Wall construction - balance of sound/thermal insulation/economy

Hello,

I am building a single-family house next year. The house is currently planned as a Kfw 70 house with 17.5cm Poroton hollow brick T18 and 18cm EPS.

The house will stand on a hilltop, about 80m away from a lightly trafficked country road, and 750m away from a two-lane highway in a valley. The noise level feels not high in open space when it is calm.

Nevertheless, I wonder if the T18 with 17.5cm and RDK 0.8 is sufficient for external sound insulation? The evaluated sound insulation value is only 43dB.

I have read that the external sound insulation for single-family houses should be at least 44dB, preferably 47dB. I have used 47dB as a benchmark.

The builder suggested simply going to 24cm T18 (46dB). However, that would take up space if the outer dimensions remain the same.

My considerations were as follows:

Alt. 1: 17.5cm sand-lime brick RDK 1.4 (48dB) plus 18cm Neopor as insulation. An advantage would be good sound insulation inside the house as nearly all walls have 17.5cm. Additional costs only for sand-lime brick about €6,000 according to the builder, since the interior walls would also be made of sand-lime brick.

Alt. 2: 24cm Poroton T RDK 0.9 as exterior wall plus 18cm Neopor (46dB), about €3,000 additional costs only for the bricks. Interior walls mostly 17.5cm (44dB).

Which construction makes more sense? Are there possibly other reasonable alternatives?

Best regards

barcardi

17.5 sand-lime brick, 16 mineral wool, clinker
42 aerated concrete
425 T8/T7
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Why do you even build like that? Why don't you take a 36.5 T9 Poroton brick? That is also sufficient for a KFW70 house and you don't need Styrofoam on the outside.

So close to the highway, I would probably choose KS. You never know how the traffic or the expansion will develop.

Thank you for your answers, that already helps me somewhat.

Cladding with facing bricks would probably be one of the best solutions for sound insulation, but is ruled out for financial reasons. Aerated concrete is basically not an option for me.

T8 with 42.5 looks interesting, although it is likely more expensive than the sand-lime brick solution and has a higher U-value.

Currently, the sand-lime brick + Neopor solution looks best to me. No loss of space compared to the wall structure planned by the builder (17.5cm T18, 18cm EPS 035), significantly increased sound insulation, can be further improved by making the ETICS more flexible. Slight deterioration of the U-value compared to the originally planned wall structure. Additionally, we also have better sound insulation in the house since almost all walls in the house are 17.5cm thick.

What speaks in favor of the T8 solution compared to the sand-lime brick structure?