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
K
Knallkörper28 Feb 2018 18:47It could work as long as wind or storms don’t cause rain or snow to enter, and the windows don’t blow away during a storm.
Knallkörper schrieb:
It might work if no rain or snow comes in during wind or storms, and if the windows don’t get blown away. I would set the roller blind halfway down to provide some protection on the weather-exposed side.
The temperature up there would naturally match the outside temperature. However, since the entire area from top to bottom is insulated, I shouldn’t get any cold from above.
Could mold develop on the windows due to constant tilt ventilation, since air only enters there? Or does parallel ventilation through the window directly opposite provide better airflow?
K
Knallkörper28 Feb 2018 19:11I wouldn't expect any mold there.
The windows are a temporary solution until we have saved enough money for a mechanical ventilation system with heat recovery. Heating is not an option up there because only underfloor heating would be possible, and as long as no one is living there or the space is not finished, it doesn’t make sense. Installing a stove upstairs that only heats that area would be pointless. So, in the end, a mechanical ventilation system will be necessary.
The fundamental mistake is that it was done halfway. Either fully or not at all.
“Not at all” means it’s a true cold floor without any insulation, like ours is. It’s dry, airy, and ice-cold, at least for now. It constantly receives fresh air through the gaps under the roof and through the tiles. Additionally, there is a Velux window set to ventilation mode.
“Fully” would mean insulating and heating this space so that it could be lived in. Like other living areas, it would also require ventilation, because modern houses are as airtight as plastic bags.
That would also work.
“Halfway” means what has been done here: insulated, wrapped up, sealed off, but neither heated nor ventilated. So, semi-cold air will remain inside and condense on the windows and similar surfaces.
The solution is forced ventilation. This means installing controlled ventilation slots in the windows, together with a Helios exhaust fan that extracts air from up there, which then pulls fresh air in through the window slots. And, under appropriate weather conditions, it will also create a draft. Karsten
“Not at all” means it’s a true cold floor without any insulation, like ours is. It’s dry, airy, and ice-cold, at least for now. It constantly receives fresh air through the gaps under the roof and through the tiles. Additionally, there is a Velux window set to ventilation mode.
“Fully” would mean insulating and heating this space so that it could be lived in. Like other living areas, it would also require ventilation, because modern houses are as airtight as plastic bags.
That would also work.
“Halfway” means what has been done here: insulated, wrapped up, sealed off, but neither heated nor ventilated. So, semi-cold air will remain inside and condense on the windows and similar surfaces.
The solution is forced ventilation. This means installing controlled ventilation slots in the windows, together with a Helios exhaust fan that extracts air from up there, which then pulls fresh air in through the window slots. And, under appropriate weather conditions, it will also create a draft. Karsten
S
Steffen801 Mar 2018 09:57Exactly for this reason, we have heated the attic (radiators instead of underfloor heating) and included it in the controlled ventilation system. The heating is set to 16 degrees Celsius (61°F)... so not much heating is needed. Humidity is around 40%.
Our architect had already pointed out this exact issue to us.
Our architect had already pointed out this exact issue to us.
Similar topics