Air Tightness Testing

What is air tightness testing? (Also known as Air Permeability testing or Air Pressure Testing). This is the process of extracting air at a high rate to create a pressure difference of 50Pa between the inside and outside using a large fan that fits within the external door. We can then measure how leaky the building fabric is and identify where the leaks may occur.

Before air tightness testing is carried out, measurements are carried out in accordance with the ATTMA Publication,  ‘Measuring air permeability of building envelopes (dwellings) as set out in Paragraph 3.14 of Part L1A 2013 of the Building Regulations.

Every new dwelling requires air tightness testing in order to determine the air permeability in m3/hr/m2. For each new dwelling, there should be a SAP Calculation carried out to demonstrate compliance with Part L1A 2013 of the Building Regulations. Within this assessment, the air permeability target is set and can vary up to a maximum of 10m3/hr/m2 depending on other factors.

The purpose of the air tightness testing is to check uncontrolled air leakage. The higher the air leakage, the more heat loss occurs. Uncontrolled air leakage also causes draughts which can cause occupants to turn the heating up to feel warmer.

Good air permeability with correctly specified controlled ventilation such as trickle ventilators and extracts along with operable windows should provide the occupant with adequate means to maintain good indoor air quality balanced with reduced heating bills.

Building Regulations requires that each dwelling is air tested. However, you can provide sample air tightness testing if you can achieve 2m3/hr/m2 below the air permeability target. If sample air tightness testing is undertaken, then at least 50% or 3 of beach house type (which ever is less) must be undertaken.
For example, if you have 4 x House Type A and the air tightness target = 7m3/hr/m2. The by testing 2 of house type A and achieve 5 m3/hr/m2 would allow the untested plots to pass (subject to agreement with the SAP energy assessor).

Are you building a new self build house to live in or sell? Then you need an air tightness test. Using Low Carbon Box, we can offer initial help and advice to help you seal the self build house as you progress the build to provide a much better chance of passing the final air tightness test.

Before air tightness testing is carried out, measurements are carried out in accordance with the ATTMA Publication, Measuring air permeability of building envelopes (dwellings) as set out in Paragraph 3.14 of Part L1A 2013 of the Building Regulations.

Our ATTMA Accredited air tightness tester will attend site with the UKAS calibrated air tightness testing equipment and install a sales door into the front entrance. The Main fine is then installed into the temporary door.

All controlled ventilation such as trickle ventilators, extract fans, cooker hoods should be temporarily sealed for the test.

Site personnel can remain within the property during the air test and carry on working. But no windows or doors should be opened during the air tightness testing.

The fan extracts air from the property during the air tightness testing to create a pressure difference of 50 Pa (pascals) in order for the air tester to detect leaks and measure how much air leakage is occurring. A series of readings are taken and the average reading. The total air flow (m3) is divided by the surface area (m2) to achieve the rating of m3/hr/m2.

An ATTMA accredited air tightness tester will be in touch to confirm the agreed date and time for the air tightness test. We will check and if required, advise on the following:

• Confirm what air tightness target is required
• Confirm what date and time is convenient
• Provide air tightness testing checklist and guide to review and be ready for the air test
• If a fail occurs, then provide on-site leak detection to advise what areas are leaking. If personnel are available to rectify the leak, then we can stay to retest should our schedule permit this.
• Same day certificate release

The architect’s drawings generally show the internal air tightness barrier. But below are details and areas to think about that are not generally shown on the drawings

• Services such as water pipes, drain pipes and other wall and floor penetrations. Ensure these are sealed before and after plasterboard, but before you fit your kitchen or bathroom. See further guidance – Read here
• Behind bathroom showers, toilets and wash hand basins leak due to services not being sealed before fitting.
• The sample applies to kitchens, the corner soil stack is generally not sealed and the soil stack boxing acts like a chimney when the air test is carried out. Seal the top of the stack in the loft (fire collar or similar) and provide mineral wool surround to soil stack pipe to reduce heat loss and air flow.
• Plasterboard on dabs onto blockwork – The air gets pulled through the gaps between the clockwork and around openings and via services going through the clockwork. The air then runs behind the plasterboard. Extra care on sealing before plaster boarding will help.
• Ensure continuous plasterboard dap to the perimeter of the wall and around sockets and services
• Further details of this at the following page –
  Read here