simulating basement wall

[tobaza]

Hey i have little problem. I am trying simulate basement wall. Wall type is:

- outside
Concrete 360mm
Vapour barrier
Xps 50mm - its going 500mm underground
block of lightweight aggregate concrete: underground: 150mm, top of ground: 100mm and 500mm underground
+ inside

The problem is that wufi,s answer is that the moisture is
rising to 100% behind the xps. Like january to may and then its going back to 60% and then coming up again. I only think that is this possible? Because xps have large moisture resistance so why the moisture is behind xps?. O
Yeah i know outside concrete is cold so can it do it?
Sorry my english is not greatest
Best regards: tobaza

[Christian Bludau]

Hi Tobaza,
that right, reason is the following:
Depending on the temperature gradient from the inside to the outside you get a vapor flow also from the inside to the outside.
This flow is stopped at your vapor barrier and so you get 100% there.
Try to do that without the vapor barrier, the moisture at the concrete will be lower as the vapor can go from the xps into the concrete.
Generally spoken that are only small amounts of vapor, as the xps is quite vapor tight.
Christian