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Purpose of the work
Despite their favourable A/V ratio, large multifamily residential buildings in Czech Republic often show worse airtightness (n50, qE50 or both) than small single-family passive houses erected by means of similar construction methods The analyses presented point out several reasons behind.
Method of approach
Information about airtightness achieved in both categories of buildings is based on statistical analysis of test results dataset. Detailed leakage detection was carried out in approx. 10 multifamily buildings. Airtightness of leakage paths was estimated by means of so-called progressive sealing method.
Content of the contribution
Statistical analysis shows that very good building envelope air permeability (qE50) is usually achieved in single-family passive houses. One would expect that similar results should be achieved as well in multifamily residential buildings erected by means of similar construction methods. However, statistical data prove that this is not always the case.
In order to find out the reasons behind, airtightness tests of several multifamily residential buildings were completed with detailed leakage detection and estimation of air leakage rate through the most noticeable leakage paths.
Firstly, each building was tested as a whole according to ČSN EN ISO 9972. Secondly, the leakage path detection was carried out. In the following steps, the airtightness test of the whole building was repeated several times with selected leakage paths sealed one by one (progressive sealing). An estimate of the air leakage through a specific leakage path was obtained by subtracting the results of two successive tests. Based on this information the share of particular leakage paths on the envelope air permeability was estimated as well as the distribution of the air leakage over the building envelope.
Results and assessment of their significance
The most noticeable leakage paths are usually located in common spaces (corridors, staircase). Their contribution to the whole envelope air permeability is usually significant. Since they typically result from a misconceived design, they are difficult to repair during the construction process.
Conclusions
The most significant leakage paths detected are specific to multi family residential buildings and do not occur in single-family houses. In general, existence of such specific issues complicates a simple transfer of proven construction rules from one building category to another. Regardless the category, the building airtightness has to be properly addressed during the design process.
For further information please contact Jiří Novák at: jiri.novak.4@fsv.cvut.cz