hi
i am going to simulate a modified bitumen roof and i need to steel deck in my simulation ,i tried to find it in WUFI database but i couldn't,how can i simulate it?
steel deck
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Amandine Piot
- WUFI International Support Team
- Posts: 40
- Joined: Mon Feb 28, 2011 11:02 pm -1100
Hi,
if the steel is at the surface, you don't need to modell it fully, just add a high Sd-value as surface resistance in the dialog "surface transfer coefficients", and choose "no water absorption".
If the steel is inside the construction, you can find it in the database, choose the source "DIN 4108-4", and then catalog "DIN 4108-4-8" (the name is in German in my version, I'm not sure if it is translated), material "8-9-1 Stahl", which is Steel. This database is just intended for thermal calculations, therefore some values are lacking. You must double click on the material to edit its properties, then click on the "unlock-button" (picture of a lock) to be able to do it.
You must add a value for the porosity (quiet small, for example 0,01, so that the material does not absorb too much water), and the vapour diffusion resistance. If you assume that your steel plate is very tight (no holes, no fastner), then just give a very high value (500000 for example). If you think you will have some perforations, or discontinuities, use a smaller value. We usually take a Sd from 50m (that is, mu=50000 if the thickness is 1mm).
Be aware that Wufi will calculate moisture flows and moisture content inside the steel, but they are not real. Wufi needs to do "as if" all materials could absorb water for numerical reasons. Those flows and moisture content do not represent anything realistic.
if the steel is at the surface, you don't need to modell it fully, just add a high Sd-value as surface resistance in the dialog "surface transfer coefficients", and choose "no water absorption".
If the steel is inside the construction, you can find it in the database, choose the source "DIN 4108-4", and then catalog "DIN 4108-4-8" (the name is in German in my version, I'm not sure if it is translated), material "8-9-1 Stahl", which is Steel. This database is just intended for thermal calculations, therefore some values are lacking. You must double click on the material to edit its properties, then click on the "unlock-button" (picture of a lock) to be able to do it.
You must add a value for the porosity (quiet small, for example 0,01, so that the material does not absorb too much water), and the vapour diffusion resistance. If you assume that your steel plate is very tight (no holes, no fastner), then just give a very high value (500000 for example). If you think you will have some perforations, or discontinuities, use a smaller value. We usually take a Sd from 50m (that is, mu=50000 if the thickness is 1mm).
Be aware that Wufi will calculate moisture flows and moisture content inside the steel, but they are not real. Wufi needs to do "as if" all materials could absorb water for numerical reasons. Those flows and moisture content do not represent anything realistic.
steel deck
Hi Amandine
thanks for great help but i am trying to simulate a steel deck in the interior side with trapped air between steel deck and upper layer ,basically it is in U shape, you can see it in this link: http://people.senecac.on.ca/steve.rakus ... dimens.htm
Thanks
thanks for great help but i am trying to simulate a steel deck in the interior side with trapped air between steel deck and upper layer ,basically it is in U shape, you can see it in this link: http://people.senecac.on.ca/steve.rakus ... dimens.htm
Thanks
Metal Decking
Where do I enter the values for "Vapor Diffusion"? Material Data?
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Christian Bludau
- WUFI SupportTeam IBP
- Posts: 1186
- Joined: Tue Jul 04, 2006 10:08 pm -1100
- Location: IBP Holzkirchen, the home of WUFI
- Contact:
Hello Kerry,
you can use a vapor diffusion resistance on the surface, maybe instead of your exterior layer, that would be entered in the surface transfer section as an sd-value outside or inside. Please keep in mind that that does not affect the rain. You probably search for that one...
You also can change the vapor resistance in a material: Go to the material data sheet and see "water vapor diffusion resistance factor" (µ-value). You also can change it depending on the moisture, see "water vapor diffusion factor, moisture dependent" in the right field. Be careful here, changing the value on the left changes only the value at 0 RH in the moisture dependent curve, if used.
Christian
you can use a vapor diffusion resistance on the surface, maybe instead of your exterior layer, that would be entered in the surface transfer section as an sd-value outside or inside. Please keep in mind that that does not affect the rain. You probably search for that one...
You also can change the vapor resistance in a material: Go to the material data sheet and see "water vapor diffusion resistance factor" (µ-value). You also can change it depending on the moisture, see "water vapor diffusion factor, moisture dependent" in the right field. Be careful here, changing the value on the left changes only the value at 0 RH in the moisture dependent curve, if used.
Christian