I've already added 2" to the wall thickness in this plan; if I go much thicker it'll start to look stupid at the doors/windows. I don't really want to give up the rockwool and fill the cavity with foam because I'll lose the sound insulation (though R42 is pretty spiffy lol)Are you trying to meet a code level requirement?
Codes usually specify cavity insulation, but when you add a continuous layer on the outside you gain a lot more than cavity improvement. Something like 20% of the wall is framing, not looking at windows now. But that framing is reducing the whole wall R-value.
Then the 2" on the outside of the framing may also covering any rim areas like in a basement ceiling.
So yes you just add up the layers in the cavity, but adding in the framing get a bit more complicated, it's an area weighted process.
More description on how your walls are built and I can go further.
Note, extra effort on air sealing helps both R-value and sound suppression.
Bud
And good morning
Codes usually specify cavity insulation, but when you add a continuous layer on the outside you gain a lot more than cavity improvement. Something like 20% of the wall is framing, not looking at windows now. But that framing is reducing the whole wall R-value.
Then the 2" on the outside of the framing may also covering any rim areas like in a basement ceiling.
So yes you just add up the layers in the cavity, but adding in the framing get a bit more complicated, it's an area weighted process.
More description on how your walls are built and I can go further.
Note, extra effort on air sealing helps both R-value and sound suppression.
Bud
And good morning
