Modelling of a brick structure on a flat roof - surface settings

[katinkar]

Hello,

I have a somewhat unusual assembly that I would like to check for moisture accumulation. See attachement. It concerns an old 5 m tall brick chimney on top a flat roof (for cultural heritage purpose only, so it is has not the air shaft through the roof).
I experienced convergence/iteration issues with my first model and I wondered if there are any suggestions of model improvement.
For instance I used 3 different exterior climates for different parts, one of which I tried to model as an exterior climate without rain... Is this generally an issue for WUFI? How can I aim to model more "simple" and avoid these calculation termination issues for this case? Could I have more adiabatic surfaces?


Thank you for all help.

[Christian Bludau]

Hi,
it is usually possible to use climates without rain in combination with other ones with rain. In your case I would guess, the insulation materials moisture storage function might be the problem. Insulation materials have very low moisture storage functions and a high increase at the end. In case the relative humidity reaches close to 100% RH, this can cause convergence issues. I would recommend to try another mineral wool, maybe the generic one (Name: Mineral Wool (heat cond.: 0,04 W/mK). This one used a generated moisture storage function and shows a much better behavior in convergence.
Christian