Air tightness testing sometimes referred to as air permeability testing, air leakage testing and air pressure testing measures the amount of uncontrolled air escaping through the external fabric of the building envelope.  

The air tightness test determines the amount of air leakage in cubic metres per square metre of internal surface area of the building. Or, to put it simply, air tightness testing measures the amount of air that escapes (drafts) through the gaps or building fabrics. Ideally, having an airtight building means that less energy will be wasted through the leakage of heated air.  

All new homes in Scotland require to have an air test carried out in accordance with CIBSE TM23

All new homes in Scotland under current regulations – Domestic Technical Handbook (June 2023) require to have an air tightness test carried out in accordance with CIBSE TM23 

Airtightness is important for avoiding heat loss as it means less uncontrolled air movement in and out of the building (cold drafts). Minimizing heat loss also means your heating and ventilation systems will work at their optimum efficiency, thereby reducing heating bills and energy wastage. 

Air tightness tests should be carried out at completion stage prior to handover. The results from the air permeability test are used within SAP software to produce the final as built EPC. 

Where a dwelling has been designed with a low air permeability target below 3 m³/hr.m² we would advise that a mid-build test is carried out once the air barrier layer has been installed. This allows early identification of any potential leaks and allows them to be sealed at source. A final test is still required at completion. 

The results of the air tightness test are given with a figure in m³/hr.m² 

Good practice target is for a result anywhere between 5-7 m³/hr.m² 

The result of the test can have an impact on the installed ventilation system and must be checked that the ventilation as installed is compatible with the air permeability result.