A dehumidifier is used to pull excess moisture from the air in your home to prevent the associated musty smell and even mold that can develop if humidity is too high. Your basement is commonly the best place to place a dehumidifier since it’s the lowest part of your house and tends to be the most humid.
But should you close the door leading to the room you have your dehumidifier placed in or should you leave it open? Does it even matter? Since a dehumidifier is normally used in a basement, let’s consider that case.
Before operating your dehumidifier in your basement, close all windows and any doors leading to the basement to isolate the humidity as best you can. You can measure the humidity in each room of your home to determine where it’s the worst but chances are it will be on the lowest floor of the home.
So not only does a dehumidifier work with closed doors, it may actually work better and more efficiently if you’re able to contain humidity in one area.
We’ll discuss this in more detail below.
Why close the basement door when running your dehumidifier?
By closing the door in the basement when running a dehumidifier, you can help to contain the humidity in the room that you’re trying to make less humid.
The basement is usually the most humid room in your home for a number of reasons:
- The basement is typically built underground and with less light so dampness and humidity is more easily available than higher situated rooms in the home that have more natural light.
- Leaks in the foundation or walls can introduce moisture into a basement that increases humidity.
- Moisture escaping from the concrete walls and floor can increase humidity.
- A leaking pipe can increase humidity in the basement.
- If your washer and dryer are in the basement, they can increase the level of RH in a home each time they are used due to the heat produced by hot water (washer) and warm air (dryer).
How to properly use a dehumidifier
Before you use your dehumidifier, read over the following list to ensure you have considered each bullet point:
- Use a humidity monitor to gauge how humid each room in your house is to determine if you need a dehumidifier and if so, which room it should be placed in. You’ll also determine how big a problem the humidity in your home currently is.
- Close all windows in your house and all doors leading into it. Leaving your windows or doors open allows more potentially humid air to enter your home.
- Set the dehumidifier to the relative humidity that you desire. For an average home that will typically fall between 30% and 60% depending on the season and your local area i.e. how dry or humid it is in general.
- If your dehumidifier is going to be located in your basement, close the basement door to keep humidity localized, particularly if you know that the humidity measures higher in the basement.
- Some people consider 60% high but over 60% relative humidity is definitely considered too high for a home. Consistent humidity over 70% makes a home ripe for mold to grow.
- Place the dehumidifier in an area that is both close enough to a plug receptacle but also to enable free airflow in and out of the machine.
- Empty the water tank before it gets full to enable the dehumidifier to keep running.
- If your dehumidifier model has a hose option, you may direct the water into a floor drain to avoid having to empty the water tank.
- Clean the dehumidifier filter if any, as the manufacturer recommends. Over time, filters can get dirty and full of water scale and may need to be cleaned and eventually replaced.
- Use a dehumidifier to match your house size and/or the size of the room you’re using it in as well as the degree of excess humidity you face.
We’ll discuss the last point below in case you don’t currently have a dehumidifier and need to purchase one.
Quick dehumidifier sizing guide
Humidifiers are typically sold according to their water capacity measured in pints. This is the maximum amount of water that the tank can hold before it will need to be emptied.
There are a number of factors that can increase the required dehumidifier capacity that you require. These include:
- Living in a region that is naturally known to be humid.
- Having a large household size.
- Having multiple windows and doors leading into your house.
- A need to have a lower relative humidity than normal (i.e. if you have allergies).
You can also refer to product guides from dehumidifier manufacturers for their respective capacities.
But in general terms, here’s a quick chart to size a dehumidifier that fits your needs.
| Dehumidifier capacity | House/room size |
| Up to 39 pints | Damp rooms up to 1,500 square feet. The more damp the room the higher capacity you will need. |
| 40 pints – 59 pints | Damp rooms from 1,500 square feet to 2,500 square feet. The more damp the room the higher capacity you will need. |
| 60 pints and up | Damp rooms larger than 2,500 square feet. The more damp the room the higher capacity you will need. |
While you can purchase a unit that is larger than you need, excessively running it can make your home dryer than you need. Still, you want to purchase a model that meets your requirements, taking into account house/room size, size of your household and current level of humidity.
