Large decrease of radon concentrations in new-built Swedish dwellings by Tryggve Rönnqvist, Radonova tryggve.ronnqvist@radonova.com 2018 International Radon Symposium™

Large decrease of radon concentrations in new-built Swedish dwellings Dependencies between building year and radon levels in Swedish dwellings were evaluated: Data from measurements analyzed during 2015-2017 Dwellings with building years from 1950 until 2016 Dependencies of foundation and ventilation type were investigated Data were compared against the Swedish reference level of 200 Bq/m3 (5.3 pCi/l) 2018 International Radon Symposium™

Large decrease of radon concentrations in new-built Swedish dwellings Building year Number of measurements Average radon conc. (pCi/l) Highest value (pCi/l) Above 5.4 pCi/l 1950-1980 (all) 7495 5.0 116 33 % 1950-1980 (blue concrete) 1886 6.8 90 53 % 1950-1980 (no blue concrete) 2519 4.4 110 27 % 1980-2000 8099 2.4 123 11 % 2000-2010 2332 1.7 52 6.1 % 2014-2016 2255 1.1 165 2.0 % Measurements in single-family houses 2018 International Radon Symposium™

Large decrease of radon concentrations in new-built Swedish dwellings Building year Number of measurements Average radon conc. (pCi/l) Highest value (pCi/l) Above 5.4 pCi/l 1950-1980 (all) 10080 3.4 124 20 % 1950-1980 (blue concrete) 2824 5.2 48 38 % 1950-1980 (no blue concrete) 1568 2.5 10 % 1980-2000 8691 1.4 56 5.1 % 2000-2010 3170 1.3 38 3.9 % 2014-2016 3942 0.8 41 0.3 % Measurements in apartments in multi-family houses 2018 International Radon Symposium™

Large decrease of radon concentrations in new-built Swedish dwellings Single-family houses = ”Småhus” Multi-family houses = ”Flerbostadshus” Number of new-built dwellings in Sweden (source: SCB) 2018 International Radon Symposium™

Large decrease of radon concentrations in new-built Swedish dwellings Measurement year Number of measurements Average radon conc. (pCi/l) Highest value (pCi/l) Above 5.4 pCi/l 2005-2006 988 1.9 136 6.6 % 2007-2008 967 106 5.7 % 2009-2010 551 2.1 43 8.5 % 2011-2012 240 2.3 46 10.4 % 2013-2014 227 1.8 18 9.7 % 2015-2016 154 2.0 52 6.5 % New buildings: are radon levels increasing with time? Measurements in single-family houses built 2002-2004 No statistical significant change can be seen, Kruskal-Wallis test (p-value = 0.4159) 2018 International Radon Symposium™

Large decrease of radon concentrations in new-built Swedish dwellings Crawl space Basement Split level Slab on grade Radon levels and foundation types in single-family and multi-family houses 2018 International Radon Symposium™

Large decrease of radon concentrations in new-built Swedish dwellings Today, most Swedish single-family houses are built with Slab on grade as foundation type and very few new houses have Basements. 2018 International Radon Symposium™

Large decrease of radon concentrations in new-built Swedish dwellings Slab on grade together with Basement are the dominating foundation types in multi-family houses 2018 International Radon Symposium™

Large decrease of radon concentrations in new-built Swedish dwellings Multi-family houses Single-family houses New single-family houses with mechanical or balanced mechanical ventilation have in average much lower radon concentrations than houses with only natural ventilation. Radon levels and ventilation types 2018 International Radon Symposium™

Large decrease of radon concentrations in new-built Swedish dwellings Today, very few single-family houses have only natural ventilation, mechanical or balanced mechanical ventilation are dominating. 2018 International Radon Symposium™

Large decrease of radon concentrations in new-built Swedish dwellings Today, most new multi-family houses have balanced mechanical ventilation. 2018 International Radon Symposium™

Large decrease of radon concentrations in new-built Swedish dwellings Possible explanations for the decreased radon concentrations in new-built Swedish dwellings : Better and more uniform building practice. Mechanical or balanced mechanical ventilation are used in almost all new Swedish dwellings. Very few new single-family houses are built with basement, the dominating foundation type is slab on grade. 2018 International Radon Symposium™

Tryggve Rönnqvist +46 706591708 tryggve.ronnqvist@radonova.com THANK YOU !! Tryggve Rönnqvist +46 706591708 tryggve.ronnqvist@radonova.com 2018 International Radon Symposium™