How is an air tightness test done?

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Accredited air tightness testing using blower doors is the preferred method of determining if the building meets the standards once constructed.

A building is tested under pressure to establish just how much air is being lost through those unwanted gaps and spaces. The external envelope is sealed by closing all external doors and windows and other unwanted openings such as chimneys, fresh air intakes etc.

Using a specialised fan in an airtight shroud, a clever piece of electrical diagnostics in the form of a manometer and a computer program to interpret the results, the fan is used to create different pressures within the building and air flows recorded.

Comparisons between what flow occurs at each pressure and what flow should be occurring, gives a final result that informs the tester how many times the building will lose its entire internal air volume per hour or how many cubic metres of air will be lost every hour through the all the external walls, floor and ceiling.

Where possible, rectification to improve the tightness is undertaken and a re-test scheduled.

The figures show:

  • How well the building is constructed;
  • How tight the building envelope is; and
  • How good the building will be at keeping the internal conditions stable in the building.

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