Adding a moisture source does not change the results

robbin · Post by **robbin** » Tue Mar 22, 2011 11:00 am -1100

I am trying to model a wall with an interior vapor barrier that has a rather large hole in it. When I create a moisture source using the air infiltration model the results are identical to the model without the source. Is there another way to model an interior vapor barrier with a hole?

Thanks,
Robbin

Amandine Piot · Post by **Amandine Piot** » Tue Mar 22, 2011 8:40 pm -1100

Hi Robbin,

could you give some more details on the settings of this source?
Using the hygrothermal sources is indeed the good way to take into account such holes in membranes.

robbin · Post by **robbin** » Thu Apr 07, 2011 12:38 pm -1100

I've set up my moisture source as a air infiltration model IBP for the whole layer.

air tightness class C

ventilation overpressure of 8

no clipping

I've tried a other tightness settings, but the results are always the same.

Christian Bludau · Post by **Christian Bludau** » Thu Apr 07, 2011 7:33 pm -1100

Hello Robin,
Where in your construction your source is placed? Can you describe it? The source have to be in a layer, where temperature falls below the dewpoint (somewhere close to the outside). In European Climates the Source will mainly appear during the winter month. You can check the amount of source in the table 'Status of Last Calculation', there is a line "Moisture Sources".
Christian

robbin · Post by **robbin** » Fri Apr 08, 2011 9:09 am -1100

Ah, I see I needed to extend my source to the plywood sheathing. I am getting much better results now. Thank you.

Tomás · Post by **Tomás** » Thu Apr 26, 2012 11:48 am -1100

Hi everybody,
I was just looking through this post as I have the same problem. I am trying to simulate a tear in a membrane in an internal insulation system but it's not working. I have tried both the moisture source and air change source and at a location within the temperature is below the dewpoint but it still wont work. Where am I going wrong does anybody know. I am relying on this test for my thesis which is due very soon.
Any help would be greatly appreciated.

Kind Regards,
Tomás

Christian Bludau · Post by **Christian Bludau** » Thu Apr 26, 2012 6:46 pm -1100

Sent you a pm...
Christian