Radon halp!

So, we have been trying to sell our awesome, beautiful, old house in new Alexandria pa since about may 2019.

The finally got a cash offer on the house and celebrated.  Too soon junior...

Radon was tested for.  Radon was found.

We had a radon mitigation system when we bought the house.  The motor apparently failed.  No big deal, put in new motor.

New motor goes in and results come back.  20. TWENTY.  Holy crap that is high!  Give it a few days and run some fans with the doors open, etc...  new result....  16.  

Great.  Needs to be sub 4.

New buyers back out of deal.  E36 M3.

Radon company comes in adds bigger motor and fan and a new duct from under the basement slab.

New number.....  13.  E36 M3.

On Saturday, just added a new duct in the basement.  This is now 3 ducts....

New number.... 10.  E36 M3. berkeley.

So, what do we do now all great and knowing ones?

Th3 house is 2700 square feet of old 4 square brick farmhouse with a 1700 sq ft detached garage.

All readings have been taken in the basement.

All new plumbing and drains in the basement that go to the new public sewage system.  All done by a professional.

Please help!

Rob R.

I've never looked into it, but here's a start.

So there are exit ducts from the slab, it do they also have inlet ducts?  I have no idea if that’s something they do, as my house went from 16 to 1 with the simplest system.

914Driver said:

I've never looked into it, but here's a start.

I'll have to check that out later, my phone won't open it right now.

AngryCorvair said:

So there are exit ducts from the slab, it do they also have inlet ducts?  I have no idea if that’s something they do, as my house went from 16 to 1 with the simplest system.

That's what is supposed to happen.

At this point, there are 3 penetration under the basement floor that all go to 1 common motor / fan.  The motor / fan has a large diameter outlet to above the roofline of the house.

Is there any water under the slab? I have this issue but my number is 4.4 without the fan running so I haven't addressed it yet.

If it is an old house, it may have an old well in the basement that was not properly sealed allowing radon into the living space.

rustybugkiller said:

Is there any water under the slab? I have this issue but my number is 4.4 without the fan running so I haven't addressed it yet.

If it is an old house, it may have an old well in the basement that was not properly sealed allowing radon into the living space.

Good thoughts.  It does have an old well.  The well has been properly sealed.  I have no way to tell if there is water under the slab.  No water comes up through the floor or anything.

You should be able to pull the pipe out of the slab. If you have dirt under the slab it will hold water close to the slab and the radon system will not work properly. This is my problem. If there is gravel under the slab the radon system will be more efficient since the water will drain away from the slab.

The literature I read when we bought our current house (required 2 fans), all suggested sealing any holes in your slab.  Nobody (including the people who did our mitigation system) seems to do that. Might be worth looking into in your case.

We have radon in my area. We tested our house and got around 600 Bq/m³ which is about 16 pCi/L. We put in a fan in a non-ideal location (near the edge on the walk out side) through the slab and got to about 200 in the winter (the Canadian suggested limit). When I started renovating one corner of our basement (the deepest end) I caulked the seam between the wall and the floor, filled the tops of the cinder block foundation walls with spray foam, then spray foamed the walls and rim joist area. That dropped the number down to about 120-130, with about 20% of the basement wall area done. When we move on to renovating other areas of the basement you can bet I'll do the same sealing again and I do plan to move the radon vent at some point to a more central location in the slab.

So from my limited experience, fans work, but they work a lot better when the foundation is well sealed. We also have very sandy soil here that drains very well, so YMMV.

Hmmm....  the house has a field stone foundation.  May be it's time to slather on some thick coating to keep the radon out.  

I will also caulk the floor to wall joints and fill all areas and cracks on floor.

I'll report back my findings.

Our new place is pretty low - under 7pCi/L with average of 2.7pCi/L over 72 hours. 

What interesting is that my neighbors are all getting substantially higher amounts, in the teens or 20s, or in some cases even higher. 

One thing I think contributes to this is that my slab is likely insulated and sealed from below being that its got hydronic radiant heat.  One of the abatement strategies I've read of is to cover exposed dirt in the crawlspace with sheet plastic and attach an end of this "tent" to a duct outside. 

pheller said:

Our new place is pretty low - under 7pCi/L with average of 2.7pCi/L over 72 hours. 

What interesting is that my neighbors are all getting substantially higher amounts, in the teens or 20s, or in some cases even higher. 

One thing I think contributes to this is that my slab is likely insulated and sealed from below being that its got hydronic radiant heat.  One of the abatement strategies I've read of is to cover exposed dirt in the crawlspace with sheet plastic and attach an end of this "tent" to a duct outside. 

I would agree with that.

We don't have a crawlspace.  It is a full basement.

Do you have a well? 

Gfs sisters house, about 10 years old has bad radon, did all the air mitigation for little inprovement, and the readings were always higher on the 2nd floor. Turns out the major radon is in the water, with 2 adults and 2 teenagers at the time taking daily showers they were releasing the radon from the water. 

They are going to need a radon bubbler? for the well. My sister just had a new well drilled and has the same issue now.