ᐅ IKEA Kallax next to a window – Problems with condensation?

Hello everyone,

I am currently considering placing my new IKEA Kallax shelving unit right next to the large window in the living room. However, I have concerns about potential issues with condensation. The windows are double-glazed, but on colder days, dew often forms on the glass, especially in the mornings. Now I am wondering if having a piece of furniture directly against the cold surface increases the risk of higher moisture levels between the window and the shelving unit, possibly leading to mold or moisture damage.

Does anyone have experience with this problem when placing a Kallax unit directly next to a window? Are there any observations on whether the furniture traps moisture at the window or affects air circulation? What measures could help if you still want to put the shelving there?

I would greatly appreciate detailed answers, including tips on moisture, air circulation, insulation, or similar factors I should consider.

Dagoix schrieb:
Does anyone have experience with the problem when a Kallax shelving unit is placed right next to a window?

Hello Dagoix,

Your question is very valid, and I faced a similar situation at my home. First of all: The Kallax shelving unit has an open design, which generally supports air circulation. However, it is important to note that if the unit is placed directly against the cold window surface, the natural air circulation between the window and the furniture is restricted. Especially with existing windows featuring standard double glazing, condensation can form more quickly on the cold surface if the room air is relatively humid.

Dagoix schrieb:
Does the furniture trap moisture at the window or impair air circulation?

Yes, that can definitely happen. The shelving unit prevents the moisture that forms on the window from evaporating properly. When air cannot flow freely, moisture accumulates between the window and the furniture. This, in turn, can lead to mold growth on the exterior wall or within the furniture itself over time.

What I would recommend:

1. Leave a small gap of at least 5–10 cm (2–4 inches) between the window and the shelving unit to ensure air circulation.
2. Make sure the window is well sealed and that regular ventilation (e.g., airing out the room) is carried out to keep indoor humidity low.
3. Additional insulation around the window reveal or installing ventilation grilles in the furniture (depending on the Kallax model) can improve airflow.
4. Regularly check for any signs of moisture on the windowsill or inside the shelving unit and respond promptly.

What is the relative humidity in your living room during winter? And how close exactly is the shelving unit intended to be to the window? Do you have curtains or other features that might affect air circulation?

These details would help to better assess the issue.

Place the shelf at least 10cm (4 inches) away from the window.
Ventilate the window regularly to prevent moisture buildup.
The Kallax itself does not cause any issues as long as there is proper air circulation.

valerie-tr schrieb:
A small gap of at least 5-10 cm (2-4 inches) between the window and the shelf is helpful to ensure air circulation.

I completely agree with this. I would like to add that with IKEA Kallax units, it often helps not to place the furniture directly against the wall. The back panel of the shelf is not fully closed, which allows some air to pass through but not enough if it is placed directly by the window.

I had the shelf in a room with a similar situation where the window’s air circulation was significantly obstructed by the furniture, and condensation actually formed. My solution was to put the furniture on small spacers and create some space at the back – this allowed better air circulation.

Also: The temperature difference between the indoor air and the window surface is the main cause of condensation. An insulating secondary window or a thermal insulation window sill can help raise the surface temperature and reduce condensation.

As already mentioned, you should definitely monitor the humidity in the room. Levels above 60% relative humidity can strongly promote condensation. A hygrometer is therefore often useful to better understand the situation.

Do you plan to keep the shelf there permanently, or is it a temporary setup?

Hello Dagoix,

I would also like to add some thoughts on ventilation behavior because it is often underestimated.

A Kallax shelf placed directly against a window not only blocks air circulation but can also prevent the natural convection along the window from working effectively. This convection normally helps warm air rise from the floor area and warms the cold air near the window surface – which reduces condensation.

If your shelf is not fully closed, there might be some chance that air passes through, but usually, this is not enough to keep moisture away over time.

I would also recommend making sure that no heat accumulation zones form behind the shelf, as these can become ideal condensation spots. If you have radiators under the window, a minimum distance of 10cm (4 inches) is really advisable and allows better airflow.

If you still want to use the space right next to the window, dehumidifiers are an option. They absorb moisture and prevent water from settling on cold surfaces. Of course, you probably don’t want to run devices continuously, but in an emergency, this can be very helpful.

Could you also let me know if the window is protected from the outside by roller shutters or blinds? This can also influence the temperature of the glass.

valerie-tr schrieb:
What is the relative humidity in your living room during winter? And how close exactly do you plan to place the shelf to the window? Do you have curtains or any other factors that might affect air circulation?

Thank you for the quick and helpful answers!

The humidity levels in the cold months usually range between 50% and 60%, but have occasionally been measured just above 65% for a short time. I actually wanted to place the shelf as close as possible to the window, either directly against it or with only 2-3 cm (about 1 inch) of space. There are curtains, but they are rather light and not thick, so I think they don’t significantly obstruct air circulation.

alvalo schrieb:
If you still want to use the space right next to the window, dehumidifiers are an option.

Would that be a recommended long-term solution? Or more of an emergency measure, as you described?

Oh, and we have external roller shutters, but they are usually fully open during the day.