Effects of Heat Recovery Ventilation Systems on Indoor Radon

• A heat recovery ventilation system enables us to control indoor conditions such as ventilation rate,temperature, relative humidity and pressure difference. These environmental conditions affect indoor radonlevels.Computational fluid dynamics (CFD) is a powerful tool for predicting and visualizing radon content and indoorair quality and is cost effective in comparison with other methods such as full scale laboratory and gas tracetechniques.In this study a mechanically balanced ventilation system and a continuous radon monitor (CRM) were usedto measure the indoor ventilation rate and radon levels. In a numerical approach the FLUENT CFD packagewas used to simulate radon entry into the building and effects on indoor air conditions.The effects of different ventilation rates, indoor temperature and relative humidity on indoor radonconcentrations were investigated in a one family detached house in Stockholm. Results of numerical studiesindicated that changes of ventilation rate, indoor temperature and moisture by means of ventilation systemshave significant effects on indoor radon content. Ventilation rate was inversely proportional to indoor radonconcentration. Minimum radon levels were estimated in the range of thermal comfort, i.e. at 21 andrelative humidity between 50-70%.The analytical solution was used to validate numeric results at 3 distinct air change rates. Comparisonsbetween numerical and analytical results showed good agreement but there was poor agreement betweensimulations and measurement results due to the short measuring period.

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