Massive construction brick question

Hello,

I am planning to build a Kfw55 solid house and am now a bit unsure which bricks are really good.

At the company, it was specified:

Exterior wall:

36.5 cm porous planar ground hollow brick with butt joint interlocking, mortared with thin-bed mortar

The requirements of an energy-saving ordinance house are met without additional insulation.

UNIPOR W07 U-value 0.18

Now, you really read very different opinions regarding bricks.

And now I would like to hear your opinion on this.

I will also receive other offers and can gladly add the suggested bricks then.

I have acquaintances who have built with it and are very satisfied with it today. What they always say is only that they would use 42 cm bricks nowadays. The question that arises for me is rather which alternatives are available?? No building material has only advantages and for me it is more about weighing what is more important (insulation value, soundproofing, monolithic, price, and so on)

And why would they use a 42 brick?

Purely for energy-saving reasons, he always says that the U-value of the 42 model is 25% better and that the extra cost was probably worth it. Whether that is the case is something everyone has to decide for themselves.

We are now facing the same question. So far, two contractors planned with filled 36.5 stones (KFW 55). The contractor we spoke to last advocates for unfilled 42.5 stones. The reasoning was, among other things, better "ventilation" as well as insulation.

What is your opinion on this:
Unfilled 42.5 vs. filled 36.5.

Does anyone happen to know (purely by chance :D) what the price differences are as well? We have a second appointment next week, where I will follow up.

The narrow stone creates a slender foot ;-). In other words, more interior space with the same external dimensions. You can calculate that yourself ...