Air Tightness Testing Services in the UK

Air Tightness Testing Services in the UK

Air Tightness Testing Services in the UK
Air tightness testing is not only carried out in the UK, it is also carried out in Canada, USA, France, The Netherlands, Norway, Sweden and Switzerland. However, although different countries undertake air tightness testing they express their air leakage criterion in different ways. For instance: Belgium, the Netherlands, Norway and the USA express the criterion in terms of ach at a specific reference pressure (4, 10 or 50Pa), However in France, Switzerland and the UK it is expressed in terms of m3/h/m2 at a given pressure difference (4 or 50Pa); whilst Sweden uses l/s/m2. However, even allowing for these differences a simple comparison can be undertaken if the correct assumptions are made about the building data, i.e. volume and surface area – building envelope) and by normalising the air leakage criteria to a standard pressure differential.

To try and make some normality of the air tightness standards, such an approach was adopted by Limb (2001). It was assumed an internal building volume of 300m3, a surface area of 250m2. Thereafter figures would be normalised to show a pressure differential of 50Pa. The Table and Figure below illustrate the results of such a comparison, for all of the countries that have air leakage criteria for dwellings.

The comparison highlights the wide range of normalised air tightness criteria that exists. Not surprisingly the most stringent criteria tend to be found in countries with more severe climatic conditions, such as Sweden, Switzerland and Norway; whilst countries with more temperate climates such as France, USA and United Kingdom tend to have less stringent criteria.

In our experience of undertaking literally thousands of air tightness tests throughout the United Kingdom, very few tests would meet the air leakage requirements of Sweden, Switzerland or Norway. Also existing UK dwellings tend to be comparatively very leaky to other European countries.

In terms of new build UK dwellings, experience suggests that the current levels of airtightness achieved over the last couple of years although improved from 2006, is still in the region of 6-8 m3/h/m2. These levels of airtightness were achieved in countries such as Sweden, Canada and Switzerland many years ago. Even dwellings that have a CfSH default rating of 5m3/h/m2 – which often fail at the first attempt) would not achieve the air tightness rates of Canada, Belguim, Sweden, Norway and Switzerland.

In our experience to match or better the best European air tightness standards, will require a better attention to detail at the design stage of the building envelope. And thereafter, careful supervision throughout the construction phase of the floors, walls and roof. Only then we will be in a position to match the best of the rest of Europe when it comes to air tightness.

Typical air leakage paths in UK homes are:

  • Around windows – under window boards and around frames.
  • Around Doors – under the door sill and around frames.
  • Through service penetrations in kitchens, utility rooms – usually behind the kitchen cupboards
  • Around service penetrations in the boiler cupboard.
  • Around services within bathrooms and toilets – usually behind the toilets, sinks and baths.
  • Around Doors – under the door sill and around frames.
  • Floors – around penetrations and between gaps in the floor boards.
  • Ceilings – through lights and poor fitting loft hatches.
  • Around sockets that have not been fully installed.
  • Around down-lighters that have not been installed or are not fully sealed with a glass cover.

Once the above air leakage paths have been located, it should be fairly easy to undertake the remedial sealing works and lower the air leakage rate in most developments.

If you would like more information in regards to Air Tightness Design, Air Tightness Site Audits or Air Tightness Testing, please don’t hesitate to contact us now at or telephone our office on 07775623464.


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