Air tightness and its impact on energy consumption in multi-family residential buildings in Montenegro

Airtightness is of key importance, both for indoor thermal comfort and for energy efficiency of buildings. Although formally regulated by the rulebook on minimum energy efficiency requirements for buildings, airtightness is not properly addressed in practice in Montenegro. Airtightness measurements are not mandatory, so there is no data in this regard for the building stock so far.
The paper presents the results of blower door measurements on a limited sample of apartments in multi-family residential buildings. Measurements were carried out in accordance with the ISO 9972:2015 standard. The aim of the measurements is to have an idea of the state of the buildings in Montenegro in terms of air permeability of their envelope, to determine which elements of the envelope contribute the most to infiltration and what is the potential of window replacement as an air tightening measure. The results of the measurements unequivocally showed that air tightness depends mostly on the type, quality of installation and maintenance of the windows. In one of the apartments, blower door measurements with wooden windows before and PVC windows after renovation showed that window replacement is an effective measure of increasing air tightness, which brought the number of air changes per hour at the reference pressure difference within the limits required by the rulebook.
In order to assess the energy impact of air tightness, energy consumption calculations were carried out for one of the apartments in accordance with the DIN 18599 standard, varying the climatic conditions, the U-value of the thermal envelope and the level of air tightness. The results of the calculations showed that the increase in air tightness is an effective energy efficiency measure, which achieves significant savings in energy consumption for heating, while savings for cooling are negligible. Furthermore, it is concluded that relative savings are significantly higher in buildings with an improved thermal envelope, located in a colder climate zone.