Hei Alltogether,
There are different papers about the sd-Value of a standing seam roof. But does anyone know a realistic value for the ventilation in a "Wirrgelegematte" (i.e. structured mat made of randomly arranged fibers) below a standing seam roof?
has anyone tips for simulating such a mat?
Wirrgelege im Stehfalzdach; Structured mat standing seam
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Schnell_MBBM
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Christian Bludau
- WUFI SupportTeam IBP
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Re: Wirrgelege im Stehfalzdach; Structured mat standing seam
You could simulate the wired mat as an unventilated air layer. In this way you also can see if there would form some dew water.
Problem is, that moisture, which is distributed to the side (out of you one-dimensional section) can not be taken in account.
Christian
Problem is, that moisture, which is distributed to the side (out of you one-dimensional section) can not be taken in account.
Christian
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Schnell_MBBM
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Re: Wirrgelege im Stehfalzdach; Structured mat standing seam
Thanks for the reply,
i thought about a similar aproach.
But to get a correct analysation of the Moisture in the roof construction it is neccessary to remove the dew water (in reality the water is drippeling inside the wired mat and running of). Therefore an aproach would be to insert some ventilation (with unknown intensity).
I thought about two other aproaches
1. possibility:
insert a moisture sink that removes some dew water shortly after it appears (first run a simulation to evaluate the amount and timestep of dew point, then create a file with a moisture sink according to the evaluated amount, then run another simulation)
2. possibility:
Run the model in Wufi2D and leave the sides of the wired mat exposed to the external surface.
But i think, the model will be quite strange when i add a Material that has quite different propertys in x and y axis (e.i. x-Achsis: 10 mm Air layer; y-Achsis: 2000 mm (
) Air layer)
What do you think about these ideas?
i thought about a similar aproach.
But to get a correct analysation of the Moisture in the roof construction it is neccessary to remove the dew water (in reality the water is drippeling inside the wired mat and running of). Therefore an aproach would be to insert some ventilation (with unknown intensity).
I thought about two other aproaches
1. possibility:
insert a moisture sink that removes some dew water shortly after it appears (first run a simulation to evaluate the amount and timestep of dew point, then create a file with a moisture sink according to the evaluated amount, then run another simulation)
2. possibility:
Run the model in Wufi2D and leave the sides of the wired mat exposed to the external surface.
But i think, the model will be quite strange when i add a Material that has quite different propertys in x and y axis (e.i. x-Achsis: 10 mm Air layer; y-Achsis: 2000 mm (
) Air layer)What do you think about these ideas?
-
Christian Bludau
- WUFI SupportTeam IBP
- Posts: 1134
- Joined: Tue Jul 04, 2006 10:08 pm -1100
- Location: IBP Holzkirchen, the home of WUFI
- Contact:
Re: Wirrgelege im Stehfalzdach; Structured mat standing seam
I thought about your first idea before, but the problem about the sink is, that you have to guess a value for the sink. Further the sink is not able to start at a kind of offset. You have to somehow teach the sink only to work if there is dew-water available.
In 2D the a layer with different properties in two directions is not the problem. A little problem may be the air layer, as the values include assumptions for radiation and a kind of ventilation. You have to somehow transform that to the length of your gap. But the problem with the running of dew water will remain.
A simplified way would be to calculate 1D with that air gap and then just do the assessment with the forming dew water, knowing in reality it may ran off and knowing that because of that you have maybe an higher amount of water in your construction than in real life. The result in this case is the maximum dew water which could occur in this layer.
In 2D the a layer with different properties in two directions is not the problem. A little problem may be the air layer, as the values include assumptions for radiation and a kind of ventilation. You have to somehow transform that to the length of your gap. But the problem with the running of dew water will remain.
A simplified way would be to calculate 1D with that air gap and then just do the assessment with the forming dew water, knowing in reality it may ran off and knowing that because of that you have maybe an higher amount of water in your construction than in real life. The result in this case is the maximum dew water which could occur in this layer.