Winter Mold: Why, How to Stop it, and More

Winter Mold: Why, How to Stop it, and More

November 11, 2021

It’s November, and with the cooling temperatures comes another bout of potential mold in your home.  In fact, winter tends to breed more mold than other seasons. Today we’re diving into winter mold - how it happens, how to treat it, and everything in between.

Why is mold common in winter?

With winter, comes wet weather & increased sustained indoor heat. This combo is the perfect mix for creating indoor mold.  Mold needs water to grow, and as the heat kicks in, the warmer temperatures help further expand mold in moist areas. Because of the continuous heat indoors, mold is actually more likely to grow in winter than in other seasons. 


Contrary to the thought that cold can kill mold, mold can go dormant or deactivated in cold weather, waiting for more viable conditions to reemerge. If a home though has a constant temperature between 60 and 80 degrees Fahrenheit, mold will continue to grow even as temperatures drop outside. 

Common areas impacted by mold & mildew in winter months:

  1. Windowsills:  As heat inside creeps up, contrasting with the cold or wintery wet weather outside, condensation can quickly occur on windows throughout a home. The constant film of mist on the panes and around the window’s moldings can breed mold and mildew.
  2. Attic walls and flooring:  When heat rises into the attic, it has nowhere else to go. Attics often also have ventilation windows that can lead to cooler air and moisture seeping inside. When the lingering heat mixes with the cooler surroundings (such as your cold roof), it can bread humidity and lead to mold growth on support beams and walls.
  3. Pipes & inside walls: Pipes during winter can also lead to condensation and mold growth behind your walls. This is more common in homes with poorly insulated walls, and mold can go months without being noticed.

Stopping the breeding grounds:

We’ve already discussed how mold needs humidity and moisture. By removing humidity, you can reduce mold. Here are a few tips to drying out your home in moisture-prone areas:

  • Weatherproof your attic: Make sure your ventilation is good and any air leaks are sealed. Have your roof inspected if it’s older.
  • Clean up existing mildew: Keeping your home, especially in areas like windowsills where condensation can happen, is key to keeping any mildew or mold at bay. We offer an excellent surface spray - our Mold and Mildew Stain Remover, Fast Acting PMC2010. Our own special blend will remove mold and mildew stains from walls, window frames, curtains, tile & grout, and more. 
  • Check your home after any winter storms. Check roofing, gutters, downspouts, crawl spaces, and anywhere your pipes run. Fix any leaks immediately. 
  • Reduce the potential for any pipe bursts by preventing freezing. Cut your water on slightly when temperatures are expected to plunge into freezing for prolonged periods overnight. 
  • Check window & door seals. Replace any cracked or missing seals. 
  • If you have a basement or crawl space, have your space periodically examined for cracks and repair any you notice. Leaving cracks gives water an opportunity to leak inside. 

What to do if you find mold:

If you notice condensation on walls, there may be a potential for mold to be inside the wall. Removing a small portion to inspect and run a surface test is a good idea.  You can also check other areas you notice dark spots, like windowsills or door frames with our bestselling DIY Mold Test. These tests are surface tests which means you are able to just swab the infected area directly and send it into our labs to test. Our tests are made easy to understand and use, and all come with free professional lab analysis and consultation. So you can find out what mold you have (if any) and the next steps for treatment from our experts at no additional charge. If you’re exhibiting allergy signs and think mold may be the culprit, we also offer a Professional Air Test, an advanced kit that tests the air in your home for various strains of mold and toxins that can’t be easily tested with a surface strip. Whether you decide to test on your own or hire a contractor though, we highly recommend taking a closer look if you have mold that keeps reappearing or if you suspect your home may have a mold issue.

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