owner builder in northern new england here. before pouring a slab i’d like some advice on dealing w/ the possibility of radon. the fact that granite is around us means the possibility of radon, so i need a preventative.i’ve planned on a 5 gallon bucket perferated with 1/2″ holes into a 3″ pvc pipe up thru some walls. i guess a fan is necessary due to pressure issues and the heaviness of radon. adding another system(more maintainance) isn’t all that desirable,but neither is lung cancer. are products like “radon seal” effective? is it like replacing one toxic vapor(radon) w/ another(ethyl-methyl bad sh*#)? what if i don’t even have a radon problem,and i do intall a vent…an unnecessary hole in my roof and slab? and what about fan noise? it must be constant.is there a trick to eliminating that?my site was wet,so we built on 10″ of crushed stone, if radon is heavier than air will radon travel thru the footing drain out to daylight? thanks
Edited 5/7/2008 6:16 am ET by stonefarmer
Replies
My thought is to install the bucket and hole in the slab, the pipe up to the attic (only) and maybe a blank electrical junction box for a future fan connection and leave it at that. When the house is done, test for radon. If there is a problem then you can install the active mitigation. (fan and hole through the roof) I wouldn't go much farther than that unless you maybe feel there is like an 80% chance of a problem...
You got the stone under the slab (I assume it is ~1" stone) which will allow the movement of soil gasses to the mitigation system if necessary. I think you are good.
Yeah, plan in advance for a problem, but don't install any active components until you have the thing tested. Do go ahead and passively vent your system if code allows, though.
Be sure to check local building codes re what may be required and any restrictions on vent lines, etc.
Keep in mind that a combined radon collector/drain tile system is sometimes a good approach, if you have some chance of groundwater problems. Basically it's just a tile system with a tight-fitting cover on the sump and a vent from there out.
I'm with the "rough it in" folks.
Also, design and build to reduce the negative pressure in the basement. (E.g., a fresh air intake into the return if using forced air heat - a fresh air supply for combustion, minimizing unintended "chimneys" etc.)
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You can't seal out radon effectively and trying to "vacuum" it out of a structure will just bring more of it in from the lower levels. The best way to deal with excessive radon is to create a vacuum _outside_ of the building envelope such as under the basement slab.
I've only done one, so I'm not an expert, but from my understanding of the NJ Radon sub-code or what ever you want to call it, you need one 4" diameter vent per 1500 square feet of foundation. My best solution was to run a 4" perforated pvc perimeter drain on the in side of the footing with 1 vent coming out of the loop. I put it where it could run straight up into a closet and up through the attic, connect to the fan and vent out the roof. I know you can also use your existing perimeter drain if you use a sealed sump pit lid that is gasketed and bolted to the slab.
Since you mention the NJ Radon Subcode - it's now on line - here is the section on construction techniques - http://www.state.nj.us/dca/codes/r_h_scode/pdf%27s/r_h_scode_10_1_071.pdf
Jeff
Edited 5/7/2008 8:51 pm ET by Jeff_Clarke
Thats where I found it.
A few inches of gravel under a slab/moisture barrier and a pvc pipe sealed to the moisture barrier run up through the interior and out the roof will draw surprisingly well as the air heats up and creates a partial vacuum at the slab level. Very little air movement, and almost zero added heating cost.
This type of passive radon system is inexpensive and vents not only radon, but other naturally occuring gases coming up through the soil. If after the house is built a radon test shows low levels are still present then add a fan.
This type of passive vent is quick, cheap and good insurance, not to mention it improves air quality with regards to more than just radon.
Best of luck.
Beer was created so carpenters wouldn't rule the world.
Radon is a big problem in this area. People try to mitigate it and can to some extent.... the biggest problem is the agregate in the concrete is the same granite that contains the radon.... oooppps.... now that's a problem.
Yesterday I was told granite counter tops contain radon too.
Here's a good manual on radon mitigation.
http://www.infiltec.com/inf-catr.htm#Manual
I've bought and used it to install a successful system. The web site is a good source of fans if you don't have any local suppliers.
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