“Mold in the Cold”
Cesar Collado
December 13, 2022
Mold Growth During Winter

7 Steps to Avoid Mold Growth During Winter

by Cesar Collado

It is a common belief that mold is primarily a fall, summer, and spring issue but mold growth during the winter can be a problem.  Mold does die, it becomes dormant.  While it may seem like an off-season issue in winter due to the unnoticeable state created by cold temperatures, household mold can be just as problematic as during warmer seasons.  While the cold temperatures of winter inhibit mold growth, dormant mold still poses risks.   Snow and ice eventually melt in most geographies.  When it melts into water, dormant mold reactivates.  Water damage is indiscriminate.  There are several species of mold that grow in places with very cold temperatures, even in Arctic temperatures.  However, in almost all cases, mold simply becomes dormant at freezing temperatures. Avoiding mold growth during winter can be very important.

What is more important to understand is that temperature changes create Mold Growth During Winteroptimal environments for mold growth. Mold behaves differently in the cold within ice, snow, and water. The constant or occasional freezing and thawing leaves outdoor surfaces wet. Temperatures below 60 degrees delay the evaporation of moisture. Freezing pipes often burst.  Outside, cold hardened ground and dormant greenery slow moisture absorption, allowing for standing water accumulation.

Mold is part of the natures decaying process of organic matter and continues to grow both indoors and outdoors. Microscopic mold spores (or seeds) easily become airborne through disturbance and ventilation.  Mold spores will begin to grow when they land on a damp surface or object.  Mold spores thrive in moist, warm environments. Winter brings lots of moisture with extra rain, melting snow, and ice. The colder temperatures can mean higher temperatures in our homes due to indoor heating. Paying attention to melting ice and snow will help ou avoid mold growth during the winter.

Indoor Condensation

Condensation is the process of change of the phase of water where the vapor transforms to the liquid state. Condensation can be achieved in one of the following two ways:

Mold Growth During Winter

  • The cooling off air until its dew point.
  • Saturation with water vapor until the point that it cannot hold any further quantity of water.
  • It is unavoidable.

Condensation is considered to be the reverse reaction of evaporation, where the liquid water turns to a vapor state.

Windowsills and door frames can often be exposed to moisture due to condensation.   Anywhere condensation has built up, and in areas with poor air circulation, such as behind walls or in closed closets or attic spaces you may have amplified mold growth.

Here are the places and objects to investigate in your home where you’re most likely to discover mold during winter:

  • Walls and wallpaper
  • Roofs – especially on the attic side where there is metal or glass
  • Windows and sills
  • Pipes
  • Wood
  • Ceiling tiles
  • Insulation
  • HVAC (including plumbing and drainage)
  • Ductwork and registers

Routing inspection of these areas makes avoiding mold growth in the winter easy.


While HVAC systems are meant to be designed to consider floorplans, ductwork systems, and temperature variances in homes, the reality is that this analysis is seldom done.  Developers use existing floorplans and HVAC systems are often placed or replaced without precise calculations or balancing.  One key factor to a healthy home is that air keeps moving, as ventilation is key to a healthy home and the prevention of mold and dust reservoirs.

Mold Growth During Winter

Some Homeowners Mistakenly Introduce Indoor Humidity

To me, adding humidity indoors is insane.  But dry cold weather can be uncomfortable for home occupants due Portable Humidifierto sinuses or other moisture concerns.  As a result, many people introduce moisture into the air via a humidifier.  It is well known that humidity should be kept below 60% to avoid mold growth.  Humidifiers are unlikely to reach these levels; however, the humidifier itself creates and distributes mold. Moldy filter Air with dust is pulled into the humidifier and introduced to water and a filter.  These filters are notorious for significant mold growth.  The humidifier then draws air through the moldy filter and introduces the mold spores into the air.


Decomposing Fall Leaves and Soil

Decomposing leaves

Mold spores from leaves and soil are often tracked inside by clinging to shoes, clothing, pets, etc. During the fall, when fallen leaves decay, crumble, and break down, mold growth is a significant part of the process.  It is also impossible to keep all leaves clear of any yard.  In my experience, leaves will always continue to fall while clearing leaves.  Any rain contributes to the breakdown.


Insulation, Attics and Crawlspaces

Moldy InsulationIn the event of a small leak in the roof, it is possible that the insulation can absorb water for long periods of time.  The insulation can become saturated with mold contaminated water.

This type of contamination may create limited little dampness on ceilings and walls.  As the weather warms, the mold will activate and grow against the paper backing of the drywall and wood studs.  Moldy insulation must be replaced along with dry wall repairs wood stud cleaning.


It is normal for people to store items in cardboard boxes in basements and attics.  Because air ventilation does not often occur in unfinished spaces, moisture and dust buildup is common.  Cardboard and other paper products absorb moisture immediately and promote moldy decomposition.

Things To Do This Winter to Prevent Mold Growth

1. Keep all areas of your home as clean and well-ventilated as possible.

2. Keep Humidity Low (< 60%) and Air Moving. Invest in a dehumidifier if necessary.

3. Keep Indoor Mold-Prone Areas Dry & Clean

Regularly cleaning all mold-prone surfaces and objects to help prevent mold from building up. Focus on windows, sills, and corners in the kitchen, showers, and bathrooms.  Be aware of any areas where leaking or flooding occurs. Wash and dry bathmats, kitchen and bath towels, and other fabrics that absorb moisture. When cleaning your home, consider using products designed to prevent mold growth on hoard and porous surfaces.  I use and recommend Citrisafe Remedy products to clean mold and avoid introducing toxic chemicals into my home.

4. Don’t Forget Outdoor Water Management Maintenance

Regularly inspect outdoors areas where water is likely to enter your home.  This includes gutters, outside windowsills, sheds, and drains. All of these can allow for the buildup of standing water, beginning the decaying process, and penetration into the home.

5. Repair Leaks Quickly

It’s a good idea to regularly check drains and exposed plumbing in or around your home for leaks. Water damaged areas, where leaking or flooding has occurred, provide a unique opportunity for mold to take hold and begin to grow quickly. That’s why identifying and repairing leaks when they occur is extremely important to prevent mold.

6. Be Careful When Storing Items Away for Winter

Many of us store summer clothes, camping equipment, outdoor gear, and other warm-weather items in the basement, garage, shed, or other out-of-the-way areas. Make sure all items are completely clean and dry before storing. When possible, store summer gear in plastic tubs (avoid cardboard boxes) , or at least on shelving units that sit off the ground. This will ensure they stay dry all winter, even if leaking or flooding occurs.

7. Get Your Home Tested for Mold & Protect Your Property and Family.

ImmunoLytics provides the most comprehensive DIY testing with mold testing plates and swabs with easy-to-use instructions and comprehensive lab analysis.  Phone support by experts is a priceless value when using ImmunoLytics mold tests or interpreting results.  Click Here to buy a DIY test Kit.

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