Do Dehumidifiers Work with Windows Open? All You Need To Know

Getting adequate humidity levels in your home is important for comfortable and healthy living. There are certain requirements for proper dehumidifier operation too though. What about opening windows of your room for fresh steam of air? With windows open, will your dehumidifier function properly?

Running dehumidifier with windows open will severely reduce its effectiveness and efficiency. The extent of negative impact depends upon airflow formed by opening windows. The solution is regulation of indoor air by artificial airflow means like fans and opening windows partially or for few minutes in the day to let fresh air in.

Well, that was the short answer. There are a couple of reasons why someone would want to open windows while running dehumidifier. In this article, I cover most of them, and also the impact of outdoor airflow in different situations and their solutions. This will allow you to know exactly how much open windows will affect your dehumidifier functioning.

Why Using Dehumidifier with Open Windows Not A Good Idea?

Most dehumidifiers are refrigerant type. They have cooling coils maintained at a temperature well below dew point. Dew point is the temperature at which water condenses from air.

Air is sucked through low temperature coils by a fan and water condenses from it. This water is extracted in a bucket or removed by using other continuous ways like drain hose or condensate pump.

Open Windows

Unlike AC, in dehumidifier dry air is also heated afterwards by passing through condenser coils to get back to room temperature. Gradually, moisture is removed from air of your room or living space by dehumidifier operation.

When you open windows in a room, an airflow is developed. Even if there is little movement of air depending on extent and location of opening and atmospheric conditions, your dehumidifier fan will suck air from outdoors and dehumidify it.

Consequently, humid air from outside will keep replacing the dehumidified air from the unit.

Your dehumidifier keeps on extracting water vapors but humidity keeps on adding from outdoors via incoming air.

Impact of Open Windows on Dehumidifier Operation

How much will be the damage caused by dehumidifying with open windows?

In other words, what will be the extent to which dehumidification will be reduced.

Well, it depends upon the amount of airflow that is developed from outside by opening windows.

This airflow mostly depends upon

  • Extent of window opening
  • Number of windows
  • Location of windows
  • Artificial airflow means (vent fans, open doors etc.)
  • Environmental conditions

For example, if there is little air coming in from slight opening then this will not affect dehumidifier operation to much extent as there is very little movement of air caused by this.

On the other hand, if window is sufficiently open, there are multiple open windows or/and there is excess ventilation by other means in the room, you will have poor or no dehumidification due to very high airflow.

You will only have dehumidification in a space if the rate at which humidity is extracted by your dehumidifier is more than rate at which air from outside adds to it.

Why Do You Want to Open Windows When Running Dehumidifier?

There are several reasons why you may like to open windows while running your dehumidifier.

I will discuss most common of them and try to provide suitable replacement and solutions in each case:

You Want to Cool Your Space by Air Movement

A fair reason for opening windows could be to keep your room at a comfortable temperature. If you want to open windows for this purpose, I have got good news for you: Running dehumidifier cools you!

The reason why this is so interesting is that dehumidifier causes almost no temperature change in the room. In fact, practically it may increase temperature a little bit.

Actually, relative humidity is linked with cooling via perspiration. In simple words, it allows you to cool more by evaporation of your sweat.

When relative humidity is higher, you feel hotter. This is due to the fact that sweat on your skin does not evaporate readily compared to when the humidity is low.

If the temperature is same, you will actually feel cool in drier air. In fact, despite that air temperature might go higher due to decreased relative humidity you will feel cooler.

Let me give you an example,

Suppose your thermometer records temperature of 94°F at a relative humidity of 60% it would feel like 110°F.

You use a dehumidifier and make your space come to a comfortable humidity level of 45%, it would feel like a 100°F.

Just by using dehumidifier without any difference in temperature you now feel 10 degrees cooler.

You Want Fresh Air in Your Home

By using a dehumidifier, you will get rid of excess humidity, if you choose the right capacity. But even then, fresh airflow is necessary to dilute odors, gases, dust and used air. You need adequate fresh air rich in oxygen to be directed indoors from outside. 

