jewishforthejokes t1_iybnx1s wrote on November 30, 2022 at 4:50 AM

Reply to comment by dirtd0g in I cannot find a straight answer anywhere: Do I need a vapor Barrier if I’m using rock wool insulation in North Alabama? by RedBeard972

And... that's why vapor barriers are bad. Air barriers are good. Vapor retarders are good. Use both. Don't use vapor barriers.

Obvious_Equivalent_6 t1_iyby2t8 wrote on November 30, 2022 at 6:38 AM

This is the correct answer. I wish I could upvote it to the top for reference. Thanks for the link - very helpful. Dr Lstiburek knows his stuff.

Ill-Poet-3298 t1_iycrb63 wrote on November 30, 2022 at 1:02 PM

What a great article.

osoALoso t1_iycsct6 wrote on November 30, 2022 at 1:12 PM

That was a great article, but am I missing something? He gave various examples of proper vapor retarded and layers, but left out the SINGLE MOST common building type in the US. Stick framed houses with OSB sheeting. All. Of his examples were concrete, brick and concrete, brick and block etc.

jewishforthejokes t1_iydulch wrote on November 30, 2022 at 5:45 PM

"Frame wall" is wood or steel, both figure 5 and 6 mention sheathing of "non paper-faced exterior gypsum sheathing, plywood, or oriented strand board (OSB)" as do several others.

The article is written using a bit more academic jargon than colloquial terms and is extremely information-dense, so it's not as beginner-friendly as it could be.

osoALoso t1_iye2dy3 wrote on November 30, 2022 at 6:34 PM

Maybe I didn't look it over close enough but every outside layer was stone or some stone mixture. Vinyl siding is incredibly common and I'm struggling to understand why house wrap, with rigid foam and osb outside should go with no insulation on the interior.

jewishforthejokes t1_iyemfyw wrote on November 30, 2022 at 8:43 PM

Figure 8 but with vinyl siding is fine, which has insulation in the cavity. Vinyl is far more forgiving of a siding material than stone, brick, or stucco so I presume the author didn't find it worth mentioning. Vinyl has lots of gaps so air and water vapor travel freely and it mounts with just nails so there's no brackets causing thermal breaks, so there's almost no way installing vinyl siding can compromise liquid water and vapor management. OTOH it's trivial to install synthetic stucco and trap water somewhere, causing rot and building destruction.