ISO 9972

This article provides a summary of a comprehensive examination of the current ISO 9972 standard, focusing on the enhancements needed to improve its reliability and validity for airtightness tests in buildings. A working group composed of international experts has identified a list of issues warranting a potential revision of the standard. New recommendations are proposed based on research and consultation, including detailed considerations of previous guidelines and existing scientific literature.

Purpose of the work

A procedure for the preparation of buildings for airtightness checks in compliance with legal requirements was to be defined in a standard. It should be possible to transfer the measurement result directly into the energy performance calculation as specified in DIN V 18599 without making any mathematical corrections. Checklists in the standard should largely eliminate the need to consult previous publications on interpretation issues.

Method of approach

The requirements concerning airtightness of the building envelope were introduced into the national standard ČSN 73 0540-2 in 2002. Until now the proof of compliance has not been mandatory. The compliance should be checked by means of testing according to the ČSN EN ISO 9972 standard (introduced in 2016 and translated into the Czech language in 2017).

However, the ČSN 73 0540-2 standard only sets the requirements but gives no further information about the time of test and the building preparation or other guidance beyond the ČSN EN ISO 9972 standard.

Even though air leakage assessment is key towards a better energy performance of buildings, Spain has still not established limitations regarding airtightness. National building regulations in Spain are gathered in the National Building Code (CTE), which was first released in 2006 and updated several times so far.

The situation in Switzerland is as follows: Neither the Swiss Energy Act nor cantonal energy acts/energy regulations stipulate a legal measurement of airtightness. The current standards of the Swiss Engineers and Architects Association (Schweizerischer Ingenieur- und Architektenverein, SIA) are the latest standards for architecture. The 2014 edition of SIA Standard 180 defines requirements for airtightness with limit and target values. The limit values are to be complied with in a voluntary measurement.

What is recommended in the way of building preparation (methods 1, 2, 3)?

For methods 1 and 2, the Austrian national annex to ISO 9972 page 6, Item 6.3, Table 1, applies. For method 3, there are no references in the national annex. In this case, ISO 9972 applies.

If method 3 is selected, is a checklist drawn up? Of interest is the issue of fixtures incorporated into the building envelope, like letterboxes, window rebate ventilation, WC fans and fire dampers.

There is no checklist for method 3.

The current French EP regulation called “RT 2012” imposes a maximum airtightness level2 of residential buildings envelope: 0.6 m³.h^-1.m^-2 for single-family houses and 1 m³.h^-1.m^-2 for multi- family buildings. The respect of these requirements must be justified either with an airtightness test of each building or by the application of a certified quality management approach on the building airtightness. In both cases, airtightness tests must be performed by a third-party tester, qualified by the certification body, Qualibat.

For approx. a year ago, the following was submitted to the Certification Committee, and no response is still seen. Especially the problem of the pressure at which Pa the measurement should start is seen as a criticism, and yet it has not been possible to find a reasonable explanation for the change.

Dear committee at ISO 9972,

I miss an explanation, of the change that came from EN 13829 to ISO 9972