ᐅ Aerated concrete vs. solid brick filled with mortar

Hello.

For our KfW55 house, we need a 36cm (14 inch) wall with a thermal conductivity (lambda) of 0.07.

This could be achieved either with a filled masonry block (which would probably end up being something like an MZ70 filled with mineral wool) or aerated concrete (such as Ytong).

In our area, aerated concrete is rather rare. At trade fairs, only the brick industry is usually present, and naturally, they don't have positive things to say about aerated concrete (for example, they claim Ytong would absorb so much water during construction that the house would be noticeably more humid in the first years compared to bricks).

I would therefore be interested to hear where you see the advantages and disadvantages. The insulation performance would initially be the same. Cost-wise, there seems to be no significant difference either.

What about thermal mass capacity?
Are there differences in sound insulation?
What are the properties of the finished wall? Does it require plastering? Can you hang pictures with just nails, or do you need anchors immediately?
How do the properties hold up after the house is about 20 years old?

Thanks for your opinions!

bluminger schrieb:
(For example, Ytong would absorb so much water during construction that the house would be noticeably more humid in the first few years than if bricks were used).

Don’t you have a ventilation system with KfW 55 anyway? That should be able to effectively remove the "extra" moisture from the house.

bluminger schrieb:
What are the characteristics once the wall is finished? Plastered? Can you hang pictures with just nails, or do you need anchors right away?

Aerated concrete is very soft—you can basically scratch it with your fingernail. So for a wall calendar, a nail alone will probably be enough, and if you hammer the nail in at an angle, it should also hold a wall clock.

Otherwise, aerated concrete anchors are recommended. I used them to hang my coat rack, the kitchen cabinets are still mounted to the wall, and millions of home builders can’t be wrong about using the right materials.

You will always need special anchors for hollow brick blocks.

Brick walls are probably better for soundproofing. I know someone in my circle of friends who now regrets having built with Ytong; the brick constructions next to theirs are clearly much better. However, this always depends on the location of the build.

This topic comes up now and then, which is why there are already several threads about it. I initially had the same question, but in the end, I clearly opted for bricks.

I spoke with two general contractors (GCs) in our area who said they build with both materials, but bricks account for about 90% of their projects. Aerated concrete (also known as cellular concrete or autoclaved aerated concrete) is slightly more expensive but easier to work with on-site. Overall, the costs are roughly the same.

Bricks are approximately twice as heavy and therefore undoubtedly provide better sound insulation. Additionally, the higher mass results in better thermal storage capacity. The thermal phase shift is roughly 20 hours for bricks, compared to only 17 hours for aerated concrete.

The main disadvantage, in my view, is water absorption. Aerated concrete can absorb water like a sponge and may take several years to dry completely. Here, bricks have a clear advantage.