Roxul ComfortBoard IS - Manual (Page 24)

ROXUL
® The Better Insulation™ 22
The most common moisture-related durability issue caused by inward moisture drives is moisture
accumulation inside the gypsum wall board as a result of a low permeance coating such as vinyl wall
paper, or on the back of low permeance materials installed on the interior of the gypsum wall board such
as mirrors, cabinetry, whiteboards, etc. This often results in the formation of mold either on the drywall
or the back of the wall covering, and in worst cases, the disintegration of the gypsum wall board.
ROXUL COMFORTBOARD IS is vapor open, so the driven water vapor will pass directly through the
insulation. To address moisture related concerns from inward driven moisture in wall assemblies with
continuous exterior ROXUL COMFORTBOARD IS, we recommend that the air/water barrier on the
exterior of the sheathing have a maximum vapor permeance of 6.5 perms (376 ng/Pa ·s ·m
2 ), and that the
interior wall covering be latex paint. All low permeance wall coverings such as cabinetry, mirrors etc,
should be installed on strapping to allow air flow between the gypsum and the covering. These
recommendations are based on BSC’s field investigation experience, and hygrothermal simulations and
analysis of wall assemblies constructed with continuous exterior ROXUL COMFORTBOARD IS in climate
zones 1-4. For more information about this topic, please see “Hygrothermal Simulations and Analysis of
Solar-Driven Inward Water Vapor”, which is available from ROXUL Technical Services