Air Tightness Testing – Commercial
Air Tightness testing is a requirement for all new buildings. Testing must be conducted by a competent person, typically a company registered with the Air Tightness Testing & Measurement Association (ATTMA). We have a number of experienced test engineers with ATTMA Level 2 registration and a lot of fans which allows us to test all types and sizes of building.
Air Tightness is a key factor in achieving an energy efficient building fabric in combination with insulation. The England & Wales Building Regulations require air tightness to be measured through site testing.
Testing is carried out by installing blower door fans into the envelope of the building (typically into a personnel door) and using the fans to create a pressure difference. The volume of air flow required to create the pressure difference is used as the basis for calculating the amount of air escaping through holes, gaps and cracks in the building fabric that it is not intended to (i.e. not through planned ventilation, which is temporarily sealed for the test). This air flow rate is divided by the size of the building to give a measure of leakage in m3.h-1.m-2 @50Pa.
There are different requirements for ‘residential’ (dwellings – just houses and flats) and ‘commercial’ (buildings other than dwellings) which includes care homes, student accommodation and similar.
In June 2022, a revised version of Approved Document L came into force. It is divided into Volume 1 for dwellings and Volume 2 for buildings other than dwellings. There are some significant changes included in this revision in order to achieve a 31% reduction in carbon emissions from new buildings, this impacts a wide range of aspects energy efficiency including insulation and fuel types as well as air tightness, as a stepping stone to the Future Homes Standard in 2025.
The highlights with respect to air tightness include:
- Maximum air permeability reduced from 10 m3.h-1.m-2 @50Pa to 8 m3.h-1.m-2 @50Pa (i.e. less draughty)
- A different test standard (CIBSE TM23)
Testing must be conducted by a suitably competent person, our test engineers are all registered with the ATTMA competent person scheme, as referred to in Part L.
For more information on air tightness and the testing, please visit our FAQ page
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Air Testing Process
Our air test engineers are home-based and well-placed to cover Greater London and the City, Kent, Essex, Surrey, Sussex, Hampshire, Berkshire, Buckinghamshire, Oxfordshire, Hertfordshire, Bedfordshire and Cambridgeshire, we are able to test all over the UK.
We are happy to talk through what is involved, what to watch out for and when to test. We can provide guidance and checklists.
The below checklists can be downloaded and used to manage air testing from design/planning, through construction to preparation for the test:
We confirm a date. Our engineer will call you ahead of the test date to talk you through the preparation and process plus agree the timings. We would also look to confirm the air permeability that has been targeted in the energy model (SAP) at this stage, if it hasn’t been discussed already. The results of the test are a key component of the calculation of the overall energy efficiency of the building and, therefore, achieving the necessary air tightness is a critical part of building control sign-off.
4. On the day of testing
We would talk you through what would need temporary sealing would need to be done in advance of our arrival.
We conduct the test. Testing is done through a pressure test whereby fans are installed into a doorway of the building and used to create a measurable difference between the pressure inside and outside of the building. The amount of air needed to maintain this difference can be used to indicate the volume of air escaping through the fabric (what would be draughts in the building’s day-to-day life).
If the building doesn’t achieve its target at the first time of asking, we can use our equipment to identify the leakage paths. If these can be addressed relatively quickly, then we can repeat the test on the same day. In order to achieve increasingly challenging energy performance targets, air tightness requirements are becoming tighter. Typically, a good level of air tightness can still be achieved with excellent attention to detail in the decorative finish but, to achieve tighter targets, consideration must be given to air permeability within the design of the fabric, including use of membranes and tapes to maintain the air barrier – please see FAQs.
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We also offer advice and support on achieving air tightness in advance of undertaking the test, including:
- Desktop design reviews – a review of the key design details that make up the air barrier
- Attendance of design meetings
- Pre-test inspections and reports – walking the building with the site team to review the air barrier and identify potential issues/solutions, plus agree pre-test preparations and practicalities of the test (timings, access, etc)
- Toolbox Talks
- Preliminary/benchmark testing at an early stage to confirm performance and identify leakage paths
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