How a dehumidifier works to remove excess moisture
A dehumidifier pulls warm moist air into the unit and through its condenser coils. The warm air contracts as it passes through evaporator coils and water is extracted. This water drips into a water tank while dry cool air is then returned to the room via a fan that pushes it out the back of the unit.
Over time, the result is that the overall level of humidity in the room is lowered as water is removed.
The water tank in the dehumidifier needs to be emptied frequently otherwise it will eventually shut the machine off when it is full.
A dehumidifier will continue to run until the water tank is full or until the desired level of humidity that has been set is reached.
While more expensive models may enable you to set the desired humidity by a specific amount (i.e. 50%) cheaper models often have a dial with a varying level from low to high water removal.
You may also have a fan speed that enables you to slow or speed up the amount of water removed from the room.
When you isolate the humidity in your home by closing doors leading to the area the dehumidifier is located in, you can reduce the time you need to run it.
Quick facts about using a humidifier
- Humidifiers are usually 300W – 700W depending on their size (capacity) and thus use a relatively low amount of electricity.
- Use a dehumidifier for about 12 hours per day for best results. If you live in an area with time-of-use electricity pricing, try running it overnight to take advantage of lower off-peak prices.
- By running your dehumidifier, you may lower your summer AC bill by making the air in your home less moist and thus feel cooler.
- By lowering your home’s humidity you can significantly reduce the chance of mold growing.
- Locating your dehumidifier near your washer and dryer can increase the time it needs to operate as these machines tend to decrease humidity, particularly the dryer. This may also increase the dehumidifier capacity that you require since it will pull more moisture from the air.
Does a dehumidifier make a house cooler?
“It’s not the heat, it’s the humidity.”
You may have heard that expression during a very hot, humid summer day. The suggestion is that if not for the humidity, the high temperature would be bearable and that in fact, it’s the high level of relative humidity that is the problem.
If you’ve ever been in a hot environment with no to low humidity, you might be amazed at how you can be out in the sun for hours and not really sweat.
Conversely, you can be in a humid environment that doesn’t even have to be terribly hot and find yourself perspiring.
When your dehumidifier reduces relative humidity, it can have the effect of making your body feel like the temperatures is lower and thus more comfortable. You might in turn find that you don’t need to run your AC as long since you feel cooler due to the less humid environment.
So reducing your humidity to a reasonable level can make it more comfortable and might even save you money on cooling your home at the same time.
Do you need a dehumidifier in a finished basement?
Any room that is built underground is susceptible to moisture and even a finished basement may require use of a dehumidifier.
When you have relative humidity at 70% or higher, your home is susceptible to mold. A dehumidifier can help to bring your RH down to around 50% which is often seen as the ideal level to keep the home less humid while also protecting against mold growth.
Regardless of what sort of basement you have, typical signs that you need a dehumidifier include the following:
- You regularly experience relative humidity of 70% or more.
- There’s a damp feeling in the room that doesn’t go away.
- There’s a musty smell in the room that doesn’t go away.
- You notice a sudden change in the air quality (dampness, smell) when you enter the room, typically the basement.
- Mold is visible particularly on walls or windows. Drywall is very susceptible.
- Allergies seem to flare up or you notice other health issues such as coughing or a runny nose.
Summary
A dehumidifier is typically best located in your basement since it’s the lowest level of the home and thus most likely to be humid. While you should shut all doors and windows in the home when running a dehumidifier, you should also close the door in your basement to try to contain humidity in that area.
In order to do everything you can to reduce humidity in your home, seal all visible basement floor cracks and window gaps and cracks that allow air or water to enter the home. Consider the levels of insulation your have in your attic and also your basement to ensure it’s adequate.
Use bathroom and kitchen fans to help reduce humidity when showering and cooking respectively.
Consider professional help if you find that your dehumidifier can’t keep up with humidity removal in case there is a larger problem with your foundation or your home’s envelope that you can’t notice or fix yourself.