Is insulation useful with Poroton bricks?

You don't need insulation on the outside. If you still want to do something, then use 42cm exterior walls or 36.5 with filling inside. We also have ordinary Poroton bricks without filling and the sound insulation is not particularly great but also not so bad that you always perceive it negatively. For interior walls, as already mentioned, don't use 11cm bricks. I would now also go for 17cm or sand-lime bricks. Otherwise, I find that Poroton is a good compromise between sound insulation and thermal insulation. Ask about your ventilation concept. I guess window frame ventilators. We also have them in combination with exhaust fans in the wet rooms/utility room. All in all acceptable for a residential area.

Since the OP replied like that, I think the shell is up and a change is no longer possible….and we have the 42cm, which makes zero difference compared to the 36cm in sound insulation … so if anything, always use with filling.

I am no longer sure about the insulation either.

What is the purpose of the additional insulation? You are already building at least a KfW 75 house. Therefore, you don't have to insulate – but you can, to increase the energy efficiency of the house.

Please note, however, that with additional insulation the house becomes larger in its external dimensions or, if the external dimensions remain unchanged, the interior space shrinks. In the first case (a larger house) you then need a new building application or your possibly already existing building permit is invalid. In the second case, a redesign of the entire house may be necessary because you lose space (and then doors or stairs no longer fit as planned).

But your original question is answered: you definitely do not need insulation (-: and you don't even want it, especially not if you don't have a ventilation system.

What does insulation have to do with the ventilation system? The house will be built airtight – whether with or without insulation. Therefore, the ventilation system is recommended anyway. Because houses cannot breathe, no matter what they are made of. Except old buildings. Breathing there, however, means old-fashioned "there are drafts" ;)

Hello everyone, we are building a single-family house with architects without kfw. Poroton bricks (the ones with the cavities) about 35 cm thick and triple-glazed windows are being used. Underfloor heating and heat pump are also included. According to the architect, extra external insulation is not necessary because the bricks have low thermal conductivity. Only around the roller shutter boxes there will be styrodur insulation. Since he advised us against a central ventilation system due to the costs and I now regret not having taken it, I am also no longer sure about the insulation. What do you think?

You can already achieve KFW 55 with unfilled Poroton (36.5 cm) and a heat pump (in our case ground-source heat pump). At least that's how it is for us and we are building a bungalow where KfW is harder to achieve. Nevertheless, we additionally decided on a controlled residential ventilation system. Sound insulation was not a big issue for us since we do not have problems with it.

In the topic of sound, in my opinion, you have a bigger leverage with the windows / roller shutter box (lightweight construction) possibly with interior inspection and the window installation itself than with the exterior wall. The standard triple-glazed windows are usually below 35db, the 36cm Poroton exterior wall somewhere around 42db (I don't remember the exact values anymore). So I would address what I see as the weakest link in the chain (soundproof glazing, no interior inspection, brick roller shutter box instead of lightweight construction...). If the window is foamed in, make sure that the foam fills completely.

Regarding the topic of sound, in my opinion, with the windows / roller shutter box (lightweight construction) possibly with internal revision and the window installation itself, you have a greater leverage than with the exterior wall.
The standard triple-glazed windows usually are below 35dB, the 36 Poroton exterior wall somewhere around 42dB (I don't have the exact values in mind anymore).
So I would focus on the weakest link in the chain there (soundproof glazing, no internal revision, brick roller shutter box instead of lightweight construction...)
If the window is foamed in, make sure that the foam fills the entire area.

Yes, the tip doesn't really have anything to do with the bricks, etc., but I also recommend windows that have a similar dB value as the bricks, because the normal windows today are a joke … yes, triple-glazed, you think great … highest standard. But that's not the case. Pay attention to the dB even if it is quiet where you are, it doesn't cost much more.

We don’t have insulation either, when I look at all the houses with full thermal protection, they look awful after a few years, on the other hand, nothing can breathe there anymore.