ᐅ Monolithic Construction: Autoclaved Aerated Concrete vs. Brick

Assuming you want to build monolithically—that is, using aerated concrete or special insulating bricks—what is better, and why do so many people actually build with bricks?

I’m going to assume aerated concrete with a thermal conductivity (lambda) of 0.08, or bricks filled with perlite and unfilled bricks also with a lambda of 0.08.

The unfilled brick has very thin webs; any drilling damages the thermal insulation over a wide area (specifically where the webs break out), and there are technically inherent strong horizontal thermal bridges.

The filled brick is basically a brick with internal insulation, so it cannot truly be called monolithic anymore, but okay. The internal insulation can settle over the investment horizon (~50–70 years), meaning significant thermal bridges may develop.

Aerated concrete is truly monolithic, meaning a uniform building material (no thin webs or the like, no internal insulation—the block itself provides insulation). A real disadvantage might be sound insulation, which is not an issue here, and the supposed drawback that the material is quite soft. You can “scratch” it with a fingernail, but in practice, when installed, this apparently does not matter.

None of the materials are optimal for hanging cabinets or similar. On the one hand, our floor plan is arranged so that heavy hanging elements (kitchen, TV) probably won’t be attached to exterior walls anyway; on the other hand, there are special anchors available for everything.

Based on the facts, assuming you are building in a quiet area, I find aerated concrete the most convincing option, and it is also the more affordable building material. So I wonder why more people don’t build monolithically with aerated concrete? Of course, there are regional specialties, but in the 21st century, traditional preferences shouldn’t decide what is invisibly built between exterior plaster and interior plaster, and where in the end hardly anyone knows whether it’s bricks, external thermal insulation composite systems (ETICS), aerated concrete, or timber framing.

So why don’t more people build monolithically with aerated concrete, or are there disadvantages I have not considered?

Just as a note: 42.5cm (17 inches) aerated concrete with a lambda of 0.08 already meets the simplified KfW 55 criteria from 01.04.2016 onwards, and 41.5cm (16.3 inches) aerated concrete with a lambda of 0.06 (which does exist, but not in Germany due to low demand) meets the passive house standard with 0.14 W/(mK). But I don’t want to compare aerated concrete with other double-shell constructions or timber framing—my question is simply: why do not more people build monolithically with aerated concrete instead of insulated bricks? Provided, as often is the case, one builds in a quiet area and sound insulation is not primarily important.

I believe it partly depends on which raw materials are available and which companies operate in the region, including both craftsmen and manufacturers.

Regarding the material: Poroton has a lower specific weight and also less heat storage capacity (both roughly by a factor of 2).

And ultimately, it’s also just a certain habit... in the southern regions, people simply tend to build with bricks (although I could be wrong about that).

BeHaElJa schrieb:

And in the end, it’s just a certain habit... in the south, they simply build with bricks (though I might be wrong about that)

That may be true, but the seismic zone also plays a role in the choice of masonry; it certainly should. In seismic zone II, you can still build with aerated concrete blocks, but you end up using many concrete reinforcements; I wouldn’t want that. This is not necessary for cavity bricks at this level.

Regards, Bauexperte

PP 2-0.35 has a bulk density class of 0.45, T8 has 0.7, and calcium silicate brick ranges between 1.2 and 2.2. Aerated concrete is therefore about 36% lower in density. On the other hand, a timber frame wall probably has only a fraction of that (mainly mineral wool with 0.02 to 0.15).

By the way, we are building in an area with no seismic zone at all (not even seismic zone 0, but simply no seismic zone).

Large parts of NRW and BW, however, are located in a seismic zone, which is interesting to know. But as I said, it’s not an issue for us.

I just watched the NDR documentary, and now I definitely want to build monolithically...

No, seriously, are there any opinions on monolithic aerated concrete versus monolithic brick construction? Assuming that sound insulation is a secondary concern and you’re not living in an earthquake zone. These two points are clear.

Hello,

I would like to know whether it is better to build with calcium silicate bricks or aerated concrete. I want to build with solid masonry, but I am not sure.

Thanks for your advice and best regards