Assessment of the air change rate of airtight buildings under natural conditions using the tracer gas technique. Comparison with numerical modelling

Under natural conditions, air change rates are very sensitive to specific building elements and to climate conditions, even more so in the case of airtight buildings. Consequently, applying general correlations to such cases may lead to inaccurate predicted air change rates. Still, this approach remains valuable because of its simplicity compared to other methods such as wind tunnelling and CFD simulations. In this paper, the tracer gas concentration decay technique was selected to contribute additional information to classical air-tightness measurements. The measurements were used to fit the coefficients of a general single-node pressure model. Simulation results were found to be consistent with tracer gas measurements most of the time. However, the closeness of the fit is strongly related to the average pressure coefficients from the literature, which were estimated more precisely using the other techniques mentioned above. From a general point of view however, it would seem promising to extend this method to other buildings.

► The air change rate of a single-room test house exposed to natural conditions were assessed.
► Measurements were achieved using the tracer gas concentration decay technique.
► Measurements were then used to fit the coefficients of a general single-node pressure model.
► Air change rate was 23% accurately assessed for various outdoor conditions.
► Wind incidence was shown by the mean of two sets of Cp values issued from literature.