ᐅ Is a 30 cm aerated concrete (e.g., autoclaved aerated concrete) wall sufficient?

Town & Country still had 24cm (9.5 inches) exterior walls as standard five years ago. We were only allowed to upgrade to 36.5cm (14 inches); they did not want to include 30cm (12 inches) or 42.5cm (17 inches) walls in the contract.
But that’s nonsense anyway. For upgrading from 0.09 to 0.08 W/(m·K) thermal conductivity with a 36.5cm (14 inches) exterior wall, they wanted to charge me 5,000 EUR (prices from 2020). For just 2 kWh/m²/year less primary energy demand.

Because the exterior walls are only part of it. According to the energy calculation, my 36.5cm (14 inches) exterior walls with 0.09 W/(m·K) lose as much heat as the windows. Even though the windows only make up 20% of the facade, and 80% is masonry.
And then there is heat loss through the ground slab and the roof or attic.

Masonry accounts for 36% of our heat losses. If you improve that by 10% with a lot of money, it only makes a 3.6% difference overall.

Take 36.5cm (14 inches) with 0.09 W/(m·K). That’s enough.

MachsSelbst schrieb:
Town & Country had 24 cm (9.5 inches) exterior walls as standard five years ago; we were only able to upgrade to 36.5 cm (14 inches), they did not want to include 30 cm (12 inches) in the contract, nor 42.5 cm (17 inches).

This does not surprise me, because it makes sense: 30 cm (12 inches) or 42.5 cm (17 inches) would shift the dimensions by a half-step in the octameter grid. For a production house provider, changing the structural design is out of the question. So the walls must grow outward, and here the half-step would disrupt the rhythm. From the provider’s point of view, the production house concept is about simplifying cost calculation. Ceiling panels, reinforcement plans, and the like: the standard designs must remain applicable without changes; special customizations are unacceptable. That is something for the individual competitors to deal with.

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We don’t need to discuss here what my Town & Country franchiser told me, discouraged me from, and then actually offered, right?

MachsSelbst schrieb:
what my Town & Country franchiser told me, talked me out of, and then actually offered

... so you mean: the headquarters said no 30 times, but the franchiser still built it for you (?)

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https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/

For us, it was Elbe-Haus that offered a package with a 30 cm (12 inches) aerated concrete YTONG exterior wall.

Exterior walls made of 30.0 cm (12 inches) aerated concrete SWE, lambda 0.09 + silicone resin plaster.

The more we look into it, the more we are moving away from this option.

MachsSelbst schrieb:
Use 36.5cm (14.4 inches) insulation with a lambda value of 0.09. That should be enough.

Thanks for the information! Although I already live in an aerated concrete house and the sound insulation is quite poor, we definitely didn’t want to build with that material anymore. According to the data, even timber frame houses provide better soundproofing than aerated concrete.