Radon testing my first basement (already has a mitigation system)

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  • #1
CPW
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Summary:
Any PF members with experience in radon testing their house?
Hi PF:

The house my wife and I purchased recently is our first one with a basement and it already has a radon mitigation system installed. Unfinished basement.

I've sent my short-term test to the lab and I have a long-term test that I intend to start this week.

Do any PF members have any experience or advice on performing this test and interpreting the results?
Should I test the main living space of the house and not just the basement?

Since radon is heavier than air, should the area underneath the vent pipe be an area in the yard to avoid sitting?
 

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  • #2
russ_watters
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Summary: Any PF members with experience in radon testing their house?
I'm a homeowner in a radon area, and took a continuing education course in it...
Do any PF members have any experience or advice on performing this test and interpreting the results?
Just follow the directions/guidance you get back.
Should I test the main living space of the house and not just the basement?
Radon is a problem in the basement because of extreme stagnation of air. Usually a main floor isn't going to have this problem. Plus the radon comes from the ground, so the concentration will pretty much always be worse in the basement.
Since radon is heavier than air, should the area underneath the vent pipe be an area in the yard to avoid sitting?
The vent should be up high, but even still, there will be substantial dilution with outside air not far from the vent. So it should not be a concern.
 
  • #3
CPW
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Thank you Russ.

One more question comes to mind:
In a few years, when we finish the basement, there will be another HVAC system for the basement level, which will circulate the air. Will that reduce radon levels too?
 
  • #4
russ_watters
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Thank you Russ.

One more question comes to mind:
In a few years, when we finish the basement, there will be another HVAC system for the basement level, which will circulate the air. Will that reduce radon levels too?
Yore welcome.

Yes, that should reduce radon levels; more due to the finishing of the basement than the HVAC; if you seal the floor it will help stop radon from percolating up. Either way, abatement systems tend to be very effective if properly implemented.

How old is the home?
 
  • #5
CPW
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Hi Russ.

We are the second owners of this nice house, built in 2016. The builder installed the radon mitigation system, and it is working (at least the blue U-shaped manometer shows the fan is working). I'll find out the radon levels with both a short-term test and a long-term test from AccuStar labs this year.

I'm now relaxing much better after my conversation with you. I'm glad you took the continuing education course on this topic and shared what you learned.

I understand alpha radiation is capable of DNA double-strand breaks, and having an alpha emitter inside your body is therefore dangerous. I've read that alpha emitters that are outside your body are not particularly dangerous and shielding can be thin, even a piece of paper or the dead layer of your skin. Just don't get the alpha emitter inside your lung tissue.

Speaking of you, I also checked out your astrophotos on your website, and I'm impressed. I think I will show your photos to my kids (elementary aged), as the science topic in the homeschool co-op this year is astronomy. I figure I can use my telescope to show the same targets, and then use your website to show what a higher powered telescope would show.

Thank you.
 
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  • #6
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advice on ... interpreting the results?
Recognize that county/state guidelines will be based on the linear-no threshold (LNT) simplification. This assumes that, for example, halving the exposure halves the risk. Thus the LNT approach allows data from very high exposures to be used to extrapolate the risk from very low exposure. The "no threshold" part means that the approach assumes that even tiny exposure carries some (tiny) risk.

For an alternative perspective, google "radon and hormesis" - this is one of those things where anyone interested can read the studies and make up their own mind.
 
  • #7
CPW
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In case anyone on this thread is interested, I received the results of the short-term radon test: 3.0 pCi/L.
I'm relieved that it is less than 4.0 since my wife and I went forward with this home purchase without getting a radon test first. As stated above, the home already has a radon mitigation system installed, and I'm leaving it running.

Curious now if I were to repeat the test without the radon mitigation fan turned on, what the results might be.

I plan to initiate the long-term radon test this weekend. (I like to measure).

Related to the LNT theory, isn't that theory somewhat less popular for today's scientists? The current point/counterpoint in Medical Physics Journal stated that.
 
  • #8
CPW
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Just received the long-term test results: 3.8 pCi/L, just below the EPA limit of 4 pCi/L.
The test kit was in the basement for 105 days, and the report states the uncertainty in the result is +/- 15%.
My wife and I intend to let our kids play in this unfinished basement some.

I see that there are professional grade continuous monitors for radon.
If you were I, would you consider purchasing one of these more expensive radon monitoring systems?

Note that the cost of finishing the basement puts that project many years down the road.
 
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  • #9
russ_watters
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Just received the long-term test results: 3.8 pCi/L, just below the EPA limit of 4 pCi/L.
Good news!
I see that there are professional grade continuous monitors for radon.
If you were I, would you consider purchasing one of these more expensive radon monitoring systems?
No, my understanding is that since the radon comes from uranium in the ground, the rate of exposure should be pretty consistent.
 
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  • #10
CPW
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This is an old thread, I know. But as the homeowner I have an update this month. I purchased a continuous radon monitor last month, and it sends details to my iPhone. There were multiple times when the peak value was greater than 4.0 pCi/L, and the average value was still close to 3.8. “Action Required” is what the app on my phone read whenever the value was above 4.0. So, I hired a pro, and I learned these two things: (1) the WHO action level of 2.7 is lower than the EPA’s level of 4.0. (2) The fan the drives the air through the pipe was too small for this size basement we have. So, simple fix: install a better fan. Done. With more long term testing I will see if that is sufficient to keep levels below 2.7 or ALARA.
 
