ᐅ Humidity permanently too high, mold growth, possible causes?
Created on: 1 Nov 2024 20:40
D
DrKingschultz
Hello everyone,
I have the following problem that has been bothering me:
We have a house of about 100sqm (1076 sq ft), all on one level, built in 2001 from clay blocks (probably similar to aerated concrete blocks?). The attic is unfinished; the ceiling consists of chipboard on top, then insulation, and paneling underneath.
The house meets the building and insulation standards from 2001, is plastered on the outside, and was repainted last year with silicate paint.
We have repeatedly had problems with clothing in the bedroom’s wardrobe developing mold or mildew.
Also, the wallpaper behind the bed (on an exterior wall) showed mold.
We hardly heated the bedroom, only occasionally during very severe frost, and never overnight. The bedroom is ventilated in the morning and evening with the window fully open.
Because of the mold issue, I recently bought three hygrometers and placed them in the bedroom, office, and living room.
In the living room (where the stove is located and in use from afternoon/evening), relative humidity (RH) is currently between 60 and 65%. This is at the upper limit but still acceptable, I think.
In the office (12sqm (129 sq ft)) the RH quickly rises to 70% when I am there. Only by heating a lot (normally I keep it at 19°C (66°F), now around 20°C (68°F)) and frequent short ventilation can I lower it to about 50%, but it rises again quickly. So I have to ventilate every 1–2 hours.
In the bedroom, the level is always 70% or higher. I heated it well for two days and ventilated crosswise several times a day, which lowered it to 60%, but it rises quickly again. In the mornings it can even be 80%.
Is all this normal? Am I doing something wrong? Could moisture be entering the building somewhere? I mean, I can’t heat all rooms constantly at 22°C (72°F) and ventilate all the time. I don’t want it that warm in the office or especially the bedroom. About 19–20°C (66–68°F) is enough for me in the office, and 16°C (61°F) is plenty in the bedroom.
In our previous apartment, the bedroom heater was never on, yet we never had mold.
What can I do to get the mold problem under control and permanently lower the relative humidity? Would renting a dehumidifier and drying out the building thoroughly be advisable? Or is that just addressing the symptoms?
I also checked for any damp spots on the ceiling or walls but found none.
I have the following problem that has been bothering me:
We have a house of about 100sqm (1076 sq ft), all on one level, built in 2001 from clay blocks (probably similar to aerated concrete blocks?). The attic is unfinished; the ceiling consists of chipboard on top, then insulation, and paneling underneath.
The house meets the building and insulation standards from 2001, is plastered on the outside, and was repainted last year with silicate paint.
We have repeatedly had problems with clothing in the bedroom’s wardrobe developing mold or mildew.
Also, the wallpaper behind the bed (on an exterior wall) showed mold.
We hardly heated the bedroom, only occasionally during very severe frost, and never overnight. The bedroom is ventilated in the morning and evening with the window fully open.
Because of the mold issue, I recently bought three hygrometers and placed them in the bedroom, office, and living room.
In the living room (where the stove is located and in use from afternoon/evening), relative humidity (RH) is currently between 60 and 65%. This is at the upper limit but still acceptable, I think.
In the office (12sqm (129 sq ft)) the RH quickly rises to 70% when I am there. Only by heating a lot (normally I keep it at 19°C (66°F), now around 20°C (68°F)) and frequent short ventilation can I lower it to about 50%, but it rises again quickly. So I have to ventilate every 1–2 hours.
In the bedroom, the level is always 70% or higher. I heated it well for two days and ventilated crosswise several times a day, which lowered it to 60%, but it rises quickly again. In the mornings it can even be 80%.
Is all this normal? Am I doing something wrong? Could moisture be entering the building somewhere? I mean, I can’t heat all rooms constantly at 22°C (72°F) and ventilate all the time. I don’t want it that warm in the office or especially the bedroom. About 19–20°C (66–68°F) is enough for me in the office, and 16°C (61°F) is plenty in the bedroom.
In our previous apartment, the bedroom heater was never on, yet we never had mold.
What can I do to get the mold problem under control and permanently lower the relative humidity? Would renting a dehumidifier and drying out the building thoroughly be advisable? Or is that just addressing the symptoms?
I also checked for any damp spots on the ceiling or walls but found none.
D
DrKingschultz2 Nov 2024 12:29Nida35a schrieb:
Place the wardrobe and bed preferably against interior walls, and never against exterior walls without ventilation behind them.
Do you sleep with the heating off and windows closed? Do the windows get fogged up early in the morning?
Is the heating installed as underfloor heating or radiators?
