Do Dehumidifiers Work In Cold Rooms?

 

Most people are aware that they need to dehumidify their homes during humid summer months.

But what about the cold season?

Will a dehumidifier work in a cold room and should you be using it when it’s cold anyway? Most portable dehumidifiers are not meant to work in cold rooms. Their user manuals typically state that the minimum operating temperature required is 65 ºF. There are some dehumidifiers that will work below this temperature. These are usually dehumidifiers with special defrost functions or desiccant dehumidifiers.

Let’s go into more detail to understand just why dehumidifiers have this kind of minimum temperature requirement and what you can do about it.

Why Most Dehumidifiers Can’t Be Used Below 65 ºF

Dehumidifiers work a lot like the air conditioning system in the average home.

Their fan takes in the air, then tries to lower the temperature of this air below the dew point so that water can be separated out from it through condensation. This part of the process happens by running the air through coils.

Since these coils have to be cold anyway, the risk exists that they may freeze over if the room itself is cold.

When this happens, the fan of the dehumidifier still continues to run but no water is being collected. The unit continues to be a strain on the energy bill and eventually breaks down because it’s malfunctioning.

As you can imagine, this isn’t usually a problem in most heated rooms, but it can be a problem in areas that aren’t being heated like basements, garages, and crawlspaces.

 

Dehumidifiers That Can Operate In Cold Temperatures

If you’ve been trying to find dehumidifiers that can work in cold rooms, there are a few things you’ll need to be on the lookout for.

 

Square Footage Capacity Diminishes with Temperature

Manufacturers will be quick to tell you just how much square footage a dehumidifier can cover. Who has a 4,000 square foot space on the same level of their home anyway?! Most average people don’t.

Something seems a bit odd when you look at those kinds of dehumidifiers.

So what’s the real deal here then?

Most dehumidifiers are tested in the laboratory first in order to determine what their advertised water removal capacity should be. In the United States, they’re often tested under what’s known as AHAM conditions, which are set at 80 ºF. Overseas, it’s common to test dehumidifiers at 86 ºF.

There aren’t that many homes that set their thermostat that high, so it seems unrealistic at any time during the year, not just the winter.

So even if you find compressor dehumidifiers that are advertised to operate at temperatures all the way down to the low 40s and even if they are said to have special auto defrost functions for their coils, they still won’t work as efficiently as advertised.

The truth is that a noticeable drop in temperature can cut the capacity of a dehumidifier by half or more, so the dehumidifier that was advertised to be able to cover 500 square feet can now barely even cover a small master bathroom.

 

Look for a Desiccant Dehumidifier

Most people think of desiccant dehumidifiers as small little things that absorb moisture through some means like a silica gel.

But desiccant dehumidifiers are now becoming more and more advanced and can prove to be the exact solution needed for cold winter seasons.

Just take a look at this 21-pint dehumidifier by EcoSeb from Amazon

Even though desiccant dehumidifiers also have a minimum operating temperature requirements, their water removal stays the same above that regardless of whether they’re operated at 65 ºF or 85 ºF.

The one I mentioned by EcoSeb makes its 21-pint removal claim under 68 ºF because, well, it can.

If you look at a chart of how this 21-pint desiccant dehumidifier performs against a standard compressor dehumidifier at twice the advertised capacity (42 pints), you’ll quickly realize that the desiccant dehumidifier does much better at lower temperatures.

Its capacity stays steady at around 21 pints, while the 42-pint claim by the compressor dehumidifier doesn’t even remotely get close to what’s advertised.

 

 

The user manual of the EcoSeb line of desiccant dehumidifiers states that the minimum operating temperature needs to be above 34 ºF. So, as long as the space isn’t allowed to freeze overnight, these dehumidifiers should work.

 

Does a Dehumidifier Even Need to Run During the Winter?

A dehumidifier will spend the bulk of its operating time during the summer. The Department of Energy (DOE) recommends that a dehumidifier be turned off entirely during the winter.

If you look at the table below, you’ll see that they recommend a dehumidifier be off between November and March.

 

MonthOperating Hours
Jan0
Feb0
Mar0
Apr14
May86
Jun231
Jul288
Aug288
Sep130
Oct58
Nov0
Dec0

(source)

 

There are two reasons for this –

First, the obvious reason that dehumidifiers cannot operate in cold rooms since their coils will freeze over.

But secondly, the air tends to be drier during the winter anyway. Even if your dehumidifier can work during the winter season, you may find that it doesn’t have to.

If you can afford it, it’s still a good idea to buy a hygrometer and verify that this is the case. The ideal relative humidity (RH) levels in a home are between 35% and 50%.

If your home stays in this range during the winter anyway, you can safely pack up the dehumidifier and bring it back out in the spring again.

But if high humidity levels still persist even during the winter, you’ll definitely need to do something about it (the EcoSeb desiccant dehumidifiers I mentioned above might be a good solution).

Just imagine how high the humidity will get during the summer if the home has high humidity levels during the winter. The last thing you want is to find yourself in a situation where mold can form and cause a very expensive problem in the future.