We have a triplex- house so the crawl space is about as big as the improved basement. The radon was measured a long time ago by another owner and it was just over the allowable amount.
We haven’t had it remediated yet. I noticed that there are only two small vents for the crawl space on one corner. They are just around the corner from each other.
Both of the vents have 6″ of un-faced fiberglass insulation on the inside of the foundation walls covering the vents.
Are the 6″ batts keeping the foundation walls damp by putting the dew point at the foundation? Crawlspace moister condensing at them?
Is the lack of vents and the fiberglass batts contributing to the radon levels?
Wouldn’t insulating the floor joists and walls to the basement living area be the right way to do this?
If they remediate the radon i think they are just going to do the crawlspace.
Could I just improve they crawlspace venting and insulate the floor and walls?
the going price to remediate the radon is $1,000. The house inspector said he would do it for $800. I could have the floor and walls insulated for that.
Edited 8/15/2007 12:34 am ET by popawheelie
Replies
Are you saying that the only place the unfaced insulation is - is over the vents?
If so, it sounds like somebody just stuffed them closed for winter.
For crawl wall insulation you do not want FG batts, you want EPS foam glued to the crete or spray foam in place.
The basics of radon control is simply to ventilate the gas out of the house and to seal against greater intrusion, generally with a membrane at the ground or under a mud slab. Some homes here that have high radon ion winter get fine readings in summer when the windows are open.
No way to know it that price is good without knowing what they would do to achieve it and if they gaurantee that you would achieve acceptable ratings after they finish.
If it were my hom,e and my money, I would first insulate and lay VB on the ground, then add a exhaust fan at the vent and see what that does for the radon readings.
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They have R-11? 6" all along the foundation wall. It looks pretty well done. There aren't any gaps or sags in it. It covers two small vents that are near one corner. It goes from the dirt up the wall ( 4' ? ) into and around the rim joist.
There is a vapor barrier on the ground but it has some tears in it and unless it is actively vented the radon just goes through or around the holes.
Maybe the home owner did it. The neighbors said he was pretty handy. But that only goes so far if he was winging it and CHEAP.
The home inspector would do the normal active venting Vb thing with a guarantee. Typical stuff.
I have seen radon vent details somewhere on the http://www.BuildingScience.com site
they always vent above the roof.
Piffin covered most of it. I thought I'd just point out that in terms of power venting (if that's the course of action chosen) the main thing you need to do is produce a slight negative pressure in the crawl. That way, air from the crawl won't tend to penetrate into the house, and any radon likewise will stay out of the house.
Of course, covering the crawl floor with plastic (if it's not already) will help significantly, and also reduce condensation problems.
Good site here: http://www.infiltec.com/
The book they sell is pretty indepth.
When I did my house with active removal, I set up a system that evacuates air from the crawlspace (under thick plastic) and under the basement slab. No more measurable radon using the normal methods.
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