We are in the process of (maybe) buying a home. It is a newer (2007) home in Northern Wisconsin with an insulated concrete form (ICF) basement in red clay. We just got the radon test back and the 2 day average is at 5.1 pci/l. I am not concerned about the levels - mitigation devices will happen. My concern is why?
Is the presence of radon in a newer home an indicator of a not tight / poorly constructed basement or is it an indicator of a very tightly built basement/home?
I have seen some people arguing that it indicates the basement is not 'tight' / poor construction - if a basement is properly built radon should not be able to enter. However, there was no sign of water in it - and it was as dry a basement as I have seen. But, with ICF you can't see voids or cracks in the wall - but then again, no sign of moisture.
Others argue that because a home is tight it tends to trap more stuff and what does get in can't get out. This also seems plausible - there was no air exchanger installed that I saw and most newer homes seem to have them up here to control moisture. Also the sump/drain wasn't sealed so that could be a point of entry.