An innovative technique for measurement of building leakage at low pressures

Conventional techniques for the measurement of adventitious leakage of building envelopes are based on steady pressurisation at high pressures (e.g. 50 Pa) that are not normally encountered with natural or mechanical ventilation. It is the leakage at low pressures (e.g. 4 Pa) that is of interest and it is shown that the conventional technique leads to large uncertainty in the low-pressure leakage. Ideally a pressurisation of 4 Pa should be used, but with the conventional technique the uncertainty due to wind effects is unacceptably large. The paper describes a new pulse pressurisation technique that allows accurate measurement of the leakage at low pressures, even in the presence of wind effects. The technique makes use of pulse pressurisation. The three key features that have led to a successful technique are described. Examples of measurements are presented and a comparison between the new technique, the conventional steady technique and a theoretical model is shown.