New ISO 9972 published

The International Standard EN ISO 9972 “Determination of air permeability of buildings – Fan pressurization method”, approved at CEN and ISO levels, was published in September 2015. The previous ISO 9972 version of this standard published in 2006 and amended in 2009 was similar to EN 13829:2000, but there were differences. The intent was to develop a unique ISO and EN standard. The new standard is progressively made available for purchase through the national standard bodies.

The major changes compared to EN 13829:2000 are:

  • The measurement extent: a new paragraph has been added to adapt to the purpose and context of the test as follows: “if the aim of the measurement is compliance with air-tightness specification of a building code or standard and measured extent is defined in this code or standard, the measured extent is defined as in this code or standard” (§ 5.1.2);
  • The building preparation methods: Method A and B have been replaced by Method 1 and 2. A new method (method 3) is introduced for specific purposes and left open to be adapted according to standard or policy in each country. This way, a specific code may require to seal specific voluntary natural ventilation openings to remain consistent with the applicable energy performance calculation. Whole building and intermittent mechanical ventilation are differentiated. Preparation methods are detailed with a new summary table (§ 5.2.3);
  • The justification for requiring the opening of interconnecting doors (to maintain a uniform pressure within 10% in the building) has been deleted;
  • A definition for “to close” and “to seal” an opening has been added. Note that it explicitly states that “if there is no way to close an opening, the opening shall remain open” (§ 3.1.10, 3.1.11);
  • Requirements on measurements devices have changed: a pressure-measuring device is an instrument capable of measuring pressure differences with an accuracy of ± 1 Pa in the range of 0 Pa to 100 Pa (instead of ± 2 Pa in the range of 0 to 60 Pa in 13829:2000) and a temperature measuring device shall have an accuracy of 0,5 K (instead of 1 K) (§4.2).
  • The informative note regarding the product of the indoor/outdoor air temperature difference has decreased from 500 m K to 250 m K (§5.1.1) (change compared to EN 13829:2000 only)
  • The reference zero-flow pressure difference for the calculation of the lowest test pressure has been modified from the positive or negative average to the general average (§ 5.3.4).
  • An allowance of 3 Pa has been introduced for the lowest pressure difference allowing the lowest test pressure to be as low as 7 Pa (if the zero-flow pressure is lower than 2 Pa) and as high as 28 Pa (if the zero-flow pressure is 5 Pa) (§ 5.3.4);
  • The definition of large building (> 4000 m3) to justify for a highest test pressure smaller than 50 Pa has been deleted;
  • The definition of the internal volume: it has changed and now includes internal walls or floors (§ 6.1.1). Nevertheless, new reference values can be defined, if needed for a specific purpose;
  • The coefficient of determination for the linear regression, r², shall be calculated and shall not be less than 0.98 (§ 6.2);
  • Requirements for the test report have changed: the net floor area, the n50, the wall and roof area and confidence limits do not need to be reported; however, the building volume is still required and the position of the sealing of the mechanical ventilation must be reported (§ 7);
  • 50 Pa is no longer the default pressure reference, any reference pressure can be chosen;
  • The informative note regarding the uncertainty in calm and windy conditions mentions overall uncertainties of 10% and 20%, respectively, whereas the previous version mentioned 15% and 40% (§ 8.3);
  • In annex, the Beaufort scale of wind has been corrected and is significantly more detailed;
  • A new annex gives information about detection of leakage.

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