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Air Leakage Testing, also known as Air Tightness Testing or Door-blower Testing is required under Part L1 & L2 Building Regulations. The results are used in the SAP/SBEM calculations and these are required by Building Control to sign off a completed development. An air-tightness test is also required for Passivhaus certification.

Uncontrolled air leakage in a building makes them more expensive to heat, and they 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.

Controlled ventilation is far better than uncontrolled air leakage. Higher levels of air-tightness have significant effects on the energy required for heating. Building Regulations require appropriate controlled ventilation. This can range from extractor fans in kitchens and bathrooms and trickle vents in the windows to full Mechanical Ventilation with Heat Recovery. These systems provide automatically controlled ventilation with a heat exchanger to heat the incoming air. They filter out dust and pollen in the air and can vary the ventilation according to occupancy. They are around 95% efficient.

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. If these are not available we take measurements on the day - this would normally take one to two hours. 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 do not cause any structural damage.

The on-site test takes about hour and we can normally give you confirmation of a pass on the day. It may take longer to identify and record the areas of uncontrolled leakage following the test. The test can also be undertaken on an existing house with fixtures, fittings and furniture in place to extablish air-tightness and areas of uncontrolled ventilation.

The Test is usually undertaken after second fixing has been completed. However where exacting levels of air-tightness has been designed and an air-tight membrane used for Passivhaus standards for instance - interim tests should be made to establish areas of leakage before second fix in order that they can be rectified. We would discuss the appropriate regime of testing with your designer.

We are experienced in identifying areas of leakage and the vast majority of buildings we test will pass the minimum criteria required by Building Control. At higher levels there will have been a method statement from the designer indicating how the builder was to achieve the required air-tightness together with interim testing. So a failure at the final test would be unexpected. 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 would incur a further charge.

For the purposes of Building Control 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/( Every new home must achieve a score of 10m3/( or less. The lower the figure the better the properties overall SAP/SBEM rating, leading to a better environmental energy rating. The test for the Passivhaus standard measures the Air Change Rate (ACH) @50Pa (the n50 measurement), or in other words the number of times the volume of air within the building is changed in an hour. There is also a requirement to take the average of a >depressurisation and pressurisation test and so takes twice as long to perform the test.

Because we can also carry out your SAP or SBEM calculations, provide new-build Energy Performance Certificates and Code for Sustainable Homes or BREEAM Assessments we can provide an integrated service that is cost-effective and helps you achieve the best rating possible.

Please call us on +44 (0)1865 600173 or email at to discuss your requirements.

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