Sufficient hygienic ventilation within the meaning of the so-called Pettenkofer limit value must be ensured regardless of the degree of tightness of a building and the type of ventilation (window / shaft ventilation or ventilation system). The realization that “breathing walls” make no contribution here should no longer have been an issue since the publication of DIN 4108  in 1952.
In  and  the current maximum limit values for the air permeability of a building are specified, which, however, apply to ventilation systems (ventilation systems) with heat recovery according to Section 4.4. should be undercut in . From a publication by the IWU Darmstadt  from 1995 it can be concluded that ventilation systems in leaky buildings do not make sense from an energetic point of view.
The specific ventilation heat losses due to a leaky building envelope can exceed the share of specific ventilation heat losses due to the necessary air exchange via the ventilation system many times over. According to , the result is uneconomical operation of the ventilation system because the energy costs saved are below the operating and maintenance costs of the system. Check out here at https://www.sustainableinteriyours.com/blog/what-is-a-blower-door-test website to get more tricks.
In addition to the energetic and economic aspects, the explanations in the section on moisture protection show that ventilation through joints and cracks, i.e. through leaks, can lead to considerable structural damage and is therefore not a sensible option. In addition, the ventilation of a building via leaks, as can be seen in the section on thermal insulation, is very dependent on the weather.
Calculations are given in  which show that sufficient air exchange (at least 0.4 air exchange per hour) via joints and cracks would only be guaranteed at an n5050 value of 20 h-1. However, this would mean that on cold winter days air changes of well over 10 per hour would occur .
A high level of knowledge of the relationships between airtightness and ventilation or ventilation system is a prerequisite for a hygienically and energetically sensible exchange of air in the building.
Standards / Regulations
The term air permeability of the components was already more than 50 years ago in DIN 4108 – thermal insulation in building construction . This first edition of the series of standards from 1952, which still exists today, shows the great importance even in the times when the word energy saving was not yet part of the basic vocabulary and DIN 4108 underpinned the importance of thermal protection with, among other things, “coal savings”. In this standard , the following is stated regarding air permeability:
It then took more than 40 years until specific requirements for the airtightness of the building envelope were set in a standard  and the regulatory authority could then adopt them . Further information on the historical and legal significance of an airtight building envelope can be found in the explanations of this book.