Moisture in new buildings increases during wet weather - experiences?

  • Erstellt am 2021-06-04 08:23:50

riverstorm

2021-06-04 08:23:50
  • #1
Hello,

I am a tenant and recently moved into a newly built apartment where I, as in my previous apartment, placed a hygrometer. While in my previous apartment the humidity was mostly between 40-45%, so rather dry, it is now sometimes between 40-55% in the new apartment, but during wet weather it remains long-term at 60 to 70%. The strange thing is that the humidity in the rooms rises so strongly only during wet weather and then does not drop again until the weather changes.
Every morning and evening effective cross ventilation is done, resulting in a complete air exchange. Over the first "wet day," that is over about 12 - 14 hours, the humidity rises sharply even though practically no moisture is generated indoors and the apartment is actually oversized. If the weather remains humid, the apartment stays humid for days until the weather improves again.

I am currently not quite sure why this happens and if, or what I might be doing wrong and could do better. In any case, at 60% in living and working areas it is anything but pleasant, and of course promotes mold. Right now it is actually a solid 70%. Since I am a tenant, I naturally have a comparatively easy way out if this issue really turns out to be a problem. What is strange to me is that there is no ventilation system at all. However, overall I lack a bit of expert knowledge on this. Does anyone here perhaps have experience and can help me?

Thank you!
 

guckuck2

2021-06-04 09:00:49
  • #2


- you ventilate too little
- if the outside air is humid, it can hardly become drier inside unless it is heated
- new buildings remain damp(er) for 2-3 years. Normal.
 

Jann St

2021-06-04 09:05:01
  • #3
Good morning,

in principle, it is initially "normal" for relatively high humidity to be present in a new building. This is because during the construction phase, especially during the finishing work, a lot of moisture is introduced into the building through plaster and screed, and at the same time the house is built very tightly, so this moisture has hardly any chance to "leave" the building. This is nowadays intensified by the fast construction times and additives that accelerate setting/drying.

Now to your specific case:

Besides the humidity, I would also be interested in the temperature. These two factors always belong together. Cold air can hold less water -> higher humidity in percent with decreasing temperature. Furthermore, the cold/wet external conditions that we often have at the moment are not conducive to drying out the building, since even with shock ventilation, the air brought in cannot carry much of this moisture out of the building because it is already "saturated" itself.

So it is not very surprising that you are experiencing this, but the values are still very high. Perhaps the building was occupied a bit too quickly or finished during this very damp winter and heated late (the water could hardly escape). No general statement can be made about the ventilation system. New buildings must have a regulated, permanent minimal air exchange. This is regulated by external vents in the walls or windows. If the apartment has many windows, sometimes the so-called "window rebate vents," which are only visible when the window is open, are sufficient. However, this air exchange is by no means enough to dry out your apartment and does not exempt tenants from regular ventilation. This is more of a protective function during tenant changes or if people are on vacation.

Now my answer has not helped you yet...

1. Continue to ventilate frequently with shock ventilation – "tilt" position promotes mold growth in the lintel area
2. Keep the apartment warm (and then ventilate even more)
3. If it does not stop, contact the landlord and possibly have condensate dryers installed, which work during your absence (they are rather annoying when present)
4. If water condenses on the windows, wipe it dry

Best regards, Jann
 

Bookstar

2021-06-04 09:59:18
  • #4
Humidity must always be assessed in relation to temperature. Room temperature and wall temperatures.

Up to 70% usually nothing happens. From there it becomes uncomfortable and from 85% it is damp.

Ideal is 50 to 60%.
 

riverstorm

2021-06-04 10:27:09
  • #5
Thank you for the many quick responses! The temperature is currently quite warm at 23 to 24 degrees, in my opinion. I still don't know where that comes from.

Ventilating more often is unfortunately a bit difficult since I am usually not at home during the day. However, this was always completely sufficient in previous apartments (including two first-time occupancies), and nowhere could I create such an effective draft as here. Regarding permanent ventilation, there really is nothing at all, not even air vents. The apartment is practically hermetically sealed when the windows are closed (Is this even allowed, [BJ 2020/2021]?).

Since it doesn't sound too unusual for now, I will probably get a dehumidifier. However, I am still surprised that this problem only occurs during/after wet weather(?).
 

Jann St

2021-06-04 10:54:54
  • #6
Regarding the question of whether this is allowed, one would have to look into the calculations. Your minimum air exchange rate is required, which is calculated based on DIN1946-6 assuming various factors. If this is not achieved through normal structural conditions, appropriate systems must be installed. Therefore, as a user, it is initially not clear to you whether this can be right or wrong. However, my experience shows that structural measures are generally necessary because the buildings are very tight and well insulated. The problem with wet/cold weather is that airing on such days hardly has any benefit. That is why the humidity then rises, as less moisture is carried out, but the walls and floors continue to release moisture to the warm indoor air. A dehumidifier is certainly a good investment at first. However, don't expect too much from it. At my home, it has helped in the sense that I no longer have wet windows in the bathroom in winter (energy-wise, a moderately well-constructed building).
 

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