In researching the subject of Radon mitigation, I came across this article, Titled "Radon - A brief discussion", by Caoimhín P. Connell (Forensic Industrial Hygienist)

Please read that whole article before posting any comments. It's a long read, but I'd like to ensure everyone who comments on this topic has in fact read and understands the article. No biases please! :)

The first paragraph states the following:


A large portion of the general population is under the misconception that the frequently published risks associated with radon are well accepted scientific facts. In reality, the vast majority of well designed studies do not support policy or positions that exposures to indoor radon pose a significant threat to health, and indeed, the majority of those studies indicate that, at concentrations typically seen in homes, as the level of radon increases, the risk of lung cancer goes down, not up.


After reading the science behind Caoimhín's well-written and thorough article, I have to say I agree with his words and message. So what does that mean to an energy auditor? What advice am I to give to a homeowner whose home is under constant depressurization causing backdrafting with their woodstove or failing to pass worst case combustion safety tests, all because of their radon fan in the (nearly-conditioned) crawlspace? I realize as a BPI graduate I am supposed to consider Radon. But what do I tell folks whose Radon mitigation system indicates levels far below 7 picocuries? Should they run that fan that consumes 526 kWh/year, costing them $70/year?

I welcome your input. Love this community!


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I was able to add the LIKE button to discussions and blogs. However, it doesn't allow you to LIKE comments. I've suggested that the platform tech team add this functionality.

Caoimhín, thank you for your incredibly elegant discussion of risk, cost benefit, and human irrationality when it comes to "unexamined postulates." 

In my mind these radon devices compete with mechanical ventilation for limited resources. Very frustrating because it seems fresh air is likely to benefit occupants to a much greater degree, but then there I go using a subjective and hoping it converts to meaning. 

Good morning, Nate –

I’m glad you enjoyed reading the post. 

Anytime you move air it will reduce the unattached SLRDs.  But, in my humble opinion, running a furnace system like that would be akin to wearing a metal helmet 24 hours per day to reduce the risk of getting hurt by a meteor.  Of course, you could do it, but would it be rational or reasonable? 

Caoimhín P. Connell

I ask because it's beneficial for a number of other reasons, IF the duct system isn't too connected to the outdoors:

1. Reduce temperature stratification/temp difference between rooms by mixing

2. Better filtration - constantly running air through the filter to reduce particles

3. Fresh Air - If the fresh air system is connected to the ductwork, it will distribute the fresh air and exhaust it as well. 

4. Right-sized equipment runs more anyway - I size equipment very aggressively to increase run times so a little bit of heat or cool is being added to the house at all times as needed.

5. Better fans are cheap to run, often in the $5-15/mo range.

This is, to me, an ancillary benefit. So if the cost was $0 (which it essentially is because I like to do this anyway), how does that change your thinking? 

PS I probably should go buy a helmet. =)

Nate   The AHRI Certificates on most of the green speed units show 5 -800 kWh per year usage.

The math still applies.

Indoor air quality is first improved by eliminating sources or at least controlling them. Then you provide adequate ventilation.

If the pollutant is already in the home, what good is filtration? What level of filter quality do you recommend? Where do you draw the line on tighter filter specs effecting the static pressure and operation of the forced air system.

You don't need the AH fan to use the duct system to distribute air or to eliminate stagnation/stratification.  Each house is the same and each house is different. The CFM generated by the AH fan creates more air movement then necessary to do those things. Increased air movement creates convective cooling and discomfort.

There are better ways to move and distribute air instead of the AH fan.

So you're going to argue with actual measurement using AHRI certs? 

On pollutants, I'm conflating, but my last post hopefully indicates that. PM 2.5 is getting a lot of press as the most important IAQ problem. A good filter helps with this. Radon is just one of many pieces in my hypothesis.

How do you know it's too much air movement? How much is too much? How little is too little? This fan does 300 cfm at 42 db. Because it ramps down to 15,000 BTUs or so, it's almost continuously adding or subtracting BTUs. Do you have feedback from actual clients on this? Or are you following GBA dogma? I normally love how you think, this piece surprises me a bit.

