Note that rock-wool insulation only comes un-faced, meaning there's no kraft-paper or foil barrier. Depending on the situation, you may need to install an independent permeable membrane to serve Ò€¦ In zone 1, zone 2, zone 3 and zone 4 (except zone 4 marine), no vapor retarder is required on the interior surface of insulated wall and floor assemblies while in the northern states, some form of vapor Ò€¦