My last house was double brick with EPS balls (the same as bean bag fill - in fact it was bean bag fill) and double glazed windows. The noise transmission to outside was virtually zero - only the very low bass could be heard unless I turned it up excessively loud. My neighbours were 3 metres away and they said they never heard it except for the occasional explosion.
Now imagine walls with 2-3 times as much EPS thickness and much denser EPS and a solid concrete core.
If your neighbours are only a couple of metres away then ICF will be their best option.
If you can I would suggest you explore getting a different builder.
Not only that but the ICF house will be a much better quality and cheaper to run home. I live in country Western Australia where it gets down to 1-2 degrees Celsius in winter and over 40 in summer and my ICF house doesn't have any heating or cooling except solar-passive and ceiling fans.
I only just noticed you are in Sydney - I can out you on to a reputable ICF company that will be able to source a builder for you if you like ?
Thanks but thats OK, We are already down the track a bit with these guys.
Like I said, theatre is down the list on our needs (I'm prioritising things pretty realistically here). I wont jump ship to another builder only because of this room. So many other reasons why I am going with these guys right now and not custom builders. Well, price is the biggest reason actually, if I change the house construction method to something left of field for these guys, apart from probably declining outright, its going to cost a ton more.
I may be able to get a thicker 100mm Hebel across the line though, or the denser 75mm, I've just realised that the PowerPanelXL is a 20% less heavy/dense version of the normal 75mm. That explains a fair bit of the reasons for the even lower Rw+Ctr numbers. I could probably still get full brick veneer to happen too, its actually the standard option. But then the house has to be rendered etc, I hate brick face. Eh, will have to weight it all up.
I might need to contact these hebel guys, because the data is conflicting, here are some figures for previous tests:
Big difference from the now more recent tests showing Rw 42 / Ctr 27
I wonder which is actually accurate.