Hello,
Last year, we bought a bungalow built in 1974.
Before the purchase, we viewed the house four times. At that time, it had been unoccupied for about six months. During the inspections, we thoroughly checked for mold and even removed wallpaper in several places to make sure there was no mold present.
At the time of purchase, the house had double-glazed wooden windows and no significant insulation. Only the flat roof was insulated with 10 cm (4 inches) of polystyrene, which, according to the previous owner, was added in the 2000s.
After buying the house, we took the following measures:
Now to my problem and possible solutions:
For about two months, we have noticed mold forming in the corners of the exterior walls. The walls are painted, no wallpaper.
The strange thing is that there was no mold in these areas before we bought the house.
My questions:
I am very grateful for any kind of response.
Best regards
Julia
Last year, we bought a bungalow built in 1974.
Before the purchase, we viewed the house four times. At that time, it had been unoccupied for about six months. During the inspections, we thoroughly checked for mold and even removed wallpaper in several places to make sure there was no mold present.
At the time of purchase, the house had double-glazed wooden windows and no significant insulation. Only the flat roof was insulated with 10 cm (4 inches) of polystyrene, which, according to the previous owner, was added in the 2000s.
After buying the house, we took the following measures:
- The roof was renovated by adding another layer of 10 cm (4 inches) polystyrene insulation on top of the existing flat roof structure.
- Triple-glazed PVC windows were installed.
- Underfloor heating was installed, and 5 cm (2 inches) of polystyrene insulation was placed under the screed.
- The exterior walls in the ground area (from the concrete slab up to about 0.5 m (1.5 feet) above ground level) were insulated.
Now to my problem and possible solutions:
For about two months, we have noticed mold forming in the corners of the exterior walls. The walls are painted, no wallpaper.
The strange thing is that there was no mold in these areas before we bought the house.
My questions:
- Can this problem be solved by adding external insulation (about 20 cm (8 inches) of polystyrene)?
- What about ventilation? There are ventilation systems that can be installed. Does anyone have experience with them? Are such ventilation systems absolutely necessary?
I am very grateful for any kind of response.
Best regards
Julia
julia123 schrieb:
Does it make sense not just to ventilate briefly but to leave the windows tilted open in two rooms to create a cross breeze? Of course, this would only happen when we are not at home, for example while we are at work.The risk with that is that cold spots will form around the windows, which can cause moisture to build up and lead to mold. The warmth inside the house plays an important role in "dry ventilation." To prevent mold effectively, the usual better approach is a combination of opening the windows wide for a few minutes (shock ventilation) and generally heating a bit more generously. This method is especially effective for removing moisture from the house when it’s significantly colder outside (even though heating costs in an older building may be a bit higher). So even if your instinct is to “keep the heat inside,” when it comes to getting rid of moisture, this is actually the perfect time for “dry ventilation.” (This is also common practice in new builds, which often still contain a lot of moisture in the walls, screed, and so on.)There is a reason why people talk about “dry heating air” in winter here. You have a hygrometer now—if you check it when you open the windows wide, you can clearly see the humidity levels drop.
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