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
G
garfunkel3 May 2018 16:51With the window tilted open, this shouldn’t be a problem anymore, especially if you tilt two windows to create a cross breeze.
I have often kept the blind halfway down for months. Neither storm nor water gets into the apartment... The blind alone blocks so much water on the weather-exposed side that you’d have to look carefully to find any splashes on the window.
You can also keep the windows closed on stormy days, which you can usually anticipate from the weather forecast.
I wouldn’t worry too much about it. Overall, it’s an unfortunate situation as long as no one is living there, but it’s not completely critical.
I would keep the IDE windows tilted open, lower the blind a bit, and simply observe the situation for a while.
I have often kept the blind halfway down for months. Neither storm nor water gets into the apartment... The blind alone blocks so much water on the weather-exposed side that you’d have to look carefully to find any splashes on the window.
You can also keep the windows closed on stormy days, which you can usually anticipate from the weather forecast.
I wouldn’t worry too much about it. Overall, it’s an unfortunate situation as long as no one is living there, but it’s not completely critical.
I would keep the IDE windows tilted open, lower the blind a bit, and simply observe the situation for a while.
Nordlys schrieb:
The fundamental mistake is that it was done halfway. All or nothing.
"Nothing" means a true cold attic without any insulation, as ours is. It is dry, airy, and ice-cold, at least for now. Hello @Nordlys,
I just came across this thread by chance and would like to ask about the current humidity levels in your attic.
By now, you insulated your cold roof 1–2 years ago (?), so I would like to know more about the “installation.”
I assume it is still unheated? How are the temperatures and humidity levels?
Good that this topic has come up again. I had the same setup done as the original poster, basically following @Nordlys’s definition. I have never had temperatures below 12°C (54°F) up there, but currently 85% relative humidity.
Something still had to be done because my mechanical ventilation with heat recovery system is installed on the roof.
I’m thinking about extracting the air from the top vent and bringing fresh air in through the window rebate.
Since I have heat recovery with enthalpy, supplying fresh air through the mechanical ventilation wouldn’t make sense, as I would just be bringing warm, humid air back inside.
What I don’t quite understand is why the floor stays dry with insulation and vapor barrier. It’s sealed too, isn’t it, or did I miss some kind of ventilation?
Something still had to be done because my mechanical ventilation with heat recovery system is installed on the roof.
I’m thinking about extracting the air from the top vent and bringing fresh air in through the window rebate.
Since I have heat recovery with enthalpy, supplying fresh air through the mechanical ventilation wouldn’t make sense, as I would just be bringing warm, humid air back inside.
What I don’t quite understand is why the floor stays dry with insulation and vapor barrier. It’s sealed too, isn’t it, or did I miss some kind of ventilation?
OWLer schrieb:
I have never had less than 12°C (54°F) up there, but currently 85% relative humidity. After adding insulation later on, I also have "moderately warm" temperatures, but a relatively high humidity of about 70%. Over the long term, of course, that is not ideal, which is why I asked.
I currently have a dehumidifier running and will monitor how the moisture levels develop and how much water is actually extracted.
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