A combined pressurisation and tracer gas technique for air flow measurements.

Building air flow is directly related to the building energy consumption and indoor air quality. As buildings become increasingly air tight, air flow through building background cracks becomes more important, and can account for up to half of the total building air infiltration. However, background leakage is not well understood, due to the lack of appropriate measurement methods. The multi-fan guarding zone or deduction technique provides a means for testing background leakage distributions, an important parameter for characterising the background leakage. However, its reliable application in buildings is limited either due to practical constraints or due to the presence of certain types of air leakage paths, namely the branched paths, In this paper an alternative method, for measuring background leakage distributions, which does not have such problems, has been examined. This method is based on the simultaneous use of the pressurisation and tracer gas technique and termed in short the combined technique. It potentially suffers from all the accuracy problems associated with the tracer gas technique, which could be made more serious by the high pressurisation flows. To counter this problem, mixing fans, among other measures, were utilised. The validity of this measure was examined and its effectiveness tested by applying the combined technique to one single and several multi-zone set-ups. Results showed that the technique is of good accuracy with relative errors consistently below 10%.