ᐅ KfW 70 - 36 cm Ytong blocks - Ventilation system

Created on: 22 Aug 2013 18:03
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Dali
Hello everyone,

we are planning to build a single-family house with the following specifications:
- one and a half stories
- on a slab foundation
- approximately 125 sqm (1350 sq ft)
- 36cm (14 inches) Ytong blocks (without additional insulation)
- mineral-based exterior plaster
- KfW 70 energy standard
- triple-glazed windows
- heating: gas/solar; underfloor heating throughout the entire house

Regarding a ventilation system, we are unsure about which option would be the most suitable.

Our options are:
- no ventilation system (our builder believes it is not necessary)
- decentralized ventilation system
- decentralized ventilation system with heat recovery
- centralized ventilation system with heat recovery

We have already read a lot on online forums, and the more we read, the more confused and uncertain we become...

Thank you very much in advance for your support!
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Buxel83
11 Jul 2014 08:26
Okay, I figured as much. I’ve already read about the squeaky house here. I assume that the polystyrene cladding creates a non-breathable exterior shell, which makes it absolutely necessary for them, right?

I don’t want to digress, but is the concept itself acceptable? Or is aerated concrete on aerated concrete preferable?
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Bauexperte
11 Jul 2014 09:55
Hello,
Buxel83 schrieb:

I don’t want to digress, but is the concept itself okay? Or would aerated concrete on aerated concrete be better?

What am I supposed to answer to that? Generally, anyone choosing this system has done thorough research and also knows that for moving in, it’s best to get a Hilti as a gift.

Personally—and this is subjective—I would never want to call a "warm wrapped" concrete block my property. I experienced that many years ago in a rental in OWL and don’t want to go through that again; only our kids thought it was cool as an extra playground.

By the way, there are no "breathable" walls in the literal sense, but there are exterior walls that allow a certain degree of vapor diffusion; this can be aerated concrete, high-porosity bricks, pumice, or expanded clay. What they all have in common is that from a thickness of 36.5cm (14 inches) on, they can completely do without externally applied insulation.

The system you are questioning here, from my subjective point of view, is justified (and I say this seriously and legitimately) by the fact that it is among the cheapest ways to build a single-family house. However, I belong to the type of person who stands by the principle: if it absolutely has to be polystyrene foam, then only on one side—and that side must be the outside. For that reason, I would avoid the wrapped concrete.

Regards, Bauexperte
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DerBjoern
11 Jul 2014 11:22
Bauexperte schrieb:

What am I supposed to respond to that? Anyone who chooses this system has usually done thorough research and knows that it’s best to get a Hilti as a housewarming gift for moving in

???

Aerated concrete? Hilti? Hello?! A cordless drill from Aldi is enough...

Edit: Or were you referring to the insulated concrete core system? Then a Hilti is probably a must...
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Buxel83
11 Jul 2014 23:36
DerBjoern schrieb:
???

Aerated concrete? Hilti? Hello?! A cordless drill from Aldi is enough...

Edit: Or were you referring to the Styrofoam concrete core system? Then Hilti is probably a must...

Styrofoam concrete core was meant.

Thanks, building expert, for your personal opinion. I also think the same and have my preferred option for the shell construction. We will build with Poroton bricks, probably the T8.