Changes in radon concentration in multistory energy efficient buildings during the first years after construction

The purpose of the study is to investigate changes in radon concentration in modern multi-flat energy efficient buildings during the first years after construction. The results of sample radon surveys conducted in several large Russian cities and the data obtained by means of radon-monitors in multi-apartment, multi-story buildings were analyzed. According to the results of the study, an inverse correlation was found between radon concentration and the age of the building at the time of measurement. In the groups of buildings of the same construction period, the geometric mean radon concentration depends significantly on the age of the building. Repeated measurements of radon time series in three apartments showed a significant decrease in radon concentration under the same meteorological conditions after seven years. The effective leakage area, estimated using radon time series analysis, increases significantly during the first years after building's construction. It can be concluded, that a systematic, gradual decrease in radon concentration occurs during the first years after construction. On average, indoor radon concentration decreases approximately twofold during the first nine years of building operation. The reduction of the radon concentration should be considered in context of the building energy efficiency as it gives evidences that, over time, the condition of the structural elements in buildings deteriorates, increasing the permeability of the envelope. For radiation protection purposes, it is important that high radon concentrations exceeding the WHO reference level of 100 Bq/m³ were obtained in new energy-efficient buildings during the first few years after construction.