Sub-slab Depressurization Systems Research Articles

Subslab ventilation system: Installation and follow-up in a high-radon house in Brittany, France

A subslab ventilation system was designed and installed in a high radon house in Brittany, France. Radon concentration in the basement of this house was reduced from an average 10 000 Bq/m 3 to less than 200 Bq/m 3, thanks to a subslab depressurization system with a double barrier and a 32 W fan. Sealing the concrete slab cracks greatly improved the system performance. Finally, the feasibility of using a passive double barrier ventilation system is shown.

Radon Entry Control in New House Construction

People exposed to high concentration levels of radon face an increased risk of developing lung cancer. The risk is directly proportional to the length and level of radon exposure. Because of health reasons, it is safer to build new houses with radon mitigation systems installed in slab-on-grade houses. However, the interrelationships between parameters and factors governing radon entry and control are highly complex. A study performed by the University of Florida has examined the effectiveness of different radon entry control approaches. The analysis was based on 47 houses from three research projects conducted by the University of Florida (14 houses), Florida Solar Energy Center (13 houses), and GEOMET Technologies (20 houses). The evaluation of the performance and effectiveness of improved floor slabs, space conditioning, and ventilating systems were analyzed. Statistical analyses of the interrelationship between various parameters were also performed. Study findings such as the important factors in reducing radon entry and the effectiveness of passive construction approach and active subslab depressurization systems are presented in this paper.

Impact of subslab ventilation technique on residential ventilation rate and energy costs

Radon is the largest source of risk to human health caused by an indoor pollutant in the industrial countries. Subslab ventilation (SSV) is one of the most effective and common methods of reducing indoor radon concentrations in houses with a basement. In this paper, the impact of SSV on the air exchange rate is quantified, through numerical modeling of a prototype house with basement for a range of permeabilities of soil and subslab aggregate and various sizes of the cracks in the basement floor. We show that a SSV system can increase the air exchange rate by as much as a factor of 4.5. Then the energy and capital costs of a subslab depressurization (SSD) system are compared with those of direct ventilation of the basement which is required to lower the indoor radon concentration to an acceptable level for a Chicago climate. We show that (1) an exhaust ventilation cannot significantly reduce the indoor radon concentration and may even increase it, and (2) a balanced ventilation with heat recovery is only effective for low premitigation radon concentrations. However, both SSV and balanced ventilation systems are probably too expensive to be recommended in houses with low premitigation radon concentrations. A SSD system is the most cost-effective technique for reduction of high radon concentrations.