Air Layer Usage

[Dan001]

I am trying to model a rain screen metal wall panel system that includes mineral wool insulation and I get substantially different results depending on the air layer used in the model (i.e. "Air Layer" or "Air Layer; without additional moisture capacity") and all other materials and settings remaining the same. The analysis location is in climate zone 6.

The components I used in the model is the following:
- Metel Deck, perforated
- Air Layer 50 mm (with 10 ACH air change source)
- Rockwool Cavityrock
- DensElement Barrier System
- Fiberglass
- PE-Membrane (Poly: 0.07 perm)
- Interior Gypsum Board

When performing the analysis with the assembly above, the moisture content of the DensElement is at an acceptable level.

If the "Air Layer 50 mm" is changed to "Air Layer 50 mm; without additional moisture capacity" (keeping the 10 ACH air change source), the DensElement layer has an excessive water content.

In all analysis, the adaptive time step control was not used. I did try the adaptive time step control with the air layer without additional moisture capacity and I got similar results as the case without using the adaptive time step control.

I'm looking for recommendations on which air layer is the best to use.

[Christian Bludau]

Hi Dan,

the air layers without additional moisture show a bad convergence behavior in case of dew water. To avoid that, you can split them up, see here:
https://www.wufi-forum.com/viewtopic.ph ... 5226#p5226

I recommend to always use the adaptive time step control in combination with the air layers.

Christian