Building airtightness tests have become very common in several countries, either to comply with minimum requirements of regulations or programmes, or to justify input values in calculation methods. This raises increasing concerns for the reliability of those tests.

There are four key sources of uncertainty in airtightness testing:

  • Measurement devices (accuracy and precision);
  • Calculation assumptions (e.g. reference pressure, regression analysis method);
  • External conditions (wind and stack effect impact); and
  • Tester’s behaviour.

While competent tester schemes and independent checking procedures show potential to contain errors due to the tester's behaviour, there have been extensive yet sterile debates about how the building pressurisation test standard ISO 9972 should address other sources of uncertainties. As a result, no change has been made on these aspects on the new version of the standard which was published in September 2015.

With the present standard, the zero-flow pressure shall not exceed 5 Pa for the test to be valid. Consequently, in moderately windy conditions, it may be impossible to perform a pressurisation test in accordance with the standard, even using precautions with a careful uncertainty analysis.

The goal of this project is to give guidance to estimate uncertainties due to wind which may be used to extend the applicability standard ISO 9972. This should allow testers to give safe side estimates of a building's permeability in windy conditions that confirm compliance to a given requirement.