Hi,
I've simulated a 1D-construction in WUFI 2D. I don't fully understand my results. I would be pleased for any thoughts! Thank you!
The construction is a wall between a ventilation shaft and a SPA area.
Construction:
Shaft side
1. Plywood 15 mm
2. Alutrix 1mm (SD >1500)
3. Aquaboard 12,5mm (I'm using the standard gypsum board in WUFI. See attached file: GypsumBoard_Data)
4. Vapour barrier 1mm (SD 50)
5. Concrete plaster 3 mm
SPA side
Climate conditions (constant):
Shaft:
Air temperatur: 23 C
Relative humidity: 50% (base on climate file: varying between 45%-55%)
SPA:
Air temperatur: 32 C
Relative humidity: 50%
Result
I'm checking the part of the aquaboard which is closest to the shaft side. Just "inside" the Alutrix barrier. As can be seen on the attached figure "Location for moisture check in Aquaboard".
The result over a 10 year period is displayed in the attached file: Aquaboard_mot torr-sida (it is in Swedish, but I guess it's understandable).
What I see, is that the moisture is slowly accumulating over time until a level of 5 kg/m3 moisture content (or 60% relative humidity).
My question is:
Why do the moisture stop buffering at that level? There should be about 15 kg/m3 moisture available? (which is the levle in the SPA air, and in the concrete plaster) I've tried replacing the SD=50 to SD=20. I've tried replacing the aquaboard/gypsum board to plywood. The result still becomes the same.
Best,
Alice
Double vapour barriers indoors
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aliceallinger
- WUFI User
- Posts: 1
- Joined: Fri Sep 16, 2022 2:02 am -1100
Double vapour barriers indoors
- Attachments
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- GypsumBoard_Data.JPG (97.58 KiB) Viewed 2913 times
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- Location for moisture check in Aquaboard.JPG (190.2 KiB) Viewed 2913 times
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- Aquaboard_mot torr-sida.png (33.66 KiB) Viewed 2913 times
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Christian Bludau
- WUFI SupportTeam IBP
- Posts: 1160
- Joined: Tue Jul 04, 2006 10:08 pm -1100
- Location: IBP Holzkirchen, the home of WUFI
- Contact:
Re: Double vapour barriers indoors
Hi Alice,
generally, an average value between the inside and outside conditions settles over the cross-section. This may deviate locally if the dew point is reached.
In this case here, a relative humidity of 62% is set at the position evaluated. Using the moisture storage function shown, the corresponding water content of approx. 5 kg/m³ is calculated. This behaves as expected.
It might be useful to create a profile of the relative humidity over the calculated section (this can be done in the user-defined curves in Wufi Graph) to see whether there are somewhere positions with higher humidities.
Christian
generally, an average value between the inside and outside conditions settles over the cross-section. This may deviate locally if the dew point is reached.
In this case here, a relative humidity of 62% is set at the position evaluated. Using the moisture storage function shown, the corresponding water content of approx. 5 kg/m³ is calculated. This behaves as expected.
It might be useful to create a profile of the relative humidity over the calculated section (this can be done in the user-defined curves in Wufi Graph) to see whether there are somewhere positions with higher humidities.
Christian