HRV for crawl space
Hello,
I need to mitigate radon concentrations in the crawlspace underneath a mobile house. There is limited space under the house, which makes the access difficult. There is some poly sheet lined on the ground, but is not sealed properly. Due to the height restrictions, uneven terrain and presence of many pillars & tree stumps underneath the house, it would be difficult to properly seal the ground. The crawlspace’s walls are insulated to prevent pipes freeze during winter.
I did cut one hole one each of the opposite crawlspace walls and that created a natural air flow that helped reducing the radon concentrations during summer months. I live in Whitehorse, YT and I can’t leave the holes open during winter, when temperatures drops to negative 40C.
I was wondering if an HRV system would work during winter months to provide enough fresh air circulation under the house. I can provide details regarding the crawlspace surface, height and other info that would be needed to assess the venting system details. Please let me know if you can assist with this matter.
Regards,
Norbert
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Replies
Hi Norbert.
I assume that you performed a radon test that alerted you to the need for mitigation. Have you done follow up tests to know that your passive airflow in the crawlspace has solved the problem?
I suggest proceeding carefully as radon can pose serious health risks and crawlspaces are sensitive areas that need to be detailed and maintained well or a host of other problems can arise. I suggest you read these two articles:
All About Radon
Building an Unvented Crawlspace
Hi Brian,
Thank you for your reply.
Yes, I did a radon test and currently I have a real time Radon tester installed inside the house. The reader records Radon concentration over the last 24 hours, short term average (7 days) and long term average (a month).
I did notice that Radon concentrations dropped inside the house during summer with the help of passive airflow on the crawl space and the house windows being kept open most of the time.
Still, I am looking for a Radon mitigation solution for the winter time.
Norbert, have you tested the radon in the living space, or just in the crawlspace itself? It's the living space that you need to worry about. I take radon concerns very seriously but there is a chance you don't need to worry as much as you think you do.
One on project I was involved with we used an HRV to reduce radon levels in a basement, but it's not really an approved method.
As for the barrier on uneven ground, you might consider using EPDM, a rubber membrane used for roofing and pond liners. It is more flexible and durable than most vapor barriers. You can buy radon mitigation mats, like a giant brillo pad, to go under the EPDM. Then get a radon mitigation company to install an inline fan exhausting to the outdoors to depressurize the area below the membrane.
Hi Michael,
Thank you for your reply.
Yes, I tested the radon concentrations inside the house; currently I have a real time Radon tester installed inside the house. The reader records radon concentration over the last 24 hours, short term average (7 days) and long term average (a month). It seems that radon concentrations are spiking whenever there is a significant increase in the outside temperature.
I did notice that radon concentrations dropped inside the house during summer with the help of passive airflow on the crawl space and the house windows being kept open most of the time.
Still, I am looking for a radon mitigation solution for the winter time.
The barrier would be very difficult to install, due to the limited height space (in some sections about a foot).
I was thinking that maybe circulating the air in the crawl space would help, if there is enough air volume that is exhausted. Any thoughts?
Thanks!
I'm sure it would be difficult to install a liner; I've crawled through 12" crawl spaces and it's not much fun. (That's why the IRC requires at least 18" clearance.) But it's possible; I was recently going to install EPDM in a crawlspace that went from about 8" on the high end to almost nothing on the low end; my plan was to pull the liner through the space with a rope wrapped around a 1x3 attached to the edge of the membrane. Plans changed but I think it would have worked.
If there is simply no way to do that, then yes, dilution is one solution to pollution (to paraphrase Joe Lstiburek). But I would still talk with a radon mitigation company--they may have other techniques.