Faced vs unfaced batts — where the vapor retarder goes

Faced batts carry their own retarder to the warm side; unfaced batts need a separate poly sheet in Zones 5–8. Never compress a batt to fit.

Two top-down sections through a stud bay, exterior at top and interior (warm-in-winter) at bottom. Faced: the batt’s kraft facing acts as a Class II vapor retarder stapled to the stud faces on the interior side. Unfaced: the batt has no facing, so in cold climate zones a separate 6-mil polyethylene sheet is run across the interior side. An inset warns that an R-19 batt crammed into a 3.5-inch 2×4 cavity is compressed and only performs at about R-17. — Source: IRC R702.7 vapor retarders; ASTM C665

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Two top-down sections through a stud bay, exterior at top and interior (warm-in-winter) at bottom. Faced: the batt’s kraft facing acts as a Class II vapor retarder stapled to the stud faces on the interior side. Unfaced: the batt has no facing, so in cold climate zones a separate 6-mil polyethylene sheet is run across the interior side. An inset warns that an R-19 batt crammed into a 3.5-inch 2×4 cavity is compressed and only performs at about R-17.

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