[ylekyote]

Howdy. I have two radon issues I’m trying to mitigate as effectively as possible for now, as soon as possible. Not necessarily permanently, but if that fits the fix that’s fine too. Reason why I don’t care about permanent fix at present is because I’m planning a bigger addition and remodel in the next 2 years. I need time to plan and fund this but don’t want to leave the radon as-is for 2 years either. Want to have it resolved.

I have radon in my household air that I think is being induced from my crawlspace area and also via my well water that is pumped to my walkout basement water cistern until household faucets call for it. So I have two radon sources: my crawlspace dirt and my water cistern off-gassing radon (confirmed to be 20,000 pCi/L by water labs). My electronic and charcoal testing has shown the radon is strongest at these two places, and weakens as the tester moves further from the areas. The strongest crawlspace reading is next to the corner concrete wall that has my cistern on the opposite side, located in the walkout basement slab addition. I may be getting some radon gas through the basement slab, but readings seem to stem from the cistern room and weaken as I move away from it.

My unfinished crawlspace is a 700 square feet rectangle that has a 4’ tall interior ceiling in 90% of it; the other 10% is 3’ tall. I have 4 passive vents from the crawlspace to the outside air that are 2” tall by 8” long. I’ve been leaving these open from May – October and closing them with foam panels during the remaining 6 months so pipes don’t freeze. It is not tightly sealed with plastic, or encapsulated. I’m sure it isn’t “airtight” but there’s no visible air leaks I can see or feel either, or big cracks in my exterior walls, etc. I calculated the cubic feet of crawlspace air to be about 2,760 Cubic Feet. This crawlspace is adjacent and upwind/uphill to my concrete slab walkout basement addition. So my basement is downhill and downwind from the crawlspace.

My upstairs addition and area over the crawlspace is about 1,800 SF and the walkout basement below is about 900 SF. Total household square footage above the crawlspace and basement slab is 2,700.

I want to accomplish these objectives with immediate action:
1. reduce radon gas in household air to under 2 pci/l.
2. inject small amount of warmed household air into the crawlspace to keep it dryer and warmer in winter (pipe freeze and condensation prevention).
3. induce enough positive pressure into the crawlspace to help block radon gas from entering it, and push out what does enter by venting it to outside air by the crawlspace air leaks and/or vents that I could also uncover.
4. draw more fresh outside air into the household by the exhaust fan pushing household air into the crawlspace. My thoughts are the right balance of exhaust fan volume and crawlspace leaks/vents might allow my household to draw air indoors from windows and doors and other common energy leak points.

Proposed soil gas solution:
If I place a variable speed fan (up to 125 CFM) in the floor of my home that blows an undetermined amount of household air into the crawlspace, might I create a positive pressure that will help keep infiltrating radon gas and mold/allergens out of my crawlspace? I thought the pressure might make the gas rise elsewhere where it’s easier to rise and escape. Or if gas does enter the crawlspace from the soil, it is pushed out leaks/vents by the incoming household air.

I have two different fixes that I think may remedy the radon-water problem I have.
1. First choice is to place a PVC pipe (maybe a 2” diameter) into the lid of the water cistern to suck the radon gas from the water’s surface area and blow it outside. I’d either tie it into the existing radon evacuation pipe and use that fan or run a stand-alone 2” pipe with a small, dedicated fan and feed it outside like a mini-radon system.

2. Second choice, release radon gas in the well water before it enters the home.by pumping it into an outdoor cistern and spraying (a coarse spray, less likely to make snow when cold). Then transfer it to the indoor cistern after it has sat for a couple of days. The cistern would either be in a heated shed, next to my outdoor multi-fuel boiler/furnace, or I’ll put a tank heater in it during the winter.

Please keep in mind I have the usual household passive vents for 3 toilets, a 3” chimney for gas water heater, chimney and breather pipe for gas boiler (furnace not in use, broken), about 3 utility floor drains that drain to daylight, a septic field, as well as a 8” chimney pipe that removes woodstove smoke in the winter, 24/7. And two 75 CFM bathroom exhaust fans. Those are the other routes air can travel more freely from or into my house. I find it hard to believe with all of these avenues for air to stabilize that my household air doesn’t stabilize pretty easily and quickly. But I’m not sure.

What do you think about my proposed fix ideas for my multiple source radon? Is my theory right, partly right, or crazy? Might it work? Its either my alternate plan or pay someone upwards of $2,500 to cover my crawlspace floor, poke a hole in my basement foundation for a radon siphon, and link the slab suction to the crawlspace soil and evacuate it to the outside as traditional radon mitigation goes. The two companies that gave me quotes aren’t sure they can connect a PVC pipe from the water cistern to the main fan, because unless the tank is very tightly sealed it might lose a lot of pressure and not pull away the soil gases strongly enough from the slab and crawlspace. But maybe a booster fan could be installed on the cistern pipe?

Thanks much for any suggestions!

 

[Bondo]

Thanks much for any suggestions!

