An investigation into the efficacy of the pulse method of airtightness testing in new build and Passivhaus properties

The latest edition of the UK government’s Approved Document L of the Building Regulations, which came into effect on the 15th of June 2022, for the first time included an alternative method of airtightness testing to the traditional fan pressurisation method (DLUHC & MHCLG, 2021). Unlike the fan pressurisation method, the pulse method operates at low pressures that are thought to be representative of natural infiltration. Despite government approval, responses to the Future Homes Standard consultation revealed that respondents did not have confidence in the method, particularly with very airtight properties, and others were concerned with the comparison between testing methods (MHCLG, 2021). In this paper, experimental investigations were performed involving the pulse method to assess its repeatability and accuracy. The results indicated an average repeatability of 4.96% from the mean for consecutive tests, and the pulse results extrapolated up to 50 Pa all fell within the fan pressurisation’s 10% uncertainty range. In addition, two empirical models were applied to the data set to explore the conversion of air permeabilities between high and low pressures. The data showed strong agreement with the power law model and even stronger correlation with the conversion formula suggested in CIBSE TS23:2022 (Godefroy, 2021).