A dehumidifier works by reducing the amount of moisture present in the air. The most common type of dehumidifier pulls humid air from the room, chills the air causing moisture to condense and fall out of the air, then exhausts the now dryer air into the room.
Moisture is all around you, particularly in the air you breathe. Too little or too much of it can be harmful. High moisture content is equivalent to a high relative humidity. At best, this can feel a little uncomfortable. Worst case scenario is it causes irreparable damage to properties in the form of fungi and pest infestation, rust, and corrosion.
To prevent your humidity issues from getting worse, remove the excess moisture and keep humidity levels within the optimal range at all times.
There is a specific dehumidifier for every type of space. Learn all about how a dehumidifier can help solve your problems and start looking for the best unit for you.
What does a dehumidifier do?
The primary function of dehumidifiers is to lower the humidity levels in indoor spaces. They accomplish this through different processes. Dehumidifiers come in different sizes and capacities and other added features you may need.
There are also some secondary benefits in using a dehumidifier. Decreased humidity makes for unfavorable conditions for mold, mildew, dust mites, and other airborne allergens. Dehumidifiers work exceptionally well in eliminating unpleasant odors and improving the air quality. A less humid environment also helps dry clothes faster, preserve stored food, protect electronic equipment, and save important documents.
How does a dehumidifier work?
A dehumidifier works using different methods. The two main types of dehumidifiers are based on the process in which they collect moisture from the air: refrigerant and desiccant. A refrigerant dehumidifier works similarly to an air conditioner. It pulls in warm, moist air and condenses the moisture. On the other hand, a desiccant dehumidifier uses a substance that absorbs or adsorbs moisture from the air until its maximum capacity is reached.
How does a refrigerant dehumidifier work?
Refrigeration-based dehumidifiers are what most homeowners are familiar with. A refrigerant dehumidifier uses condensation to remove the excess water from the air. The fan draws moist air from the room. The air passes through the cooling coils. As the temperature decreases, the air loses its ability to hold water vapor. Moisture condenses and the water formed is collected in a tank or pushed out through a drain hose. Once moisture is removed, the air is then reheated and exhausted back into the room.
For further information, this video shows the dehumidification process of a standard refrigerant dehumidifier in detail.
Since this type of dehumidifier relies on the cold coils to extract moisture from the air, its performance declines dramatically in lower temperatures. Most consumer grade refrigerant dehumidifiers can only operate in temperatures as low as 41°F, while their efficiency starts to decrease at 55°F. This is because the ambient air is almost as cold as the coils and cannot be cooled further.
Additionally, condensate may freeze in temperatures about 65°F/18°C or below. To avoid this, some refrigerant dehumidifiers feature an auto defrost function which automatically stops operation to melt the ice on the coils. Some refrigerant dehumidifiers, specifically ones designed for commercial purposes, use advanced technologies to allow operation in lower temperatures without having to defrost periodically.
Because of its dehumidification process, this type of dehumidifier is most ideal to use in warm climates. It works more effectively and efficiently in temperatures above 65°F.
How does a desiccant dehumidifier work?
There are different types of desiccant dehumidifiers depending on the capacity, area of coverage, and renewability. The smallest and cheapest ones are the disposable desiccant dehumidifiers or moisture absorbers, which contain substances that absorb excess moisture. As the name suggests, they are disposed of after one use. They have very low dehumidifying capacity and do not need electrical power.
Similar to the disposable desiccant in terms of size and capacity are the renewable desiccant dehumidifiers. They typically contain silica gel which removes moisture from the air through adsorption. They also do not need to be plugged to work, but they do need to be recharged every few weeks to dry out the moisture collected.
Full-size desiccant dehumidifiers are about the same in appearance as refrigerant models but lighter and quieter since the desiccants do not need large compressors. They feature a desiccant wheel or rotor which constantly rotates inside the unit to process the air. Moisture clings to the surface of the desiccant material, thereby separating from the air molecules.
