36.5 cm brick: Same U-values with and without filling?

Hello.

When I recently spoke with a planner regarding the bricks to be used for a single-family house, he said they currently always use a 36.5 with mineral wool filling. When I asked whether it wouldn't be better to use a 42 without filling, he said that the values for insulation are not sufficient and only a 50 without filling is equally good. I have now compared the values using the Wienerberger bricks that the company also uses:

Wienerberger Poroton T8 36.5 mineral wool: U-value 0.21 W/m²K, thermal conductivity 0.08 W/mK
Wienerberger Poroton without filling T8 36.5: U-value 0.21, thermal conductivity 0.08

OK, the sound insulation is better with the filled brick, but it really can’t be that the other two values are the same. The price difference is not that big either (€370 and €514 per pallet as a guideline price)

What other advantages do the bricks have?

I fear that there could be problems with the mineral wool mixture at some point regarding disposal, even though I don't want to think about disposal when building a solid house....

Best regards & thanks

Hello,

What other advantages do the bricks have?

An unfilled T8 brick has roughly the sound insulation properties of a tent... I would only use something like that in a very quiet single location without any neighbors.

And they are very delicate. Getting a plug firmly into the bricks is already tricky. If you’re unlucky, you might end up buying a bunch of adhesive anchors first. Regular plugs are already difficult there.

And regarding the disposal of your house... don’t be mad at me, but that won’t be your problem anymore... ;-)

In short, with T8 I would always opt for filled bricks. We installed T14 with external thermal insulation composite systems (ETICS) on the outside and I find that already borderline.

Best regards,

Andreas

Slightly exaggerated, but generally correct. However, I would go for perlite filling, as mineral wool collapses when exposed to moisture and then loses its insulation effect. The thermal insulation is the same because the unfilled one has more thin-walled ribs and thus chambers. However, this also makes it more sound-transmitting and less stable. The filling therefore does not provide more insulation compared to it but compensates for the reduced insulation caused by the increased number of air chambers. This way, fewer chambers with thicker ribs can still provide the same insulation.

but it actually can’t be that the other two values are the same.

Yes, they can, one possible (and probably correct) explanation is this:

So the filling does not provide more insulation instead but compensates for the reduced insulation of the additional air chambers. Thus, fewer chambers with thicker ribs can still provide the same insulation.

But even with the same "profile," "no filling" (= actually: air filling) and a filling with a different medium can be equivalent in the end. The "conductivity" of the filling is one thing, but the "damping effect" of the non-solidity also exists. Two times three plus one is just as much seven as two to the power of three minus one.

The price difference now is also not that big (370€ and 514 euros per pallet as an indicative price)

Thirty-nine percent more is a "not that big" price difference? – well then, have fun with the construction costs! I advise you, as always, to follow the 11ant #Steinemantra: do not build your house with just any data sheet test winner stone, but choose a wall structure with which your builder has experience. And then fill it as needed, provided it is hollow-block.

Ok, thanks for the info.

So you think that the 36s with perlite filling are better and more stable for hanging things, milling slots for electricity, etc.? From a cost perspective, I see it more as the proportional cost of the house—whether all the bricks now cost 5,000 euros more and are worth it; you can spend more money elsewhere.

My friend built with 42s because it only cost 5,000 euros more for the whole house.

Regards and thanks

My acquaintance built with 42,

"42" may not actually be the answer to the question of all questions, but from my point of view rather a kind of team jersey of the disciples of the "more is better" faction. The "energy saving commissioner" explains quite clearly why castle walls are not "better".