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Radon and Winter

With the colder weather slowly starting to seep its way into a Chicago winter, our thoughts start to turn towards… radon!  I know, not exactly in keeping with the holidays, but still it’s something that we need to consider.  While spending more and more time in our homes due to the pandemic, the importance of radon testing becomes paramount.  So why is it so important to know if we have elevated levels in our home?

Radon – A Primer

First, a radon primer.  Radon is a part of the radioactive decay chain of uranium.  It makes its way as a gas through the cracks and crevices of the soil and through openings in the foundation of a building.  It can be a serious health hazard because it is the number two leading cause of lung cancer (second only to smoking).  There is no safe level of radon, but for most real estate transactions, the accepted level is below 4.0 pCi/L.  

That being said, we need to understand that radon levels can fluctuate widely throughout the day, month, or year.  Oftentimes, it is the highest during the winter season.  How on earth can this be?  

Snow and frozen ground

As we noted, radon enters a building through the soil underneath.  During warmer seasons, this radon gas escapes through the ground surrounding the house and is mixed with the outdoor air to help keep indoor radon levels lower.  However, during colder months, the ground surrounding our home can freeze and trap the gas.  A blanket of snow further prevents radon from going through the exterior ground.  So where does this radon go?  To the area of least resistance, underneath your home!  Before you know it, the radon inside the property can often rise to highly elevated levels.

During the summer it’s possible to have the same effect with heavy rainfall and flooding.  However, winter time is the greater culprit.  It’s especially important to test when you are in a climate that experiences greater cold temperatures and regular snowfall.

Closed doors and windows

I don’t know about you, but when it’s 15 degrees Fahrenheit outside I like to keep my doors and windows open (kidding!).  Of course, during winter months we have the tendency to close our doors and windows to help retain valuable heat.  But by keeping our homes sealed up, we prevent radon gas from leaving the building.  The trapped gas starts to build up and increases elevated radon – sometimes to dangerous levels.  

The mere act of installing energy efficient windows can trap radon in a building.  The same is true for a new roof.  It’s even possible to see elevated levels after newly remodeling a basement!  The only way to know for sure is is to have the home tested shortly after any renovation, but especially during the winter months.

Stack effect 

Remember that radon gas moves from the ground and into the lowest area of a house.  The “stack effect” refers to pressurization in the home.  Air pressure is lowest in those sections of a building that are closest to the ground and highest at the top.  This creates a draw of the gas and pulls the radon at a greater rate throughout the building.  The effect is greatest when there is a major difference between indoor and outdoor temperatures.   

Radon and Winter – Conclusion

Oftentimes, homeowners make the mistake of testing radon with a “one and done” attitude.  This is a mistake!  Most real estate transactions are usually performed during the spring and summer months.   A far better time to do testing for radon is during the winter months by a trained radon professional.  The numbers during the summer test might pass, but be on the high end of the range (3.9).  This is a warning sign.  A building inspector usually tests in a single location for a very short period of time.  Radon levels can not only fluctuate from season to season, but also from room to room.  If a single reading is at the upper range during the summer, a winter measurement might be much higher in another room.   

As times change, so does radon.  We recommend having your home tested every couple of years in alternating seasons.  But for safety and peace of mind, you will never regret testing during the winter season by a trained radon professional.

Scott Wieringa

Scott Wieringa

Scott Wieringa is a Project Manager that performs indoor air quality assessments with a specialty in radon and odors. Mr. Wieringa holds a Bachelor of Arts degree from Calvin College. He is an ACAC Council-Certified Indoor Environmentalist (CIE) and Illinois Licensed Radon Professional with residential and commercial building endorsements. Prior to working at Indoor Science, Scott was a residential real estate appraiser with over 23 years of experience inspecting properties in varying capacities. In his words… “I have a special interest in helping clients track down how their homes or businesses might be making them sick. In my spare time, I’m involved in songwriting, sketching, and spending time with my family.”

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