Why Home Humidity Control Matters
- Is It a Winter Cold or Allergies?
- Dust Mite Control
- Mold Control
- What is Relative Humidity?
- How Can I Control Home Humidity?
- Questions to Ask When Looking for a Dehumidifier
- Other Mold and Humidity Control Tips
This is a tough question to answer in a few sentences, and especially without knowing your unique symptoms and their frequency. However, there could be more to your winter sniffles than it simply is the season for coughs and colds. I have a friend who seems to have chronic colds that last for months. She went to her parent's home in the mountains for the holidays and felt much better. It could be that the home cooking and time with family improved her symptoms, but maybe she is allergic to something found in her own home.
Two common home allergens that are year-round problems are dust mite allergen and mold spores. The good news is both can be controlled in a variety of ways. If you suspect that your sniffles and congestion have lasted too long to be a simple cold, or your mucus is running clear, you might first consider visiting an allergist to see if mold, dust mites or other allergens may be causing your symptoms.
Americans spend many more hours indoors during the chilly, often wet, winter months than during other seasons. And the reason most of us enjoy being inside so much in the winter is that it is warm and cozy. Sounds like a recipe for indoor allergens. The more time we spend cozying up in areas like our bedroom or family room, the more food we are providing for dust mites – remember, they feed on our dead skin cells and other organic matter.
One way to control the dust mite population in your home is by lowering relative humidity. Countless studies have shown the link between humidity and the prevalence of dust mites. The reason is simple: 70-75% of the weight of the common house dust mite is water. They maintain this needed water level through the absorption of water vapor in the air. So high relative humidity is crucial to their survival. Two of the leading experts in the field of dust mites and dust mite allergen wrote the following:
"Maintaining RH [relative humidity] below 50% is one of the most common recommendations for reducing dust mites and their allergen levels in homes because ambient RH is the key factor that influences dust mite prevalence. Mites must obtain sufficient water from the air to survive. Laboratory studies have shown that adult mites die of dehydration in 5 to 11 days, depending on temperature (25°C - 34°C) [77°F - 93°F], when continuously exposed to RHs of 40% or 50%."
Larry G. Arlian, PhD and Thomas A. E. Platts-Mills, MD, PhD. "The biology of dust mites and the remediation of mite allergens in allergic disease." Journal of Allergy and Clinical Immunology. March 2001: part 2, Volume 107; Number 3: 406-413.
Read more from our learning library on controlling house dust mites.
Moisture in your home's air not only makes the environment more hospitable to dust mites, but it also sets the stage for mold growth. Molds thrive in humidity at or above 50-55%. A musty smell in your basement or bathroom is likely a mold or mildew problem as a result of excess moisture ‒ from leaks or spills or from consistently high relative humidity. Even in wintertime, when outside air does not hold as much moisture, the home is not immune from leaks and condensation (like sweaty windows). Extra care should be taken to monitor your home's relative humidity throughout the year, especially if your region is prone to heat and moisture.
To battle the dry conditions of winter, some people use humidifiers as a way to bring moisture into the air. For many who suffer from colds or have asthma induced by dry conditions, a humidifier can mean a better night's sleep and less symptoms. However, humidifiers can present a mold or bacteria hazard if improperly used or cared for.
First, invest in a germ-free humidifier that discourages the growth of mold and bacteria. Also, be sure to regularly clean your machine following the manufacturer's instructions. Keep surrounding areas from gathering moisture, and monitor the humidity level where the humidifier is being used with an accurate humidity gauge.
To read more about mold allergen, see our learning library feature on mold and indoor air quality.
We know that relative humidity in our home should be between 45-50%, but what exactly is relative humidity? It is the measure of the amount of water in the air compared with the amount of water the air can hold at a specific temperature. For example, a 77°F room with 60% relative humidity means that the air is holding 60% of the total amount of water vapor it could possibly hold at that temperature. The higher the temperature, the more moisture the air can hold. So a reading of 60% humidity at 77°F is more severe than that same reading at 50°F.
