Perforated Plywood layer

[Schnell_MBBM]

Hallo Forum,

I am trying to estimate the hygric behavior of a roof construction. The interior layer is a perforated plywood, coverd with plaster. About 10% of the plywood consits of holes. It seems, that the holes are more or less filled with air and on one side covered with Plaster, on the other side is mineral wool.

Any idea how to adabt the material properties of the plywood layer?


Ich versuche gerade das feuchteverhalten einer Dachkonstruktion zu bewerten. Die raumseitige Verkleidung der Konstruktion besteht aus einer verputzten gelochten Furnierschichtholzplatte. Der Lochanteil beträgt ca. 10%. Ich vermute stark, dass der Putz nur die Unterseite der Löcher bedeckt und die Löcher voraussichtlich mit Luft gefüllt sind. oberseitig grenzt Mineralwolle an die Platte.

Irgend eine Idee wie ich die Materialparameter der Furnierschichtholzplatte abschätzen kann?

[fostertom]

Good question.

I am not convinced it's correct to just apply a proportional area ratio, interpolating between the characteristics of 2 materials (90% plywood : 10% air in your case) to give characteristics of the composite. This is commonly done for composite U-values (brick and mortar, or insulation between studs) - but doesn't 'feel' right to me.

I somehow suspect that your 10% air is enough to make the whole almost vapour transparent, regardless of whether it's perforated plywood, or perforated polythene. I should think though that at anything below 10%, then the significance of the surrounding material would increase.

[guyEANZ]

Kia or,
Just wondering if anyone has come up with a way of modelling perforated sheet materials as per this query from 10 years ago?