Thanks for some great information and resources. Much of what you posted, I did not know.
I am also am an old EPA certified radon mitigator. Depressurizing slabs works for extreme cases.
Pressurizng the basement with main floor air reduces infiltration from the soil into the basement in most cases.
Using a ventilating whole house dehumidier with enough fresh to provide an air change in 5-6 hours and a 150 cfm of mainfloor floor is very effective at reducing basement radon levels while maintaining <50%RH in the basement and rest of the home. This concept provides extreme postive pressure and fresh air throughout the home.
An ERV/HRV will make the home wet during wet cool weather and excessively dry during cold dry weather. An unbalance HRV will not maintain positive pressure in a basement with a strong stack effect during cold weather.
I have had some good ones. The best was an 2,500 sqft. earth home in WI. We reduced 35 pc to 2-3 pc with continuous 175 cfm of make-up with a whole house ventilating dehumidifier. Plus we eliminated a serious mold problem.
All that was missing from the radon problems where the bodies. Everytime, I here of lung cancer death of a non-smoker, I get the ich to go test the home for radon!
"The committee's best estimate is that among the 11,000 lung-cancer deaths each year in never-smokers, 2,100 or 2,900, depending on the model used, are radon-related lung cancers."
I personally am convinced after spending a lot of time and effort learning what I can, that the threat is vastly overblown, and not just because agencies account for 117 deaths for every 100 that occur. One of the skeptics battle cries is "where are the bodies?" because when you add up the death statistics from all the things that allegedly kill people, it's a lot more than the actual number of deaths.
EPA wants you to mitigate if your radon levels are above 4 pCi/L, and to consider it if it's over 2 pCi/L.
In my own home, after my research, I would not consider mitigating at less than 20 pCi/L, and probably wouldn't even at 50 pCi/L, although I would refresh my reasearch. I might even charge admission (that's a joke, son) - try googling "radon spa" just for fun.
I have known people (at least 1 friend and 1 customer who wanted to protect her young family from radon, which she assumed was what was killing her) who, to the best of my knowledge, have never smoked and yet died from lung cancer. That breaks my heart. But I have known more who died from auto accidents and other items on the list of leading preventable causes of death. I won't go so far as to say radon mitigation is always a waste, but I will express very strong doubts in many, probably most cases. At the same time I have met people in the business that I think were very sincere in believing they were doing something good.
By the way, if anyone is serious about doing this work, PM me and I'll sell you my continuous radon monitor and if you're really serious, my radon progeny test equipment (ERPISU) as well.
Since none of the contractors I have worked with over the past decade do radon mitigation, and I had noticed that there is little being advertized about radon these days, I figured the radon scare had run it's course. Evidently, there are some out there who still have radon mitigation product to sell and so they are keeping the radon issue alive.
One such company was represented at the Comfortech Show this year. I was curious as to how I could teach contractors the value of radon mitigation as another tool in their sales toolbox. As it is, I have been teaching the use of HRV's to keep the houses slightly under pressure to alleviate ever having a radon issue. Since reading teddy bears post, I will also add whole house dehumidification with outside air to that sales toolbox for preventing radon while ridding the home of severe humidification.
Anyway, I stop by the booth for radon mitigation and explain that I consult with HVAC contractors on prevention of radon in the home by pressurizing the homes. The gentleman I was talking with even agreed that positive pressure resolves radon issues.....but....contractors should be selling radon mitigation instead of preventing radon issues in the first place.
OK....the idea is for this person to sell radon mitigation systems and the idea behind my services is to get contractors to have more ways of making money, including dealing with radon. So I tell this guy that there does not seem to be much radon mitigation in my area, where the radon debacle started. He corrects me by telling me there are many companies doing radon mitigation in my area. I come back with the fact that my HVAC contractors do not provide this service, and that I am advising them to use HRV's to dilute the stale air in the home while pressurizing the home. He then tells me that the radon mitigation companies are home inspection and dedicated radon mitigation companies.
Now, I have already told this person that I am already advising contractors to use methods of preventing radon. I have told him that none of the HVAC contractors in my area are doing radon mitigation. He is in a booth at an HVAC show. When I ask him to give me reasons to advise HVAC contractors to mitigate radon rather then to prevent radon, he starts telling me how to sell against what I am already advising.
I finally just took as much information as I could and left. I don't think he ever got my point. I don't think he ever truly understood that I am currently advising ways for HVAC contractors to sell against his product, but am willing to also advise using his product if he could give me a way to approach it as a benefit.
There are elegant ways to correct the problem that have other benefits as well. Circulating air in the home works brilliantly even if you *don't* lower radon levels. Radon isn't the real culprit. It's the radon progeny, specifically polonium ions. Again quoting the BEIR VI report, and by the way, the reason I quote it so much is that it's what EPA's case is built upon:
"Radon itself does not directly cause lung cancer but alpha particles from radon progeny directly damage target lung cells to cause cancer."
The alpha particles are from polonium ions. Ions are charged particles, and they like to stick to things, or "plate out." I spent several thousand dollars buying equipment that would test for progeny so that I could advise my customers based on the true health risk, not the once-removed indicator. All you have to do is circulate the air and those ions bump into the walls, furniture, curtains, ducts, whatever, and stick where they will do no harm. My most extreme example was in a guest house with over 90 pCi/L of radon and progeny consistent within reason of EPA's way of estimating it from radon. When I added a circulating fan, the progeny levels dropped to the level that would be expected from radon levels of less than 3 pCi/L. The potential harm dropped to less than 1/30 of what it had been, and all that was needed was a $15 oscillating fan.
If circulating air is good, circulating fresh air is even better, and it will do far more good for you than some $2000 to $5000 system will.
I don't mean to go off on the radon mitigation industry too much, and yes, most mitigators are stand-alone businesses or tied in to home inspections, but if I can solve one real problem and one questionable problem instead of only the questionable problem, I will do that every time.