Outdoor relative humidity levels can soar during the summer months, but even in winter, when outdoor humidity levels are lower, home humidity levels are not always in the "humidity safe zone," so it is important to monitor all year round. An instrument called a hygrometer (or humidity gauge or monitor) is used to measure relative humidity in the home and is an important tool for keeping tabs on your home's humidity levels. These inexpensive devices are a "must have" if you want to control mold and dust mite allergen. Some monitors, like this Acu-Rite Humidity Monitor, not only give indoor humidity readings, but also provide indoor/outdoor temperature readings and time of day ‒ all at the same time!
Air conditioning and electric dehumidifiers are the most effective ways to keep indoor humidity at a healthy level. Air conditioning works because cool air cannot hold as much moisture as warm air. Most dehumidifiers use this principle by using a fan or a blower to pull air in, where it then passes through a cooling coil and is chilled to its dew point. This process results in condensation on the coils, which then flows into a bucket. Some dehumidifiers allow for the collected water to be pumped through a hose and into a sink, bathtub or out a window. After passing through the coils, the moisture-reduced air is then heated back to room temperature and released into the room.
It is important to note that even dehumidifiers can harbor mold in the coils and tank if not properly cleaned. I recommend using Goodmorning Purifying Spray on vents and coils as part of a regular maintenance routine for your dehumidifier.
There are several key questions you should ask when looking at the various models and options for home dehumidification:
- Monitor and regulate relative humidity levels in your home. Humidity levels should be kept around 50%. Do keep in mind, that extremely low humidity can aggravate asthma and cause skin dryness, too low is not necessarily better.
- Provide adequate ventilation and air circulation in the home by installing exhaust fans and opening room doors and windows (individuals allergic to pollen or sensitive to other outdoor pollutants should use discretion about keeping windows open, or use a window filter).
- Keep a close eye on areas prone to condensation. Cover cold surfaces with insulation and increase the air temperature when condensation begins to appear. Excessive condensation means that the relative humidity may need to be lowered inside.
- Use products that help control mold and mildew – whether it's testing for mold, removing it, protecting surfaces from regrowth, remediating large areas of growth, or even adding a mildewcide to paints to protect walls from mildewing – there are many products that can help.
- To keep mold spores from circulating into or through your home's ductwork, use furnace filters in your central HVAC system, an air conditioner filter for your room AC unit, and vent filters to cover vent registers in rooms you use the most.
- In the bathroom, run the vent fan or open windows during and after a shower so that the moisture can dissipate. Also be aware that carpeted surfaces will absorb moisture.
- Use a mold resistant shower curtain or one that can be easily laundered.
- Through daily living, adults lose 2-3 pints of water per day (not including bathroom trips). This means that upholstered furniture and bedding can also be prone to moisture and mold growth. Our BedCare Classic mattress covers are a good precaution against mold growth and they keep away the dust mites and bed bugs, too!
- Remove mold spores in targeted rooms with a botanical air treatment system or a heat convection device, or choose from several filtered room air purifiers designed to remove mold spores.
- Keep a limited number of houseplants, and try adding a mold-preventative to the soil.
- Vent your clothes dryer to the outside of the house, and do not let clothes sit for long in damp heaps, in or out of the washer.
- Periodically check carpet laid directly on concrete surfaces, as the carpeting can absorb moisture. Consider covering concrete floors or crawl-space floors with plastic sheets or tarps in moisture-prone areas.
I hope you and your family are in good health during this coming winter's cough and cold season. And remember, if your symptoms are lingering for more than a few weeks, you may be having allergic reactions and should see an allergist. For those who know you have dust mite or mold sensitivities, try to keep indoor allergen levels under control, and make monitoring your home's humidity a habit in the coming year. Dust mites may not thank you, but your family will!