Dehumidifiers

Eliminating Allergens

Dust mites and mold are the two most common allergens present in higher humidity environments. These allergens do not require water to grow – they only require humidity levels at or above 65% to 99% at the surface on which they grow.

Dust mites live in upholstered furniture, carpets, and mattresses. They absorb their moisture needs from the air. If the relative humidity is below 50%, according to Dr. Larry Arlien at Wright State University, dust mite infestations will be eliminated.

Molds are fungi. They only require high humidity and an organic-based material on which to feed. It is no surprise that they are plentiful in humid environments. Cooler surfaces create a perfect breeding area for mold because the relative humidity at the surface will be near 100%. The surface may even be wet with condensation.

Mold growth can be eliminated in the home through humidity control that maintains reduced relative humidity levels and prevents cooler surfaces from becoming damp. To avoid the problems caused by moisture, and to create a comfortable environment, a dehumidifier is necessary to maintain relative humidity between 45-50% throughout the home. Keeping your relative humidity at 50% or less eliminates mold, mildew and dust mites.



Humidity problems in the basement?

Basements are naturally cooler than the rest of the house, which makes them subject to high humidity. Because the basement floors and walls are in contact with the soil, and soil temperatures several feet below the surface remain at a constant temperature of 50°-60°F or less, basement floors and walls tend to remain cool. Also, basements generally do not have windows and so there is no solar heat gain. Therefore, since basements tend to be cool and cool air holds less moisture than warm air, basements will have higher relative humidity.

Moisture is the most common problem in basements—either entering from outside sources or being produced inside by the occupants’ activities. The soil around the walls can contain a large amount of moisture from surface water that is seeping down or from a high water table. Water can find its way inside by gravity or through a crack or flaw in the water protection layer of the foundation. Water can also be pulled up by a “wicking action” or “pushed up” by hydrostatic pressure from the soil under the walls or floor.



• High humidity levels in the basement encourage rust, mildew, mold and odors.
• Most anything stored in a basement is vulnerable.
• Additional health risk is added where there are allergies to mold and dustmites or if a family member has asthma.
• To protect your family and the investment you have made in your home, maintain 50% relative humidity as recommended by the EPA.

Excess moisture, introduced by way of unsealed, vented crawlspaces, contributes to wood rot, mold growth and increased pest activity. Moisture in crawlspaces often migrates to the upper levels of the home through a “stack effect.” In essence, whatever air is below the house is also in the house. As warm air rises and escapes through the upper levels of the home, new air finds its way into the home to replace what’s been lost. Intake air comes in at the lower levels – through unsealed crawlspaces. This may lead to costly problems such as cupping of hardwood floors, mold growth, increased air conditioner loads, and swelling of millwork/cabinetry. Air infiltration from the crawlspace often carries odors and may contribute to poor indoor air quality and uncomfortable humidity levels.



Excess moisture in crawlspaces has also been associated with contributing to increased energy consumption. Wintertime ventilation cools the crawlspace contributing to heat loss from the home. In the summer, introducing warm outside air under the home contributes to heat gains, increasing cooling loads. Ventilation of a crawlspace to control relative humidity only works consistently in an arid climate. In most climates, ventilation can actually add significant quantities of moisture during humid times.

Venting a crawlspace will either add moisture to, or remove moisture from, a crawlspace depending on the moisture content of the ventilation air compared to the desired conditions of the crawlspace. Venting with dry air reduces moisture levels in the space, while venting with moist air contributes moisture. It is false to assume that venting will automatically bring in “good” air and push out the “bad” air. If the outside air is humid and the crawlspace air is humid, you’re not making any improvements by venting. Since venting either wets or dries the space depending on outside conditions, there is no way to guarantee a specific moisture level in a vented crawlspace.