[Z-man]

Remediation is possible. My home had high radon levels when we inspected it upon purchase. The house was already built with contingency in place, but not fully hooked up.

My system: a cavity is created under the basement floor. an open PVC pipe runs from that cavity through all floors and up to the attic. This was already in place when we purchased the home. All that was needed was to add a pump (ie fan) to the pipe in the attic, and run the pipe through the roof to vent out the radon.

How the system works: by creating a low pressure pocket under the basement floor, the radon gas will populate that space. It will then get pulled out of that cavity by the vacuum created by the fan in the attic. The fan continues to push the radon out through the roof. Since installing the system, my radon numbers have been in an acceptable range.

For your parent's home, they will likely need to bust through the basement slab to create a similar pocket. Then depending on the house size and ability, they will run a PVC pipe either up through the roof, or out the side of the house. Either way will work, but roof exit is more ideal.

I will take some pictures to illustrate the system...