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Radon & Moisture

Posted by geesh (My Page) on
Thu, Aug 12, 10 at 20:54

My old home has a new vapor barrier ( 6 mil plastic). There are higher Radon levels & moisture in the crawlspace. I have 4 foundation vents ( 4 x 12 ), and have added two 6 x 12" vents to the doors. I am thinking of adding two fan inserts on two of the foundation vent holes. (One on each end of the crawlspace) my main concern is Radon. After installation of fans I will get another Radon test to ensure that two fans are enough.If not I will add two more. Now the questions, apprecheaite any help:
1) With Radon hazard, do I leave these fans run 24-7 year around summer-winter? (temps get low 20s in winter at night here).
My assumption is these fans are quiet & inexpensive to run & I also assume Radon still seeps in during all seasons..AND does it do any good to instulate the walls of a crawlspace?

Thank you for your help.


Follow-Up Postings:

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RE: Radon & Moisture

First, what kind of test was used? The most reliable test is one done over several days, since the movement of radon varies.

And second, where is the vapor barrier and is it sealed to the foundation and around any pipes?

The problem with radon intrusion is there have been no conclusive tests done which point to radon as a health risk. Most of the attention is simply because it is a radioactive gas. And it is actually the compounds after the radon decomposes that are thought to be the most dangerous. I just bought a house with a full basement in Kansas City, a known radon area. I have not tested and probably will not test for radon. Why? Because I am 63 and it is estimated that any health problems from radon DAILY exposure takes 25 to 30 years to show. I probably won't make it 28 more years.

If the vapor barrier is laid on the ground in the crawl space, it is not sealed properly. That actually may be concentrating the area where the radon is collecting.

By placing one fan blowing into the crawl space and one blowing out on the opposite side, you might be able to vent the space.

Is it possible that too would cause a problem? Depends on where the vapor barrier is and whether the house pulls air in from the crawl space.

Do some research on radon and abatement processes. Very simple ones often do a really good job.


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RE: Radon & Moisture

"By placing one fan blowing into the crawl space and one blowing out on the opposite side, you might be able to vent the space."

If you are trying to mitigate radon the last thing to do is push air into the space.

That can have the effect of pressurizing the space and forcing Radon into the living area.

The best solution would be to seal the vapor barrier to the foundation and at all penetrations, then put a pipe through to under the barrier and pull air from under the barrier and exhaust it outside and high enough that you are not going to be exposed.

The whole radon danger is based mainly on uranium miners long term exposure in mines.

The problem is that nearly all of them also smoked, confusing the data.


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RE: Radon & Moisture

Thanks for the replies. long term exposure ?? She is 45 I am 53... We had a test done over a 2 day period.. At the time of the test, ALL vents in the crawlspace were closed. House was empty for about a year. Leaky air handling ducts are sucking air FROM crawl space & pumping it straight into the living spaces above.. So you see, I have multiple issues to resolve. Just concerned about the week long exposure while vacationing at that house "until I get everything resolved"..We have addded two more vents & OPENED them all. Thank you both for your suggestions...


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RE: Radon & Moisture

Here is some additional information.. 2000 sq ft ranch. Crawlspace tapers from 2 feet high to 4 feet high. There are 5 "FIVE" 5"x13" vents in the crawlspaces block walls. I have found these little humiodistat controlled fans to install in these small vents. I see them online from $40-$175 (not found locally) How many of these fans should I install ? and how long will they last running 24-7 ?
* In addition, I am in the process of getting bids to tear out ALL the old heatpump units & ductwork & have new ducts installed, and the new unit installed on main floor utility room. This will solve alot of my problems with stinky air getting sucked in from the crawlspace.
Thanks for the assistance.


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RE: Radon & Moisture (alternative)

Along with the existing open 6 foundation vents, AS an alternative to foundation powered vents/fans, I am thinking about installing a fan in a mainfloor utility room to suck out the moisture, radon & smell from a crawlspace straight up & out the roof. Fan sized accordingly with insulated dryer vent type ductwork. This would allow me to run fan also in the winter (for radon). IS THIS A BETTER IDEA ? and how long can I expect the fan to last running 24-7 ?
Thanks for your replies.


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