ᐅ Which masonry is best? Aerated concrete blocks or calcium silicate blocks?

Hello everyone,

We are planning to have a semi-detached house built.
The builder said, "We only build solid constructions. Both exterior and interior walls are completely made of Ytong."

Ytong certainly has its advantages for exterior walls in quiet new residential areas. However, for interior walls in terms of sound insulation—especially if you have children—it probably doesn’t perform as well. Or is the sound insulation of Ytong interior walls better than that of exterior walls?

Since the area is not particularly noisy, I could potentially accept Ytong exterior walls if the windows are suitable. However, I would clearly prefer the interior walls to be made of sand-lime brick.

I am now wondering if applying brick slips to a Ytong exterior wall would improve sound insulation? Currently, we want brick slips because there is no roof overhang, and we want the facade to remain visually appealing for as long as possible.

If brick slips on Ytong do not improve sound insulation, the next question is: How thick does the mineral wool insulation (no polystyrene or similar!) need to be on an exterior sand-lime brick wall to meet the current KfW standards?

Thank you!

Best regards