Jiří Novák
Bibliographic info:
11th International BUILDAIR Symposium, 24- 25 May 2019, Hannover, Germany

Purpose of the work

The aim of this study was to evaluate the evolution of the building airtightness over the time and to assess the long term performance (durability) of the air barrier system. For this purpose, several passive houses were repeatedly tested over a period of 6 to 11 years.

Method of approach

In this study, 5 passive houses were tested several times over a period of 6 or 11 years. Besides the repeated testing, information about the conditions of the buildings service over the period between the successive tests was collected in order to explain the differences between the test results. The buildings were tested by the same technician using the same equipment. If possible, the technician always prepared the building in the same way and followed the same measuring procedure. The tests were carried out preferentially in the same period of year under similar climatic conditions. Therefore, the differences between the test results should reflect namely the impact of ageing and the impact of the air barrier system modifications. Information concerning interventions to the building envelope was collected from the building users or the caretaker. Therefore, the impact of such interventions on the building airtightness is traceable.

Content of the contribution

The buildings A, B, C and D belongs to the same pilot project. They have a very similar size, the same timber structure and the same air barrier system, but they serve for different purposes.

This allows a comparison of the potential impact of different user’s behaviour on the airtightness durability. The buildings A and B were tested at the commissioning, 3 years after and then each 2 years or even each year. The buildings C and D were tested only twice, at the commissioning and 11 years later. The building E is an experimental passive house with single-layer massonry wals. It was tested at the commissioning and 6 years later.

Results and assessment of their significance

In all the buildings, the airtightness has deteriorated over the period of monitoring. The n50 increased from 0.5 h-1 to 0.7 h-1 in buildings A and B and from 0.22 h-1 to 0.27 h-1 in the building E. The n50 of building C and D increased more significantly from 0.5 h-1 to 1.3 h-1 and from 0.7 h-1 to 1.4 h-1 respectively (due to improper maintenance works carried out with little concern about airtightness).


The results show that a good airtightness durability can be achieved if:

  • the air barrier system is designed and executed carefully
  • the users respect some basic restrictions concerning the modifications of the building envelope which aim to protect the air barrier system
  • all interventions into the air barrier system that can occur e.g. during refurbishment or repair works are properly repaired (inversely, improper interventions can significantly deteriorate the airtightness)

The results confirm that the airtightness decreases namely during the first years of the building service

The proposed paper is an extended version of an article already published in the proceedings of the 39th AIVC Conference.


For more information, please contact the reference author at: jiri.novak.4@fsv.cvut.cz