Review on ventilation rate measuring and modelling techniques in naturally ventilated buildings

Direct and indirect measuring techniques are available for determination of ventilation rate in naturally ventilated buildings. Direct measuring methods include measuring fan, propeller gauge, hot wire anemometer, particle image velocimetry, laser Doppler anemometer, and transit time sonic anemometer. Basic disadvantage of direct measuring techniques is that they are generally used for point or local measurements of air velocity. In order to have the total ventilation rate through the whole building, a system is required to measure simultaneously the airflow both in magnitude and direction at a number of locations. Indirect measuring techniques are; heat balance, CO2 balance, pressure difference, CFD analysis, tracer gas measurements, multizone modelling, and zonal models. These methods consider the whole system, and therefore, provide a possible tool for determining air flux through the building envelopes. Methods based on computer simulations (CFD, multizone models, etc.) should be validated against experimental data. However, in most of the cases, those validations are lacking, or do not indicate the accuracy of the method. Tracer gas measurements are mostly used as reference method in validations. However, accuracy of this technique should also be studied. Most indirect measuring techniques suffer from the problem of imperfect mixing of air within the ventilated structure. Therefore, the accuracy of tracer gas measurements should be improved by using information of imperfect mixing within the building