During last decades, energy saving in new buildings became relevant within the energy efficiency strategies in various countries. Such energy efficient building characteristics as air tightening and low ventilation can compromise indoor air quality, in particular, increase radon concentration. In Russia, a significant part of the new buildings is the energy efficient multi-storey apartment houses. The aim of this study is to assess the significance of possible radon concentration increase in new energy efficient buildings in comparison with typical conventional multi-storey houses of previous periods. Radon surveys were conducted in Russian cities Ekaterinburg, Chelyabinsk, Saint-Petersburg and Krasnodar. The radon measurements were carried out in 478 flats using CR-39 nuclear track detectors. Energy efficiency index (EEI) was assigned to each house. All buildings were divided into six main categories. The smallest average radon concentration was observed in panel and brick houses built according to standard projects of 1970–1990 (four-city average 21 Bq/m3). The highest average radon concentration and EEI were observed in new energy efficient buildings (49 Bq/m3). The trend of radon increase in buildings ranked with high EEI index is observed in all cities. The potential increase of radiation exposure in energy-efficient buildings should be analyzed taking into account the principles of radiological protection.

Modern energy-efficient architectural solutions and building construction technologies such as monolithic concrete structures in combination with effective insulation reduce air permeability of building envelope. As a result, air exchange rate is significantly reduced and conditions for increased radon accumulation in indoor air are created. Based on radon survey in Ekaterinburg, Russia, remarkable increase in indoor radon concentration level in energy-efficient multi-storey buildings was found in comparison with similar buildings constructed before the-energy-saving era. To investigate the problem of indoor radon in energy-efficient multi-storey buildings, the measurements of radon concentration have been performed in seven modern buildings using radon monitoring method. Values of air exchange rate and other parameters of indoor climate in energy-efficient buildings have been estimated.

Analysis includes review of 63 national and regional indoor radon surveys in kindergartens and schools. Preliminary assessment of the worldwide population weighted characteristics of radon concentration in children's institutions is: arithmetic mean = 59 and geometric mean = 36 Bq/m3. Higher indoor radon concentrations in children's institutions in comparison with the dwellings can be explained by characteristics of ventilation, attendance regime and construction features. Special protocol of measurements in the kindergartens and schools is required.

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