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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Yeah, this all has a history, yet today if it's sealed as most are with a food-contact rated finish the odds are very low for the radon to get into the air.

Air is how it's deadly able to stick to your lungs, otherwise it's emitting radiation yet prevented from being inhaled, so, that's quite low in risk since this will be close to background radiation as Mr. Connell states.

That's the difference, having the emissions free to get into breathable air or not.


My point is countertop sealer's do not stop radon release. By design they are not designed to do so. For a sealer to fully seal off the breath-ability of a granite surface would cause the material to spall and fail.  

Radon is a natural fact of life. Ventilation is the only source for remediation. Everything else is a band-aid.   

Also, 99% of sealer's for granite countertops are not regulated and are not certified by the FDA as food safe. If they were the bottle would say so and then they need to comply with the FTC rules for marketing.  

Well having installed a number of them I'll argue with you over a pro doing the work for food-contact yet I've also done commercial kitchens so not quite DIY on materials chosen & methods used for safety on this.

Until then I'll assume no practical continued release of radon in a slab 2" thick matters, if you have a crawl space with soils down to bedrock is one thing, a 'sealed' counter-top quite another context.

I'd want to see actual test results on new & used granite counter-tops being unsafe, imagine the market to remove them all !!!

Tom Mallard,

There's no argument here. What I said specifically is "99% of sealer's for granite countertops are not regulated and are not certified by the FDA as food safe." I never said granite was unsafe.

Should you disagree with this please support future arguments with material safety data sheets (formerly MSDS, now SDS / Safety Data Sheets) for the products you believe are FDA approved. 

I'm only questioning the blanket statement, "... 99% of sealer's for granite counter-tops are not regulated and are not certified by the FDA as food safe."

I'm assuming they sell restaurants as well so if you buy at big-box it'll be food-contact rated in general for kitchen anything.

The FDA approves finishes for food-contact rating as well as my fav thermal-fluid and an issue where food is processed the view of this.

It's up to who seals them to know that it's a kitchen item thus requires food-contact safety commercially, not aware of any major mfg of them not aware of this.

Hey folks, can we try and stay on topic please? The devil is in the details, and not everyone who is following this thread (and there are many) are interested in the nitpicking and tangential topics.

I want to remind folks about the topic... Are radon mitigation systems and EPA recommended action levels based on scientific data? If not, how does that affect us as home performance contractors and building scientists?

Sheesh! Don't make me tell on you! :) Seriously though, can we stay on topic please?


Replying to Rodney's post not having a reply on that comment as a builder-contractor satisfying code, my comments are pertinent, a 2" slab of granite has a finite emission rate of radon not worthy of worrying about, eh?

Post your scientific assessment of radon emissions from a slab of granite 2" or less thick as a counter-top in a kitchen will you?

I agree totally that's going too far with Mr. Connell's assessment disagree on low-level radiation effects on this issue.


Is it possible to make the crawlspace more air tight? If the crawl was more air tight, it would require less air volume to keep it at a negative pressure relative to the conditioned volume I suspect. Less air volume, smaller fan?

What do you think?

Tightening the crawlspace would increase the negative pressure in the living area, further exacerbating the problem of woodstove backdrafting. Although I imagine it would also remove more toxins from the crawlspace, further reducing the radon "problem" :)

Yeah, it's all a mess, eh?

Thus consider it's due to the floor not being airtight, mainly at the edges is the fundamental.

So if having to do the work consider adding insulation board below the joists and caulk it to become a vapor barrier and by insulating below the joists greatly reduces both radiative & conductive heat-loss to the crawl-space.

Most people use plastic to reduce condensation & moisture transport below the joists around here, that's not the same as what the board does, caulked it's a vapor barrier, has radiant foil both sides & 1-1/2" thick adds R9.

There is no possible way to insulate and caulk below the joists in this home. It's a mess down there, with about 6" to 18" of work space throughout. Even foaming all of the penetrations through the floor is impossible. Totally cost ineffective.

Based on this lengthy and educational discussion, I've already informed my client that they should simply turn off their radon mitigation system if they don't want their woodstove to backdraft, understanding the so-called "risks" involved in doing so. Otherwise, if they want their radon mitigation system to continue running (it reports about 2 pc/l), then they should get rid of their woodstove and find another heat source.

End of story. Elvis has left the building. Everybody go home now.


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