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Username_wahl6 Jan 2017 11:39Hello, we have a huge problem.
We have been living in a new KfW 55 house since early summer, and now there is significant condensation on the lower part of all the windows, both on the glass and the frame, with damp joints/corners on the windowsill (unfortunately made of wood -> mold). Room temperature about 23°C (73°F), relative humidity around 55%, decentralized ventilation system. The blower door test was good, so everything is airtight. The installation looked professional to me; in the timber frame house, everything fits very precisely, with sealing using self-expanding foam rubber tape, and polystyrene insulation wedges below the window.
The architect and window fitter are coming on Monday. But maybe someone from the forum can already offer advice or has had similar experiences. I believe that in new buildings with new windows, this should not happen.
Unilux plastic windows, "ISO STAR"
Profile depth 88 mm (3.5 inches) with six profile chambers, outer frame 76 mm (3 inches), sash 78 mm (3 inches)
ISO thermal insulation glazing Ug 0.5 – Glass construction: ISO 4-18-4b-18-4, 26 mm (1 inch)
Warm edge spacer
Thermal transmittance value 0.76 W/m²K
We have been living in a new KfW 55 house since early summer, and now there is significant condensation on the lower part of all the windows, both on the glass and the frame, with damp joints/corners on the windowsill (unfortunately made of wood -> mold). Room temperature about 23°C (73°F), relative humidity around 55%, decentralized ventilation system. The blower door test was good, so everything is airtight. The installation looked professional to me; in the timber frame house, everything fits very precisely, with sealing using self-expanding foam rubber tape, and polystyrene insulation wedges below the window.
The architect and window fitter are coming on Monday. But maybe someone from the forum can already offer advice or has had similar experiences. I believe that in new buildings with new windows, this should not happen.
Unilux plastic windows, "ISO STAR"
Profile depth 88 mm (3.5 inches) with six profile chambers, outer frame 76 mm (3 inches), sash 78 mm (3 inches)
ISO thermal insulation glazing Ug 0.5 – Glass construction: ISO 4-18-4b-18-4, 26 mm (1 inch)
Warm edge spacer
Thermal transmittance value 0.76 W/m²K
Passivhaus schrieb:
Pronounced condensation forms on all windows at the lower part of the glass and frame, with wet joints/corners on the windowsill (unfortunately made of wood -> mold), indoor temperature around 23°C (73°F), relative humidity about 55%, decentralized ventilation system. Blower door test was good, so everything is airtight.Exactly, that’s the point. The window is the weakest link. This is where the greatest temperature differences occur, causing the indoor humidity to condense on the cold glass.
I find 55% relative humidity quite high, considering you have a ventilation system. Is it possibly not set correctly? You likely need to ventilate additionally to get rid of the moisture.
Do you still have a lot of construction moisture inside, despite the wooden construction, from plaster or screed? In any case, your body perspiration as well as daily showering and cooking increase the indoor humidity, which needs to be removed from the house.
There is a risk of mold starting at around 70% relative humidity.
I really feel sorry for you.
Heat recovery ventilation systems without enthalpy control would lower the indoor humidity to around 25% in a well-insulated house during current subzero temperatures.
Cold air contains very little water vapor, while warm air can hold significantly more moisture.
For example, when 1m³ (35.3 ft³) of air is warmed from -5°C (23°F) and 90% relative humidity to 20°C (68°F), the relative humidity of that same volume of air—without influences from kitchens, showers, breathing, or plants—drops to only 17.6%.
A level of 55% humidity in winter indicates that something might be wrong.
Could this possibly happen in a room with ventilation blockage, or is the ventilation system’s airflow rate set too low?
Cold air contains very little water vapor, while warm air can hold significantly more moisture.
For example, when 1m³ (35.3 ft³) of air is warmed from -5°C (23°F) and 90% relative humidity to 20°C (68°F), the relative humidity of that same volume of air—without influences from kitchens, showers, breathing, or plants—drops to only 17.6%.
A level of 55% humidity in winter indicates that something might be wrong.
Could this possibly happen in a room with ventilation blockage, or is the ventilation system’s airflow rate set too low?
U
Username_wahl6 Jan 2017 16:23The problem occurs throughout the entire house. There are a total of 8 Marley heat exchangers installed, 4 on the ground floor and 4 on the upper floor. They mostly operate on a low setting (1 out of 3), except in the utility room where they run on setting 2, because the noise level at setting 2 is already quite disturbing. According to the manufacturer, at setting 1 the air exchange rate is 16 m³ per hour (565 cubic feet per hour).
There should no longer be any construction moisture. The windows were left open all summer, and aside from the screed, there was no wet material present.
There should no longer be any construction moisture. The windows were left open all summer, and aside from the screed, there was no wet material present.
AOLNCM schrieb:
55% in winter, something doesn’t add up.It may seem unusually high if you assume constant ventilation, but at the same time, it’s not too high and can actually feel quite comfortable for people during winter.
I’d agree with ypg here. Yes, it’s unusually high considering there is a controlled ventilation system, but it’s not alarmingly high. Water condenses on the windows and needs to be wiped off, otherwise the wood will, of course, start to rot.
Here is a comparison: in our open-plan kitchen and living area (just under 60m² (645 sq ft)) in the evening, WITHOUT a ventilation system (2 people), the humidity is 55% lower.
Windows 4-12-4-12-4 mm (4-12-4-12-4 mm) / U-value: 0.7 W/m²K, with no signs of moisture in the corners.
However, the building standard is only KfW70. I don’t know how much that affects things. Moved in August 2015.
I agree with Alex, 55% is good, but relatively high considering controlled mechanical ventilation.
Even in the bedroom (65%-70% relative humidity in the morning, 13m² (140 sq ft)), with venetian blinds in the window corners, there is no moisture. Here the window is 6-12-4-12-8 / U-value 0.7 W/m²K.
Good luck tomorrow, and don’t fall for the usual “You’re ventilating incorrectly.”
Good luck
Heiko
Windows 4-12-4-12-4 mm (4-12-4-12-4 mm) / U-value: 0.7 W/m²K, with no signs of moisture in the corners.
However, the building standard is only KfW70. I don’t know how much that affects things. Moved in August 2015.
I agree with Alex, 55% is good, but relatively high considering controlled mechanical ventilation.
Even in the bedroom (65%-70% relative humidity in the morning, 13m² (140 sq ft)), with venetian blinds in the window corners, there is no moisture. Here the window is 6-12-4-12-8 / U-value 0.7 W/m²K.
Good luck tomorrow, and don’t fall for the usual “You’re ventilating incorrectly.”
Good luck
Heiko
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