How is the building airtightness quantified?

The airtightness of a building is quantified by means of the measured air leakage rate through the building’s envelope in m³/h at a given reference pressure difference, often 50 Pa. The building airtightness may be expressed by other quantities, derived from the air leakage rate at a reference pressure difference, and normalised using, for example, one of the following measures for the size of the building:

  • Internal building volume V. At 50 Pa, the associated indicator is called air change rate at 50 Pa and noted n50 [unit h-1].
  • Envelope area AE. At 50 Pa, the associated indicator is called air permeability at 50 Pa and noted qE50 (former: q50 in EN 13829) [unit m3/(h.m2)[.
  • Net floor area AF. At 50 Pa, the associated indicator is called specific leakage rate and noted qF50, (former: w50 in EN 13829) [unit m3/(h.m2)].

Other indicators of airtightness exist in national regulations.

Is building airtightness testing mandatory?

Requirements depend on the country and the context of the measurement. Most EU countries include in their regulations either required or recommended minimum airtightness levels with or without mandatory testing. There are several countries (e.g.United Kingdom, France, Belgium, Ireland) where, by regulation, airtightness testing is mandatory for certain building types or in the case of specific programmes [1].


[1] Leprince V., Kapsalaki M., & Carrié F., R., “VIP 37: Impact of Energy Policies on Building and Ductwork Airtightness”. AIVC, 2017.

What is TAAC? How can I be involved?

TAAC  is the TightVent Airtightness Associations Committee, launched in September 2012 by the TightVent Europe platform, with the primary goal to bring together national associations and experts in order to promote reliable testing/inspection and reporting procedures.

The scope of TAAC includes various aspects such as: building & ductwork airtightness requirements in the countries involved; competent tester schemes in the countries involved; applicable standards and guidelines for testing; inspection of ventilation systems; collection of relevant guidance and training documents; share of knowledge and experience; and information on ongoing research work in the field of building and ductwork airtightness.

At present the participants are from Belgium, Czech Republic, Estonia, France, Germany, Hungary, Ireland, Latvia, Netherlands, Poland, Portugal, Spain, Sweden, Switzerland, UK and the US.

In case you are interested to join this initiative, please write an email to:


For more information please see:


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