Effects of Heat Recovery Ventilation Systems on Indoor Radon

Keramatollah Akbari, Jafar Mahmoudi TDI researcher at ACECR, Iran and Mälardalen University, PhD student, School of Sustainable Development of Society and Technology, Västeras, Sweden [email protected] Mälardalen University, Adj Professor at School of Sustainable Development of Society and Technology, Västeras, Sweden [email protected] Abstract 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 radon levels. Computational fluid dynamics (CFD) is a powerful tool for predicting and visualizing radon content and indoor air quality and is cost effective in comparison with other methods such as full scale laboratory and gas trace techniques. In this study a mechanically balanced ventilation system and a continuous radon monitor (CRM) were used to measure the indoor ventilation rate and radon levels. In a numerical approach the FLUENT CFD package was 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 radon concentrations were investigated in a one family detached house in Stockholm. Results of numerical studies indicated that changes of ventilation rate, indoor temperature and moisture by means of ventilation systems have significant effects on indoor radon content. Ventilation rate was inversely proportional to indoor radon concentration. Minimum radon levels were estimated in the range of thermal comfort, i.e. at 21 and relative humidity between 50-70%. The analytical solution was used to validate numeric results at 3 distinct air change rates. Comparisons between numerical and analytical results showed good agreement but there was poor agreement between simulations and measurement results due to the short measuring period.