We also have a bungalow with expanded clay aggregate and no mold issues. The wardrobe is placed against an interior wall. The bed is positioned with the headboard against an exterior wall. It’s not possible to arrange it differently. One exterior wall has the window, so nothing can be placed there, and the other has the bed. We could swap the bed and wardrobe, but that wouldn’t improve the situation.
We turn the heating off at night. Usually during the day as well, but now I heat during the day and ventilate regularly to let the moisture out. The window is closed at night now, but in summer it stays open if the temperatures allow. When it’s cold outside, water also condenses on the window.
We don’t have underfloor heating, just standard wall-mounted radiators installed.
D
DrKingschultz2 Nov 2024 12:37This morning after getting up, I ventilated the bedroom and then turned on the heating. The humidity was 69%, and after 10 minutes of airing out, it dropped to 45%. Then I closed the window and turned the heating back on.
In the office, I reduced the humidity from 60% to 42% within ten minutes of ventilating.
Let’s see how long the levels stay like this, or how quickly they rise again.
In the office, I reduced the humidity from 60% to 42% within ten minutes of ventilating.
Let’s see how long the levels stay like this, or how quickly they rise again.
DrKingschultz schrieb:
Let's see how long it stays this way, or how quickly it rises again. Then ventilate every day.
It takes about 2 weeks for moisture to dry out from walls, furniture, belongings, etc.
When sleeping with closed windows, heat the room enough so the windows no longer fog up.
Or sleep with the window open.
That's what we do, using thick all-season blankets—one already a winter blanket and another a fall blanket.
D
DrKingschultz2 Nov 2024 13:02That’s a manageable period of time.
Now airing out the house works better too, with sunny high-pressure weather. Last week it was mostly mild but wet outside.
I don’t mind sleeping with the windows open, but I can’t convince my wife.
But won’t it get damp inside then, if it’s not really cold? I mean, when it’s above 0°C (32°F) and cold and wet outside, moisture should still come in, right?
Now airing out the house works better too, with sunny high-pressure weather. Last week it was mostly mild but wet outside.
I don’t mind sleeping with the windows open, but I can’t convince my wife.
But won’t it get damp inside then, if it’s not really cold? I mean, when it’s above 0°C (32°F) and cold and wet outside, moisture should still come in, right?
D
DrKingschultz5 Nov 2024 16:54So, I have now gotten a pinless moisture meter, one that you just place on the surface and read the value (Mestek WIM700A).
Depending on the wall (interior or exterior) and how the room is used, the moisture levels in the wall range between 20% and over 60%. In my opinion, this does not initially indicate any water ingress.
Even behind the nightstand in the bedroom (where there was mold), the values were in the yellow range.
But two things make me suspicious:
When I measure in the bathroom, inside the shower (tiled interior wall), the device immediately jumps to 100%. Does this point to a leak, or is it caused by water that seeps through the grout during showering? On the other side of the wall, the readings are not unusual.
And when I measure the bathroom floor (tiled, no basement underneath), I also get values between 80–100%. In the hallway (tiled as well), the values sometimes reach the 70s, but that is still in the yellow range.
The indoor humidity in the house is also not that high anymore. With the windows closed, it rises to about 60%, but when you ventilate, it quickly goes down again.
The only exception is the bedroom, where morning humidity levels are still around 80%, which can be ventilated away, but of course, I would prefer if it did not rise that high at all.
Depending on the wall (interior or exterior) and how the room is used, the moisture levels in the wall range between 20% and over 60%. In my opinion, this does not initially indicate any water ingress.
Even behind the nightstand in the bedroom (where there was mold), the values were in the yellow range.
But two things make me suspicious:
When I measure in the bathroom, inside the shower (tiled interior wall), the device immediately jumps to 100%. Does this point to a leak, or is it caused by water that seeps through the grout during showering? On the other side of the wall, the readings are not unusual.
And when I measure the bathroom floor (tiled, no basement underneath), I also get values between 80–100%. In the hallway (tiled as well), the values sometimes reach the 70s, but that is still in the yellow range.
The indoor humidity in the house is also not that high anymore. With the windows closed, it rises to about 60%, but when you ventilate, it quickly goes down again.
The only exception is the bedroom, where morning humidity levels are still around 80%, which can be ventilated away, but of course, I would prefer if it did not rise that high at all.
DrKingschultz schrieb:
Only in the bedroom do humidity levels still reach around 80% in the morning. Of course, the room is ventilated to reduce this, but ideally, it wouldn’t get that high in the first place. That’s why I recommended a decentralized ventilation system!
ypg schrieb:
If you only have this issue in the bedroom, you can install a decentralized ventilation unit. And yes, moisture builds up in the room while sleeping. From what I know, an adult releases about 1.5 liters of moisture during a sleep phase. You can counter this by ventilating manually (daily airing) or with an automatic ventilation system. Similar topics