Finally finished my office insulation and settled the vapor barrier debate

I went through a similar debate with my 1982 split-level over in Chesapeake. When I redid the master bedroom, I also pulled out that old pink stuff that looked like it had been through a blender. I upgraded to the R15 Rockwool Comfortbatt specifically because my neighbor’s AC unit sits right outside that wall, and the sound dampening is honestly the best part.

For the vapor barrier, I actually spent weeks reading up on the "sandwich effect" because of our humidity. I ended up using the CertainTeed MemBrain just like you did. In our climate, putting up a 6-mil poly sheet is basially asking for mold to grow behind the brick when the dew point shifts in July. Even with the smart retarder, I made sure to leave a small gap behind the brick where I could, though it’s tough with those older builds. It’s been three years now, and the room stays at a steady 50% humidity even during the worst August heatwaves. You defintely made the right call avoiding the plastic; it allows that inward drying that these old brick houses need.

I did a similar project on my 1974 ranch in Richmond, but I ended up skipping the smart retarder entirely. With the brick veneer and that 1-inch air gap behind it, I was worried about trapping condensation between the barrier and the brick during our humid July heat. Instead of Rockwool, I went with CertainTeed Kraft-faced fiberglass batts. The paper backing acts as a Class II vapor retarder, wich felt like enough of a middle ground for our climate without sealing the wall cavity shut. I spent a lot of time checking the weep holes at the bottom of the brick exterior before I closed the drywall. If those get clogged with mortar or debris, that moisture has nowhere to go but into the sheathing. I acutally found a couple that were completly blocked. Clearing those out made a bigger difference in my wall's moisture levels than any extra layer of plastic ever coud have. It’s been three years now and the humidity in that room stays around 45% even when it's 95 degrees outside.

Nice to see people actualy thinking about inward drying. I'm down in Norfolk and the humidity's just brutal. One thing I'll add—don't sleep on air sealing while the walls are open. I did the same Rockwool setup last year but spent a full day foam-sealing the top plates and electrical boxes. Doesn't matter what vapor retarder you've got if the air's just whistling trough the outlets. It's the only way to relly keep that "swampy" feeling out for good.

Solid call on the MemBrain. I’ve seen too many guys use 6-mil poly in Zone 4 and end up with a biology project behind their drywall. If you really want to dial it in, make sure you hit the seams with Tescon Vana tape. I usually skip the staples and go straight for the Siga or Pro Clima adhesives to keep the permeability consistent. Since you're already in the walls, did you check the rim joist? I usually spray those with a Froth-Pak 210 kit before the Rockwool goes in. It’s the only way to truly stop that coastal humidity from creeping in from the foundation.