Can You Run a Dehumidifier with the Window Open

Can You Run a Dehumidifier with the Window Open?

Should you run a dehumidifier with a window open?


A dehumidifier requires that a room be sealed off, at least windows and doors closed to function optimally. Letting outside air in while the dehumidifier is running dilutes the process and introduces new moisture that increases the amount of energy it takes and decreases the effectiveness.

Opening the window in lieu of running the dehumidifier is an option if the humidity inside the room is higher than the humidity outside.

For instance, you’ve recently taken a steamy shower and you want to air out the room. Opening the window or turning on the extraction fan is a better option than running a dehumidifier.

Other similar indoor humidity problems can be related to running an evaporative air cooler or simply washing clothes and dishes.

These are usually temporary humidity problems that can be alleviated by letting some fresh air in.

But typically the indoor humidity is relative to the outdoor humidity. A rainy season outside will cause the indoor humidity to rise as well.

Hot humid temperatures outside will gravitate inside.

“Opening a window while you’re using the dehumidifier when the outdoor humidity is as high or more than the indoor humidity, you have zero chance of decreasing the humidity indoors with a dehumidifier.”

Indoor humidity problemsIn fact you will get a better result out of your dehumidifier if you take steps to seal up the windows and doors even further while you’re using a dehumidifier.

Most indoor humidity problems are related to the outdoor humidity affecting the indoor humidity levels.

Basements for instance, are usually built directly next to dirt that has a heavy moisture content. That is why the basement usually seems damp compared to other rooms.

Concrete walls can develop cracks where moisture can seep in from the ground and depending on your style a basement, pipes can be exposed and introducing moisture if there is any leakage.

Other areas like crawl spaces beneath the house can be continuously moist which has a direct effect on the moisture level inside of the house because of moisture coming up beneath the floor.

  A typical problem with crawl spaces is water in the yard that has etched out a ravine running to underneath your house. Broken gutters or dirty stopped up gutters can also be a cause of water seeping under the house instead of being directed out from the house.

Crawl space encapsulation is a process that uses a barrier to keep moisture from the ground from keeping moisture that is in the ground from humidifying your house through the floor.

Crawl space encapsulation can also include putting a large industrial dehumidifier beneath the house to extract the moisture.

But if the indoor humidity is much higher than the outdoor humidity, then you need to locate the source of the moisture and take steps to stop it.

Anywhere you have a leak, you have extra moisture in your home. A broken pipe, gaps in your windows or doors, or a leaky ceiling can all be a continuous source of humidity inside the home that if not fixed will cause the humidity to be high indoors.

  And running a dehumidifier even though it may be necessary to maintain a good comfort level in the meantime is only an expensive Band-Aid till you get the problem fixed.

Indoor humidity problems.


Humidity can do a number on the indoor structure of your house.

Window sills can warp and rot, wood flooring can expand as well as warp as well become creaky.

Ceiling texture can start cracking and flaking off and wallpaper can start coming loose.

And though very important, more important is the fact that your air quality can be compromised and cause allergies, headaches, fatigue, and even other more serious symptoms if mold has been allowed to take root and become part of your ambient air makeup.

How do you know?

How do you measure the humidity in your home?

Of course humidity is a relative term that means one thing to a person living in Arizona and quite another thing for a person living in Florida.

Certain climates especially if they are near the ocean are going to naturally have a higher level of humidity in the air.
And your personal comfortability meter is going to be a lot higher.

But if you are used to living in a dry climate and you take a vacation to the ocean, you may be completely overwhelmed by the humidity level.

So comfortability is not necessarily the best measuring stick for what is acceptable indoor humidity.

To be more exact and to keep an indoor relative humidity that is not only healthier but better for your home, you have to have a way to measure it.

The hygrometer is a gauge that usually comes in the form of a digital thermo hygrometer that you can install on a wall to be able to keep up with your indoor relative humidity level.

These little tools are inexpensive and can be placed in multiple locations throughout your house as a way to gauge where the higher humidity is coming from.

How do you measure the humidity in your homeWhat should the humidity level be inside your house?


The national library of medicine says that most health issues related to humidity can be curbed by keeping the indoor relative humidity between 40 and 60%.

The homeowners association says that the humidity should be between 30 and 60%.

So the ideal humidity to try to achieve inside the home is about 50%.

Dehumidifiers typically come with a built-in hygrometer and humidistat to gauge the indoor humidity so that the machine will run until the set humidity is reached.

Humidifiers can be purchased with built-in hygrometers and humidistats as well when the indoor humidity has dipped below 30 to 40%.


Can you use a dehumidifier with the window open?

To increase the effectiveness of a dehumidifier, close any windows and doors to the room that you are trying to reduce the moisture in.

Since the outdoor humidity is generally one of the main causes for excessive humidity indoors, opening a window with the dehumidifier running will only cause a never-ending cycle of extracting humidity from the air. And cause the energy hog dehumidifier to be even more expensive to run.

  If on the other hand, the fresh air outside is dryer than the air inside, then opening the windows in lieu of running the dehumidifier could be the better option.

Extraction fans in the bathroom and kitchen as well as the washroom will reduce the humidity without running a dehumidifier as a necessity also.

If the indoor relative humidity is consistently higher than the outdoor humidity, then you are more certainly looking at an indoor problem such as a leak from a pipe.

Fixing the issue is the only solution at that point.

If the outdoor humidity is continuously high then reducing the exposure indoors by sealing the house and fixing any issues with moisture and water humidifying from beneath the house is the key.

Maintaining an indoor relative humidity between 40 and 60% is the main objective.
You can use a hygrometer and even place them throughout your house to measure your humidity and gauge where the higher humidity levels are sitting in your home.

Published by

Dennis Reed

Dennis Reed Owner and Author @