We're doing a room by room remodel at home(built in 55) including upgrading insulation and new drywall. The exterior sheathing is a fiber like material,heard it called blackjack and sound board. Between the 16" on center studs there's 3- 2x4's spaced and toe nailed as backers for the blackjack which really limits insulation,has 1 1/2" rockwool batts now. If I remove those backers to have the whole 3 1/2" stud space for insulation will it compromise the structure? The house has brick on the bottom 3' and siding above that so replacing the blackjack with osb and house wrap like I want isn't really an option for the whole wall. Willing to do the area above the brick if it will help but not sure if it's worth the trouble since we're talking a lot of work to eliminate 7" of compressed insulation.
Suggestions or advice?