ᐅ After installing the fabric covers, the doors on the Kallax start to sweat – why does this happen?

Hello everyone,

I have been experiencing a strange issue with my Kallax shelf from IKEA for a while and would like to understand it better from a technical perspective. Whenever I place some fabric storage boxes in the shelf compartments, the inside of the Kallax doors starts to slightly sweat – small fine droplets or a kind of condensation form on the inside surfaces of the doors. At first, I thought it was due to the room climate, but I measured and found the humidity to be normal (around 45-50%) as well as the temperature.

So I wonder: Why exactly do the doors on the Kallax shelf sweat when filled with fabric boxes? Is it related to air circulation? A physical property of the fabrics in the shelf? Or are there other factors triggering this phenomenon? Could it be related to thermal bridges, the hygroscopic nature of the fabrics, or possibly moisture coming from the fabric boxes?

I look forward to well-founded answers that will help me understand this better technically, and of course tips on how to prevent the problem without having to completely replace the doors.

Thank you in advance!

Hello rosemaried,

first of all, a brief explanation of the phenomenon you described: the “sweating” of the doors on your Kallax shelf is a typical example of condensation. This occurs when warm, moist air comes into contact with a cooler surface and releases its moisture in the form of water droplets.

rosemaried schrieb:
Why exactly do the doors on the Kallax shelf sweat when filled with fabric boxes?

The fabric boxes can retain moisture – they are hygroscopic, meaning they absorb humidity from the air. This causes the humidity inside the shelf to increase. At the same time, especially the plastic or MDF doors are often cooler than the room air because they provide less insulation than walls. Combined with poor air circulation behind the doors, this increases the risk of dew formation.

My advice: improve air circulation or reduce the fabric boxes as a source of moisture, for example by using less absorbent materials or occasionally ventilating the compartments. Alternatively, you could modify the doors slightly, for instance by adding ventilation slots, to prevent moisture buildup.

Hello everyone,

I would like to add to RonJarrett’s explanation and go into more detail about the physical principles involved, so that rosemaried can have a clearer understanding.

1. Temperature difference: The inside of the Kallax doors cools down when the room temperature is lower. Especially in summer, when warm, humid air comes into contact with the cold surface, water condenses.

2. Fabric boxes store moisture: Cotton or felt boxes absorb moisture from the air through their fibers. This moisture does not evaporate immediately. As a result, the humidity level inside the shelving unit increases.

3. Air circulation: Kallax shelves are often designed in a way that restricts proper air circulation. Closed doors and filled compartments limit airflow, causing moisture to accumulate locally.

4. Hygroscopicity and evaporation: Fabric materials release moisture only slowly; when the air’s capacity to hold moisture is reached, condensation forms on cooler surfaces.

Summary:
The combination of moisture-absorbing fabric boxes, poor air circulation, and cooler doors leads to condensation.

Recommendation: Make sure the shelving unit is placed against a wall that is not cold and damp (e.g., an exterior wall), ventilate regularly, and above all ensure adequate air circulation (for example, by leaving doors slightly open or adding ventilation slots).

If problems occur frequently, more moisture-resistant materials or ventilation systems might be advisable.

I hope this helps you.

RonJarrett schrieb:
Fabric storage boxes can retain moisture – they are hygroscopic, meaning they absorb humidity from the air.

This is indeed a very important point!

I would like to explain again why condensation tends to occur more with fabric boxes and less with plastic ones: Fabrics are usually made from natural fibers (cotton, linen) or synthetic fibers that absorb water and release it slowly. This means they act like small moisture reservoirs.

When the air temperature drops at night, the inside surface of the shelf also cools down. Since the moisture inside the boxes does not evaporate immediately, it moves as vapor pressure and condenses on the colder, hard surface of the doors.

If you want to prevent this, you could try using a dehumidifier nearby or ventilate regularly to better control the humidity. Sometimes it also helps not to close the doors completely, but to leave a small gap open, even if that may not look ideal.

It is also important to ensure that the shelving unit is not placed against cold exterior walls. That is where the risk of condensation is the highest.

Best regards!

The doors sweat because the warm, moist air inside the shelf meets the cold surface and condenses. Fabric boxes absorb moisture and release it slowly, which increases the humidity inside the shelf. Improving air circulation or leaving the doors open helps.