ᐅ Attic Issue: High Humidity – Mechanical Ventilation with Heat Recovery?
Created on: 28 Feb 2018 13:28
S
slygon
Hi
I need your help.
We built a solid structure with Ytong in 2017.
We don’t have a basement but we do have a large attic of 70m² (750 sq ft).
Inside the attic, the walls are plastered.
The entire attic roof space is insulated with a vapor barrier and covered with drywall sheets, but not finished yet (ran out of money).
The ceiling between the second and third floor is also insulated.
Upstairs, there are two triple-glazed windows installed, lying parallel.
Now we have the problem that the humidity inside the attic is above 80% daily. The temperature is always between 5-10°C (41-50°F).
Condensation forms every day on the inside of the window frames and also in the middle of the windows between the frame and the glass.
There is no heating up there, of course, since no one lives there. It serves as a substitute basement.
Can you help me figure out how to control the high humidity problem?
I would prefer not to climb up and down the attic stairs every day to ventilate and then close everything again.
I also left both windows tilted open with half the blinds down for two days. The humidity was high, but the temperature dropped below freezing.
I wasn’t sure if that’s a good long-term solution.
A controlled mechanical ventilation system costs €2000-3000 (about $2200-3300). I already received a quote.
However, no one can explain why this is happening in the attic.
On one side, a stubborn mold stain has already formed on the plaster.
Currently, I run a dehumidifier all day every two days.
But that can’t be a permanent solution.
We really had many problems during the construction phase. And now this too :-(
Can you give us tips or help on how to solve this problem?
Thank you
I need your help.
We built a solid structure with Ytong in 2017.
We don’t have a basement but we do have a large attic of 70m² (750 sq ft).
Inside the attic, the walls are plastered.
The entire attic roof space is insulated with a vapor barrier and covered with drywall sheets, but not finished yet (ran out of money).
The ceiling between the second and third floor is also insulated.
Upstairs, there are two triple-glazed windows installed, lying parallel.
Now we have the problem that the humidity inside the attic is above 80% daily. The temperature is always between 5-10°C (41-50°F).
Condensation forms every day on the inside of the window frames and also in the middle of the windows between the frame and the glass.
There is no heating up there, of course, since no one lives there. It serves as a substitute basement.
Can you help me figure out how to control the high humidity problem?
I would prefer not to climb up and down the attic stairs every day to ventilate and then close everything again.
I also left both windows tilted open with half the blinds down for two days. The humidity was high, but the temperature dropped below freezing.
I wasn’t sure if that’s a good long-term solution.
A controlled mechanical ventilation system costs €2000-3000 (about $2200-3300). I already received a quote.
However, no one can explain why this is happening in the attic.
On one side, a stubborn mold stain has already formed on the plaster.
Currently, I run a dehumidifier all day every two days.
But that can’t be a permanent solution.
We really had many problems during the construction phase. And now this too :-(
Can you give us tips or help on how to solve this problem?
Thank you
slygon schrieb:
So we have the foil between the attic and the ceiling.I still don’t understand:
Question: Do you have a vapor barrier (barrier – not just a retarder) on or in the floor between the living space and the attic?
In other words, is there a plastic sheet on the attic floor or not?
If there isn’t one, you need to insulate the attic and fully heat it.
Regards,
Andreas
Since it was built with solid construction, I assume there is a reinforced concrete slab between the upper floor and the attic. Normally, you wouldn’t need an additional vapor barrier there. I thought it functions like a vapor barrier.
You can also place the insulation directly on the attic floor, since usually no moisture should come from below...
Or am I mistaken about something here?
But regarding the topic:
You should describe the build-up in detail, both for the roof and for the ceiling between the upper floor and the attic.
Regards
Specki
You can also place the insulation directly on the attic floor, since usually no moisture should come from below...
Or am I mistaken about something here?
But regarding the topic:
You should describe the build-up in detail, both for the roof and for the ceiling between the upper floor and the attic.
Regards
Specki
Hi,
Yes, you are mistaken. A reinforced concrete ceiling is not vapor-tight, so an additional vapor barrier is definitely needed. Otherwise, all the moisture from the concrete ceiling will move upward into the attic.
In our old house (fortunately only rented), this exact vapor barrier was missing. The attic was very damp for the first few years, and some of our belongings got moldy there. It improved later but never fully resolved.
According to our neighbor (a project manager at a very large construction company), this is a clear defect, which has happened to them as well. As a result, they had to replace the entire roof structures in a whole settlement built for the US Army.
This vapor barrier is often “forgotten.”
It doesn’t have to be the cause in the original poster’s case, but it could be.
Best regards,
Andreas
Specki schrieb:
There is a reinforced concrete ceiling between the upper floor and the attic. Normally, you don’t need an additional vapor barrier there. I thought it functions like a vapor barrier. You can also place insulation directly on the attic floor since no moisture should normally come from below... Or am I mistaken somewhere?
Yes, you are mistaken. A reinforced concrete ceiling is not vapor-tight, so an additional vapor barrier is definitely needed. Otherwise, all the moisture from the concrete ceiling will move upward into the attic.
In our old house (fortunately only rented), this exact vapor barrier was missing. The attic was very damp for the first few years, and some of our belongings got moldy there. It improved later but never fully resolved.
According to our neighbor (a project manager at a very large construction company), this is a clear defect, which has happened to them as well. As a result, they had to replace the entire roof structures in a whole settlement built for the US Army.
This vapor barrier is often “forgotten.”
It doesn’t have to be the cause in the original poster’s case, but it could be.
Best regards,
Andreas
We have a knee wall. Only the ground floor has a concrete ceiling. The second floor has been finished with drywall.
In the picture, you can see the second floor and the attic. The wooden beams were insulated from the second floor up into the roof and sealed with a vapor barrier. The second floor also has a vapor barrier on the ceiling between it and the attic.
So when I stand in the attic, I can see the insulation wool. On top of the insulation wool, we laid chipboard panels.
In other words: all the wooden beams, both above and below, were insulated and covered with a vapor barrier.
In the picture, you can see the second floor and the attic. The wooden beams were insulated from the second floor up into the roof and sealed with a vapor barrier. The second floor also has a vapor barrier on the ceiling between it and the attic.
So when I stand in the attic, I can see the insulation wool. On top of the insulation wool, we laid chipboard panels.
In other words: all the wooden beams, both above and below, were insulated and covered with a vapor barrier.
K
Knallkörper28 Feb 2018 18:03So. Now it is cold and unventilated at the top. In the living space, you have high vapor pressure. The moisture is slowly but steadily being carried into the attic. Here, in winter, the humidity will eventually reach 100%. Therefore, you urgently need proper ventilation. The insulation in the attic will then be useless.
Knallkörper schrieb:
So. And now it’s cold and unventilated at the top. In the living area, you have a high vapor pressure. Moisture is transported slowly but steadily into the attic space. In winter, the humidity there will eventually reach 100%. Therefore, you urgently need proper ventilation. The insulation in the attic is then basically ineffective. And what if I keep the windows at the top permanently tilted open?
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