Winter is one of the most overlooked seasons for mold growth, but it’s also one of the most important times for homeowners to pay attention to moisture, ventilation, and indoor air quality. Cold weather changes how a home “breathes,” and with windows closed, heaters running, and humidity collecting in new places, small problems can quickly turn into hidden mold issues.

As a home inspector, you have a unique opportunity to help clients stay ahead of winter moisture concerns. Here are nine practical, easy-to-share tips you can pass along to homeowners to help them keep their homes dry, healthy, and mold-free all winter long.

1. Watch for window condensation

In winter, warm and humid indoor air meets cold surfaces like window glass, and condensation forms. Left untouched, that moisture can soak into window sills and drywall.

What clients should do:

• Manage indoor humidity to minimize condensation
  • Central humidifiers attached to HVAC units should be adjusted based on the outdoor temperature
• Wipe condensation off windows daily.
• Open blinds and curtains to improve airflow.
• Consider upgrading to insulated window treatments.

Use exhaust fans in kitchens and bathrooms to reduce humidity.

2. Always use exhaust fans

With homes sealed tight for warmth, moisture has fewer places to go. Cooking, showering, and even breathing all increase indoor humidity.

Best practices to remind your clients:

• Run kitchen and bathroom fans during use and up to 15–20 minutes after as well (to eliminate residual moisture in the ambient air).
• Make sure exhaust fans vent all the way to the exterior (not into the attic or crawlspace).
• Clean fan grilles so they move air efficiently.

3. Replace HVAC filters frequently

Heaters run constantly in the winter, which means more dust, debris, and particulates are circulating through the home.

Tell clients:

• Replace HVAC filters every 30–60 days during peak heating
• A cleaner system helps control moisture and improve indoor air quality.

4. Prevent ice dams

Ice dams form when heat escapes through the attic, melting roof snow that refreezes at the edges. Water backs up behind the dam and seeps into the attic and walls.

How clients can help prevent them:

• Keep attic insulation in good condition.
• Seal air leaks between the living space and attic.
• Use a roof rake to safely remove heavy snow buildup.
• Ensure gutters are clear regularly, especially before snowfall.

If they see water stains on ceilings or soffits, that’s a sign that moisture may be entering the home.

5. Avoid overhumidifying the home

Humidifiers can make winter more comfortable, but too much humidity is one of the leading causes of winter mold. It is often a balancing act to control humidity for comfort while avoiding condensation issues.

Simple guideline:
Keep indoor humidity between 30–50%.

Homeowners can easily pick up a cheap hygrometer to track humidity throughout the season. Remember that the outdoor temperature is a major factor in condensation, and during particularly cold weather you may need to reduce the humidity indoors to avoid condensation. 

6. Check basements and storage areas

Basements can stay cool and damp in winter, especially with melting snow around the foundation.

Advice to pass on:

• Avoid storing items in cardboard boxes on the floor.
• Use airtight plastic bins instead.
• Check for damp odors around stored holiday décor.
• Keep dehumidifiers running if humidity rises past 30 – 50%.

7. Monitor for frozen or leaking pipes

Frozen pipes can burst behind walls or under cabinets, and leaks in winter often go unnoticed longer.

Tips for prevention:

• Keep cabinet doors ajar or open on particularly cold nights.
• Insulate exposed plumbing in basements, attics, and crawlspaces.
• Allow faucets to drip slightly during deep freezes (this allows water flow, preventing pipes from bursting if a section of pipe in the circuit freezes over).

If a pipe thaws and a musty smell appears, mold may already be forming.

8. Promote good air circulation

Stagnant indoor air = a higher chance of moisture settling where mold can take hold.

Tell clients to:

• Keep interior doors open to improve airflow.
• Avoid blocking vents with furniture or holiday decor.
• Run ceiling fans on low, clockwise, to circulate warm air.

9. Consider Winter Mold Testing

With everyone indoors for long stretches and heaters pushing air around the home, winter is actually an ideal time for a mold or air quality test.

It can help homeowners:

• Identify hidden moisture issues early
• Understand unexplained musty odors
• Catch attic or wall moisture caused by condensation or ice dams
• Get ahead of problems before the spring thaw

Final Thoughts

Winter may feel like a “safe” season for mold, but cold weather actually creates a unique set of risks that homeowners often overlook. By sharing these simple steps with your clients, you can help them protect their homes, avoid costly surprises, and maintain better indoor air quality throughout the season.