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Baby, it’s cold outside!!

snowy building in the winter time

During this time of year, I love to hear the old song “Baby, it’s cold outside!” play on the radio.  It sums up winter time in the Chicago area.  And with this frigid weather, we retreat to the comfort and warmth of our homes.  

But the warmth that we feel inside our homes can bring hidden dangers that can spell “M-O-L-D”.  Now, how can this be?  We usually associate mold with summertime flooding or a leaking pipe.  How can mold develop in the absence of a major water event?  I can answer that in one word – “Humidity”.  

Mold needs moisture more than anything else in order to survive and grow.  On days when we experience extreme cold outdoors, it is possible to have humid indoor air (humidity is a form of moisture) hit a super cold surface, like a window, and create condensation.  This moisture can roll down a window pane and lead to mold on the window sill, or worse, in the wall below.

What’s the best way to prevent this mold growth?  We recommend that during periods of extreme cold, make sure your indoor humidity level is reduced.  A handy gadget to help you monitor the level of humidity indoors is a hygrometer.  Some professional organizations recommend that your humidity level should be below 60 percent, but I would recommend continuing to reduce the humidity level until you no longer have condensation on the windows. You may need to keep humidity down below 20% to prevent condensation on some inefficient windows. 

If you see condensation on windows, we recommend turning down your humidifier, or turning it all the way off if that is the only way to keep windows dry.  Be sure to always operate your bathroom exhaust fan when showering and kitchen exhaust when cooking (if you have one that exhausts to the outdoors).  Only on rare occasion would you need to operate a dehumidifier during the winter time; it’s better to catch the moisture at the source.  
“Baby, it’s cold outside”, but you can still be comfortable and mold free inside your home.

Ian Cull

Ian Cull is a nationally recognized expert in the field of indoor air quality. He is the Chief Science Officer of Indoor Science, a company he started in 2004. He speaks around the world on air quality topics and is a training provider of the Indoor Air Quality Association. Mr. Cull is a Licensed Professional Engineer (PE) and Certified Industrial Hygienist (CIH). His degree is in Environmental Engineering from the University of Illinois - Urbana Champaign. Mr. Cull has developed 50 air quality related courses for the IAQA University and is the author of the book, “Fundamentals of Mold Remediation”. In his words… “Besides being passionate about indoor air quality, I enjoy cycling, music, the Chicago Bulls, and having fun with my three kids.”