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
I disconnected the ventilation system in the attic today and aired it out thoroughly. Let's see how things develop.
Because of the moisture and heat recovery from the enthalpy exchanger, I had been bringing in relatively humid and warm air, which was then cooled down to about 12°C (54°F). The result was a constant indoor humidity of over 80%. Let’s see where this goes now.
My original plan was to use trickle vents in the window rebate and then extract air at the top. The downside of that is that it somewhat reduces the efficiency of the heat recovery.
I think I will now just install the fans and observe the results.
Because of the moisture and heat recovery from the enthalpy exchanger, I had been bringing in relatively humid and warm air, which was then cooled down to about 12°C (54°F). The result was a constant indoor humidity of over 80%. Let’s see where this goes now.
My original plan was to use trickle vents in the window rebate and then extract air at the top. The downside of that is that it somewhat reduces the efficiency of the heat recovery.
I think I will now just install the fans and observe the results.
netuser schrieb:
I currently have a dehumidifier running and will monitor how the moisture levels develop and how much water is actually being extracted.What is the long-term experience? I also have a dehumidifier running upstairs now. I just need to go up regularly and empty the container. Of course, each time warm, humid air is released.
OWLer schrieb:
What are the long-term experiences? I now also have a dehumidifier up there. I just have to go up regularly and empty the container. Of course, every time warm, humid air comes back up. Well, I don’t have long-term experience yet... it’s only been in use for a week, but about 10 liters (2.6 gallons) have been collected so far, and currently the humidity is between 55-60% with low dehumidification (water amount). So I don’t have to go up that often to empty the water. We’ll see how it goes.
OWLer schrieb:
Thanks! I’ll try plugging the dehumidifier into a smart plug. It already vibrates quite a bit through the ceiling. Let’s see how much water I can extract from the wood and plaster.We haven’t noticed any vibrations or noise yet; it doesn’t bother us upstairs.
At least put your device on a rubber mat or something similar.
I expect the amount of water you collect will decrease significantly over time, so the effort to empty it should be manageable. If necessary, there are also simple dehumidifiers with a hose connection, which can drain into a larger container (or even outside).
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Bauenaberwie13 Jan 2022 17:30I'm completely lost on this topic by now 😀 There is a very similar parallel thread where a user has an unheated attic and stores all kinds of things there without any insulation or anything similar. I don't understand how the problems can be so drastically different.
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