The job of a dehumidifier is to remove moisture from the air in a room. It is logical to ask whether windows should remain closed during use, or if a little fresh air actually does no harm. The answer is more nuanced than a simple yes or no.
Why closed windows usually work better
A dehumidifier works most effectively in a closed space. If a window is open, new, often humid outside air is constantly entering, especially on a cloudy or rainy day. The device then has to keep removing this additional moisture, which means it takes longer to see results and the device consumes more power for the same effect.
When an open window does make sense
- After an activity involving a lot of water vapor. Just showered or finished cooking? Briefly ventilating to let the main peak of moisture escape immediately is often faster than letting everything go through the dehumidifier.
- In very dry and cold outside air. In winter, outside air is often drier than indoor air. A brief air exchange can do some of the work, although this requires closing the window again as soon as you are finished airing out the room.
- For general fresh air and CO2. A dehumidifier only regulates humidity, not the CO2 level in a room. For sufficient fresh air, regular ventilation remains necessary, regardless of the dehumidification.
The practical approach
A workable combination is: first ventilate briefly and thoroughly to refresh the room, then close the windows again and turn on the dehumidifier to gradually lower the remaining humidity. This way, you benefit from fresh air without the device constantly having to work against an open window.
If you use the Dynter AirPure DH251, for example, in a bedroom or basement, our advice is to keep the door and windows closed during dehumidification and only ventilate briefly at set times, for example in the morning. This way, the space remains dry for most of the day without you having to completely forgo fresh air.
Also pay attention to doors within the house
It is not just windows leading outside that are important. If the door of the room where the dehumidifier is running is open to another, more humid room, such as a bathroom, that moisture will simply migrate into the room you are trying to dehumidify. Therefore, also keep internal doors between a humid and a dry room closed as much as possible, especially during use.
In short: closed windows during dehumidification provide the fastest and most predictable results, but that does not mean you are never allowed to ventilate. Alternating between short periods of ventilation and longer periods of dehumidification is a smart way to keep both the air fresh and the humidity under control.
And what about the front or back door?
The same principle applies to external doors that open regularly, for example in a storage room or a garage with direct access to the outside. Every time the door is opened, new air flows in with its own humidity level. That is not a problem in itself, as long as you take into account that the device needs a little extra time to return the humidity to the desired level after each time someone enters or exits.