radon readings in Dane CountyThat is the question!

Some homeowners do the laundry in the basement, some have finished basements with offices or playrooms for the kids, others have a Master bedroom suite or a guest room in their finished lower level. But over the years I've had dozens of clients buy or sell homes without testing for radon gas. One of my clients, who was concerned about radon because she had small children, had gone to the trouble of testing for radon twice in two homes she purchased during the last 10 years. She then tested a third time when she bought the home that she is now in the process of selling on Madison's West Side.

The test had been negative for radon gas when she and her husband purchased the home years ago, so when they received an offer recently that included radon testing, they weren't the least bit concerned. But when the test came back in excess of the EPA standard (4pCi/L), they were stunned. How could such a thing happen? After all, the test they did when they bought the home revealed only trace levels of radon. What caused the change?

While I'm not a radon expert nor a home inspector, newer homes do tend to have radon more often due to the disturbance of the soil, whereas older homes don't normally have those kinds of disturbances unless major remodeling is done that affects the foundation. That was the case in this particular home. The homeowners had put in a Master suite in the lower level when their newborn (now 3 years old) came along which involved jack-hammering the cement foundation and disturbing the concrete and soil underneath. Since baby and mother had slept there every night with the door closed, Mom was naturally concerned about tests that showed unacceptably high levels of radon. She worried what that meant over the long term for her and her baby's health. Furthermore, she wondered how the EPA had established an "acceptable" level and whether recent remodeling could have released gases into the home in otherwise settled soil. So they decided to have their own test done to ensure that placing a radon mitigation system in the home was indeed necessary. They braced themselves though, expecting the same results as before. 

To the surprise and considerable relief of the homeowners, no radon was detected in the retest. You see, radon is a tricky thing. Everything affects it. Atmospheric pressure affects it, weather affects it (including heavy rain and wind) - basically any change in temperature such as a storm front, humidity levels, or any disruption in the immediate area of testing such as recent remodeling. The timeline for the first test had been 48 hours, and during more than 24 hours of that time, Madison was hit with torrential rains. It turned out to be the 8th wettest day in recorded history in Dane County, with 3.6" of rainfall occuring in a single day! Turns out that when soil is that saturated with water there's no room for the radon gas to dissapate, so it rises up out of the soil and into the air. It kept raining over the weekend that their second test was launched and the starting levels were even higher than the acceptable limit. But then another front came through, with cold and wind, and the levels dropped exceptionally fast to average out well below the acceptable level of 4pCi/L (the average annual amount a person may absorb during a lifetime). This test was run over a total of just over three days, instead of the 48 hours, but boy what a difference a day made!

Bottom line: if you're going to invest in radon testing, consider testing for more than 48 hours. Even better, if you've got time on your side, do what's known as an "alpha track" radon test. That's a longer term test, usually six months in duration. An alpha test will cover all kinds of different weather patterns and conditions and will enable you to avoid relying on a superficial 48-hour test. It's no secret the real estate industry lobbied hard to get the radon testing timeline squished down to 48 hours for the purpose of buying and selling real estate (longer term tests just aren't practical for most transactions), even though many radon experts admit that testing for a minimum of 90 days is needed to conclude the presence of radon gas and the need to put in a radon mitigation system.

So if you're thinking of listing your home in a few months, say, next Spring, consider doing an inexpensive alpha track radon test. If prospective buyers test for radon because you didn't, they'll be using a relatively unreliable 48 hour test that may produce inaccurate results. If you've got time on your side and can rule out radon in your home for a mere $30-$40, buyers may not bother with a superficial 48 hour radon test. And if you do discover you have high radon, you can either disclose it or put in a system to mitigate against it, depending on how your basement is used. You'll save money, get more accurate results, and most importantly, you'll know for sure whether you have radon gas in your home or not. Sure beats wondering if the weather caused a bad result and you just paid for a totally unnecessary upgrade just to close the deal. 

Good luck with your testing!

Posted by Jolenta Averill on


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That is very good information. It hasnt come up here on any homes but i am sure it will. Thank again for a great post

Posted by Mike in Dallas on Friday, October 2nd, 2009 at 9:27am

Fabulous commentary!!

Posted by Shelli on Friday, October 2nd, 2009 at 7:20pm

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