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This article answers the question How Does A Dehumidifier Work and tells you how humidity levels can be lowered to make your home safer and more comfortable.

Everyone has felt that heavy sticky feeling in the air, especially during the summer. It feels hard to breath and you sweat all the time. Humidity is not only uncomfortable but it can be a health hazard as well, worsening asthma and allergy symptoms. It can also cause a lot of problems in your home. Excess moisture can create breeding grounds for mold and fungus as well as dust mites, centipedes and other pests. The best solution to high humidity levels in your home is a high quality dehumidifier. We have a list of some of the best dehumidifiers on the market on this site. Before you go out and buy one though, it’s good to know how they work, and understand a bit about what humidity is and how it’s measured.

When it’s warm and humid outside dehumidifiers are great at removing the excess moisture from the air. When humidity levels are higher it feels hotter. If the temperature is 80 degrees Fahrenheit (27 Celsius) and the relative humidity is 70% then it will actually feel like it’s 85 degrees F. On the other hand if the humidity levels drop to 30%, then the temperature will feel like 78 degrees F (25 C). You may not think so, but 7 degrees (3.8 Celsius) can make a huge difference in your comfort level.

Humidity levels are measured based on relative humidity. This is the amount of water vapor present in the air compared with the greatest amount of water the air can hold at a given temperature. So the relative humidity levels are different for different temperatures. For example, the air can hold a maximum of 18 grams (.6 ounces) of water at 68 degrees Fahrenheit (20 C). This is 100% relative humidity. So at the same temperature and 50% relative humidity the air can hold 9 grams of water.

Optimal humidity levels in the summer, indoors, should be 30 to 50%. In cooler weather 30-40%. If you can keep the relative humidity in your home between 45-50% then it will feel exactly the same as the temperature showing on the thermometer. Any higher than this and it can feel uncomfortably warm and any lower can dry out and irritate your skin and lungs. Dehumidifiers work to keep the indoor relative humidity within the optimal range. Not only will it feel better, but more importantly keeping an optimal relative humidity range in your house will protect your valuables from water damage, control musty odors, and keep harmful mold, fungus, dust mites, and bacteria from growing.

Dehumidifiers work by using built-in fans to capture and pull humid air from the surrounding area into the dehumidifier. The air passes over a set of refrigerant filled cold coils. The coils are cooled using a refrigerant like Freon. When the humid air passes through and hits the cold coils the moisture is pulled out of it. To understand this process think about the condensation that builds up on a cold soda (or beer) can during the summer. When the hot air around the can hits the cold surface it is not able to retain its moisture. The cold surface is able to pull and collect moisture from the warmer air. Hence the wet can and the need for a coaster.

Now that you’ve had an ice cold drink, back to dehumidifiers.

The water collects on the cold coils of the dehumidifier and then drips into a collection container. The water builds up in a reservoir container. Most units will automatically shut off when the container is full. With some units you need to come along and dump the water out by hand. If you have to manually remove the water then most dehumidifier containers have collection reservoirs with covers and handles to make moving them and dumping the water easier. Another option is to have this water drain to a drainage basin. Many dehumidifiers have hook ups where you can add a hose and drain the water automatically.

After the air passes over the cold coils and has the moisture pulled from it, it is then passes over warm coils where it is reheated. It is then released back into the room drier and warmer than when it entered the unit. The effect on the room is much lower levels of moisture in the air.

A dehumidifier works similar to an air conditioner. The difference is that an air conditioner doesn’t have a warm coil to reheat the air, it only has cold coils. It also only detects temperature whereas a dehumidifier has a humidistat to detect relative humidity.

Another component of the dehumidifier is the humidistat. This device lets you set the level of humidity you want in the room. It does this through a sensing element and a relay amplifier. The sensing element has two different metal conductors. When the relative humidity changes an electric resistance sparks up between the two conductors. The resistance level is then measured by the relay amplifier which sends a signal to turn the dehumidifier on or off.

You can effectively use dehumidifiers when the indoor temperature is 65 degrees Fahrenheit or higher (18 C). If the temperature goes below that, dehumidifiers will ice up and not work as efficiently. As a result you can waste of lot of money on energy. If you absolutely need to dehumidify a room that is under 65 degrees, then look for a unit that has an auto-defrost function to prevent ice formation. To save power make sure that it is Energy Star certified down to 42 degrees.

If you’d like to learn more about Choosing A Dehumidifier, we have another article on this site that tells you what to look for before you buy.

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