ᐅ Which of the two wall assemblies is "better"?

Created on: 24 Dec 2018 22:25
D
donny
Hello,

we are currently exploring our basic construction method. We have two regional suppliers who differ significantly, especially regarding the exterior wall structure:

Wall construction A: Fermacell / wood fiberboard (installation layer) / OSB / cellulose / soft wood fiber insulation board / plaster (total wall thickness for KfW55 standard 37cm (15 inches))
Wall construction B: Fermacell / cellulose / wood fiber insulation board / plaster (total wall thickness for KfW55 standard 31cm (12 inches))

Both manufacturers produce their walls in a closed facility, including windows and interior components. I believe that if the construction is done properly, the installation layer can be omitted. This also creates additional living space.

For us, the question remains whether wall construction B has any disadvantages compared to wall A. In house A, the OSB board acts as a vapor barrier. In house B, there is no classic vapor barrier.
Does this give me an advantage, a disadvantage, or perhaps both? Does anyone reading this possibly live in a house with wall construction B?

I hope you can help shed some light on this topic 🙂

With that said, thank you and Merry Christmas

donny
blackm8827 Dec 2018 13:22
We live in a house with wall construction type A. For us, this was the only logical and suitable solution regarding airtightness and the associated installation cavity.

The exterior wall consists of a double-layer plaster with two coats applied over mesh, followed by a skim coat that is pre-applied in the factory. Then, a wood fiber insulation board, OSB board, 180/200 mm (7/8 inches) wood studs filled with cellulose insulation, another OSB board, an installation cavity, and finally a Farmacell board.