ᐅ New Construction – High Humidity in the Roof Space – Decentralized Ventilation System
Created on: 21 Dec 2023 21:29
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EFHNeubauerE
EFHNeubauer21 Dec 2023 21:29Good evening,
this year we built a single-family house and moved in three weeks ago. The house has two floors plus an attic. Between the upper floor and the attic, there is a concrete ceiling with 22 cm (9 inches) of insulation. The attic is not additionally insulated because it is intended only as a storage space.
We have a decentralized ventilation system with heat recovery in the house. The attic also has supply and exhaust air connected to the ventilation system.
However, the attic humidity recently reached almost 90% despite the ventilation running. Of course, the system does not dehumidify the air, but the high value is surprising and concerning. Some items have already started to mold. We checked and found that the air coming from the ventilation system has 85% humidity.
We are now wondering:
a) Why is the humidity generally so high in the attic? Is it probably due to the temperature difference? Currently, the attic temperature is about 10°C (50°F), while the upper floor is around 20°C (68°F) — we are currently adjusting the heat pumps.
Could the high humidity also be related to the property or the natural humidity in a new building?
b) Why is the ventilation system supplying air with such high humidity?
c) And of course: what would be the best long-term, effective, and efficient solution? For now, we have set up a dehumidifier and already extracted about 15 liters (4 gallons) of water in approximately 30 hours.
Thank you in advance for your help!!!
this year we built a single-family house and moved in three weeks ago. The house has two floors plus an attic. Between the upper floor and the attic, there is a concrete ceiling with 22 cm (9 inches) of insulation. The attic is not additionally insulated because it is intended only as a storage space.
We have a decentralized ventilation system with heat recovery in the house. The attic also has supply and exhaust air connected to the ventilation system.
However, the attic humidity recently reached almost 90% despite the ventilation running. Of course, the system does not dehumidify the air, but the high value is surprising and concerning. Some items have already started to mold. We checked and found that the air coming from the ventilation system has 85% humidity.
We are now wondering:
a) Why is the humidity generally so high in the attic? Is it probably due to the temperature difference? Currently, the attic temperature is about 10°C (50°F), while the upper floor is around 20°C (68°F) — we are currently adjusting the heat pumps.
Could the high humidity also be related to the property or the natural humidity in a new building?
b) Why is the ventilation system supplying air with such high humidity?
c) And of course: what would be the best long-term, effective, and efficient solution? For now, we have set up a dehumidifier and already extracted about 15 liters (4 gallons) of water in approximately 30 hours.
Thank you in advance for your help!!!
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xMisterDx21 Dec 2023 21:44Uh. You are blowing your warm, humid air at 20, 22, 23°C (68, 72, 73°F) from the house into the attic?
There, the dew point is naturally much, much lower, and the moisture immediately condenses on everything.
Why does a cold roof need to be actively ventilated?
There, the dew point is naturally much, much lower, and the moisture immediately condenses on everything.
Why does a cold roof need to be actively ventilated?
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RotorMotor21 Dec 2023 21:51If the attic is neither insulated nor heated, and ventilation supplies air from outside, conditions there are similar to those outdoors!
Currently, in Germany, temperatures are around 5°C (41°F) with 100% humidity.
For you, it’s a bit warmer at about 10°C (50°F) with 90% humidity.
Everything as expected.
It will become drier when the weather is less humid.
Currently, in Germany, temperatures are around 5°C (41°F) with 100% humidity.
For you, it’s a bit warmer at about 10°C (50°F) with 90% humidity.
Everything as expected.
It will become drier when the weather is less humid.
EFHNeubauer schrieb:
In the house, we have a decentralized ventilation system with heat recovery. In the attic, we also have supply and exhaust air through the ventilation system.So, which is it? Decentralized or centralized?
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