Development of Airtightness of Estonian Wooden Buildings

Abstract

The field measurements of airtightness in Estonian detached and apartment buildings conducted between2003 – 2017 were combined into a large dataset for further analysis. The buildings were classified basedon building structure, number of storeys, year of construction, energy classification and compactnessfactors. A subset with all wooden buildings (313 in total) was statistically analysed to determine theaverage (median) air leakage rates at 50 Pa and tested (Kruskal-Wallis test with post-hoc Conovertest) for significant differences within the grouping factors. As expected, the median air leakage (q50)of older buildings between 10.7 and 13.9 m3/(hm2) has decreased to 1.1 m3/(hm2) after the minimumrequirements for energy efficiency have taken effect. A more detailed analysis on newer buildings showedthat quality of the workmanship combining systematic measurement routines as well as prefabrication,yields significantly lower median air leakages compared to on-site construction. The buildings with betterenergy classification targets also achieved lower median air leakages compared to buildings designedto meet minimum requirements. Further analysis showed significant differences between buildingswith lightweight timber construction and those with log construction. This can be due to fact that theairtightness has been predominantly measured in prefabricated buildings compared to on-site buildingtechnology. Surprisingly, the analysis showed no significant difference between buildings with a differentcompactness factor or a different number of storeys. For use in energy calculations, the base values ofair leakage rates for each group are calculated and presented accounting for variation of measurements.