Question

Why do we include a moisture barrier on exterior walls and why do we put it between the sheathing and the siding of the wall?

Answer 1

Moisture barrier keep the water vapours from passing through the walls.Condensation occurs whenever warm air meets cold air. This same process occurs inside the walls of your home. Without a vapor barrier in place, condensation inside the walls could ruin the insulation and promote the growth of harmful mold and bacteria.

Moisture barriers stop that water or vapor from getting any farther and potentially rotting your studs, the drywall or greenboard installed behind the enclosure.

For exterior walls,Warm air inside the home will produce condensation inside the exterior walls wherever it comes into contact with the colder outside air.Any condensation on a properly installed continuous plastic vapor barrier will eventually be reabsorbed into the ambient air of the home’s interior and not produce any damage to the wall components.

For interior walls,a continuous plastic vapor barrier behind the drywall will protect the interior walls of these areas from water damage.