Radon in my Conditioned Crawlspace – GreenBuildingAdvisor

Dear GBA friends,

I just finished reading “All about Radon” with the comments as well as a few other articles. Thank you for the advice.

I wonder if my situation would have been less problematic with a vented crawlspace rather than conditioned.   Anyway I have an unvented crawl now.  House has been built over the last 5 years, and I moved in 2 months ago.

I installed a 10 mil vapor barrier, taped at seams, sealed to concrete stem wall with adhesive and pins (https://crawlspacerepair.com/crawl-space-foundation-pins) at least 12 inches up.  Under the plastic I laid down landscape fabric to protect the plastic from the 3″ round rock.  There are about 4-6 inches of this round rock throughout the crawlspace.  

Obviously there are no vents in the crawlspace wall to the exterior.  I have 3 vents between house & crawlspace and was about to install fans (with inline carbon filters for minor smell) for intermittent air circulation.  Crawlspace temps are about 55 degrees F and humidity in the 70% range.  Would be good to get it closer to the house which is 65 F and generally 55-50% humidity.

I’d hesitated to install the air circulation due to the minor but noticeable smell, ordered the carbon filters from ac infinity.  Then thought of testing for radon.

Radon in the crawlspace comes back at 24.4 pci/L (2 bottle short term tests https://www.prolabinc.com/radon-gas-test-kit/).  Tested the interior of home and results are 10.5 pci/L (average of 2 bottles).

So.  This is high, but crawlspace (I’m ashamed to admit) has been unvented for quite some time (although it has the liner).  During dry summer months I’ve often run fans and generally aired it out some.

So I’m living in a house with 10 pci/L.  I have contacted two remediation companies, first one quoted me $5700 which seems high (no visit to my site).  So I’m waiting on a 2nd company and a site visit this week.  

Is it worth doing a 3 month test right now, or should I move straight into investing in remediation?

Question 1

Is it responsible or irresponsible to wait for 3 month test results before acting/remediating?  I am living in this space already.

I have ordered the 3 month test from prolab.  I can also pick up a 2nd short term test but at this point i have 4 bottles  confirming my levels are elevated so perhaps it’s a non issue.

Any money I throw at this seems cheaper than lung cancer.  At the same time I don’t want to panic and waste money.

I am likely to proceed with remediation, and I would LOVE to be able to resolve my issues with a passive system.  I do not have an attic, so I eagerly await the conversation with the remediation contractor (https://cascaderadon.com/ of portland OR) regarding the specifics of whether this can work.  I think adding a fan if passive is insufficient seems doable as a follow up. 

Question 2

I did read about the HRV in the crawl as another possible approach.  Should I add that to the mix or just start with a passive system?  How do I think about HRV conjunction with remediation.  I did a blower door test a while ago and we concluded that my house is not quite air tight enough to recommend using an HRV system.

Question 3

I think the 10 mil plastic I have now is already sturdy enough to be used for the depressurization system.  But one company specificed 12 mil plastic, a special type.  Opinions on that?  If I use what I have now I forsee the contractors cutting holes in it to install the pipe, then re-sealing the cuts.  

Question 4

type of pipe for depressurization system.  I used sched 40 perf pipe around the outside of my foundation for foundation drains.  For the radon system, first contractor said perforated schedule 40 pipe.  2nd contractor said socked ADS pipe, which doesn’t sound as strong.  Strong opinions on these options?

Question 5 

I have a centrally located utility closet, but the question of how to get a pipe up & out of the house with minimal turns seems tricky, and I hate to cut holes in the roof.  Run a pipe up an interior wall and then exit high in the wall? (it becomes an exterior wall further up)  I might have to show drawings to make this make sense.

Thank you all, I’ll keep you posted and watch this space for replies.