ᐅ Significantly excessive humidity in the basement

Hello everyone,

In the house we bought just over a year ago (built in 1990), I am currently facing major issues with high humidity in the basement. I measured the levels with a hygrometer, and they are around 83%. The rooms also smell musty and damp. The light wells of the basement windows are also damp and musty, with humidity around 88%. The stones inside are even covered with green moss (or whatever it is). However, this is not the case for all the light wells around the house.

Since our previous owners claim they did not have such problems, I think we might have caused this issue ourselves due to incorrect ventilation. Shortly after moving in, a musty smell developed quickly in the basement, so I tried to keep the windows open as often as possible, even in summer. Now I have done some research and read that in summer, basements should only be ventilated at night because it is more humid outside during the day.

I have several urgent questions about my situation:

What actions can I take to speed up the reduction of humidity? The windows are now closed during the day. Would it help to use a fan at night to push the humid air outside? How can I prevent the wooden paneling and furniture in the basement (there are no wallpapers) from developing mold? Are there ways to keep the light wells of the windows dry? What effect does the sauna have on the humidity? Generally, the sauna provides very dry heat, but every 2-3 weeks about half a liter of infusion liquid evaporates there, which then escapes into the room air.

Additionally, there is the problem that the storage room (open clay floor with sandstone) got wet from below due to flooding in the Württemberg region. This room has only a small window, which has been kept open continuously since then. Also, a company installed a fan here for over a month, which ran nonstop during that time. Shortly after the floor got wet, mold started to develop. The company then removed the fan, but now the mold has spread to the wooden shelves in the room.

My question here is how we should proceed with this room. It is clear that the shelves must be removed. But how can we get rid of the mold spores that are obviously airborne? After all, this room is meant for storing our food. Should we use a fan? Should the door be kept open or closed?

I realize I have written quite a long message about my problem, but I hope you can still help me with some of these points. The situation is quite stressful for me.

I would really appreciate any answers!

Best regards,
Markus

From the way it sounds, I would set up an electric dehumidifier. You can adjust it to the desired humidity level, and it will switch off once that level is reached.

Regards

I also believe that Blockhauspoer’s suggestion is a good solution. The problem is that the basement is too "cold" for the soup air.

It’s about 25 degrees Celsius (77 degrees Fahrenheit) and 70% humidity outside, sometimes higher when there is light drizzle. When this air cools down in the basement, the humidity quickly reaches around 90%. So the only solution is a dehumidifier/dryer and otherwise, in such weather, keeping the windows closed.

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Hello,

Thank you very much for the tips. Based on the matching posts, the situation seems clear. I need a dehumidifier.

The question is how to approach this now. Is it better to buy a smaller unit that I can move between rooms, or a larger one to be placed centrally in the basement hallway to dehumidify all rooms at once?

The problem with the second option is that the staircase to the ground floor is open, and only at the entrance area are there doors that can be closed. This significantly increases the volume the dehumidifier has to handle.

@Bauexperte: I, of course, updated my profile right away.

Why buy? Rent a proper device to reach the base moisture level. After that, avoid intense ventilation. That’s how I would do it. Continuous dehumidifying shouldn’t be the goal.