Moisture, Mold, and Mites: How to Control Humidity in Your Home

Excess moisture in the air can negatively affect your household’s comfort and health as well as damage your home’s structural integrity. Uncovering moisture issues isn’t always as easy as noticing drops of water running down your walls, so you’ll want to keep an eye out for all the potential signs. Take a few minutes to learn how to uncover moisture issues, what hazards excess moisture can pose, and how to address problems before they lead to lasting damage.

Does moisture matter in winter?

Humidity, which is the amount of water vapor in the air, might seem antithetical to cooler weather. But moisture buildup can actually increase during fall and winter months, when outside temperatures fall and indoor temperatures are high. The air is able to hold less moisture when it’s chilly, so water droplets condense on cold surfaces. Poorly insulated windows, walls, and doors accumulate these droplets as warm, humid air comes in contact with them.

How much moisture is too much?

Measuring the relative humidity (RH) of your environment can help you understand what adjustments you should make to the moisture levels in your home. According to the EPA, the optimal indoor RH is between 30-50%. Once your relative humidity level rises above 50-60%, there is enough moisture in the air to allow mold and mildew to flourish. At 70% RH and above, mold formation is practically to be expected. You can measure moisture easily with a moisture meter, which you can buy for around $10 at your local hardware store.

How do I know if I have a moisture problem?

If you don’t have a moisture meter, you can look for other telltale signs that there’s excess moisture in your home. Perhaps the most obvious evidence of a moisture problem is the presence of mold. Another sign that there’s too much moisture is a musty, damp smell. Because moisture tends to seep underneath wallpaper and latex paint, you can also search for peeling wallpaper or bubbles forming under the paint. Likewise, examine any wood surfaces for signs of rot. As discussed, condensation on cold surfaces marks high moisture content, so check your windowpanes. You can also see if any pipes are starting to rust.

Why mold matters

The key to mold control is moisture control.  There are many types of molds, and all require water to grow. Under the right conditions, mold can grow almost anywhere, including on carpets, between walls, on wooden furniture, and in food.

Most molds produce allergens, and breathing or touching mold can cause allergic reactions like sneezing, a runny nose, irritated eyes, and skin rashes. Asthmatic individuals are especially susceptible to mold. During an asthma attack, allergens in the environment cause the airways in the lungs to narrow, making it more difficult for air to leave the lungs. Reducing the amount of humidity in the air leads to fewer allergens in the environment, which allows the airways of asthmatics to stay open.

If you do find mold growing in your home, make sure you identify and fix the root cause. Act quickly because the longer it grows, the more damage it can cause.

The impact of dust mites

Like mold, dust mites are likely to cause respiratory issues and allergic reactions. Dust mites are made up of roughly 75% water, so their survival depends on maintaining a high water content. They must absorb water vapor from the air; therefore, the more humid a home's air, the more dust mites can be found. Maintaining an RH of under 50% has been showed to effectively reduce the growth of mite populations.

Which areas should I monitor?

In some areas of your home, moisture is unavoidable. Basements are commonly humid because of their contact with damp soil and because moisture can seep into the air through your house’s foundation. Their RH level has a large range, with some basements having an RH as high as 95%. If your basement feels damp compared to other areas of your home, you might need to address its RH. Poor ventilation in your attic can lead to condensation, encouraging mold growth and affecting your house’s structural integrity. Additionally, if you have crawlspaces, moisture from the soil can enter your home and increase the level of humidity. The RH in all of these areas can be decreased by using an effective dehumidifier (more on that in a minute).

Moisture problems can also occur in other areas with poor ventilation such as the laundry room, bathroom, kitchen, or even closets. Long showers, boiling or steaming food while cooking, drying clothes in a confined space, and even having indoor plants can cause excess moisture. Use exhaust fans in the bathrooms and kitchen to remove moisture, and as with basements and attics, a dehumidifier can be a great help in reducing moisture in these areas.


Using a high-efficiency dehumidifier is one proven way to achieve the ideal household humidity level of 30-50%. These devices are practical and cost-effective aids in lowering and maintaining the RH in your home, helping to reduce mites, mold, and other allergens over time. Dehumidifiers can be useful in laundry rooms, basements, bathrooms, kitchens, and any other room that has poor air circulation.

Whole house dehumidifiers can be installed by professionals, while you can purchase a portable dehumidifier yourself. When shopping for a dehumidifier, you’ll want to look for Energy Star certified models, which consume less energy than conventional dehumidifiers. Make sure you know what tank size you’re looking for and pay attention to how much water the dehumidifier can collect at a time. Many dehumidifiers come with a meter that measure the RH, and you can set the humidity to the percentage you desire.

For effective Energy Star certified dehumidifiers, we recommend the Honeywell TP50WKN, TP70WKN, or TP70PWKN. Each one would be a great choice for reducing the RH in your home, but you can see the chart to find the best model for you.






2019 DOE Capacity

30 pints/day

50 pints/day

50 pints/day

Tank full volume

7 pints

14 pints

14 pints

Room coverage

3000 sq. ft.

4000 sq. ft.

4000 sq. ft.

Drain pump




Ideal for

Laundry room




5-year limited

5-year limited

5-year limited



Dehumidifiers can improve your health and prevent you from having to spend thousands of dollars on damage mold might cause in the future. If anyone in your household has asthma or allergies, a dehumidifier can help relieve symptoms since a reduction in moisture means a reduction in allergens. The eradication of mugginess in the air also makes your environment more comfortable.

Note that if the temperature in the room with your dehumidifier frequently falls below 60F (15C), ice can develop on the coils inside your unit. When this happens, you need to defrost your dehumidifier, unless it’s specifically designed for lower temperatures or has an auto-defrost feature.

Other solutions

There are also some simple tricks to decrease your home’s RH. Circulation moves heat to the cold surfaces that amass moisture, so increase air circulation by opening doors between rooms (especially closet doors) and using fans. Carpets can absorb lots of moisture and serve as a tempting home for mold and mildew, so try to use washable rugs instead.

Because rain can seep into your house’s foundation and lead to moisture problems, make sure your gutters are clear and that they direct water away from the foundation. Winterizing windows with caulk can keep the interior glass warm and reduce condensation. Water from leaky pipes and dripping faucets can also introduce moisture into the air, so make sure you repair all leaks (including those in the roof or walls) and cover sweating pipes with insulation.

By taking a few steps to prevent moisture buildup in your home, you protect your home from moisture damage, improve indoor air quality by discouraging the growth of dust mites and mold, and stay comfortable. And remember: The best way to avoid moisture problems in the home is to prevent them from occurring in the first place.

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