There are many things you can do if you happen to fail an air tightness test. Here we outline a number of things to do if this happens to you.

What Is an Air Tightness Test?

An Air Test is the process used to determine the total conditioned air lost through leaks in a building’s fabric. Air Test are also known as Air Tightness Testing; Air Permeability Testing; Air Leakage Testing and Air Pressure Tests. All new developments need to have an Air Test, as stated in Part L of the building regulations. The final Air Test is always completed towards the end of the construction process, before the occupier has moved in. 

In Construction Air Tightness Testing

If you want to adopt a best practice approach you will need to carry out two air tests. These are called ‘In Construction’ and ‘Final Phase’ tests. An In Construction Air Test happens after the building envelope is complete but before any additional fittings are in. (These can include things like kitchen units, skirtings, flooring, and other additional elements.) This early-stage test is done to see how well the house is basically performing. We identify the majority of major air leaks and our clients find it much easier to fix any issues at this stage.

Final Phase Air Tightness Testing

The Final Phase Air Test is undertaken at the last stage of construction, when everything except the final finishing, such as carpets, have been fitted. If all of the issues have been addressed from the In Construction Air Test, then the dwelling should achieve its Air Tightness score or lower. 

If the dwelling fails the Final Phase Air Test there are a couple of options. Our testing specialist will go around the dwelling to find all air leakage sources. Sometimes we can fix your issues by sealing small apertures and resolving minor issues. Our testers are keen to help with this and will always make an effort to support you. They will stay whilst you address the issues they have identified. They will then perform another test, free of charge, which will hopefully bring the air tightness score down to a level that will pass the SAP requirements

If there are multiple air leakage issues that require remediation, your tester will prepare a report. This will show all the issues they have identified that will need fixing before the dwelling will pass. We will then arrange to come back for a retest when the issues have been resolved. 

What Happens If It Fails?

If the dwelling fails to achieve the design air permeability score, even after sealing any quick fixes identified on site, It does not necessarily mean the dwelling has failed Part L requirements. As long as you achieve a score of less than 10 m3/h.m2 you have passed the minimum standards of Air Tightness set by the Building Regulations, providing the SAP calculation also passes. The best course of action is to ask your SAP assessor to input the higher air permeability score into the SAP calculation to see if it will pass.

If the SAP is failing, your SAP assessor will require you to further reduce the Air Tightness score. Sometimes this isn’t practical, so you will need to look at improving other building elements. Once the building’s fabric energy efficiency has been met, you need to look at additions. These often involve the addition of Solar PV or mechanical heat recovery fan installation. If the building’s fabric energy efficiency target has not been met, you need to improve either the insulation or the air tightness score. 

Undertaking these additional measures will lower the required air leakage target. This means that your property will be more likely to pass the dwelling emission rate set by SAP and Part L of the Building Regulations. 

What’s next?

Our testing experts have extensive experience in getting dwellings to meet the air tightness thresholds required. We work hard to go beyond mere compliance with building regulations. Our approach is to help our clients prepare and be ready to pass first time on the day of the test.

If you need support from our experienced team of ATTMA-qualified air tightness testers, get in touch.

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