When a home already has an active radon mitigation system, is it even worth testing for radon? That’s a great question. To answer that, allow me to share a quick story.
Back when I answered the phones and did all of the home inspection scheduling for Structure Tech, I used to be in the habit of telling people that radon gas was mostly something that affected basements. I’d tell people that if they didn’t have a basement, there was probably no need to test for radon. That was my message… until I got some doctor buying a slab-on-grade townhouse in Plymouth. He wanted a radon test no matter what. I told him it probably wasn’t necessary, but he wanted the radon test anyway, just to be safe. I shrugged and thought to myself “It’s your money.”
I did the radon test, and it came back at 8.7 pCi/L. Yeah. That’s over twice the EPA recommended action level of 4.0 pCi/L for a real estate transaction. Insert foot in mouth.
“An expert is a man who has made all the mistakes which can be made, in a narrow field.” – Niels Bohr. I’m getting there.
After that experience, I stopped telling people that they probably don’t need to test if they don’t have a basement. I started saying that the only way to be sure of low levels of radon is to test. That’s all. If you don’t have a basement, your potential for high levels of radon will go down. If you have a Minnesota home that was built after 2009, it should have a passive radon mitigation system. Passive radon systems will lower the potential for high radon. We’ve found that about 20% of homes with passive systems have high levels of radon, compared to about 40% of homes without any system. See Radon in New Minnesota Homes.
Active radon mitigation systems
So what do I tell people about active radon mitigation systems? I tell them the same thing. The only way to know if you have a high level of radon is to test. To date, I’ve never found radon levels over 4.0 pCi/L at houses with properly installed, active radon systems running. If I were buying a home and the radon mitigation system appeared to be properly installed and functioning, I’d probably skip the radon test… but I’m a risk-taker. I may have a higher tolerance for risk than others.
To help determine if a radon mitigation system is properly installed, check out this checklist developed by the American Society of Home Inspectors (ASHI): Radon Checklist. Additionally, a few hardworking folks at ASHI have put together a proposed set of standards for inspecting radon mitigation systems. This standard has not been made official yet, but here’s a draft: Radon Inspection SOP Draft.
The quick and dirty way to see if a radon mitigation fan is running is to take a peek at the radon pipe in the basement. If it’s an active system, there should be a monitoring tube installed. This tube gets filled with a liquid which gets offset by the suction created by a fan. If the liquid levels are even, there’s a problem. If the levels are offset, that’s good news.
But still…
According to the “authorities that be”, you’re supposed to test for radon every two years. You’re also supposed to test your GFCI devices monthly. We all do this, right? 😉
Author: Reuben Saltzman, Structure Tech Home Inspections
A Overbee
September 12, 2017, 8:57 pm
This was interesting; thank you! We just sold our home which had two radon tests done over the years – one that took about 3 months, and the other that took a year. Both passed. Then the buyers had a short test done in connection with their inspection which showed unacceptable levels of radon. What are the best types of tests for radon?
Reuben Saltzman
September 19, 2017, 4:20 am
The best type of test is a long-term test. Out of curiosity, what were the results of the short-term and long-term tests?
JS
September 20, 2017, 8:14 pm
What are your thoughts on devices like the Airthings Home and Wave products? We found an issue (8), and sealed our sump. We’re hoping the cheap/easy fixes can save us the hassle of active mitigation. We don’t currently use the basement as a living space.
Reuben Saltzman
September 21, 2017, 5:05 am
Hi JS,
I assume you’re referring to the radon alarms? They seem like a great idea, and they’re not all that expensive. I’ve never tested one out before, however. That inspires me. I ought to ask those folks to send me one to test out.
lidiya jacobson
October 1, 2017, 11:04 am
I would like to know what to do and what not to do if the test is set in your basement? I kniw not to open any windows, but what else? Any hints not to svrew the test? Thanks. Lidiya
Reuben Saltzman
October 1, 2017, 1:10 pm
Here are the instructions that we leave for sellers:
All windows must be kept closed. All doors giving access to outside must be kept closed except for normal, momentary, entering and exiting.
Radon monitors are not to be moved, covered or altered in any way. Heating, air conditioners, clothes dryers, cooking hoods and bathroom fans can be operated normally. If any heating, air conditioning or ventilation equipment has a built-in outdoor air supply that is manually controlled, it shall be turned off or the inlet closed. HRVs / air exchangers should be operated normally. Fireplaces or wood stoves are not to be operated unless they are a primary heat source.
These test conditions are to be maintained 12 hours prior to the start of the test, unless the test is longer than four days duration.
Any installed radon mitigation systems are to be operated normally.