ᐅ KfW55 with 36 cm brick wall – feasible or not?

Don’t scare the original poster!

wpic schrieb:

In general, with 36.5cm (14.4 inches), it already becomes difficult under the new Energy Saving Ordinance 2016.

No, not more difficult than under the old Energy Saving Ordinance – because nothing has really changed.

wpic schrieb:

With aerated concrete building materials, there may be structural issues, and also hollow bricks as building materials might no longer be sufficient since they can only bear loads in one direction (anisotropic building materials).

That can’t be correct, otherwise we would have had problems long ago. And not every construction project is overseen exclusively by our structural engineer/energy consultant – so don’t bring up accusations of nepotism before making that argument.

wpic schrieb:

Insufficient sound insulation can come with very lightweight wall materials, which is an important issue in inner-city or village-edge areas with traffic exposure.

But certainly not with 36.5cm (14.4 inches) aerated concrete walls. When I read some of the comments here, you’d think no one should install an operable window anymore or everyone should move to the middle of nowhere away from traffic.

Best regards, Bauexperte

@Bauexperte: This is not about fearmongering. These are experiences from a current new construction project using aerated concrete. It is important to thoroughly examine all building materials for possible disadvantages alongside the apparent benefits promoted by the building material industry, which the builder often perceives first and sometimes as the only aspect. The λ-value (thermal conductivity) is only one of many material properties. Unfortunately, everyone tends to focus solely on this and gets excited when it is as low as possible, without being aware of the associated drawbacks. Thermal insulation and soundproofing, for example, are physically opposing qualities. There is no material that can excel at both to the highest degree. Ask a structural engineer what they think about high-performance wall materials designed primarily for thermal insulation.

For instance, I would never want to build again with an ultra-light aerated concrete "block" with a λ-value of 0.08, which crumbles under your fingers, let alone one with a λ-value of 0.07, which is basically just chalk. These requirements arise from the demands placed on soundproofing, thermal protection, moisture protection, etc., which today are often also legally mandated and partially anchored in the DIN standards. Insufficient soundproofing of an external wall is not a minor offense, especially not for the planner. Hopefully, they managed to leave for Tackatuckaland in time.

wpic schrieb:
There is no material that can deliver both to the highest degree.

Well, it is not really a material, but rather the complete absence of any such thing... Vacuum!

SirSydom schrieb:
.. Vacuum!

Well, maybe in theory. The majestic silence of space is unlikely to be found in a vacuum insulation panel on a façade. Initial measurement studies by the Fraunhofer Institute on this subject have so far shown no or slightly negative effects on sound insulation, similar to the unpredictable changes sometimes caused by external thermal insulation composite systems (ETICS) on façades, when they start to resonate at certain frequencies and reduce soundproofing.

Our KfW55 bungalow could not be built using 36.5cm (14.4 inches) aerated concrete as originally planned. The thermal insulation verification showed that we were quite far from meeting the requirements. According to the structural engineer, this was largely due to the complex building geometry. In the end, 24cm (9.5 inches) aerated concrete with 14cm (5.5 inches) insulation was used, despite having geothermal heating and controlled mechanical ventilation.

If it's that extreme, even 42.5 probably wouldn't have helped you anymore, right? Alternatively, you could have skipped KfW55, or you simply didn't want to!?