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Snowfall looks beautiful at first glance, but once the weather warms it tends to leave behind quite a watery mess. And if you aren’t careful, all that moisture build-up can cause mold and mildew to grow quickly in and around your house. We asked some home improvement experts to share with us the likely trouble spots for mold and mildew growth. Read on to see what they had to say.

Daniel Kuchlik is the owner of American Restoration Solutions.

Attics, Crawlspaces, and Ductwork

There’s a common misconception that mold does not grow in the winter, but that cannot be further from the truth. We heat our homes throughout the season so the ambient temperature is much higher inside than outside. Some species of mold have also adapted to grow in colder extremes. Any location with trapped moisture is a candidate for mold growth.

In some cases, we’ve seen significant mold growth in as little as 72 hours after water intrusion. Once the snow melts we recommend homeowners check their attics, crawlspaces, and ductwork for any signs of water intrusion, leaking or damaged pipes, and visibly wet areas. Kitchens and showers that do not vent outside but vent moisture directly into an attic are a major contributor to mold growth.

When the water vapor from one of those sources meets cold winter air or a cold surface, it will condense back into a liquid and that spot becomes a prime candidate for mold growth. This also includes dryer vents, attic vents, in and around HVAC components, skylights, and crawl spaces.

Attic Walls, Underside of the Roof, Vents, and Edges of Roofing Seals

When it comes to snow thawing, you’ve got to be careful especially around your roof/attic area. Even if your roof successfully drains and runs off water adequately when it rains, you’ve got to remember that snow lingers for longer and also takes more time to melt, exposing your roof to moisture for an extended period. Once the snow melts, begin to check around the walls in your attic and the underside of your roof, vents, and the edges of the roofing seals. If you have skylights/windows in your attics be sure to look at these closely for signs of excessive moisture. These are the areas most likely to succumb to mold following lengthy exposure to snow and subsequent thawing.

Niamh Ryle, Principal Engineer at Homecheck.Jill Taylor, Full-Time Homesteader at Happy Farmyard.

Around the Home’s Foundation

After the snow thaws, mold, and mildew growth are likely to be found in areas that are shaded and damp. This could be on the north side of a building where snow has melted and pooled, or in any low-lying areas where water has collected.

Mold and mildew typically thrive in areas with high moisture levels, so it’s important to take steps to reduce moisture levels in these areas to prevent mold and mildew growth. One way to do this is to make sure that gutters and downspouts are clear of debris so that they can effectively drain water away from the foundation of the building.

Additionally, ensuring that there is proper ventilation in moist areas can help to reduce the risk of mold and mildew growth.

Roofs, Walls, Outside Areas and Other Damp Parts of the House

Molds and mildew affect roofs, gardens, house plants, lawns, walls, and damp parts of a house. The spores of fungi remain passive in summer but are activated by the moist and cold climate under the snow.

If the ground, porch, or lawn gets covered by heavy snow without getting fully frozen, fungal growth gets in on the action. Mildews and molds are likely to appear on the roof, mainly in the lawn or garden, or on leaves in this situation. In contrast, light snowfall throughout a cold winter isn’t likely to cause mold damage.

Effects of snow molds mostly appear on lawns as a form of patchy grass and discoloration. Due to snow molds, several inches to several feet across, straw-colored circular patches appear on the lawn when the snow melts. The grass tends to be matted down and crusty in these areas. However, molds inside the house appear due to prolonged dampness with no availability of sunlight.

Aaditya Bhatta, Editor, and Founder of Plantscraze.
Andre Kazimierski, CEO, Improovy.

Windows, Attic, and Basement

Once snow thaws, it’s smart to check the windows in your house for mold and mildew growth. Mold is most likely to form wherever warm air from inside your house comes into contact with cold air from outside, and windows—especially older or poorly sealed ones—are a prime target for this. Also be sure to check less-insulated parts of the house like the attic or basement, which can also be rich environments for mold and mildew to accumulate.

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