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7 Common Dehumidifier Questions

1. Why do I need a dehumidifier?4087-16m

Dehumidifiers are vital for environmental control in areas where humidity can rise above 50% naturally. At humidity levels above 60%, increased water vapor in the air can begin to warp furniture, accelerate wood rot, and harbor toxic mold and fungi (which will cause odors and health problems). A dehumidifier draws water from the air and collects it into a holding tank or pushes it out through a hose connection.

If you notice rooms in your house that have excessively high moisture (condensation on walls and windows), mold growth problems, or you have recently had a plumbing problem that has left your house with moisture everywhere then you should look into a dehumidifier.

If you're not sure if you need a dehumidifier or not, a hygrometer is a great way to find out how humid your area is. Typically room humidity between 30% and 60% is considered normal but this can vary greatly in cooler temperatures. This article from outlines good wintertime humidity levels. Below are their recommendations for wintertime humidity:

Outside TemperatureInside Humidity
20° to 40°FNot over 40%
10° to 20°FNot over 35%
0° to 10° FNot over 30%
-10° to 0°FNot over 25%
-20° to -10°FNot over 20%
-20°F or belowNot over 15%

2. How does it work?

Dehumidifiers work by cooling the air past the dew point and collecting the water that condenses out of the air. They do this by using a compressor system that is nearly identical to an air conditioner. Imagine a glass of cold water left outside on a hot day, the water that gathers on the outside of the glass forms because of the same principal that a dehumidifier relies on.

Once the water is condensed out of the air it is collected in a bin inside the unit and the air is heated back to room temperature and released. This process is controlled by a humidistat that measures the amount of water in the air and automatically stops the unit once the desired humidity is reached.

The biggest differences between a dehumidifier and an air conditioner are that a dehumidifier doesn't circulate the cooled air or vent the warm exhaust air out of the room. A dehumidifier actually slightly warms the air inside of a room due to the heat given off by the running components.

3. Are there different types of dehumidifiers?

There are actually two different types of dehumidifier, passive and active. A majority of the dehumidifiers on the market are active. This is because the mechanical process of an active unit is far more effective at removing moisture from the air.

Active units use the process explained above to remove moisture from the air. Passive dehumidification relies on specifically engineered silica called Desiccant that absorbs moisture. This same material can be found inside new shoes in small packets that are designed to absorb moisture and prevent damage from moist environments. Unfortunately, passive dehumidifiers often have a limited lifetime and can only absorb a fraction the amount of humidity that active units can.

4. How much moisture can they remove?

Typical humidifiers remove between 20 pints (2.5 gallons) and 70 pints (8.75 gallons) a day. Some heavy duty humidifiers can remove more than 90 pints per day and miniature Desiccant humidifiers remove less than a pint a day (ideal for keeping small spaces like a closet or cabinet dry).

5. Is there any regular maintenance?

Dehumidifiers typically require very little maintenance besides draining the water that is collected in the bin. Depending on usage and mold content you may have to occasionally wash the collection bin with a light bleach solution to prevent excessive buildup of mold. Some dehumidifiers can be set up with continuous drainage that eliminates the need to drain the unit and can be a real time saver.

Some dehumidifiers also have filters that need to be cleaned or replaced from time to time. This will vary greatly depending on the model you choose and type the type of filter it uses.

In addition, most units include a humidistat that measures the humidity in the room and tells the unit when to run. If this is incorrectly set or broken the unit may constantly run and waste energy or never turn on and leave the room humid. Checking the unit for correct operation at the beginning of the season is enough to ensure that it is in working order.

6. Will it be noisy?

Most humidifiers are designed to be used in a regular room and as such do not produce a loud noise. The noise of the compressor is similar to that of a portable or window air conditioner except without the fan noise associated with an air conditioner. A low hum should be all you notice from most dehumidifiers.

7. How much energy will it use?

This will very greatly from model to model depending on capacity, design, and usage but you should expect a typical unit to use anywhere from 50 to 800 watts. Many models are energy star rated so you can have peace of mind that your energy bill won't go through the roof.

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