First time posting here. I’m a remodeler / house flipper by trade.
I’m planning an addition to my personal 1953 ranch on the northern edge of Zone 4A. Hot Humid summers, cold winters.  The addition will be done with ZIP R6 and R15 Rockwool walls, R-49 vaulted ceiling and decently well air sealed. Additional cellulose will be blown in to the exsiting attic. The areas of the front of the house that the addition is not touching have the typical uninsulated 2×4 wall framing, rock lath interior, 1×12 board sheathing (not T&G), felt and then a mix of painted shake siding and full depth brick.
I’ve had cellulose and fiberglass blown into existing walls on houses I’ve flipped but never owned the house long enough to experience the results and frankly had to be very cost conscious.
I am planning on blowing insulation from the interior into the 60 ft of wall that I’d rather not tear out.
Whats my best option here? Dense pack cellulose?  Foam injection?
-Spence