A vapor barrier installs just under the drywall in a heating climate, on the exterior in a cooling climate. You may be thinking of a water-resistive barrier (vapor permeable)-- required by Code under the siding material. Around here, the WRB is installed in order to pass electrical inspection, especially on the non-sheathed gable ends to dry-in the house walls.
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17,000 dryer fires a year, when did you last clean the inside of the dryer near motor or the exhaust ducting?