Damp air from the room is drawn into the dehumidifier and runs through the process zone of the desiccant rotor. The desiccant removes excess moisture and the now dryer air reenters the room. A heater warms the circulated air before it passes through the remaining part of the rotor in the opposite direction of the processed air. Moisture is then desorbed or transferred from the desiccant to the warm air, thus renewing the desiccant so it can adsorb more moisture. These processes occur continuously and simultaneously and the cycle repeats.
How the warm, moist air is exhausted from the machine differs between consumer and commercial models. Consumer desiccant dehumidifiers use condensers to form the water that is collected in a bucket or drained out of the unit. Commercial units release the warm, moist air outside the room and do not produce any condensate. As opposed to refrigerant models, there is almost no risk of frost buildup in this scenario since the air is warmed beforehand.
Since desiccant dehumidifiers use adsorption instead of condensation, they don’t need to cool the air in order to remove the moisture. Therefore, they can continue to operate even in low temperatures. Because the heater constantly warms the air, the condensate doesn’t freeze. This makes desiccant models perfect for colder climates. Watch this video for a comparison between refrigerant and desiccant dehumidifiers.
How does a Peltier dehumidifier work?
Another method of dehumidification that mini dehumidifiers often use is called the Peltier effect or thermoelectric cooling. It is based on the idea that a voltage of electricity creates a temperature difference between the two sides of a Peltier module.
Humid air is drawn by a small fan on one end of the unit and enters through the other, colder front side. As the air cools, the moisture condenses and drips down to the water tank. The cold, dry air then passes through the hot side. Warmer, dryer air exits through this side.
The process is not that different from that of a refrigerant-based dehumidifier, but instead of using a compressor to cool the air, a Peltier dehumidifier converts the current into a temperature gradient. As is the case with compressor models, the efficiency also decreases in cooler temperatures.
Do you need a dehumidifier?
High humidity and excessive moisture in your home can be uncomfortable. If left unattended, it can cause serious damage to structures and materials. There are many ways you can decrease humidity level or eliminate extra moisture. The best solution is by investing in a good dehumidifier. If you’re still not sold, watch out for the following common signs that you need a dehumidifier.
The most obvious reason for getting a dehumidifier is if your place has consistently high levels of humidity. The optimal indoor humidity range is 35-50%. Anything above 60% can be considered too high. These conditions either feel cold and clammy or hot and sticky. Aside from causing discomfort, prolonged exposure to high humidity can negatively impact your health. If you live in a place with humid climates or in an apartment with poor ventilation, you can expect high indoor humidity levels.
If you notice water droplets on the windows and walls, this may be a sign that your home is too humid. Condensation occurs when the warm and moist air touches a cold surface, such as the window glass, mirrors, and metallic surfaces. In worse cases, you may find water stains or damp spots in the ceilings or walls. Check your basement or crawl space. These areas are often overlooked and they usually suffer the most from high humidity.
A musty or moldy smell is a sure indicator that you need a dehumidifier. Damp and humid conditions are the perfect environment for common allergens such as mold and dust mites. Mold spores and dust mites may trigger allergic reactions or cause irritation in people with allergies or asthma. Poor air quality also takes a toll on otherwise healthy individuals.
Little black spots, especially in the bathroom walls, around the toilet and bathtub, are signs of mold growth. Wooden surfaces and other porous building materials are highly susceptible to mold and mildew if moisture levels aren’t controlled. Some common spots for hidden mold are behind furniture, under permanent carpeting, or between walls and insulation.
Rotting wood and termite infestation may be caused by excess moisture. If you notice cracks in drywall and gaps between the floor and baseboard, this may also be signs of an underlying humidity problem. The right dehumidifier can tackle all these issues while minimizing your power consumption.
Summary
There are many purposes for a dehumidifier. You can use it at any time of year to maintain proper levels of humidity indoors. In emergencies such as water damage due to leaks or flooding, high capacity dehumidifiers are used to effectively dry and restore the space. Businesses of various kinds and sizes also utilize dehumidifiers to provide good service. Dehumidifiers work using different processes depending on the environmental conditions they need to operate on. To learn more, check out our guide on the typical parts of a dehumidifier.