Go ahead, buy the $10,000 helmet, but don't pretend it's a smart decision to ignore valuing the risk you are mitigating. And if you get into the metal helmet business, don't be disappointed when it fails. The market will do some things based upon unmeasured fear, but that doesn't make them smart or sustainable. 

"The AHRI Certificates on most of the green speed units show 5 -800 kWh per year usage.

The math still applies."

What math is that? Mythical math? Modeled math? 

John, homeowners don't care about AHRI - they care about having affordable, comfortable homes, with low bills. (This is why HERS can't survive in a real marketplace without government mandates, it can't provide all of these things, and often can't provide any of them.) You really think telling them NOT to deliver fresh air using their existing infrastructure because it costs a couple of hypothetical pennies more per day has logical basis?

"Increased air movement creates convective cooling and discomfort."

No it doesn't. If it does, how much, how much does it cost, measurements or your argument has no basis. 

"You don't need the AH fan to use the duct system to distribute air or to eliminate stagnation/stratification. " 

Sure, you can add a dedicated HRV system costing $15,000, and save that hypothetical 3c a day off Nate's measured 11 cents. 

Exactly, yet it's the intrusion of regulation that makes having to do something about it the cost-vs-returns view.

And, if stuck with paying for radon mitigation for any reason to not also add in a full blanket of foundation insulation and separate totally any crawl-space with a fake sub-slab system as a thermal battery for space heating also mitigates to code.

Consider that, do a spreadsheet.

The problem is there is no money in NOT performing "Radon Mitigation".

Interesting historical perspective by Tom Macy -


But what of the miners?

They really died of lung cancer, we are told.

The most likely explanation for this entire scenario goes something like this:

1. The mining company is negligent in providing the miners with adequate breathing equipment

2. The miners breathe the mining dust containing at least 14 different radioactive elements

3. The miners get sick and die

4. The company seeks a way of avoiding any liability for the problem and hires someone to invent a cover story -- it is very successful; they can hardly be held responsible for something that occurs naturally

5. The story is picked up by the American Tobacco Institute which is looking for an alternate explanation for the causes of lung cancer in smokers

6. The ATI provides funds for research, hoping to avoid liability, as did the mining company

7. The ploy did not work, but misguided researchers confused laboratory data from the research by applying it to field conditions to make it appear that radon is a major health hazard.

8. The radon abatement industry is born!

This is a very brief treatment of a complicated subject. There is obviously much more that could be said about it that space limitations do not permit. This writer recommends that each reader do a little research of his/her own. You may be surprised at the amount of contradictory information that is available.

I loved this one:

I never heard of Tom Macy, but I think I would like his views; an interesting read – Thanks!


Also, I forgot about the dialogue… Thanks for the reminder!



As you point out Caoimhin, radon is not the health's the progeny, yes? Mr. Macy's article never refers to the progeny, only to the radon. Isn't he using 'red herring' argumentation? I hope he made it out of the Malheur refuge w/o incident. 

Hello Mr. Cullen –

Your question is predicated on a false premise.  You state:

Mr. Macy's article never refers to the progeny, only to the radon.


When I read Macy’s article, I see that he does refer to the progeny, (and often) and does not exclusively refer to radon.  Indeed, even in the little summary provided by the poster “tedkidd”  we see:


2. The miners breathe the mining dust containing at least 14 different radioactive elements


When we look at Macy’s article we also see:


1. Radon is but one of 14 radioactive elements that are created as Uranium 238 disintegrates to become Lead 206


When we look at Macy’s article we also see:


2. The half-life for the whole 14-step process is 4.5 billion years -- it takes 10 half-lives for 99.9 percent of the radioactive material to decay


When we look at Macy’s article we also see:

3. The half-life for radon is 3.8 days -- 99.9 percent of the radon in any given sample will be gone in 38 days


When we look at Macy’s article we also see: 

4. It takes seven tons of uranium ore to produce 1 gram of radium (radium is radon's parent)

In fact, Macy’s article is rife with references to the progeny and parent elements and does not refer "only to the radon."   Perhaps you are thinking of another article? 


I didn’t know that Tom Macy was involved in the Malheur Refuge incident, was he a reporter there or a participant?


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