Simplified Radon
blackfeet
| Posted in Expert Exchange Q&A on
Hello all,
Have you seen The Build Show architect Steve ? describe this very simplified radon system? It is at 15 minutes into the 20 minute show.“Radon Mitigation” Build Show Build: Boston – Bonus Episode
I live in a high radon area and a drain tile loop is insalled all around the perimeter of the interior of crawlspace foundations, then piped up.
I don’t think there is anything that Steve is doing that is against IRC?
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Replies
blackfeet,
Can you expand on what is "simplified" about this system? What are you trying to avoid doing that other systems include?
Steven Baczek is well known for being an expert in all things Building Science. I don't watch videos, but it sounds like you're describing a typical setup, using the interior perimeter drain as a radon loop. I wrote about that approach here: https://www.finehomebuilding.com/2016/07/08/radon-big-deal. Since researching and writing it, I have always combined the two and although I design homes in a moderately high-radon zone, I have never had to add a fan--passive ventilation has done the job.
Michael,
"it sounds like you're describing a typical setup, using the interior perimeter drain as a radon loop"
No it's separate. They just use two eight foot pieces of perforated pipe in the rock layer.
That is correct Malcom. And someone commented that the two 8 foot pieces were not neccessary. They just use a PVC "T" in the gravel, with the poly well sealed to the stack pipe going to the roof. I makes a radon system cost so low low and so easy to install. Is there any actual code about the design of the radon system other than that it works? Proved by testing.
blackfeet,
Assuming you are under the IRC (which I'm not that familiar with), this section appears to show acceptable systems:
https://codes.iccsafe.org/content/IRC2018/appendix-f-radon-control-methods#IRC2018_AppxF_SecAF103
Randy Williams also recently wrote a good blog on the subject:
https://www.greenbuildingadvisor.com/article/radon-mitigation
Typical radon systems just use collection "pits", which are holes excavated under the slab a bit and then piped into the system. Some collection systems will use several of these pits spaced around a basement slab to get even suction on the soil layer. I don't see any reason a PVC "T" wouldn't work here if it' in the gravel layer, but the pipe would spread things out and probably work a bit better. It's pretty well accepted that using a drain tile loop will provide superior radon collection performance to just using a pit, for example.
The system described seems to be a basic passive system. I think it's a good idea to put those in in any areas where radon might be an issue, because it's pretty easy and cheap to add such a system (which is basically just a vertical pipe up through the roof from the drain tile) at build time. Just be sure to allow for space to add a fan OUTSIDE the living space (usually in an attic for these systems), since sometimes the passive system isn't sufficient to keep radon levels under control, but upgrading it to an active system by the addition of a fan solves the problem. All you need to do is allow a place for the fan and a power source to run the fan and you're good to go in the future if you need to upgrade the system.
Bill
Bill, I wouldn't call collection pits a typical system--I've been researching radon systems for at least 15 years and I've never seen that used on new construction. I have seen existing or new sumps used on existing homes that need radon remediation.
Being in a relatively high-radon area and designing relatively airtight homes, I consider dealing with radon to be very important. I think of the required gas-permeable layer--typically clean crushed stone here, but it could be sand or any aggregate of reasonably consistent size--as the main collection zone, and any perforated pipe as a superhighway to funnel the gas to the collection point--in my case, just a 4" solid PVC riser. I also always spec an electrical outlet or at least a junction box near the terminus.
The pits are commonly used in my area for retrofit systems. I wouldn't ever spec one for a new system though: perforated pipe in the gravel layer is a way better way to go, and should provide much more even suction over the entirety of the subslab area.
3" risers are more common here, partially because they can fit inside a 2x4 studwall if you use schedule 30 pipe. In my own home, I ran two parallel 3" pipes like that in a studwall, then transitioned to 4" in the attic (for the fan and vent) and in the basement, where the 4" main run branches off to the sump and to a perf pipe loop in a crawl space that got encapsulated, since that area didn't seem to draw enough from the drain loop on the usmp.
BTW, the way I like to spec the electrical supply for the attic radon fan is to install a SINGLE outlet (not a duplex receptacle) in the attic near the radon fan location, then feed that from a utility circuit in the basement fed through a stand alone GFCI (a GFCI that mounts in a standard box using a decora-style plate, but has no outlets). I like to use a 4" square plate and add a pilot light to the plate. This gives a positive indication that power is active to the fan, and the GFCI can be used as a switch to shut the fan off for testing, if needed, without going up into the attic. I try to put that GFCI and pilot light somewhere within sight of the radon system manometer. This makes it easy to check the status of the system from one location, which helps to encourage people to actually check periodically. My concern is always that people will forget about these systems, then the fan will die some day and no one will notice -- thinking they're protected from radon when they no longer are.
Bill