In most European countries the building preparation is based on ISO 9972 requirements. However, the interpretation of these requirements may differ from one country to another, and based on different building preparation rules.
Building preparation errors are probably the dominant source of uncertainty in an airtightness test. The reference testing protocol in Europe is described in ISO 9972, in the USA in ASTM 779-19, and in Canada in CGSB 149.10-2019. Nevertheless, ISO 9972 proposes 3 different methods (with different preparation requirements):
- Method 1: Test of the building in use
- Method 2: Test of the building envelope
- Method 3: Test of the building for a specific purpose according to a standard or policy in each country
Many countries have developed specific guidelines to detail or adapt to the ISO 9972 requirements.
A study has been performed to compare building preparation rules for airtightness testing in 11 European countries . Information has been collected through a questionnaire sent to TAAC (TightVent Airtightness Associations Committee) members . It has been found that building preparation differs significantly from one country to another and that methods 1 and 2 described in the standard are either too detailed or insufficiently described to fit the specificities of each country. This has supported the creation of “method 3” in ISO 9972:2015 (which is one of the major changes compared to former EN 13829:2000). "Method 3" needs to be defined at the national level which allows to adapt the measured extent and the building preparation to the purpose and context of the test. More specifically, it allows each country:
- to describe more precisely the basic principles of the preparation to avoid ambiguities; and
- to have some flexibility to specify rules consistent with their energy performance calculation method.
The main obstacles to harmonize pressurization test methods between countries are:
- In each country the test method shall be consistent with the energy performance calculation method. But there are significant differences in calculation methods between countries in the way airflow rates are taken into account.
- There are specific devices and construction traditions in each country that may require tailored rules.
Therefore, it is clear that building airtightness should not be compared between countries unless precaution is taken in the sample analyzed and in the interpretation of the results.
The figure below shows how 6 openings categorized as "other" in the standard are prepared in the countries asked in the above-mentioned study. It shows, for example, that in some countries the air exhaust of a clothes dryer will be left open while in others it will be sealed.
 Leprince V. & Carrié F.R, "Comparison of building preparation rules for airtightness testing in 11 European countries", 35th AIVC Conference "Ventilation and airtightness in transforming the building stock to high performance", Poznań, Poland, 2014