Breathing Fresh Air

There are many ways you can have sufficient ventilation with effective dehumidifier operation.

One way is to install ventilation fans in your home, far away from the room you are using your dehumidifier. This will freshen up environment in your home and at the same time prevent excessive airflow in your room.

Secondly, you can open up windows, for few minutes in the day, to allow fresh air in. This will help get rid of contained air in your home.

It is a good idea to open windows in your room partially. This will allow reduced quantity of air to come in. Just make sure it is very little, otherwise effectiveness of dehumidifier will reduce. Also, try opening windows a little bit farther from room in which you are using dehumidifier.

In the end, goal is to carefully adjust ventilation according to the capacity of your dehumidifier.

If you are using a large capacity dehumidifier compared to room capacity then you will have more flexibility in improving airflow. As the capacity reduces, it would still be possible, but with more constraints and limitations.

Does Opening Windows Affect Humidity?

With dehumidifier you will surely get most directed operation for normalizing humidity in your home.

But what If we don’t take dehumidifier into consideration? What will open windows do for us then? Will humidity increase or decrease? There are two common scenarios for this situation:

Scenario 1: Hot Weather (Summer)

High Temperature on Thermometer

No matter what is the season of year, fresh air is a requirement. Opening windows will allow fresh air to come in replacing used damp air consisting of pollutant and pores.

You should try to develop a crossflow of fresh air by opening multiple windows or using forced ventilation.

Relative humidity specifically will decrease by opening windows in summer due to replacement of moist used air by fresh air.

Scenario 2: Cold Weather (Winters)

In winters, opening windows will allow fresh air to come in but at the expense of making your room cooler.

In this scenario too, suitably controlling airflow rate is the solution.

Relative humidity of the air coming from outside will be higher due to open windows i.e., low temperature causes high relative humidity. However, the concept of relative humidity needs to be understood due to its relation with temperature.

Cool Weather

Actually, when temperature of the cool air coming from outside is increased to room temperature, its relative humidity decreases lower than the relatively damp air inside. Thereby if you are heating the air coming from outside then you are lowering relative humidity inside.

But there is downside.

You replace air that you heated up with cool air that you have to heat up again. This is very inefficient and uneconomical compared to a dehumidifier that solely works to reduce humidity and slightly heats up your room too.

How To Keep Air Inside Fresh With Use of Dehumidifier?

When you use dehumidifier humidity will reduce but used air needs to be evacuated.

I have discussed some techniques in the section above to allow you to keep using your dehumidifier while at the same time allowing fresh air in your living space. They include:

  • Use ventilation fans away from your room to allow limited airflow.
  • Open windows partially to let only little air to come in without affecting dehumidifier working.
  • For few minutes in the day, open windows to replace used air with fresh air.
  • Try opening windows in other portions of your home and slightly opening the door of the room you are dehumidifying.

You can also use these techniques in combination if you like. But keep in mind that moisture coming from outside needs to be lower than moisture removed by your dehumidifier.

Commonly Asked Questions

Does Dehumidifier Work Through Open Doors?

This depends on the capacity of dehumidifier compared to the size room you want dehumidified.

If its capacity is exactly what is required for the room (or less), then opening doors will reduce effectiveness of your dehumidifier and lower the rate of moisture extraction due to larger space.

On the other hand, if you have a whole house dehumidifier then opening doors will actually improve extraction of humidity from your house.

With larger sized dehumidifier (compared to space) you can open the door for more coverage of dehumidifier operation.

Sizing a dehumidifier is easy. In fact, I discuss simple and easy step-by-step approach to sizing your dehumidifier in this article.

Where To Place Dehumidifier for Maximum Effectiveness?

The best location for a dehumidifier to placed is where you have maximum humidity to be reduced. It could be a basement, laundry room, crawl space etc.

Just make sure that you have enough airflow for dehumidification to be effective and accessible in other portions of your home.