inveresk
Platinum Member
Heehaw, in North America normal convention is to use 1000 gauge polythene sheet inside prior to fixing drywall. The polythene acts as the vapour barrier. In the UK they mainly use foil-backed drywall. Some diffusion can occur at joints when foil backed is used but it's not significant enough to cause problems. On the outside, on top of the sheathing, its usual to staple a breathable membrane, normally Tyvek, to provide a waterproof barrier to protect the sheathing but to allow any trapped moisture to escape.
I remember reading some time ago about a problem in schools in Florida when they were finding condensation and mould inside during summers. The ambient outside conditions were humid and hot whereas the inside was air conditioned. As a result condensation was occuring almost like the reverse of the normal climate conditions. Traditionally there's a risk with internal high humdity wet zones - bathrooms, showers, laundry rooms - and the outside temperature would be cooler with around a 65% r.h. I don't know if they ever solved the problem but I would have thought the designers were likely held liable. In my experience, those hot, humid outside conditions are pretty normal in southern summers, certainly the states I've visited. I don't know if Arkansas is similar but this might explain why someone thought the answer might be to remove the vapour barrier. I would have thought that those sorts of conditions were perfect for using breathing walls because they'd function pretty well in summer and in winter.
I remember reading some time ago about a problem in schools in Florida when they were finding condensation and mould inside during summers. The ambient outside conditions were humid and hot whereas the inside was air conditioned. As a result condensation was occuring almost like the reverse of the normal climate conditions. Traditionally there's a risk with internal high humdity wet zones - bathrooms, showers, laundry rooms - and the outside temperature would be cooler with around a 65% r.h. I don't know if they ever solved the problem but I would have thought the designers were likely held liable. In my experience, those hot, humid outside conditions are pretty normal in southern summers, certainly the states I've visited. I don't know if Arkansas is similar but this might explain why someone thought the answer might be to remove the vapour barrier. I would have thought that those sorts of conditions were perfect for using breathing walls because they'd function pretty well in summer and in winter.