The steady pressurisation method measures the building leakage in a range of high pressures, typically 10-60 Pa. It is implemented by creating a steady pressure difference across the building envelope and measuring the corresponding airflow exchange rate between the indoor and outdoor simultaneously. This method has been widely used and accepted as the standard test for demonstrating building air-tightness compliance. Conversely, the novel pulse technique, has been developed to measure the building air leakage at low pressures typically in the range of 1-10 Pa. The method is implemented by rapidly releasing a known volume of air from a compressed air tank into the test building, thereby creating an instantaneous pressure rise that quickly reaches ‘quasi-steady’ conditions. The pressure variations in the building and tank are monitored and used for establishing a correlation between leakage and pressure.
Although both techniques are designed to make measurements at different pressure levels, direct comparison between the results has always been of interest. In typical dwelling tests, it is not possible to achieve a direct comparison in an overlapped pressure range due to the low-pressure nature of the pulse technique. In this study, two small chambers, each with a volume of about 22 m3 and with different leakage levels, were utilised to allow both testing techniques to measure the enclosure leakage in a much wider overlapped pressure range (up to 50 Pa). Blower door tests were performed in both pressurisation and depressurisation modes. Initial tests showed that due to the very small testing environment gaps around the blower door frame could account for up to 60% of the air leakage in the more air tight pod. As the pulse test requires no penetration of the building envelope, sealing of the door frames was essential to ensure a fair comparison. In the sealed condition it was found that there was less than 13% deviation between the blower door and pulse results across the range up to 50 Pa. However for the highly airtight chamber there was less agreement with up to 42% deviation.