Insulating 1940s house!

Hi,
I have a 1948 house in Portland Oregon,
purchased last year, we have been slowly remodeling it, and would love to run some insulation questions by you.

Previous owners re-sided a few years back with hardiplank + housewrap over existing 1x6 horizontal siding.

my question is, this house being so old of course didn’t have insulation in the 2x4 cavity’s. We opened up most of the interior walls.

our contractor who also happens to be a friend recommended r15 rockwool for insulation, drywall and then a vapor retardant paint on drywall. I know now ideally we should have added a 1x2 to fir it out.

from my research I know the 1x6 siding is not ideal vs sheathing and can cause air leaks which could lead to mold growth. With the siding having been replaced and a house warp installed is there less concern for issues? Reason I ask is the walls are already up, insulated and taped.

 

So the current siding has been on the house for a number of years, just because you have added another layer of siding why would that all of a sudden cause mold? Mold is associated with long term water issues so if you haven't seen it so far just because you added siding and house wrap (which is not a water barrier just water retarder) your situation would not be worse.

Air leaks should have been addressed when the wall cavities were open, not much you can do now!

 

My concern with the air leaks is now that the cavity has been filled with rockwool, it’s possible it won’t be able to breath or dry out like before when empty.

 

Again, your mixing air leaks with water leaks, they are not associated!