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
So you have _no_ vapor barrier between the living area and the attic?
There must be one, otherwise it will be your problem. Without it, moisture from the warm living space will diffuse upward through the ceiling (even through a concrete ceiling). Then you will never really be able to keep the attic dry, no matter what you do.
Regards,
Andreas
There must be one, otherwise it will be your problem. Without it, moisture from the warm living space will diffuse upward through the ceiling (even through a concrete ceiling). Then you will never really be able to keep the attic dry, no matter what you do.
Regards,
Andreas
slygon schrieb:
We also had the interior upper part plastered.
The entire attic space is insulated with a vapor retarder. It is covered with drywall sheets but not finished yet.What exactly is the roof build-up? From the outside you have tiles, ventilation gap, weather-resistant membrane, insulation (?), vapor retarder...? No drywall or similar... What did you plaster?
S
stefanc8428 Feb 2018 14:57At least I can tell you where the moisture is coming from:
Warm air can hold more moisture than cold air. When normally humid air at 22°C (72°F) rises from below into the attic and cools down to 5°C (41°F) there, the relative humidity can increase to around 80%.
What could help, I think:
- ventilating to remove the moisture
- insulating to reduce the temperature difference
- installing a vapor retarder between the lower and upper areas to prevent too much moist air from rising
Warm air can hold more moisture than cold air. When normally humid air at 22°C (72°F) rises from below into the attic and cools down to 5°C (41°F) there, the relative humidity can increase to around 80%.
What could help, I think:
- ventilating to remove the moisture
- insulating to reduce the temperature difference
- installing a vapor retarder between the lower and upper areas to prevent too much moist air from rising
We have installed the vapor barrier foil between the attic and the ceiling. No moisture can come from there. The roof structure is standard, including insulation, foil, then drywall, and finally the roof tiles on top. The drywall does not go over the vapor barrier foil.
My question is: Can I leave the attic windows open permanently for ventilation without causing mold? This way, the attic would be continuously ventilated, and I might be able to avoid using a mechanical ventilation system.
My question is: Can I leave the attic windows open permanently for ventilation without causing mold? This way, the attic would be continuously ventilated, and I might be able to avoid using a mechanical ventilation system.
K
Knallkörper28 Feb 2018 15:37slygon schrieb:
No moisture can come from there.Moisture still comes through, just more slowly. Leaving the windows open isn't a real option; they wouldn't be storm- and heavy rain-proof then. What about heating?
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