I've got a radon issue, and we've recently had a membrane with active depressurization installed. That helped, but the house is 80 years old, the crawlspace is leaky and difficult to seal (cracks and irregularities), and there's still some radon. In the basement and crawlspace the radon is around 3 or 4, and in the kitchen on the main level it's around 2.5 - so it's not off the charts, but it's higher than I'd like for working at home. We'd also like the basement to be safer.

I'm considering an inexpensive ERV to exchange air in the crawlspace. I don't really care if it's an ERV or HRV... it's just that I see this affordable thing on Amazon (Panasonic FV-04VE1) and I figure it's inexpensive enough that maybe I'll experiment. Not that I'm made out of money - I just don't want to breathe radon all day. I'm in Western CO at about 6,000 feet.

The house is 1200 sq. feet on the main level, and the crawlspace is maybe 800-900 sq. feet. With this thing exchanging 10-40 CFM, that seems adequate.

The question: is this a reasonable approach to further reducing the radon levels? We suspect that the imperfect membrane installation is part of the problem, so I'm thinking I'd install this in the crawlspace (and separate the duct terminations by at least 10 feet of course). Assuming I don't increase negative pressure in the house, could I make things a whole lot worse?

Or... for $150 more I could get an HRV. Instead of ducting it into the living area, I'd probably just leave all ducting/airflow in the crawlspace since that seems to be the source of the problem. The house itself is plenty leaky, although I have sealed the crawlspace as well as possible (sealed the rim joist to foundation and filled any visible cracks).

Thank you for any insight.

If its 2.5 picocuries/liter upstairs do you really care what it is in the crawlspace?

At 6000' of elevation the cosmic ray radiation may be a bigger risk factor.

Rather than ventilating the crawl space, you'll probably get better bang/buck out of ventilating the living space.

The Panasonic ERV core would almost certainly succumb from frost damage in short years in your location.

As a DIY retrofit the ductless Lunos e2 HRV is probably going to be the easiest, but it's about a grand per pair and 20 cfm max, but very robust from an icing damage perspective. https://foursevenfive.com/product/lunos-e%C2%B2/

Thanks Dana. It's the living space in the finished basement I'm most concerned with (it's seems to sit around 4 during the winter).

So it might still be best just to ventilate the living space in the basement instead of messing with the crawlspace. Not sure if that changes anything about freeze damage (the crawlspace gets down to about 45 on VERY cold nights but the basement stays more like 65 with heat).

Thanks for the link to the beefier ERV. Might be one of those things "if it's worth doing, it's worth doing right" instead of picking a cheapie to see how it goes.

Thanks again - I really appreciate it.

If there are summer humidity concerns, then a crawlspace should either be sealed up and dehumidified or well ventilated directly to the outdoors (no HRV or ERV needed). Very slight negative pressure in the crawlspace would help with radon (just as it does with sub-slab depressurization) . Otherwise stack effect will pull the crawlspace air into the house.

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Thanks jonr. The crawlspace is very dry from what I can tell and what everybody says - lots of fine dust floating around (before the radon system went in) and I live in a pretty dry area. So the main goal of ventilating is to try and get the radon levels lower.

The little gizmo went off again last night with a new reading of 4.6 in the basement. I had left a window a tiny bit cracked over the full 48 hours, and there were a few windows wide open for an hour or two when we were exercising a day or two ago.