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Air Tightness Testing

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Harmil Environmental's team specialise in carrying out Air Tightness Tests in new build houses and other dwelling types e.g Flats. Our specialist team is fully accredited in accordance with ATTMA, giving us acceptance from formal bodies such as building control officers. 

When do I need Air Tightness Testing?

Air Tightness Testing also known as Air Pressure Testing or Air Permeability Testing, is a method of measuring the amount of air leakage in a dwelling. The test does not include air leakage through ventilation and focuses on uncontrolled air flow; such as cracks in the external envelope and poorly fitted pipes.


Since 2006, Air Tightness Testing has become a compulsory requirement under Part L of Building regulations. The Test is mandatory requirement for both domestic and commercial dwellings.

How do I pass?

Part L of Building regulations states dwellings can have a maximum air permeability value of 10 m3.h/m2. However, the air permeability target score for your dwelling is unlikely to be this. Your target score can range from 1-10 and is assigned by your SAP assessor during his/her calculations and we test your dwelling to meet this target set by your SAP assessor. Providing your dwelling meets your target score; building control will review our Air Tightness Test Certificate and your SAP calculations during the acceptance process of your project.

How many plots do I need testing?.

If you're working on a large site, you may have multiple dwellings of the same build type and size. This does give you the option to use a sampling approach to prove the air tightness of all dwellings building control declares the same type and size. Unfortunately, this sampling method forces you to apply a 2 m3.h/m2 penalty to all houses that have not been tested. In most cases this penalty means your other dwellings do not meet your target score. To allow for this substantial penalty, developers would need to increase either the build specifications of the dwellings to allow for a higher target score or increase the quality of the build itself. This can be both time consuming and expensive! From our experience, having all of your dwellings tested to avoid this penalty is often the simpler and most cost-effective approach to gaining approval from building control.

How can Harmil help?

Harmil Environmental offer an exceptional service making passing your test as easy as possible. We offer support through every stage of your project to ensure you get the score you require. All of our engineers are thoroughly trained and ATTMA registered allowing for a quick and easy acceptance from building control.

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Tel: 01782 308418



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