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  • #11
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Bunch of things, hang tight.
You mention HVAC. These systems frequently use the basement as the return air source for at least some of the return air. The basement air is usually higher in radon. The HVAC system spreads this throughout the house if it draws any air from the basement so your 3.8 may be the same throughout the house.
Bigger Fan. This generally makes sense, but not always. We sometimes see a bigger fan raise the indoor radon level. This is because of pressure gradients. It is the pressure gradient that "causes" the radon problem. I'm from Maine. Indoor radon levels are usually higher in the winter when the heat is on. This is because hot air rises, decreasing pressure in the basement, the furnace uses indoor air for combustion and sends it up the chimney further decreasing basement air pressure, any exhaust fans (kitchen, bathroom) decrease indoor air pressure, clothes dryers typically vent outside and decrease indoor air pressure. People usually seal everything above the ground carefully to try and decrease any cold air infiltration so the house is left with the ground level or basement to get it's make up air and it sucks the radon right out of the ground. So you need to carefully seal the cracks or penetrations in the basement before you finish it. The floor is poured after the walls have dried so there is a "cold joint" between the floor and wall this needs to be sealed. If the basement isn't well sealed the bigger radon fan may decrease the negative indoor pressure by sucking more air out through the basement penetrations. Good radon diagnostics can determine if your "pressure field" below the slab is distributed enough to cover most of the slab. A bigger fan may extend that pressure field but an additional suction point might do it better. Good radon sealants (caulking) say they are designed for radon or they are urethane or polyurethane based and are frequently called adhesives.
Guideline levels: the EPA and WHO levels you mention are correct, but these levels are based on year long average radon concentrations. Most people base their decisions on a two day test. You are alarmed by the fact that sometimes it goes above 4. I just wanted to point out that the guidelines are usually misapplied. You know a lot more about your radon level than most people. Additionally, I should point out that we have a lot of data that tells us a radon mitigation system that is installed correctly (ASTM standard 1465) will get your radon level down below 2. There are naturally unique situations where this is not possible, but mostly it is.
Standards: the ASTM standard is a withdrawn standard, this means that ASTM has not updated it in more than 7 years. They are waiting for the industry to develop their own standard (which they have).
 
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  • #12
CPW
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Thanks for all the information, Jayhyland.
The pro's week-long test came back with this result: 2.2 pCi/L.
So that's good, although I would like my equipment to give the same result. My CRM is reading about 1 pCi/L higher, on average. My plan is to do a long-term test again this winter. Include the main part of the house too.
The pro did do diagnostics for the sealant, and with the home only 5 years old, the builder did create the cold joints. He was also supposed to measure pressure gradient under the slab. I will ask about that.
After reading what you said about HVAC, I'm thinking I will see if the HVAC we purchase can be independent of the air circulation in the main part of the house.
With all the good advice for PF members, I intend to keep chronicling my experience with this basement.
 
  • #13
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Good news!

No, my understanding is that since the radon comes from uranium in the ground, the rate of exposure should be pretty consistent.
No, it's not consistent. The production of radon occurs at a very steady rate, but it's a gas produced in (more-or-less) porous solids just below a very dynamic atmosphere. Even before we consider building-specific physics, it is obvious radon is more likely to remain and decay underground during a fair-weather high pressure system than when the pressure is dropping and the wind is blowing, although the wind will mix the resulting radon pulse. Once buildings are involved, there are a huge number of additional factors. For example, consider the stack effect where during the winter heating season, the warmer indoor air is at a lower pressure than outdoor air - sometimes exacerbated by combustion devices utilizing indoor air as fuel - causing subsoil radon to be drawn towards and into the building. Indoor air pressure drops also result from the use of ventilation fans or clothes dryers. Some water supplies are contaminated with radon, and the radon is more likely to be released when the water is hot and has a large surface area exposed to the air, such as when taking a long shower. Other variables include the number of and duration of window and door openings - even interior doors if they lead to higher-radon areas like the basement.

This study of the radon levels measured in a house shows hourly variations in radon of an entire order of magnitude. It also shows considerable variation over days and weeks (probably due to passing weather systems), seasonally, and even between one year and the next.
 
  • #14
CPW
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A basement waterproofing contractor visited my unfinished basement to quote the cost of an interior drainage system (which I deemed as overkill for my dry basement, at least currently), and he explained the stack effect to me. Takeaway lessons for me as the homeowner:
1. Even with the door to the basement closed, we are breathing the basement air on the main floor.
2. There never is a reason to open the windows in the basement and leave them open.
(Much of this waterproofing lesson was unrelated to radon, but pertained to humidity control in the basement).
 
  • #15
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I'm not sure I'm buying l#2. Opening a basement window will essentially eliminate the pressure gradient from the stack effect, and the lesser amount of radon making it into the basement will be diluted with fresh outdoor air. Humidity is not like radon, because radon levels are almost always lower outside, but humidity is not so constrained.
 

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