Block Building- vapor barrier issue-help!
Cynbou
| Posted in General Questions on
We have older block (hollow core) building . Interior has poly Behind stud wall against interior of blocks, insulation between studs, drywall…now what? I’ve read too many conflicting things and need help ….do we Not use a heavy paint type sealer on the outside …we are in SC so humid summers. Have sealed along bottom up above grade on outside already and planned drainage, gutters etc.
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In coastal SC, the poly layer in the wall may not be too bad. But up in the mountains, there is a significant risk of condensation on the surface of the poly in winter when the block gets cold. In either area, installing a layer of permeable foam insulation on the exterior would help. Unfaced EPS would work. If you like the aesthetics, block buildings are perfect substrates for EIFS. Use an EIFS that includes roll-on water resistant barrier, and make sure the WRB has perm rating of 5 or more. You could also install strapping over the insulation and hang any other siding. I'd still use the roll-on WRB, though. That's a great product on block. With 2" of exterior insulation, the poly film will be near the middle of your thermal barrier, and not subject to condensation in summer or winter.
Thank you for the quick reply! We are / were hoping to get away with just painting the exterior of blocks ( DIYers ) but worry about over sealing and trapping moisture inside? Does that make sense? would a good exterior paint that has some permeability be ok? The building is Not airtight at all...we know we have to fill all cracks etc. prior to painting. We really cannot afford to apply another layer covering outside....
I will have to look up EPS and EIFS ; -)...got it. We are in the southern end of the Upstate...Greenwood County, SC
As the building is old and obviously not airtight, will painting with a WRB of 5 or higher be suitable on exterior?