thermal properties of a building envelope and the power of the HVAC systems are known, then air infiltration becomes the only one unknown component of the thermal balance of a building and could be defined from it. In reality, all data are approximate. Modern measurements and data processing techniques allow one to evade this obstacle.
In modern and large commercial buildings heating power for ventilation can be measured accurately. It is many times more than the transmission heat losses through the envelope and in that way diminishes influence of the inaccuracy of heat losses. The bulk of logged data eliminates accidental errors and gives reliable mean values. Thus, data logging and developed thermal insulation create a possibility to define the infiltrations air rate. The thermal balance equation is solved, assuming heat gains are constant and the infiltration air rate is constant or dependent on the outdoor temperature in accordance with certain laws.
This approach was applied to 80-thous.m3 shopping center main halls. There was found that the infiltration rate is 0.15 h-1 during the night hours and 0.20h-1 at weekend work hours. The advantage of the considered method is that it does not need any intervention in the operation of a building.