Dehumidifier for basement: a complete guide post image

Dehumidifier for basement: a complete guide

Most homes have a basement which is used both as a storage unit and a functional living space. Just as it is important to control the humidity in our rooms, the relative humidity in our basements too need to be regulated, to prevent damages to both home and health.

But unlike our other spaces, humidity levels in basements are more. It needs a stronger controlling measure, such as with a dehumidifier. But not any usual dehumidifier, but a basement dehumidifier.ย 

If your home has a basement, then this article will be of helpย to you, as we have covered everything you need to know about keeping your basements humidity-free by using dehumidifiers.

What causes damp basements?

Have you ever wondered why your basement was so damp and cold? Typically damp basements occur due to water leaking into the space. The source of water leaks can be:

Ground and rain water seepage. Source: University of Minnesota Extension

  • Cracks in the foundation, lack of effective grading,ย  gutters and downspouts due to which there is seepage of ground or rain water.

Exterior humid air. Source: University of Minnesota Extension

Gaps in windows or walls, through which outside humid air enters and condenses on the cooler inner surfaces of the basement.

Interior water sources. Source: University of Minnesota Extension

Leaking pipes and other sources of moisture like appliances (dryers, improperly vented air conditioners) and daily activities (cooking, washing and taking showers).

Often, the dampness in your basements can be attributed to one of these causes.

How to look out for damp basements?


These are the top 5 signs by which you can identify if your basements are damp:

  • Musty odor, mold and mildew growth.
  • Peeling paint, which indicates that water is seeping in through the wall.
  • Damp or patched walls.
  • Rotting wood.
  • Spalling and efflorescence. Both these issues are caused due to salt deposits forming on the walls. Spalling describes the flakes of wet concrete or bricks, while efflorescence is used to describe the grayish, white ash seen on the walls of the basement.

Do we need basement dehumidifiers?

When the humidity level in your basement exceeds 50-55% and you spot the above mentioned signs, you know that you need a dehumidifier. But it must be noted that dehumidifiers used in your rooms may not suffice for your basements.ย  Instead we need a specially designed basement dehumidifier.

What are basement dehumidifiers?

Basement Dehumidifier. Source: The Soothing Air

Basement dehumidifiers are nothing but portable dehumidifiers with additional features and settings that allow it to to function effectively in a basement.

Why use a basement dehumidifier?

For tackling humidity in basements, we recommend the use of basement dehumidifers for two main reasons:

  1. Low temperature: Temperature in basements are lower thanย  temperature in other areas of the house. Dehumidifiers used in rooms are effective only when used in an environment of 65 degree Celsius or more. However, since basements are cooler (with temperature of 55 degree Celsius or lesser), dehumidifiers used in the house may not be effective in removing moisture from the basement. Basement dehumidifiers, on the other hand are specially designed to function in low temperatures effectively.ย 
  2. Drainage: Most basement dehumidifiers are equipped with an automatic switch off and drainage feature (internal condensate pipes orย  gravity-fed pipes), which saves us the trouble of manually draining the water. As basements are rarely occupied, these features are crucial as it enables us to maintain our basement humidity easily and without additional efforts.

How does a basement dehumidifier work?

A dehumidifier regulates the amount of moisture in the air to ensure that your space has the desired relative humidity.ย 

Image result for basement dehumidifier working mechanism

Source: AchooAllergy

This is attained through the following steps:

  1. Air from the room is drawn into the system.
  2. The air is cooled as it passes over the cooled coils.
  3. The cooled air loses its moisture. The moisture or dripping water is collected in a tank or bucket.
  4. The air then passes through the heat recovery system and is reheated (to a temperature 2 degree Celsius lesser than the original temperature).
  5. The drier and warmer air is circulated back into the room.

The advantage of basement dehumidifiers is that it willย automatically switch off when the drainage tank is full or if it has achieved the desired or selected level of dryness in the basement.

To summarise the working mechanism of dehumidifiers can be stated as: damp air which is drawn into the dehumidifier is cooled, dried, heated and circulated back into the room.

What does capacity of dehumidifiers mean?

Dehumidifiers come in a variety of sizes and designs. The capacity of a dehumidifier is the measure of the amount of moisture that it can draw from the air within 24 hours. Therefore we can classify dehumidifiers as:

  • High capacity dehumidifiers which are capable of drawing a lot of moisture from the air within the specified time. These are optimal for use in medium and large spaces.
  • Low capacity dehumidifiers which can be used in small spaces.

How do I choose a dehumidifier for my basement?

When selecting a basement dehumidifier, you must consider the following factors:

1. Size of basements: The recommended size of dehumidifiers vary from model to model and manufacturers. Therefore, to start with, you should know the size of your basement. For instance:

  • An extra large basement (5000 square feet) will require a high capacity dehumidifier that can pull up to 90 pints of moisture from the air within a day.
  • Medium sized basements (up to 3000 square feet) require a 70 pint humidity control system.
  • Smaller sized basements (500 to 1000 square feet) can be dehumidified using a 30 pint or 50 pint capacity dehumidifier.

