How to choose a dehumidifier?

How to choose a dehumidifier? post image

In recent years, more and more homes are turning to the dehumidifier to simply and effectively solve the problems caused by excess moisture in both houses and apartments.

Problems range from the appearance of mold on the walls and furniture through to peeling of wallpaper, including the more serious issue of physical symptoms like coughing, and also rheumatism.

Dehumidifiers have long been in use by professionals. They have a simple function: dehumidify the air in a room or even an entire house. They do so efficiently and simply, and, we are delighted to report that, in recent years, models with a good quality / price ratio have invaded the home dehumidification market.

A quiet and simple device in your room

A quiet and simple device in your room

Thus, at The Air Geeks, as we try to explain the essential technical terms to make the right choices ; we don’t want to drown you in technical terms. Our buying guide reviews all the elements to be taken into consideration in order to make the right choice. The very best dehumidifier is one you can set and forget!

Your questions, our answers!

What is a dehumidifier and why would I need one?

Air always has a moisture content which is necessary for you to feel good. However, in the confined space of a well-insulated house in winter, our daily activities (shower, kitchen, dryer …) may lead to the air being charged with moisture that cannot disperse as it normally would.

The humid air then condenses in the cooler parts of the house (walls of non-heated rooms, cool windows…) which leads to deterioration of the room conditions.

As a result, many problems arise: mold appears, wood elements are damaged, damp smells emerge, and individuals can suffer, especially those suffering from rheumatism!

A dehumidifier is a rectangular device, approximately two feet high, that sucks in moist air, removes excess water (in a process called condensation) which it lets running into a small tank, or directly in the wastewater from your home before returning the air into the room.

Placed in a room of your home, connected and automatic, this device protects your home by maintaining optimal relative air humidity without you having to intervene! (The device can also be locked if necessary as a safety measure).

Does a running dehumidifier make noise?

Yes. And this is of course a factor to be taken into account. A dehumidifier, even running, makes no more noise than an air conditioner. If you remain in the levels of 40 to 55dB , you will not have any problems with noise.

Are you particularly looking for a silent dehumidifier? Our selection is here !

And precisely, what is a dehumidifier?

The physical underlying principle is nothing less than condensation ; like deposited drops of condensation on your windows in winter, and droplets of water on the windows. The cold contact surface of certain materials provides suitable circumstances for the moisture suspended in the air to transfer into a liquid state , and is thereby making it easier to collect.

A dehumifidier has a compressor, which maintains an internal cold system, in which moisture from the ambient air naturally becomes condensed. It is often aided by a fan so that the air flows. The water in the liquid state thus produces droplets of water in the recovery tank, and the ambient air, free from the damp overload, is heated and returned to the room … and voila !

Buying Guide

As a preamble, let’s get a little bit technical. The amount of moisture contained in the ambient air is generally expressed as a percentage of relative humidity. This is the proportion ranging from 0 to 100% water vapor contained in a volume of air at room temperature as compared to what this volume of air may contain, in absolute terms, of amount of water vapor.

If the relative humidity is 60%, it means that the air contains 60% of the water vapor it would be able to contain if it were saturated (relative humidity would be 100%).

A relative humidity of 45% to 60% is ideal for humans: below 45%, our skin dries out and we have trouble breathing well. Above 60-65%, moisture and creates an environment conducive to mold growth, sweat, rheumatism and developing a cough. You guessed it: the role of the dehumidifier is to keep the relative humidity of a room between 45% and 60%. As simple as that!

A handy little humidity chart

A handy little humidity chart (thanks to fixmyroof)

What to look before embarking on the purchase of a dehumidifier? Here are the criteria that, in our buying guide, deserve special attention:

β†’ The Air Geeks’ criteria to buy a dehumidifier in June 2017:

  1. Scope of the dehumidifier: or number of pints collected per day, to effectively dehumidify the space you need!
  2. Airflow (daily): understand what this means and why this is important
  3. Noise level: the best devices are those that you can forget!
  4. Strength and reliability for a good long term investment
  5. Hygrostat system and advanced functions for more features
  6. Design: having a box in the living room needs to be unobtrusive
  7. Compact and easy to handle: for trouble-free transport

Scope of the dehumidifier

The scope of the dehumidifier is, in square feet, the surface of your home, a room or several, that your dehumidifier covers. This criterion is also crucial: the greater the surface you want to dehumidify, the more you should choose something long range.

In slightly more technical terms, manufacturers have, over the years, used the number of pints collected per day as a proxy for the power of a dehumidifier. What this means is that the larger amount of water drained from the ambient air in a certain period, the larger the area the dehumidifier can cover.

