Where do you start the wall with a sloped ceiling?

[Anna1984]

Probably doesn't matter much why you isolate it? It should be heat-insulated anyway, the outer roof doesn't (normally) have insulation and then you get decent noise reduction for any "creaking sounds" anyway.

Now I don't quite understand what you mean. The roof is insulated so, in terms of heat, it should make no difference. I'm building the kneewall because I don't want a sloped ceiling all the way down to the floor. So the question was whether the insulation in the wall against the kneewall improves soundproofing or if it's enough just to insulate the wall against the adjacent room.

 

[injonil]

Unless you ventilate the kattvindar, the insulation is useful from an energy standpoint. Sloping roofs are not always particularly well insulated.

 

[Anna_H]

Now I don't quite understand what you mean. The roof is insulated, so in terms of heat, it shouldn't make a difference. I'm building the knee wall because I don't want a sloped ceiling all the way down to the floor. So the question was whether the insulation in the wall against the knee wall improves soundproofing or if it's enough to insulate the wall against the adjacent room.

I mean that normally the roof of the knee wall is NOT insulated, it's usually the wall and the floor of the knee wall, which is the ceiling of the ground floor, that are insulated.

 

[Mikael_L]

Overall, adding insulation inside regular partition walls contributes relatively little to soundproofing. However, insulation at least absorbs any resonance sound within the cavity that the wall itself constitutes, even though it has a relatively small effect on sound transmission through the entire wall structure.

Soundproofing the wall between the room and the kattvind can be significant; if multiple rooms face the same kattvind, the kattvind itself can provide a path for airborne sounds between the rooms. If this is the case, it may be a good idea to place sheet material on both sides of the wall studs and fill at least about half of the space in the wall to dampen natural resonances in the cavity and in the wall.