Radon gas anyone?

[kcflhrc]

We are hoping to have foundation built soon. Is there a way to check levels prior to building? Sensor in an upside down bucket?

We are just going to have a crawlspace with dirt floor. Is this only a concern on enclosed basements without ventilation? Is there a strategy if no slab?

I would ask your builder. Radon levels can vary widely across the country. They would typically put down a vapor barrier over the soil and then vent from under the vapor barrier. It can be a concern just like a basement. I would be proactive and install it anyway. Very reasonable to do yourself

 

[prichard]

I'm the builder. I haven't worked actively in construction in a while and when I did I never saw radon remediation systems. I'll have a chat with the county or state.

So I checked EPA site. Basically, it's cheaper and easier to seal (caulk, plastic, etc) and install piping and test after construction.

 

[Paddy]

I just got my first reading with my new Safety Siren Pro3, 5.8 pCi on the main living area next to the elevator shaft. It's also 7 feet from the stairs to the basement. I'm glad it's close to the 4 pCi, but will proceed with my remediation plans. I'm glad I bought this tester vs. the $25 mail in types. I now can move the tester to my bedroom, where I spend a good 8 hours a day, hey a man needs his rest. Last I'll measure the basement but I know it will be high.

 

[Paddy]

prichard,

I recall when I lived in S.C., most foundations were really ventilated. Like nearly half open, decorative brick and all. But no doubt you need to look in to Radon. 1) certain areas are noted as bad, some very good. check with your local health dept. 2) Google if you can do a bucket test on the soil where you are planning to build. 3) plan to use the vapor barrier regardless if not just to keep moister out. But if Radon is real in your neck of the woods, take Neumanns advice and use the heavy vapor, not box store sheet plastic. Walk on it once and there are holes!

 

[prichard]

According to what I see we're in a high area. Granite is a large contributor and we sit on granite. So yes I'll follow Neumann' s advice after more research of course.

Florida, where I lived most of my life, is low. Guess that's why I never saw a system while working construction.

 

[RNeumann]

RNeumann,

Do you build houses, or just when you built your own you implemented the under slab tubing? If I understand your system, you are pulling outside air from your perf pipe that exists to daylight? Wouldn't that pull mostly cold air under the slab and limit the negative pressure elsewhere?

What is your though regarding the sump size? For example, in a system that does not have the pre planned tubes. I've seen references where they recommend cutting a hole in the floor and removing 30 gal of soil/gravel. Then sealing the 4 in pipe over the void. I'm not sure how a large pit would perform any differently than a small pit/void

We have been builders for over 50 years. My wife is an architect. I used to get sucked into some of the detail design but not too often anymore- her business has far exceeded my expertise at this point- haha!

Radon is newish to us. It’s been the last decade or so. We tried adding the drain to daylight on a project about 5 years ago and haven’t looked back. The initial thought was to just cap the daylight if we needed- we haven’t needed to. Like I said before we rarely have had to add a fan. In fact it was just one project that required a lot of blasting. They got one reading that was high- I have no idea what the number was- so we added the little inline can and haven’t had an issue since.

With regards to your project-
I’m thinking the pit size isn’t as important as ensuring the pit ties into the existing under-slab sand/rock layer that you imported before pouring the slab. That’s the layer that will provide the best chance of moving air- it should be the driest and obviously porous.
Practically I’d excavate down and back to match the under-slab grade, import material to match the under-slab detail and make the pit big enough to add your sump or whatever else you need down there.
We aren’t scientific about length but we would do say 30’ or 4” perf under 2000sf of floor. I know you aren’t going to get that much but maybe 20-25’ if you run around the edge of your 7’x7’ hole.

 

[RNeumann]

Concrete Vapor Barriers - Vapor Retarders - W. R. Meadows

This is the vapor barrier we use. Our local wholesaler has it. They carry the tape too. Plan on using the excavator or backhoe to lift it into place. The rolls are heavy!

 

[prichard]

I was just looking at meadows products. I'll have to look for a local distributor.

 

[RNeumann]

I just watch a show about a Canadian company that does Radon mitigation in existing structures. Their method is to core a 4” hole in the slab, insert a 3” pipe into the hole, seal it to the slab and run the pipe with an in-line fan up and through the rim joist.

Number one it was way simple. And number two they went out of their way to say once radon is outside the structure it poses no risk because of dilution. That’s why they claim the rim joist to daylight is fine over having to route it through the roof.

.....just one company’s approach.

 

[PHD12]

Here is another good reference for radon mitigation, with some good strategies for how to deal with it on a new house construction:
All About Radon | GreenBuildingAdvisor.com

We just built our house a few years ago and spec'd the sub-slab details in the link above, but I wasn't on site while that work was being done and it didn't exactly end up perfect (less than 4" of gravel, only a foot or so of horizontal run of under slab pipe, that pipe was "perforated" only a handful of times with a drill and so on). But we do have a "passive radon pipe" that runs straight up and out through a roof penetration. I had an outlet installed in the attic right next to the pipe so we could add a fan later if we needed to.

I've done 2 short term tests (3 days) and 1 long term test (90+ days) on my basement and main floor level. The basement levels were 5.7 a year ago, 9.3 a few months ago and 5.5 recently. Following the 9.3 reading I very carefully caulked and sealed the slab edge, drain penetrations and relief cuts throughout the basement so I was expecting a huge drop, but it ended up only 0.2 less than the test I had done this same time last year.

The main floor of our ranch-style house ranged from 1.7 to 3.1, so below the EPA recommended action level of 4.0 but above the World Health Organization level of 2.7. Apparently several European nations actually REQUIRE mitigation if above 6.5 or 6.7 (can't remember which).

So I have the data from the mail-in test kits, both short and long term, with another long term test underway now. I ordered the AirThings Home monitor, which seems to be highly regarded: Radon Detector for Everyone - Airthings - Receive Your Detector Now! and I would be glad to post back how it compares with the mail in kits. It's a little more than the SafetySiren monitor.