How Does a Dehumidifier Work to Prevent Mold?

Depending upon the temperature of the air, it can hold a certain amount of water vapor.  This ratio of water vapor contained in the air compared to the total amount it can hold is called the relative humidity.  In an effort to prevent mold growth, it is important that the relative humidity in your house be maintained at less than 50%.  This can be measured very easily by use of a humidity monitor. The use of proper ventilation including exhaust fans can help achieve this level of humidity, but sometimes you need extra help in order to keep the level within this range.  This can be achieved by use of a dehumidifier.  So how does a dehumidifier work?  It uses the same principle that causes your nice cold glass of iced tea to “sweat” on a warm summer’s day.

A fan in the dehumidifier pulls in moist air from the surrounding environment.  This moist air is then passed over cooling coils which decrease the temperature of the air thereby forming condensation.  This drier air is then redistributed into the room.  The condensation which forms on the cooling coils is collected in a reservoir which is then emptied either manually or by a hose.

PictureNameCapacityEnergy Star CertifiedPriceRating
Frigidaire FAD704DWD Energy Star 70-pint Dehumidifier70 pintsYes$$4.3
Danby DDR70A2GP Dehumidifier70 pintsYes$$4.5
Soleus Air DP1-70E-03, 70 Pint Portable Energy Star Dehumidifier, White70 pintsYes$$$4.1
Friedrich D70BP 70 Pint Dehumidifier with built-in drain pump, front bucket and continuous drain70 pintsYes$$4.0
DeLonghi DD70PE Dehumidifier70 pintsYes$$$3.5
Sunpentown SD-65E 65-Pint Dehumidifier65 pintsNo$3.5

Choosing a Dehumidifier

When choosing a dehumidifier, there are several important questions to ask yourself.

  • How many square feet am I trying to dehumidify?
  • Is this a crawl space or unfinished basement?
  • Do I live in a humid climate?
  • Will the dehumidifier be exposed to low temperatures?
  • Do I have a mold problem or musty smell?

These questions can help determine which dehumidifier would be most appropriate for your individual situation.  If in doubt, it is better to purchase a larger unit rather than a smaller one as a larger unit will have an easier time maintaining the correct humidity.  Many dehumidifiers are sized based on the amount of water that they are capable of removing in a day.  For instance, let’s say you are looking to dehumidify an area that is 900 square feet in size.  You are better off choosing a unit that is rated to remove 70 pints of water a day and cover 1400 square feet rather than a unit that is rated to remove 50 pints a day and cover 1000 square feet.  Even though your 900 square feet would fall within the range of the smaller unit, it will have to work much harder to maintain the correct humidity than if you purchase the larger unit.  Keep in mind that manufacturers assume you have 8-foot ceilings when calculating the area that each dehumidifier will cover.  Therefore if you have 12-foot ceilings, you need to add 50% more area to your square foot calculation to get the correct size.  If the size of your room is 20 x 20 with 12-foot ceilings, you need a unit that is rated to cover at least 600 square feet, but if you only have 8-foot ceilings, then you only need a unit that will cover at least 400 square feet.  If you are looking for a dehumidifier to place in the kitchen or other living area, it is also important to choose a quiet model that will not interfere with your daily activities.  For the lowest operating costs, look for a model that is energy star certified.

Top Dehumidifier Picks

Frigidaire Energy Star 70-pint Dehumidifier

The Frigidaire 70-pint Dehumidifier is an excellent choice if you are looking for an energy star certified unit that can cover up to 1400 square feet. This is a quiet unit which can be placed in any room of the house. It offers electronic controls with digital readout and has two fan speeds. The caster wheels make it easy to move the unit to any space where it might be needed. It will automatically shut off when the tank is full and will alert you that it needs to be emptied. The bucket is easy to remove and empty or the unit can be hooked up to a hose or optional pump for continuous drainage. It also includes a washable filter and indicator light to let you know when the filter needs to be cleaned.

Danby 70-pint Dehumidifier

The Danby 70-pint Dehumidifier is also a quality unit that is energy star certified and among the quietest units to operate. It has electronic controls, two fan speeds, a washable air filter, and casters for ease of use. It also has an automatic shutoff when the bucket is full. An auto de-icer and low temperature operation mean that you can use this unit in temperatures as low as 41 degrees. The Danby is a dependable unit that comes with a two-year warranty.