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
DrKingschultz5 Nov 2024 20:31Apart from that, are the wall values acceptable? In other words, is there any indication of moisture penetration?
Is this normal for the shower and the floor tiles?
Is this normal for the shower and the floor tiles?
D
DrKingschultz5 Nov 2024 22:09I am doing that as well. However, I was also advised to check if water is penetrating anywhere.
DrKingschultz schrieb:
I do that as well. But I was also advised to check if any water is seeping in anywhere.You would notice something like that immediately. From your posts, it’s clear that your heating and ventilation habits are incorrect. How long have you been ventilating and heating the wrong way?D
DrKingschultz6 Nov 2024 15:15We have actually been heating and ventilating this way ever since we moved in—so about 10 years. It is possible that there were no issues in the first years because we were out of the house during the day and therefore did not generate much moisture.
Of course, this does not apply to the bedroom, which has always been used the same way as it is now.
Nowadays, we often work from home, meaning two people are present plus a dog, and we cook more than before. Over the past few days, I have been heating and ventilating a lot and am trying to solve the problem.
However, it is currently foggy and overcast with temperatures around 8°C (46°F) during the day, so even after ventilating, the relative humidity only drops to 50%. It was better over the weekend with sunny and cold weather.
Of course, this does not apply to the bedroom, which has always been used the same way as it is now.
Nowadays, we often work from home, meaning two people are present plus a dog, and we cook more than before. Over the past few days, I have been heating and ventilating a lot and am trying to solve the problem.
However, it is currently foggy and overcast with temperatures around 8°C (46°F) during the day, so even after ventilating, the relative humidity only drops to 50%. It was better over the weekend with sunny and cold weather.
D
DrKingschultz12 Nov 2024 13:17So, I moved the bed away from the wall, and there was no mold behind it. That’s a good sign.
The exterior wall in the bedroom shows a moisture reading of around 55-60% on the moisture meter. Not ideal, but not critical either—I’m currently drying it with heat.
However, behind my nightstand (which is placed exactly in the corner where two exterior walls meet at a 90-degree angle), there was some mold again. The affected area isn’t large, and I plan to remove it. But there I measured about 80% moisture on the wall, which is too high. When I measure right in the very corner near the floor, I get values above 90%.
Now my question: How can I find out if moisture is penetrating from outside? Or is it just accumulating there because it’s a corner with two exterior walls, probably the lowest point, the coldest spot, and with the nightstand blocking air circulation?
My idea is to move the nightstand about 10cm (4 inches) away from the wall to allow air circulation. Remove the mold, then dry the wall (maybe use a fan heater) and wait for a while. If the moisture readings rise to similar levels again, the moisture is coming from outside. If not, it’s indoor humidity.
The exterior wall in the bedroom shows a moisture reading of around 55-60% on the moisture meter. Not ideal, but not critical either—I’m currently drying it with heat.
However, behind my nightstand (which is placed exactly in the corner where two exterior walls meet at a 90-degree angle), there was some mold again. The affected area isn’t large, and I plan to remove it. But there I measured about 80% moisture on the wall, which is too high. When I measure right in the very corner near the floor, I get values above 90%.
Now my question: How can I find out if moisture is penetrating from outside? Or is it just accumulating there because it’s a corner with two exterior walls, probably the lowest point, the coldest spot, and with the nightstand blocking air circulation?
My idea is to move the nightstand about 10cm (4 inches) away from the wall to allow air circulation. Remove the mold, then dry the wall (maybe use a fan heater) and wait for a while. If the moisture readings rise to similar levels again, the moisture is coming from outside. If not, it’s indoor humidity.
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