Quote from: fletcherpearson on March 06, 2025, 09:59:31 AMHey, this all makes a ton of sense really appreciate the breakdown! I like the idea of testing first instead of jumping straight to a fan. The clean stone fill part really clicked for me too hadn't thought about how it helps direct air into the pipe instead of through random cracks.
Also, I had to laugh at the "sin" of running the pipe horizontally sometimes you just gotta do what works! Did you ever test your radon levels after setting it up? Curious how well the passive system worked on its own.
Quote from: NathanS on July 28, 2018, 08:30:19 PMHi Will, yes.. the main thing I remember about the radon vent was we put it in after I spent all day in the stone screeding it level... didn't go for the camera. I asked my wife if she has any pics, I don't think she does but I will post if so.Hey, this all makes a ton of sense really appreciate the breakdown! I like the idea of testing first instead of jumping straight to a fan. The clean stone fill part really clicked for me too hadn't thought about how it helps direct air into the pipe instead of through random cracks.
I think it was actually two lengths of 3' schedule 40 4" pipe that ran into a sanitary T, then the vertical we used a bushing and shrunk to 3" where it comes out of the slab. We drilled a bunch of holes in the 4" pipe and capped the ends. I used schedule 40 cause we had it, and the perforated drain pipe at the stores is a lessor thickness and probably doesn't work with other sch 40 plumbing fittings.
Anyway, it comes out of the slab, and does run horizontally through the first floor ceiling (a sin), then up through a bedroom wall and into the attic and out of the roof. It is powered by stack effect.
The clean stone fill is now depressurized and all the air or potential radon leaks into that pipe instead of through any unintended cracks elsewhere. Radon is more dense than air, so it will prefers to sink into basements like a swimming pool. If I had a basement I would use the same system (clean fill under the slab is important), and would then test for radon in the basement after using just the passive vent. If levels were still high, only then would I add a fan inside the tube. I might even look for cracks and try to tighten things up and retest before adding a vent. If you vent straight outside at ground level you will have to use a fan, because there is not going to be enough stack effect.
I didn't really need the poly under my slab, and is not there for radon... at the time I was concerned about the inspector. we had 4" of XPS foam which is already a vapor barrier. A lot of times people mix up air barrier and vapor barrier... lots of confusion over that one. The slab is your air barrier, the joint between slab and wall needs to be air tight too. Going from memory I think radon can actually migrate through concrete... so if you are in a high radon area you do still need to vent it.
Hope this makes sense.