Our reviews are segmented into three main types of capacity :

Note for picky users (which they should be!) ; obviously, a dehumidifier works “for all the air of an interior”. Thus, if a dehumidifier is effective, it will cover a distance greater than its reach once it has dehumidified air that surrounds it. To illustrate, when an air conditioner cools a small room, the door would be opened onto the rest of the house as its action will spread to other parts. It’s the same for humidity: the flow test and the test range go hand in hand.

Airflow per day

Sometimes called dehumidification capacity, this is the amount in pints per day, that a dehumidifier can absorb to dehumidify and clean. This is the decisive factor regarding the effectiveness of a dehumidifier.

If you purchase a dehumidifier with too low an airflow compared to the volume of the room or space to be dehumidified, the process will take more time to adjust the humidity of the ambient air at the selected relative humidity value.

Thus, the higher the air flow per day, the more your dehumidifier will be effective!

Caution here: dehumidification technology of your device (compressor or silica gel) will influence the effective air flow that your device will be able to handle.

How it all works!

How it all works!

Compressors are simple devices: a fan draws humid air and carries it through a refrigerated evaporator – air and water cools and condenses, and then dry air is heated and returned to the room . The advantages are efficiency, and good performance under conditions of high humidity (more in the following paragraph)

Apparatuses silica gel (or natural) using a blower that pushes the air in front of the silica gel, the moisture absorption properties are well known. The benefits are silent, economic, and ecologic.

The “trap” laid by classical compressors dehumidifiers manufacturers is to test their devices under extreme humidity conditions (30Β°C and 80% humidity for example, where the air contains up to 10 times more water than air at 0Β°C and 70% humidity). Under these conditions, the compressors equipment performance falter. By contrast, in “normal” conditions (20 Β° C and 70% humidity) devices with silica gel do a better job, are more energy efficient and quieter.

Noise level

In the same way that, as with all electrical appliances that make our lives easier, we do not want to notice them. Thus, a good dehumidifier dehumidifier is a silent!

What we hear and what we bear!

What we hear and what we bear!

Obviously a dehumidifier that is less powerful, or more compact, or set to a lower start, usually emits less noise than a powerful dehumidifier or when launched at full flow.

The sound also varies depending on the technology: a silica gel dehumidifier will emit less noise (and a softer sound!) than a compressor dehumidifier. A measure of the emitted sound level will be given in our tests.

Consider that silent dehumidifiers will emit a noise below 55 dB while very silent ones can be around 45 dB.

Strength and reliability

Maybe you’ll be surprised to find this criterion so high in our priorities, but take our word for it, a dehumidifier should be able to do its work for as long as possible. A higher price can, for instance, turn actually cheaper if you are able to keep your dehumidifier for a long time without having to worry about it.

Therefore, a criterion that we tend to look at closely throughout our tests is the ability of a device to operate effectively in the long term – but it is included in our ratings!

Hygrostat system and advanced functions

The “hygrostat” is the humidity controller. This is the command with which you set the desired relative humidity, and which the unit will strive to achieve progressively to dehumidifying your home, then it will hold the relative humidity.

Sleek controls at Delonghi

Sleek controls at Delonghi

Remember, an ideal relative humidity for the inside of a home is between 45% and 60%.

A basic dehumidifier hygrostat allows you to adjust your desired moisture level via a simple command. A more advanced dehumidifier hygrostat is equipped with an LCD display indicating the ambient humidity and other information.

Some models are equipped with a timer that will start a function at a specified time, stop the dehumidifier at night, etc. All of this is accounted for in our tests.


If we accept a box the size of a suitcase in our homes, it needs to embellish the room and not look like a Toshiba air conditioner from the 80s!

Deshumidifying doesn't have to mean the end of design!

Deshumidifying doesn’t have to mean the end of design!

The elegance of a dehumidifier is obviously not the first criterion to seriously consider if one is faced with moisture problems, but it certainly is among the factors that weigh in the balance, especially given the disparity of models in the field!

Compactness and maneuverability

If a dehumidifier is not intended to be moved often, it is still important that size and weight are not deterrants to the general practicality of its use. Some are fitted with casters for easy movement.


What is required of a dehumidifier is for it to do its job effectively, reliably, intelligently and discreetly. The efficiency of a dehumidifier, is indicated by two complementary metrics which are air flow per unit time and scope of action. This is the number one criterion to keep in mind when choosing a dehumidifier.

Then comes the test of reliability and versatility. Finally, the discretion of the device (the fact that it is compact, quiet and elegant), comes into play. You are now equipped with the essential knowledge to make the right choice.