FAQs Air Leakage Testing

Why do I need an Air Leakage Test?
Air Tightness Testing, also known as Air Leakage Testing, Air Permeability Testing or Pressure Testing is mandatory under Part L1 & L2 Building Regulations. The Air Leakage ’score’ is used in the SAP/SBEM calculations to give the new building a final environmental rating. This is required by Building Control to provide the Building Regulation Certificate on completion of the property.

Why is air tightness important?
Uncontrolled air leakage in a building makes them more expensive to heat, they are draughty and are susceptible to potential failure of the envelope fabric due to condensation. An air tight building will also not have to meet such a high build specification in other areas to comply with SAP/SBEM, potentially saving a developer a significant amount.

Aren’t buildings supposed to breath?
Yes, but in a controlled way. Uncontrolled air leakage is not an appropriate way to ventilate a building. An air tight property, combined with controlled ventilation is much more comfortable and energy efficient. Approved document F of the Building Regulations requires all new buildings to have an appropriate controlled ventilation system. This can be achieved through extractor fans in ‘wet’ rooms and trickle vents or better still by incorporating a whole building mechanical ventilation system with heat recovery.

What is involved in an Air Leakage Test?
We require a set of scale plans from you a few days before we carry out the test. We use these to calculate the total envelope, volume and floor area of the property. The on-site test involves depressurising the property using a computer controlled fan fitted into a temporarily sealed door opening. We seal certain allowable openings including chimneys and extractor fans and ensure all doors, windows and trickle vents are closed. We take a number of readings at various pressures to give a final accurate result. The pressure changes in the building are small and therefore should not cause any structural damage.

How long does the Air Leakage Test take?
The on-site test takes about an hour and we can normally give you confirmation of a pass on the day. Contractors and other personnel can still work inside the property as the test is undertaken.

At what stage is the Air Leakage Test carried out?
The Test is usually undertaken after second fixing has been completed.

What happens if our property fails the test?
Our role is to help ensure your property passes the test. To reassure you, the vast majority of buildings we test will pass the minimum criteria required by Building Control (approx. 98% of dwellings). We will provide you with practical information prior to the test to ensure the property passes. If your property was to fail, when possible, we give you time to make improvements to the property so that we can do a re-test on the day at no extra cost. If it is not practical to carry out the improvements on the day we will give you full information on where the problems are together with tried & tested advice on how to take remedial action prior to a re-test (which is chargeable).

What does an Air Leakage Test measure?
An Air Tightness Test measures the number of cubic metres of air that are lost through each square metre of envelope area per hour, at a pressure difference of 50 Pascal’s (m3/(m2.hr)@50Pa). Every new home must achieve a score of 10m3/(m2.hr)@50Pa or less. The lower the figure the better the properties overall SAP/SBEM rating, leading to a better environmental energy rating (improving a property’s sales appeal).

Why should I use MES Building Solutions?
We are members of the Royal Institution of Chartered Surveyors (RICS), we are registered with the Air Tightness Testing and Measurement Association (ATTMA) and we are highly experienced in carrying out successful air leakage testing to fulfill Building Regulation requirements.

Because we can also carry out your SAP or SBEM calculations, produce new-build Energy Performance Certificates and Code for Sustainable Homes or BREEAM Assessments we provide a cohesive service saving you money as well as helping you to achieve as good an overall environmental rating as possible.

What area does MES Building Solutions cover?
We cover the whole of the UK. How much does it cost? We provide a highly cost effective service. Either fill out the Contact Us section on the website, give us a call on 01636 653055 or email us for a fast, highly competitive quote.

For larger developers we are also able to offer very attractive contract arrangements.

To download our guide to Air Leakage Testing please click here.


“Oliver was very pleasant to deal with on site, and methodical in his work as always. He obviously has extensive knowledge & experience, and approached his work in a very professional manner. The office were also a pleasure to deal with both before and after the test was carried out. I would recommend MES to anyone for their air testing service.”


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