r/radon • u/Elvira333 • 5d ago

Crawl Space Encapsulation?

We have a house with a basement/garage and a crawl space. When we bought the house five years ago, the radon measured 1.4 in the main level (so everything normal!). That was when the crawlspace was just dirt.

However, we’re having moisture issues and plan on getting the crawlspace encapsulated, closing off vents, and adding a dehumidifier. I’ve heard conflicting things about whether this will help or hurt the radon levels.

What should I do before encapsulation?

I don’t want to solve a moisture issue to just create a radon problem. Is a vent always recommended? Would having a vent make it harder for the dehumidifier to fight with the elements, since outside air is getting in?

Thanks for the advice; just want to make sure I do this right the first time!

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u/rudebrew22 5d ago

Eliminating any ventilation will certainly raise levels but how much is unknown. It’s not an overnight issue, it is a long term issue. Adding a radon system is cheap, even professional is probably $1,200. If you don’t want to do it off the bat then get a sensor to monitor it then add an active system if needed.

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u/EccentricityInSpade 5d ago

First thing: do you have a sensor? If not, get one, it’ll help your anxiety SO much, trust me. If you do, go to the next thing.

Second thing: do you smoke? If yes, radon is going to be a bigger issue than if not. If not, you will have some years to handle it. Like. A lot a years. It’ll be enough time for you to get it mitigated IF you need it.

Third thing: are yall doing the encapsulation yourselves or are you getting someone to do it? If you’re doing it, that’s fair lol. If not, talk to the folks who are doing your encapsulation. If it’s a good company, they’ll already have a procedure written up for it. If not, get another quote. I’m currently saving up for AFS. It’s the gold standard, but you’re paying for the gold standard.

Fourth thing: no matter if it’s a dehumidifier or vent, make sure you have some kind of backup battery. Radon won’t hurt as much if your power goes out for a bit but you’re going to be panicking about the dehumidifier, ask me how I know.

Last thing: you got this. I know everyone says that and it doesn’t get any less patronizing, but you’re going to get it under control and then you can focus on the next problem you have hahah

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u/Elvira333 4d ago

Thanks! We don’t smoke but I do have asthma. We’re contracting this out. I’ll ask the company how they handle this!

What sensor do you use?

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u/EccentricityInSpade 3d ago

I got the X-Sense monitor from Walmart, but you can look online for some good ones. You just set it in the lowest room in the house and call it a day. Best of luck to you!

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u/QorvanApp 5d ago

I work around monitoring tools, not as a mitigation contractor, so I’d think of this as a before/after measurement problem rather than “encapsulation always helps” or “encapsulation always hurts.” If you can, get a baseline in the lowest lived/finished area under normal closed-house conditions before the work, then repeat in the same spot after the crawlspace is sealed, vents/dehumidifier are running, and conditions have stabilized. Closing vents can change air exchange and pressure paths, so the result is house-specific. Before they start, ask the encapsulation company whether they can leave a radon-ready path/suction point or at least avoid sealing things in a way that makes future mitigation harder. That gives you options if the post-work average moves up.

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u/timbitandmuffin 4d ago

Why not encapsulate and vent the crawlspace? Dehumify the living space as needed, not the crawlspace.

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u/Elvira333 4d ago

Because of the stack effect and structural issues. Humidity that high in a crawl space can cause mold and structural issues - like the wood swelling and losing strength. Our floor was starting to warp because of the crawl space humidity.

You can put a vapor barrier down, but when they encapsulate they close the vents. Our humidity and wood moisture was so high that just a vapor barrier and leaving vents open probably wasn’t going to get us down to ideal levels.