Mold problem in the new kitchen – how to prevent it in the future?

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Our kitchen, which was completely renovated in mid-2020, has a mold problem:

It was noticed when water suddenly leaked from under the refrigerator. At first I thought it was a defect in the appliance, but it probably wasn't. We removed the built-in refrigerator and the cabinet it was installed in, and there was horror behind it: There was mold in the bottom corner of the room and on the wall to the side of the refrigerator (see photo). There was mold between the refrigerator and the built-in cabinet. The entire right side wall of the appliance was covered with water droplets.

The craftsmen we know (tiler + plasterer) looked at it and said that it is condensation from the humidity in the air. The air can't circulate properly in this cabinet, hence this problem. Also, the refrigerator is right in the corner of the room on the two outside walls (northeast).

How should this problem be addressed? Removing mold and good drying of everything first is logical.

The tiler said I should install a vent system in the wall above the refrigerator to regulate the humidity. I think this makes sense, but I'm worried that since the cabinet is next to the wall (0.5-1 cm of air at most), condensation will continue to form there despite the ventilation. Are there any additional measures here – perhaps some way to fill in the small cavity?

Additional info: The exterior wall is 30 cm brick masonry with no additional insulation. (Built in the early 70's)

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Answers

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As an "active" solution, I see two other possibilities besides insulation:

1. install an extra heater in the corner to warm the corner (and that usually increases air circulation as well).

2. install a small fan in the vents to create faster airflow.

These are crutches, but they are routinely used in other cases as well.

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Now this confuses me a bit, I see two opposing pieces of advice: Some say that you need to create more space, more distance from the wall, so that the air can circulate. Others say to insulate the gap, perhaps with mineral wool. This will stop the circulation completely. I don't agree with that.

  • +2
    These are not conflicting recommendations: Insulation helps keep the wall warmer (move the dew point). Ventilation helps dissipate moisture. It's helpful to do both. If the space is too tight – don't use insulation to prevent moisture removal, so definitely don't caulk it.
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The only thing that helps – besides ventilation – is insulation. But you probably don't have room for that inside, and of course you have to insulate the outside more carefully.

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I think the cause is location, lack of clearance, and a cold exterior wall.

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The first approach is to follow the manufacturer's recommended spacing, which is usually at least 5 cm.

If this is not enough, you can also increase the surface temperature of the wall with a capillary-active insulating material and thus reduce condensation.

Be careful, the dew point in this case always shifts to the unfavorable side, so try to do without internal insulation.

An additional fan can even draw moisture from outside to inside because the insulation material has capillary activity in both directions.

Too thick interior insulation has exactly this effect, so it is usually recommended that no more than 5 cm of insulation thickness be unchecked.

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I would measure the temperature of the exterior wall at that location.

If it is colder than the surrounding exterior walls, then the problem is not lack of circulation, but the wall insulation.

Otherwise, I think it's a planning error. You shouldn't place a refrigerator on two exterior walls.

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I think you understood the reason perfectly. If I were you, I wouldn't fiddle with it, but fix the cause once and for all (which is what we did with our problematic bedroom corner after fiddling with it – other than the fact that it cost money – had no effect). From my perspective, it would be to insulate the exterior walls in the affected corner with climate control panels. They come in 3 cm or 5 cm thicknesses. Depending on the temperature of the wall, it should be a thin or thick climate panel. However, a thin one (3 cm) is usually sufficient. Install the climate control panels on both exterior walls and replace the built-in refrigerator with a floor standing refrigerator.

  • So, insulating exterior walls is, of course, a REALLY big deal. After all, you're not just insulating the outside walls of that one room. The idea ends up being that you need to insulate EVERYTHING. Then everything needs to be plastered or decorated in some way. It ends up being some kind of five figure sum, which I honestly don't have. That's why I'm looking for a temporary fail-safe solution. 
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The problem, most likely (beware of remote diagnostics), is condensation (cooking, warm air) and a cold corner (exterior walls, "old" house).

There are really only two reasonable options:

1. complete exterior insulation (expensive)

2. remove the interior plaster in the affected corner, glue special boards for interior insulation (see above -> "climate boards"), and then re-plaster.

Any other option would be a real "sucker," and I'm afraid it will get moldy again sooner or later.

P.S.: There are special paints that contain mold protection. I used it to repair a corner in my rental apartment 10 years ago, and it worked well for 5 years. I don't know if it would work on the scale of your home.

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