A Beginner’s Guide To Dehumidifiers

It is possible that there might be excessive humidity felt at some point in time. However, it might not be obvious for you to explain it precisely. When humidity is high, the air seems to be quite heavy, due to which it feels as if you are wearing thick-coated attire like a sweater. This soggy and bulky feeling is because of the high moisture content in the air, also known as high humidity.

In a hot and humid climate, a residence needs to have thick insulation, low solar gain windows, and energy-efficient appliances. In such a home, an air conditioner will not work like that in your neighbour’s, which is commendable.

However, a major con here is that the air conditioner will rarely operate, especially when there is no active cooling. This can consequently lead to increased humidity levels indoors. This is exactly the time to use a dehumidifier.

Understanding Humidity and High Humidity

The air tends to embrace a fixed quantity of water vapor depending upon the temperature. The ratio of actual vapor to what the air can hold is termed relative humidity, which is referred to while speaking about the air’s humidity level. When this ratio rises, it leads to high humidity. A humidity level of above 50% is too high.

It might seem that the air is dry, perhaps due to central heating, but there can be much moisture around. In case you take frequent showers in a day, do stove-cooking or dry laundry without suitable ventilation, or ventilate more during summers, there is no doubt that the humidity levels are amazingly high.

While causes of high humidity are not most cared about, effects are what users mostly focus on. The most common effects or symptoms are as follows:

  • Frizziness in hair.
  • The disrupted ability of the body to cool down, which can invite different disorders, including stroke and upset stomach.
  • Allergy including asthma.
  • The stuffy and overcrowded room, even if there are two people.
  • Wet stains on ceilings or walls.
  • Moldy smell.
  • Increased dust mites, fungus, and mold.
  • Condensation on windows, blistering paint, and peeling wallpaper.
  • Rotting wood stuff.
  • A sudden attack of unwanted pests, such as bugs.

Several types of molds are possibly risky enough to trigger many health problems. This is a major reason why indoor humidity level matters.

High humidity can lead to different problems, from moldy clothes in a closet to computers short circuits and malfunctioning ocular devices to a disrupted respiratory system.

As per a scientific review of humidity’s effect on health published by Arundel et al in 1986, high indoor humidity levels can bring in breeding bacteria, fungi, mites, and viruses along with more respiratory infections. To avoid this, the Relative Humidity (RH) level should be brought down to 40 -50%.

This is exactly what a dehumidifier can help you achieve in humid spaces. It can also relieve respiratory problems due to fungus, mold, and mites thriving in too moist areas.

You can check out the humidity level in your residence as per your region by using Indoor Humidity Meter at weather.com.

Overview of a Dehumidifier

A dehumidifier is a simple appliance designed to bring down the air’s excessive humidity or moisture level. If we have to take an analogy, a dehumidifier is much like a refrigerator that is not entirely clad. It might sound strange, but it is true. The basic powered functionality of a dehumidifier is identical to that of a refrigerator. Expansion and gas compression occur to reduce the temperature of metal coils to a freezing point.

Nevertheless, rather than the cooling action-oriented into a closed box, moist and warm room air is blown over the cold coils. The moisture present in the room air condenses on these coils to get transformed into liquid water. This water gathers into a pan or gets drained. This moisture is removed, and the room air returns to the room a bit warmer than its original state.

In both commercial and residential settings, a dehumidifier is often installed in regions that are most susceptible to excessive moisture. These regions or areas are kitchens, basements, bathrooms, pools, spa rooms, crawl spaces, workshops, and warehouses.

Benefits of a Dehumidifier

Listed below are the major advantages of a dehumidifier:

  • Highly inhospitable home for allergens.
  • Quiet to run in the background without guests noticing it.
  • Efficient performance.
  • Reduced moldy or rotting odors.
  • Lowered risk of mold on furniture, clothing, and linens.
  • Reduced skin and respiratory irritation for easier and more comfortable breathing.
  • Less humid environment, giving way to faster drying of clothes, lasting freshness in cereals and bread, and fewer chances of rust or corrosion on electronics and other tools.
  • Reduced dust levels, meaning no frequent cleaning.
  • Reduced energy bills, as it contributes to efficient running and more lifespan of an air conditioner (more humid air means harder working of air conditioner, which may result in its wear and tear sooner).

How Dehumidifier Works

A dehumidifier is also somewhat like a vacuum cleaner, as it pulls in air from room air, removes moisture from it, and releases it back into the room. The procedure of removing the moisture is much like an air conditioning unit working a bit similar to a refrigerator.

Let’s look inside a dehumidifier and find out what all the bits do. There is no need to get confused due to all these analogies. Let’s directly explore the parts and procedure straight away.

The Principle

According to the type, the working of a humidifier may vary a bit, although the basis remains the same. The most common type works by utilizing the vapor-compression refrigeration cycle.

