Air Tightness Testing of Existing Buildings

Reduce Energy Bills

We undertake air tightness testing of existing houses, flats, offices and other buildings as part of a wider strategy for improving their energy performance.

Projects range from refurbishment of large offices seeking BREEAM Excellent to individual homeowners wishing to reduce their energy bills and draughts.

Air tightness is a key element of an effective energy strategy for any building. It works alongside insulation in ensuring the building fabric allows you to retain heat/keep the cold out and make the most of any other energy-saving measures that have been put in place.


Insulation alone will not prevent cold air infiltration and loss of heated air through the fabric of the building, it needs to be upgraded alongside reducing air leakage to maximise the benefits.

Our approach is typically along the following lines:

Initial air tightness test on the building/property to establish the current levels of air permeability and relate these to performance/requirements for new builds.

Identify/demonstrate the air leakage paths (using air flow and/or smoke).

Quantify the contribution to the overall leakage by isolating areas and repeating the testing.

Air tightness needs to be backed up by good levels of insulation so, as an optional extra, we can undertake a basic thermographic survey of the external facade to indicate if there are insulation issues that may need addressing as well to maximise the improvement in energy efficiency.

Provide a written report confirming performance levels (relative to standards for newbuilds/low energy schemes), list the key areas of current leakage with solutions for how to address them

We can recommend sealant companies that could carry out the remedial works if you are not confident of doing the work yourself.

If desired, we can carry out a further air tightness test to confirm the improvement in air permeability performance following remedial works. This figure can be used as part of an energy calculation model  (SAP/SBEM) to confirm the impact on the overall energy efficiency of the building and produce a higher energy rating on the Energy Performance Certificate (EPC).

How it works

Air Leakage Testing Team MemberOur Air Test Engineers are home-based and well-placed to cover Buckinghamshire, Kent, Essex, Surrey, Sussex, Hampshire, Berkshire,  Hertfordshire and Bedfordshire.



Our process is as follows:

  1. We provide a quote based on the size of the building and location
  2. We provide a checklist and agree a date
  3. We call you ahead of the test date to talk you through the preparation and process and agree the timings.
  4. On houses and flats we would typically complete the temporary sealing for the test when we arrive on site. For larger buildings, we would talk you through what would need to be done in advance of our arrival.
  5. 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).
  6. We use our equipment to identify the leakage paths, typically by identifying air paths when the building is depressurised but smoke can be used as well. If some of these issues can be addressed relatively quickly, then we can repeat the test on the same day to get a feel for the likely improvements.

The below checklists can be downloaded in preparation for the test:

Why use ALT?

  • Helpful – we work with you to achieve the best result, identifying potential issues and repeating the testing once these have been addressed. We are on hand to answer any questions before, during and after the testing
  • Knowledgeable – we have been air testing since 2002 and all our test engineers have a vast amount of experience
  • Flexible – we try to fit in with the dates and times you need the test, we try to work around other trades to minimise disruption on site
  • Responsive – we issue quotes and certificates within 1 working day, our lead-times are typically around a week but we will try and fit you in sooner if required
  • Great value – our prices are very competitive but we can also undertake air and sound testing on the same visit to save you more money. If you do manage to find the testing cheaper, we will beat any quote.

Call 01799 540220 – or send us a message

WhatsApp 07956 893606 – out of hours

© Air Leakage Testing Limited 2020

7 Lawson Way, Aylesbury, Buckinghamshire, HP18 0UW

Tel: 01799 540220 – Email:

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