PULSE

Building air infiltration rate is required as an important input in the calculation of building heat loss. Tests to directly measure infiltration rates are complex and time-consuming to perform, and are therefore usually substituted with an airtightness test as a more efficient alternative. An empirical ratio, or sometimes an infiltration model, is then used to predict the building infiltration rate from the measured airtightness value. For instance, in the United Kingdom the building air permeability measured by a steady pressurisation test and reported at 50 Pa

Previous studies have compared the airtightness measurement of test enclosures utilising both the novel Pulse technique and the conventional blower door method.  Discrepancies between results of the two test methods were observed and it was concluded that differences either caused by wind or blower door installation integrity would have had an impact upon the results.

Across different territories there are various normative models for assessing energy demand of domestic dwellings, which use simplified approaches to account for the heat loss due to the air infiltration of a building.  For instance, the United Kingdom uses a dwelling energy model, known as the Standard Assessment Procedure (SAP), and this utilises a process where the measured air permeability value (q50), is simply divided by 20 to provide an infiltration rate (subsequent modification factors are then used for factors such as sheltering etc.).

Air infiltration contributes to a heat loss typically representing up to one third of the heating demand of a building. The building airtightness, also quantified as air leakage, is the fundamental building property that impacts infiltration. The steady (de)pressurization method (blower door) is the widely accepted standard process for measuring building air leakage. However, this method requires the enclosure to be pressurised to a typical range of 10-60 Pa, which is not physically representative of the pressures experienced by buildings under natural conditions.

The air infiltration of a building, which fundamentally depends on its airtightness, can be a significant contributor to its heat loss.  It can also be affected by other factors such as external terrain, leakage distribution, sheltering factor and environmental conditions. The infiltration rate of a detached UK house was monitored for 2 months in early 2018 using constant concentration and decay tracer gas methods under various temperature and wind conditions.