In this process, the moisture is removed by passing the air through a cold surface for it to condense. This is similar to the process of adding icy cold drinks into a glass with the external glass getting damp with moisture from the air.

Pulling moisture from room air to reduce overall humidity is all dehumidifiers’ basic working principle.

The Parts

Each dehumidifier comes with a few basic components packed within the external plastic case.

  • Fan Compressor: Compresses and expands gas, pulls in air and spreads a cooling agent over the coils.
  • Condenser: This is a black part similar to a radiator and becomes warm when the humidifier runs.
  • Fan: Moves the air over the evaporator coils and condenser.
  • Evaporator: This is a set of aluminum fins that get cold.
  • Compressor Cooling Coils: Cool down the air to consequently remove the moisture.
  • Re-heater: Reheats the air blown back into the room.
  • Reservoir: Gathers condensation from the coils.
  • Collection Tank: Collects condensed drops and shuts off if it is full (a sensor is there for detection).
  • Optional Parts: Include a humidistat to detect the current humidity level, a hose hookup for the reservoir, and a condensate pump to push out water from the unit.

The Working Process

Now that you know the components let’s see how they work in coordination to remove moisture from your room’s air.

The entire process is quite straightforward:

  1. The fan moves the highly moisturized air from the room and pulls it profoundly within the appliance.
  2. The air now goes through the compressor cooling coils for cooling down.
  3. The coils bring down the air’s temperature for transforming the moisture from steam to drops, which is called condensation.
  4. On the coils, this water rests and becomes bulkier, with more water being added. This leads it to trickle into the reservoir.
  5. The de-moisturized air is reheated and emitted from the reheater into the room.

If there is a humidistat, it senses the humidity level to decide whether to shut down or continue operating. It enables you to program the dehumidifier to continue operating until the air reaches up to a specific level of moisture, after which it can be shut off automatically.

The humidistat usually has two parts: Relay amplifier and sensor, which are a bit complex. Changes in the moisture level of air passing over the sensor trigger an electrical resistance between the sensor’s two metal strips.

When the right level of resistance is achieved, the relay amplifier comes into action to turn the dehumidifier on or off, as per the setting you prefer. You can set the unit to the maximum setting for continuous operation.

There is usually a plastic bucket shipped with the unit for removing water from the reservoir. If there is a hose hookup, it runs directly into a drain, making sure that you do not have to empty the gathered moisture.

Many models have an auto-shutoff mechanism to read the reservoir’s water level and shut down the process to prevent overflow.

Basic Functionalities

Most dehumidifiers come with a few basic functionalities, which you should consider for your model.

  • Auto Humidistat: For maintaining a preset humidity level by automatically turning on or off.
  • Auto Reset: For turning the appliance automatically on after a power cut, which is handy if you are away from home.
  • Automatic Shutoff: For turning off the unit when the water collector is full, which not only gives peace of mind but also saves energy and keeps overflowing at bay.
  • Washable Air Filter: For cleaning the air by taking away dust and other contaminants causing allergies, especially convenient if it is washable and detachable easily.
  • Timers: For automatically turning the unit on and off at some times during the day, which saves both time and power costs.
  • Internal Pump: For continuous use without bothering about emptying a tank, as a hose reaches up to a sink.
  • Direct Drain: For draining water via a hose into a drain at the floor level for non-stop usage of the device without bothering about emptying the tank or bucket, which is essential to have if you are away from home.
  • Water Tank or Bucket: For gathering water after being absorbed from the air.
  • Caster Wheels: Casters: For carrying the unit effortlessly from one place to another.
  • Auto-Defrost: For automatically switching off the device until it defrosts if frost is seen on coils when the temperature goes below 65 degrees Fahrenheit, which saves much energy when frost does not allow it to work properly.
  • Remote Control: For conveniently adjusting the settings from across the room.
  • Multi-Speed Fan: For changing the fan’s speed as per the time, the quantity of moisture, or as per the room in which the unit is running, which contributes to noise control and energy saving.
  • Signal Light: For knowing when the tank is filled with water.
  • Filter Indicator: To alert you when to change the filter.

Types of Dehumidifiers

Experts have classified dehumidifiers into various categories according to different criteria. When selecting one for your home or office, it is essential to choose the right type of dehumidifier. It is perhaps the first thing you need to consider.

Below are the two major classifications.

Types of Dehumidifiers as per the Technology Use.

There are mainly four types of dehumidifiers in this category, each differing in terms of the working mechanism. A majority of them are available in the capacity range of 15 to 60 pints (473 ml = 1 pint) as well as retain an efficiency rating of 60% RH level per kilowatt-hour.

However, when buying any of them, it is also essential to find out the efficiency rating.

Heat Pump/Refrigerant/Mechanical/ Condensation Type Dehumidifiers

These models are ideal for home applications, as they are suitably the most effective ones for that purpose. They work with the help of a heat pump, fan, and heat exchange coils for removing moisture.

