The Active Soil Depressurization (ASD) concept is quite simple. In the lowest level of the home a penetration is made into the sub-slab. Soil and/or stone is removed through the cored hole. Then, a series of pipes are run vertically and exit the conditioned area. Once entering unconditioned space, being the exterior or the attic, a fan is installed in series with the piping and is exhausted in a safe manner (according to the EPA requirements). In addition, radon entry points will be sealed, and post testing will be done to ensure that the mitigation system is drawing only the gases beneath the slab. An Active Soil Depressurization system is quite affordable. Most systems are installed from $1350-1600. The ASD system will lower radon levels 99.9% of the time.
When a typical ASD system is not conducive, An Energy Recovery Ventilator can be used. The operation is quite simple. Where as an ASD system will remove the radon before it enters the house, the ERV system will treat the radon once it has entered the house. How? The system is an air exchange system. It pulls air from the outside, pumps the air into the basement space. The it pulls bad air from the inside, and exhausts the air to the outside. Thus diluting the radon filled air with good air. The systems price will range between $2200-$2800.
First a hole is cored though the lowest level slab. Then a series of piping will travel through the stud walls into the attic. In the attic, space will be made for the fan, and electrical provisions will be left (optional), and the pipe will exhaust through the roof. By installing a radon mitigation system during construction, thus allowing the installer to "hide" the system aesthetically.