Latex Paint as Vapor Retarder
bradthewolf
| Posted in Energy Efficiency and Durability on
Building a house for a client in Saskatchewan Canada. The building is framed with 2×8 walls, will be insulated with double r14 roxul and has r12 zip sheathing on the exterior. I know the zip will be the air barrier once taped and sealed, and I’ve read repeatedly that using a 6mil poly vapour barrier on the interior will trap in moisture. So the plan is to leave out the poly and rely on the latex paint as the vapour barrier. Is this my best plan of action? Thanks
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Depending on your climate, you'll most likely need at least a class II retarder. A smart vapor retarder (or faced batts) is a generally a good idea as it allows for drying towards the interior during the warmer months. You can check here if your wall has the correct ratio for your climate (Table 9.25.5.2):
https://www.nrc-cnrc.gc.ca/obj/doc/solutions-solutions/advisory-consultatifs/codes_centre-centre_codes/revisions_errata-revisions_errata/2010_nbc_revisions_errata_november2013_2nd_printing.pdf