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

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

Hello

I have worked with both wall constructions. I would always choose a wall design with an installation cavity. This limits many potential sources of error to just a few. Subsequent work is also easier to carry out.

Furthermore, in timber construction, I would always separate weather protection from thermal insulation/external wall.

Olli

donny schrieb:
We currently have two regional suppliers who differ significantly, especially regarding the exterior wall construction:

Are you sure that these are the most crucial differences and not just the ones that stand out to you the most?

Often, it’s not the parameters initially considered important that ultimately influence the decision.

Are the two suppliers otherwise really comparable (both major brands or both small carpentry businesses, etc.)?

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11ant schrieb:
Are you sure that’s where the main differences lie, and not just the ones that stand out most to you?

Since I’m not an expert, I can’t rule that out 🙂. My idea was to start from the outside and work my way inwards. So, to begin with the exterior wall. Do you think that’s the wrong approach here? What would you pay special attention to?

wrobel schrieb:
Further, in timber construction I would always separate weather protection from thermal insulation/exterior wall.
Olli

What do you mean by that? Does one of the two walls not have weather protection?

Thanks to you both

Hello

Both have weather protection. The plaster. I would only change the wall structure as follows, for example: from inside to outside—stud frame with insulation, wood fiber insulation board, air cavity, plaster baseboard, plaster.

Olli

donny schrieb:
My idea was to work from the outside in, starting with the exterior wall. Do you think I’m approaching this the wrong way? What would you pay special attention to?

So I was right: You just picked one thread from the jumble of facts to pull on first :-)
"Wrong" – well, it’s an understandable, intuitive approach, and you’re in good company with it. But it’s not really that effective.

I wouldn’t focus on anything too specific right away. Instead, I recommend starting by creating your wish list. For example, begin with a detailed room list. That might start with "living room," described as "about 30 square meters (320 square feet), with dining area, but kitchen separate, maybe a fireplace."

Personally – though this is not a one-size-fits-all method – I would always start my own home planning by looking at my current apartment: asking why I wouldn’t just recreate it exactly, and then identifying what would need to be different. Then you can consider adding rooms (for children still planned, or for separating functions you want – e.g., moving the wardrobe out of the bedroom). After that comes a fundamental question: split the room list or build a single-story house, for example.

What have you already sorted out: found a plot, visited display homes, …?

wrobel schrieb:
I would only change the wall composition to this extent

To respond to that properly, you’d need to know which suppliers are involved: small carpentry firms might accommodate wall structure changes, but with the big brands, it could mean choosing a different one entirely.

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