ᐅ Is a 30 cm aerated concrete (e.g., autoclaved aerated concrete) wall sufficient?
Created on: 9 Feb 2026 13:16
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sarajevo83
Hello everyone,
We were offered a new solid construction house with aerated concrete system wall elements 30.0 cm (12 inches) thick, lambda 0.09.
(Thermal conductivity 0.09 W/m K, U-value 0.35)
In your opinion, is this still up to date or no longer state of the art?
We were offered a new solid construction house with aerated concrete system wall elements 30.0 cm (12 inches) thick, lambda 0.09.
(Thermal conductivity 0.09 W/m K, U-value 0.35)
In your opinion, is this still up to date or no longer state of the art?
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nordanney12 Feb 2026 13:45sarajevo83 schrieb:
I only see little difference between the 30 cm and 36.5 cm that would justify the significantly higher price We are moving from 30 cm Ytong to 36.5 cm (14.4 inches) insulated Poroton. There is a huge difference. And it’s not just the bricks. Windows, doors, heating, ventilation, and especially the costs for energy consultants and certification—this last part alone is already five figures. THAT’S when you reach the costs needed to qualify for funding.
sarajevo83 schrieb:
Strange, since the last 4 new builds in our town (all with different companies) used the 36.5 Poroton T9 without insulation sarajevo83 schrieb:
Not strange, I still think it’s modern with good insulation values and reasonable stability and durability. Otherwise, everyone here wouldn’t be building like that.
I only see little difference between the 30 and 36.5 (cm) (12 and 14.4 inches) that would justify the significant extra cost. I have always argued that the 365 size (36.5cm (14.4 inches)) is sufficient for anyone who doesn’t explicitly want to waste space on external walls. For porous clay bricks, the wall thickness of “two and a half bricks” (30cm (12 inches)) is probably even more expensive on the market (at least for general contractors as major clients) than the “three-brick” thickness (36.5cm (14.4 inches)), for the trade-related reasons already mentioned. With aerated concrete, the price difference tends to be slightly less than proportional. I would take both as monolithic walls, with clay bricks not unfilled. But as I said before: in our region, including your building site, my first choice would be pumice (gray pumice KLB or Meurin, red pumice Bisotherm).
I don’t understand why you’re unnecessarily wandering around instead of letting a neutral consultant (for example, an architect whom you will need anyway) guide you.
user 301 schrieb:
Use the filled Poroton RX60 from JuWö:
With the 30cm (12 inches) you can reach KfW55, with the 36.5cm (14.4 inches) even KfW40. But probably not under *all* circumstances: otherwise Massivhaus Mittelrhein — who actually build with the generally even better insulating aerated concrete — would not have switched to size 425 about three years ago. This provider always uses the version above the current legal minimum as standard, so it was EH55 when the 2016 Energy Saving Ordinance applied, and now that the Building Energy Act has nearly reached EH55, they are calling for 425 instead of 365.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
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sarajevo8312 Feb 2026 20:51The KfW40 subsidy will not be achievable without insulation, unless the wall thickness soon reaches 50cm (20 inches).
It will probably be the Poroton T9 36cm (14 inches), which almost everyone here has built or is building and is more than satisfied with.
It will probably be the Poroton T9 36cm (14 inches), which almost everyone here has built or is building and is more than satisfied with.
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nordanney12 Feb 2026 21:29sarajevo83 schrieb:
The KFW40 subsidy won’t be achievable without insulation, unless the wall soon reaches 50cm (20 inches) thickness? That’s not correct.
A 36.5cm (14.4 inches) wall thickness is sufficient for KfW40. There are plenty of bricks to choose from.
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sarajevo8312 Feb 2026 21:35The T9, however, will not be, and it will be.
The additional cost for the filled blocks and energy consultant is unfortunately far above what the KFW40 subsidy would provide me.
The additional cost for the filled blocks and energy consultant is unfortunately far above what the KFW40 subsidy would provide me.
sarajevo83 schrieb:
The KfW40 subsidy will not be achievable without insulation, unless the wall soon becomes 50cm (20 inches) thick? The KfW40 subsidy requires the EH40 standard, which can probably be met in several ways. In my opinion, a thickness of 490mm (19 inches) would be almost "wasteful use of area for its own sake."
sarajevo83 schrieb:
It will probably be the Poroton T9 36cm (14 inches), which almost everyone else here is building or has built and is more than satisfied with. And which general contractors do almost all of them use in your area? Choosing the builder based on the masonry material would not exactly be "the tail wagging the dog," but it would be like "putting the cart before the horse." Hopefully, you will realize the importance of the masonry choice early enough.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
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