Aerated concrete 42.5 lambda 0.08 or 0.09

Hello everyone,

I hope you can help me. I am faced with the question of whether to build my exterior walls with 42.5 aerated concrete with a lambda value of 0.08 or 0.09.
I am not building according to [KFW], heating technology is gas and solar. Is there a big difference here?

Thanks in advance

approx. 20-30€ heating cost difference per year

If you don't build according to KfW, then the 42 cm brick doesn't make any sense at all. But everyone does as they please. Because I can easily achieve Lambda 0.09 or 0.08 with a 36 cm brick, which is also unfilled.

Aerated concrete 425mm Lambda 0.09 = U-value 0.204
Aerated concrete 425mm Lambda 0.08 = U-value 0.182

Aerated concrete 365mm Lambda 0.09 = U-value 0.237
Aerated concrete 365mm Lambda 0.08 = U-value 0.211

If there is no energy standard to be met, I would save myself the upgrade. Presumably, the additional costs are in the four-digit range? Not worth it.

However, I would consider going for 365mm masonry. That should be sufficient, especially with Lambda 0.08.
The additional costs for the better brick should be compensated by the reduced thickness; in return, you get narrower walls and accordingly more living space.

If you are not building according to KfW, then the 42 cm brick makes absolutely no sense. But everyone to their own. Because I can easily get Lambda 0.09 or 0.08 with a 36 cm brick as well, and that is also unfilled

Basically yes, a 42 cm brick makes little economic sense. But Lambda is only the resistance; a 42 cm wall with 0.08 naturally insulates better than a 36 cm wall with 0.08.

Aerated concrete 425mm Lambda 0.09 = U-value 0.204
Aerated concrete 425mm Lambda 0.08 = U-value 0.182

Aerated concrete 365mm Lambda 0.09 = U-value 0.237
Aerated concrete 365mm Lambda 0.08 = U-value 0.211

If there is no energy standard to be met, I would save myself the upgrade. Presumably, the additional costs are in the four-digit range? Not worth it.

I would consider going for 365mm masonry. That should also be sufficient, especially with Lambda 0.08.
The additional costs for the better brick should be compensated by the reduced thickness, in return you get narrower walls and correspondingly more living space.

Additional costs are about €2000 for our project. Good approach. Thanks!