An air tightness test measures the flow of air in and out of a building. Air leakage is the uncontrolled flow of air through gaps and cracks around the junction of the various elements and in the fabric of a building. It has been estimated that approximately 33% of building energy losses can be attributed to uncontrolled ventilation & air infiltration.

Improving air tightness in a dwelling will reduce air leakage, greatly improve heat retention, and noticeably improve overall energy efficiency. The aim of air tightness is to “build tight, ventilate right”.

In building energy calculations – BER – this is measured through the use of building pressurisation / depressurisation testing by carrying out a blower door test, from which we can quantify the air leakage rate from a building and to also assess exactly where this leakage may be taking place. It is now mandatory, with the improved building regulations, to demonstrate that buildings are built to achieve a minimum standard of air-tightness on completion. In particular this applies to Passive House construction and the strict adherence to specific air-tightness standards.