The heat pump pulls the air from your room via the fan and the coil. This coil retains itself at a freezing temperature point. As the air passes through the coils, the moisture switches from gas to a liquid, then gathered into a reservoir.

Another heated coil warms up the dry air and exhausts it at room temperature. The process recycles to retain a favorable humidity level and is ideal for homes.

Usually, these dehumidifier models are priced at $150 to $400, while a few upscale ones may cost $1,500 or even more.

Chemical Absorbent / Desiccant Dehumidifiers

These models work ideally in industrial processes, as they consume a lot of energy. However, they are more economical than the above ones when dehumidification needs to occur at low humidity or low-temperature level.

They are composed of a chemical drying agent or desiccant. Most of them come with silica gel and desiccant adsorbents for absorbing the air’s moisture.

The gel is usually heated and wedged onto a wheel to absorb water molecules from humid air pulled with a fan. In contrast, a distinct loop dries it and exhausts the moist air through an external vent.

Dehumidifying Ventilators

These models are the simplest ones and are ideal for a few crawl spaces, attics, and basements. They work by pumping out the humid air from the room through an external vent.

These units have an exhaust fan and a sensor controller that activates the dehumidifier while coordinating with the fan when humidity is up at a particular level. These dehumidifiers are fairly economical but do not work as effectively as a heat pump or desiccant ones in sticky conditions, as they pull outside air into the house. At the same time, they might depressurize the area and result in gas spillage.

Thus, you need to ensure that proper ventilation is there for gas furnaces.

Homemade Dehumidifiers

These models are made at home using de-icing salt containers to absorb moisture from the air. The salt then trickles the trapped dampness into the bucket below.

For proper working, you need to replace the salt regularly.

Compressor Dehumidifiers

These are much like a fridge or an air conditioner. They consist of a metal plate that cools down and allows moisture from the air to condense.

A fan also pulls the room air constantly and moves it over the cool plates. The cool, dry air reheats while going over a hot coil before being blown back into the room.

These models are generally shipped in larger units and remove big moisture volumes most effectively at standard room temperatures. However, they can consume a lot of power and be somewhat noisy.

Moreover, they require maintenance after two years for gas refilling, are heavy, and unsuitable for cooler rooms. They are only ideal for home’s normal living areas.

Electronic Dehumidifiers

These models have a heat pump to create a cool surface for condensing moisture from the air. There are no moving parts, and the design is simpler. These units are quieter than other types but have poor energy efficiency and the quantity of moisture removed.

Therefore, this technology is used in small models designed for small areas with mild issues, including a kid’s sleeping room, boats, and a hallway.

Types of Dehumidifiers as per Usage or Applications.

By scope and usage, there are three types of dehumidifiers.

Portable Dehumidifiers

These are handy when you wish to dehumidify only one room or a single space without carrying much load in hand or carrying a heavy unit weighing over 100 pounds upstairs.

A portable dehumidifier works well with a long cord to cover every corner. Those with built-in humidistats directly as well precisely get the required RH level. These models can remove only up to 30 liters per day.

Basement Dehumidifiers

These are for the basement and other areas where molds and moisture levels tend to exacerbate. While you can use portable models, these are specifically for basements.

However, it is essential to repair a few unfavorable conditions such as cracked floors or walls, condensation, and mold stains before using these units.

Whole House Dehumidifiers

These units tend to cover the entire house, due to which they better safeguard your furniture items and keep cracks, rust, molds, and warping away.

A few of these can remove even 100 pints of moisture each day. Well, they are costlier and demand frequent maintenance.

Industrial or Commercial Dehumidifiers

They are designed for industrial applications and remove up to 1,200 liters per day. They are either fixed by being mounted to the ceiling, floor, or wall or are portable with wheels carrying the bulky size.

Types of Dehumidifiers as per Capacity.

  • Small: These models discard 25-40 pints of moisture per day and are ideal for small damp but not wet areas. Consider it for the living room or bedroom.
  • Medium: These units discard 45-60 pints per day and are ideal for areas that smell wet, have leakage, and have sweating floors and walls.
  • Large: These units discard 65-70 pints and are ideal for too wet areas or big rooms. Consider it for big unfinished basements susceptible to excessive leakage.


You should choose a dehumidifier as per your specific requirements. Most models tend to last from 3 to 15 years, but the exact lifespan is significantly dependent upon the manufacturer’s suggested maintenance. As a tip, always go for an Energy Star rated model, as it indicates energy-efficient design.

Further, always evaluate the models based on three factors:

  1. Capacity.
    Pints of water discarded in 24 hours in a standard condition of 60% RH and 80 degrees Fahrenheit.
  2. Efficiency.
    Liters of water removed per kilowatt-hour of power consumed – it should be larger.
  3. Function.
Mas Broto

Written by: Mas Broto

Mas Broto is a small business owner with 30 years experience in the real estate industry. He is the founder and editor of theDailyThrive.net, the most comprehensive free home improvement website on the planet!