Ayuh,.... Seal the ground under the crawl space, 'n over the water cistern with 6mil poly, 'n retest yer air,....

Keep it in the ground, rather than tryin' to pump it out,....

 

[Bud9051]

I would recommend a traditional approach for mitigation in the basement and crawlspace. I have never heard of an approach as you are suggesting and my confidence level would be low.

As for the water, that is a different problem and has a different solution. I suggest you research removing radon from well water and go from there. At the level you mentioned, you are going to need a professional recommendation.

Bud

 

[beenthere]

For the cistern. Make a bubbler for it. Cover it with plastic, and vent it with a separate exhaust fan.

 

[Daniel Holzman]

According to the EPA website, 20,000 picocuries per liter of radon in water is expected to add 2 picocuries per liter to air. I did not see anywhere in your post how much radon you have in the air. I think the action level set by EPA is 4 picocuries per liter, so based on your post I can't tell if you actually have a problem.

 

[ylekyote]

The 20,000 of radon in water probably does only add 2 to the radon in household air under normal use. But my 1,000 gallon cistern is filled 950 gallons at a time and I believe it is venting that radon quickly to my house air, increasing those readings, which are 20 in the cistern room, and reduce to 5 as the tester is moved away and upstairs from the cistern location. So I think the radon in water (in the cistern), which is refilled every 3 days, is off gassing more air radon than normal because of my cistern filling with fresh radon tainted water every 3 days. In a normal well household, the water is aerated for first time at the tap. But in my house it is released to air as it sits in my cistern for 3-4 days, and then replenished.

I'm installing a DIY cistern exhaust radon fan this week and will post results. I found the lowest CFM fan I could find (190 cfm) because it shouldn't take much. I'm hoping it's my main or sole source of elevated radon.

 

[gregzoll]

You would have a better chance of being affected by Radon, working or living in a Granite mine area, then you will in your house.

Even the EPA got it wrong on the effects of Radon and living or working in buildings.

The main goal is keeping the earth and rock under any poured concrete floors dried. As for the crawl space, it would have to be a Concrete floor to help keep any molds from getting introduced into the HVAC system, along with getting rid of any smells from any cellulose based materials breaking down in the soil.

Just placing the fan in the crawl space if there is only plastic down there, will do nothing.

Ground water captures it from the aquifers and also from going through the soil and any stone layers to get to the aquifers.

 

[GottaFixIt]

I just took my basement & crawlspace from nearly 30 pCi/L to under 2 pCi/L using what I call "Impermeable encapsulation and depressurization". Essentially, this just means using impermeable materials to create an envelope around the conditioned space and active sub-slab / sub-membrane depressurization to mitigate soil gases and moisture. I won't address the water part as we had no such problem.

The arguments against the necessity of residential radon mitigation may be valid, but there was no telling my wife that, so I mitigated. This is also part of a bigger basement remodel, so it was sensible for me. Overall, this method will increase the quality of indoor air by allowing greater control and isolation.

First off was the crawlspace. My goals were to condition the space for warmer floors and to contain moisture & soil gas. I chose 2" Polyiso insulation sealed with foam, foil tape and caulk for the walls, up over the sill plate and into the rim joist (pretty standard encapsulation technique). 6 mil poly is then draped over the floor, sealed and taped to the insulation. 1 1/2" PVC feeds to the mitigation fan and creates negative pressure under the poly ground cover.

In the basement, a new french drain & sump pump basin were installed. The key here is a completely sealed system including a special sump pump lid. The french drain allows the system to draw gas from the entire slab. The same insulation & encapsulation method is applied here with the polyiso. 3" PVC sealed to the cover connects to the mitigation system.

The active mitigation is a standard fan installed outside and vented to the roof line. The 2 interior areas are joined at a tee and stepped up to 4" before exiting the building & connecting to the fan.

I would not recommend a positive pressure approach. If you're not ready to invest in insulation, I'd encapsulate with 6mil poly (taped and sealed) and install a sub-membrane depressurization system connected to both areas (or even 3 including the water if it makes sense logistically).

 

[gregzoll]

Are you going to place anything over the foam to protect it from damage or possible off gassing if there is ever a fire?

You could probably use a 5 gallon bucket brigade to poor a slab over it, to further help make the house a lot better. Also it would give you more storage space.

Adding the fan does help more in keeping any mold spores and fungi down.

We have hardly any houses in my area with the systems, because it is not a problem. Those areas that were previously Wetlands, wooded areas or Farm fields are better having them. Because they end up with the smells and methane given off by the Cellulose breaking down.

I would not even want to see what the levels are in the homes and businesses in St. Louis, near those areas they buried the building materials and byproducts from the old Uranium plants and the Monsanto plant that produced Agent Orange. The readings are most likely off the scale.

 

[GottaFixIt]

Are you going to place anything over the foam to protect it from damage or possible off gassing if there is ever a fire?

Not sure if this was directed at my post, but I'll answer anyway. The basement will be drywall'd. The crawlspace is separated by a block wall and did not require a fire barrier.