Background ventilation testing was introduced to the industry through retrofit. There was a need to prove that dwellings subject to retrofit improvements under PAS 2035 had adequate ventilation within the existing systems that the requirements for additional ventilation could be bypassed. This was given the term ‘background ventilation’ as it referred to ventilation happening in the background of the building in its current state and measures the air change rate. Ventilation is crucial for retrofit projects as improvements to the dwelling can decrease the air exchange rate which in turn can increase the risk of damp and mould. Air exchange rate or the number of ‘Air changes’ is the amount of air that is circulated in the property and replaced with fresh air which prevents moisture and pollution build up in the dwelling.

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The test method for background ventilations is The Installation Assurance Authority (IAA) guidance. The test method requires that whole house and bedrooms tests are carried out. Preparing the property for the test includes closing trickle vents and turning off or closing any other vents or ventilation systems but not sealing them, as you would in an air pressure test. This gives an indication of the buildings worst case background ventilation. The test can be conducted by using Pulse or Blower Door test equipment, however the test does lend itself to our Pulse equipment which allows for the testing of the door undercuts in bedroom tests where a blower door would need to be installed.

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Background Ventilation is measured in Air Change Rate (ACH) which is defined as the number of times the entire volume of the space (dwelling/room) is replaced. A rate of 1 means that all the air inside the building is exchanged with the air from outside the building, once every hour.