Back in June 2015, I wrote a couple of posts about the radon issue that I discovered in my house. I won’t rehash the details here, other than to say that the theory proposed by Marc Rosenbaum…that the problem may have been caused by they improper balancing of the ERV…has proven to be true over the past year and a half. If you’re interested, you can read the details about the problem, and his theory with regard to the cause, in the posts that I wrote during that time.
What I want to communicate today is, since that time, and without exception, every time the house radon level has risen, I have found that the air pressure in the house (which I measured with an appropriate manometer) had changed from positive to negative. And without exception, correcting the pressurization issue returned the radon level to the norm of 1 pCi/L, or less. This has happened about a half-dozen times over the past year-and-a-half.
In each instance, the change in pressurization was caused by an accumulation of bugs and dirt on the ERV intake. The ERV is balanced to pressurize the house at +1 to +2 pascals, so it takes little to change that positive to a negative. So, in effect, the two radon detectors that I have in my basement have proven to be a definitive way to determine, not just when radon levels have risen, but also when my house pressure is out of balance and the ERV intake filter needs to be changed.