For best performance, you should ensure that the size of your basement is smaller than the recommended size.

2. Level of dampness:ย You must match the capacity of the unit with the level of dampness in your basement. The more damp the area, the higher capacity unit you will require. Here is a sizing chart given as per the recommendation by Association of Home Appliance Manufacturers (AHAM), listing the size of basement, level of dampness and capacity of unit for basements.


3. Accuracy of Humidistat: Every dehumidifier is equipped with a humidistat to detect the humidity level in your basement. This sensor automatically regulates the dehumidifier (switches it on and off) till it attains the required relative humidity (between 30-50%) within the space. When selecting the unit, check the reviews and choose one which has an excellent rating in humidity-accuracy tests. That unit will be more accurate in bringing down the humidity to the selected levels.

4. Noise levels: The internal fans and compressor of the dehumidifiers are responsible for the noise emitted by the unit. As noisy and loud units are not appealing, it’s best to choose units that have low noise levels ( less than 50 decibels).

5. Type of unit: Dehumidifiers work in two ways:

  • Refrigerant method: In this method the air is dehumidified by means of a compressor and refrigerant similar to an air conditioning system. This model is best suited for basements that are humid and hot, but can also be used in basements with low temperatures (below 50 degrees). However in low temperature basements,ย  the unit may remove the moisture less efficiently and will need a defrost mode.
  • Desiccant method: Dessicant dehumidifiers remove moisture from the air by adsorbing it using a desiccant material. When compared to the refrigerant model, desiccant models have lower efficiency. But these units are actually suitable for use in basements which records lower temperatures as it is not affected by frost.

Having said this, if your primary goal is to reduce the humidity the refrigerant model is still a better choice as dessicant models have poorer efficiency.

6. Defrost mode: For units used in basements with low temperatures a defrost setting is essential. This is to prevent frost formation on the evaporator coils. The anti- frost sensor will temporarily switch off the compressor, which in turn stops the cooling of evaporator coils allowing the frost to melt.

7. Energy Efficiency: Check reviews to choose units that are rated high in energy efficiency .

8. Water drainage: Most dehumidifiers come with a reservoir for holding the accumulated water. The capacities of these reservoirs vary from one model to another. In high humidity environments, a dehumidifier can fill its reservoir a couple of times in a day.ย  To avoid overflow of water, choose units with an automatic shut off feature. This triggers the unit to switch off when the reservoir tank is full.

Similarly you can avoid the hassle of manually draining water, by choosing units that have gravity – fed pipes, through which water is drained away to an external sink by means of gravity.

If this method does not work for you due to issues of vertical distances, then choose a unit which has a built in pumping mechanism or internal condensate pumps. This mechanism allows the unit to pump the accumulated water to sinks that are a couple of feet above them.

Where should you place the dehumidifier?

If your unit has a top air discharge then it can be placed against the wall. Otherwise the unit must be placed at least six inches away from walls or other structures to prevent obstruction to airflow both in and out of the dehumidifier. Make sure to place the dehumidifier on level ground for it to work properly.

How to install a basement dehumidifier?

Before installing a dehumidifier, ensure that your basement is ready for one, by sealing the room. In order to be effective a dehumidifier must operate in a sealed space. Close all windows and doors, leading to and away from the basement. This helps to seal the room and prevents outside air from entering the room.ย  Installation of the unit can be easily done by:

  • Placing it in the correct position, near a grounded electrical outlet and away from dust and dirt sources. This helps to keep your unit clean.
  • Connect the unit to a proper draining facility. When setting up water drainage system, make sure that it is not near electrical circuits and other devices. Also keep drain hoses away from other electrical cords. If you are planning to use a hose to drain the dehumidifierโ€™s water bucket, make sure the unit is placed near the floor drain or sump to avoid the need for a long hose, as these can be a tripping hazard.
  • Plug it in.

What temperature should be set?

Initially, when the dehumidifier is being used for the very first time, set the relative humidity level to the highest setting (or driest). Usually the unit can be set at a range of 30% to 90%. Once the unit has been used a couple of times, or undergoes some cycles, you can activate the unit’s automatic humidistat and set the level you require.

How to maintain a basement dehumidifier?

The air filters must be cleaned regularly, as clogged filters can reduce the performance of the system by obstructing airflow. You must also keep the reservoirs clean and ensure that it is properly drained to keep the unit functioning properly.

Basement dehumidifiers are therefore a powerful tool against high humidity levels in basement. Even so, the unit can be effective only if the root causes or sources of humidity has been addressed.

Thus you can attain hygienic and damp free basements by resolving the sources of humidity along with the use of a basement dehumidifer.

FYI: The Air Geeks' top-rated dehumidifiers tested in 2021:
1. Frigidaire - FAD954DWD : the best of the best (very large rooms)
2. Homelabs - 70 Pint: great value (large rooms)
3. Homelabs โ€“ 50 Pint: good brand, good price (avg. rooms)
4. Black+Decker - BDT30WTA: a very good entry-level option (small rooms)