What is Air Tightness Testing?

Air Testing

Many of us have heard of Air Tightness Testing, or maybe you have been told that you need an Air Permeability test. But what exactly is it? When do you need it? And what is the Air Tightness test procedure? Here we will outline the basic understanding you should have before you begin your research into Air Tightness testing companies.

What is Air Tightness Testing?

Air Tightness Testing is a recognised method of measuring the extent to which uncontrolled flow of air is lost through the gaps and cracks in the fabric of a building. It is also called Air Testing/ Air Pressure Testing/Air Leakage Testing. 

Air Testing falls under Part L of the Building Regulations and the Scottish Building Standards. England and Wales have had separate building regulations since 2011. However as far as carrying out an airtightness test, there’s no difference.  Reducing air leakage results in reduced heating energy use and lower CO2 emissions. It therefore decreases the heating costs associated with the building and improves the occupant comfort. As the government strives to reduce CO2 emissions from new buildings, greater emphasis is on the quality of the fabric of a new building.

Do I need an Air Tightness Test?

Building Regulations require that all new buildings carry out energy calculations. There are specific air pressure regulations that all new dwellings need to conduct in compliance with Part L of the Building Regulations, therefore in accordance with ATTMA Technical Standard (ATTMA TSL1). Buildings other than non-dwellings also need it in accordance with ATTMA Technical Standard L2 (ATTMA TSL2). Furthermore, air tightness testing plays an integral role in ensuring that the energy calculation Building Carbon Dioxide Emission Rate (BER) is less than the Target Emission Rate (TER). 

So whether you’re a small developer or a large housing contractor, you will need to perform an Air Permeability test on your new builds before completion. An air tightness test is usually completed towards the end of the construction process and then the results are used to determine your overall energy rating, (SAP for dwellings and SBEM for commercial buildings). You need to complete an air tightness test to ensure that your building is compliant with building emission rates.

Your building’s emission rates must be lower than the target emissions rate to comply with all building regulations. This is because the government is constantly making steps to reduce overall emissions, hence the rates and targets now implemented on dwellings and commercial buildings. It’s estimated that construction makes up approximately 50% of all emissions, so it’s very important to aim for a good air tightness test result. A high level of air tightness can improve your emissions rate and keep heat from escaping through small cracks in the building work. However, we also don’t want the building to be too tight because this can cause mould and condensation.

When should you perform an Air Permeability Test?

Before you request an Air Leakage test, ensure that you have met certain requirements. Ensure that the properties are in fact, up to a standard of readiness. This includes:

  • Fitting all trickle vents
  • Fitting loft hatch
  • Sealing or filling drainage traps 
  • Fitting down lights and ceiling roses
  • Completing external door thresholds
  • Sealing mains water feed penetration
  • Masticing required for air seal complete
  • Sealing boiler flue penetration
  • Fitting and sealing extractors 
  • Sealing SVP penetration to loft space 
  • Closing all windows
  • 240v or 110v power to dwelling

If you have completed the above lists and are confident that everything is up to a high quality standard, you are now ready to perform an Air Tightness Test.

air-tightness-test

What is the process of an Air Tightness Test?

Before the test takes place, you will need an initial assessment (usually free) to establish your air testing regulations and requirements. 

On the day the process is very straightforward and our experienced engineers will get to work right away. Although hard to understand, the basics of the process you need to know are as follows:

  • A fan is used to pressurise the test area (this can be either a positive or negative air pressure)
  • This allows a building differential pressures to be obtained and a pressure across the fan to be obtained
  • We collect data across a range of pressures, ensuring that readings greater than 50Pa test pressure is obtained
  • The building differential pressures are adjusted for the building condition in its resting state (wind and stack effect) and the calculated fan flows are adjusted for environmental factors
  • Then, the adjusted building differential pressure is plotted against the adjusted calculated fan flow on a logarithmic scale to identify the air permeability at a test pressure of 50Pa

This test procedure would normally take no longer than an hour to perform after setup and once complete. Once we are finished you will be issued with an on-site draft certificate. In short, we measure the ratio of volume of air passing through our fan to the pressure difference between the outside and inside of the building. This determines the Air Permeability Index in the form of something that looks like this m3h-1m-2 (air permeability rate per hour, per square meter of envelope area). In the UK the Maximum Air Permeability is 10 m3h-1m-2.

Air Tightness Testing is a necessity for all new build developers and requires consideration at all stages of the build process with the final test being undertaken at completion stage. If you are in need of an Air Permeability test or would like to understand more about the process, please give us a call and we’ll be happy to discuss your specific requirements.

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