Commercial Air Testing

Commercial Air Testing

What is Air Testing?

Air leakage, air permeability and air tightness are all terms that refer to the uncontrolled loss of air from inside a building to the outside and the infiltration of air coming from outside to inside. This loss or gain of air through cracks, holes or gaps in the fabric of the building is often felt to us as draughts

Achieving a good level of air tightness is important for the energy efficiency of the building. The benefits of improved insulation and more energy efficient heating systems are lost if warm air can leak out of the building and cold air can leak in. Poor air tightness can be responsible for up to 40% of heat loss from buildings. 

How is an air test carried out?

A temporary airtight screen is fitted into the entrance door of the dwelling with water traps filled (or temporarily blocked), trickle vents closed (sealed under Part L 2010) and extract vents sealed.

A fan is then mounted in the screen and operated to blow air into or out of the dwelling to create a pressure difference between inside and outside of approximately 50 Pa.

The air tightness of the dwelling is quantified by measuring the rate of airflow through the fan while a range of pressure differences between the inside and outside of the dwelling are maintained.

What result is required to pass and Air Test?

To pass an air leakage test in England and Wales, a dwelling must achieve an air permeability result of 10 m3/(h.m2) (a minimum requirement in England and Wales; a recommended 'back stop' in Scotland).

However, the air permeability rate (APR) defined in the design stage SAP often imposes a more stringent target. If the tested APR is greater than that used in the design stage SAP, the as-built SAP may not comply.

The model specification used for Part L 2013 (England)* and Part L 2014 (Wales)** both assume an APR of 5 m3/(h.m2) so designers specifying the minimum required APR value will need to compensate by increasing performance in other areas of the specification in order to demonstrate compliance.

A test that does not achieve a Building Regulations minimum performance requirement would be classed as a fail. Should tests fail to achieve the necessary performance level, the property may need remedial work and re-testing. You may also be asked to test further examples of that dwelling type to restore confidence and show that remedial actions have been carried forward into the remainder of the build.

Why carry out Air Tests?

Building Regulations require that builders/developers prove the air tightness of a sample of new buildings on any development. The regulations set a maximum allowable air permeability measure for all buildings but the specific performance required on any given unit will depend on the SAP or SBEM calculations which determine whether the building's Design Emission Rate (DER) is below the Target Emission Rate (TER).

With over 35 years in the construction and testing industry, and with In-house RIBA accredited Architects, FEP is able to offer not only direct air leakage testing for buildings but also excellent advice on the construction techniques for ensuring compliance under the new Building Regulations.

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