ᐅ Very high humidity levels in all rooms

xMisterDx schrieb:

Then all houses from the 1960s would be moldy. Since that’s not the case, there must be other problems here (at least for now).

Many actually do have mold issues. With the old windows, it wasn’t such a big problem because they allowed constant ventilation. In older buildings, you also get cold feet quickly, so 20 degrees Celsius (68°F) doesn’t feel the same as 20 degrees in a new build. That’s why heating is usually set much higher. This gradually puts you in a situation where you only find mold behind the furniture and it’s not visible.

In this case, the original poster replaced the windows and now has to manually achieve a certain air exchange rate per day. But almost no one manages this. With little wind, the windows would have to stay open too long; in weather like today, you don’t get a proper cross breeze. The cold air from outside is unpleasant anyway. Ventilating after showering is nice, but ideally, you should ventilate again an hour later to remove residual moisture from towels and the bathroom. Most people are at work by then, and even with home office, hardly anyone does this.

The walls from the late ’60s and early ’70s are also quite a disaster—energy was cheap, and so was construction. Therefore, I’m not surprised that the previous owner already added interior insulation. Removing it was, of course, absolutely counterproductive and could only be topped if it were reinstalled by the owner themselves. Poorly installed internal insulation often leads to serious mold growth between the insulation and the wall.

The big question now is: should the root cause be treated, or just the symptom?

With the current temperature differences between outside and inside, especially in the mornings, you don’t need a “draft” to achieve good air exchange. On the contrary, drafts are often counterproductive because they spread the particularly humid air from the bedrooms and bathrooms throughout the entire house… I have even heard of people who created an ice cave in their cold attic because the hatch was constantly open and was located right next to the bathroom, where the door was naturally left open after showering. Humid air, freezing cold roof... ice cave...

Whether the interior insulation installed by the previous owner was done correctly is another question. We don’t know.

In the short term, it can only relieve the symptoms anyway. Before getting a new kidney, most patients undergo dialysis for years. Very few spend just two weeks on the operating table because they know someone willing to donate a kidney.
The same applies here. He won’t find any contractors this winter to install a decentralized ventilation system or insulate the walls, whether inside or outside.
So, treat the symptoms: heat, ventilate, heat, ventilate, and so on.

And when you read “oil heating,” it should be clear that an energy retrofit will be inevitable in the medium term. Unless “back to the 70s”-Sahra joins forces after the 2025 election with “back to the 30s”-Tino and magically pull a brand-new six-line oil and gas pipeline through the Baltic Sea out of a hat, which is about to start operation.
I like my gas heating system, but I’m realistic enough to know it will probably be the last of its kind in my lifetime.

An open hatch to the attic is already a bad idea. There is no need to argue about that level of understanding, and that is not the point right now. The issue is that the original poster’s wall is developing mold because, with normal indoor temperatures in their house, it is impossible to keep the air dry enough.

The topic of "relative vs. absolute humidity" has already been mentioned, as well as the continuous generation of moisture in the air. Therefore, I would like to bring up once again the idea of a humidity-difference-controlled exhaust fan in the bathroom. It operates only when necessary. I would place it a) in the bathroom and b) anywhere there is a specific moisture problem.

Of course, this does not solve the problem of the all too common and illogical wall construction, which here has been taken to the extreme by removing insulation during the window insulation process. This issue must be resolved as quickly as possible.

Thank you very much for the numerous responses and tips.

I have planned the following to-dos for myself.

• Test insulating the north wall in the bedroom from the inside using climate boards.
• If that is not enough, install blown-in insulation and a ventilation unit.
• Does anyone need a kidney? Wants to insulate the house?

Regards, Andre

andre007 schrieb:

3. Does anyone need a kidney? Want to insulate the house?

Do you feel confident insulating the house exterior yourself (with friends or possibly through classified ads)? Then you can do it for just some "pocket money." The materials for a KfW55 building shell will cost well under €10,000. Insulation, adhesive, anchors, mineral plaster, mineral paint, reveals, aluminum window sills.