KfW55 with 36 cm brick (im)possible?

Don't scare the OP!

In general, with 36.5 cm according to the new Energy Saving Ordinance 2016, it will probably already become difficult.

No, not more difficult than with the old Energy Saving Ordinance - because nothing is really different

With aerated concrete building materials, there may be problems with statics, and also the perforated bricks as building materials may no longer be sufficient because they are only load-bearing in one direction (anisotropic building materials).

That can't be true, otherwise we would have already had problems a long time ago. And not every construction project is accompanied exclusively by our structural engineer/energy consultant - so nepotism is out of the question before this argument comes up.

Insufficient sound insulation can go hand in hand with very light wall building materials, which is an important issue in inner-city or village edge locations with traffic load.

But definitely not with 36.5 cm aerated concrete. When I sometimes read this here, no one should install an openable window anymore or everyone should move to Tackatuckaland to join the sheep

Rhenish regards

: This has nothing to do with fearmongering. These are experiences from a current new construction project with aerated concrete. It is important to thoroughly examine all building materials for possible disadvantages alongside the apparent advantages promoted by the building materials industry, which the builder often perceives first and sometimes solely. The λ value (thermal transmittance value) is just one of many building material parameters. Unfortunately, everyone only focuses on it and gets excited when it is as low as possible, but they are unaware of the associated disadvantages. Thermal insulation and soundproofing, for example, are physically diametrically opposed. There is no material that can provide both to the highest degree. Ask a structural engineer what he thinks of the high-performance thermal insulation wall materials.

For example, I would never want to build again with an ultra-light aerated concrete "stone" with λ=0.08 that crumbles under the fingers, let alone one with λ=0.07, which is basically just chalk. The requirements arise from demands placed today—also legally—on soundproofing, thermal protection, moisture protection, etc., and are partly anchored in DIN standards. Insufficient soundproofing of an external wall is not a minor offense, especially not for the planner. Hopefully, he was able to escape to Tackatuckaland in time.

There is no material that can perform both to the highest degree.

Well, it is not really a material, rather the total absence of the like.. vacuum!

.. Vacuum!

well, maybe theoretically. The majestic silence of space will hardly be found in a vacuum insulation panel on the facade. Initial measurement investigations by the Fraunhofer Institute on the subject have so far shown no or slightly negative effects on sound insulation, similar to the uncalculated changes that sometimes occur in ETICS on facades when they start to resonate at certain frequencies and reduce sound insulation.

Our KfW55 bungalow could not be realized with 36.5 cm aerated concrete (although desired). The thermal insulation verification showed that we were actually quite far from the requirements. According to the structural engineer, this was also significantly due to the complex building geometry. It is now a 24 cm aerated concrete with 14 cm insulation despite geothermal energy and controlled residential ventilation.

If it is that extreme, 42.5 probably wouldn't have helped you either, right? Alternatively, you could have waived KfW55 or did you not want to!?