posted 9 hours ago
The purpose of house wrap is to be vapor-permeable, while also being liquid-impermeable. This reduces the risk of moisture buildup on the sheathing.
Rockwool is vapor-permeable, but last I checked it isn't rated to be liquid-impermeable, which means building code inspections won't approve it.
Practically speaking, I saw someone soak a scrap of rockwool in water and it didn't absorb anything in about an hour and water just ran off it.
I think the best building-science case for house wrap is to protect the sheathing in case the rockwool somehow fails.
Beyond that, the building code requirement may be the most compelling reason for house wrap.
Rockwool has the advantage of not tearing easily like house wrap. Rockwool won't irritate skin like fiberglass, off-gas like foam, or settle over time like cellulose. It also gives you continuous insulation, which seems to be way better than the equivalent cavity insulation.