Cathedral or vaulted ceilings present some unique ventilating situations that need to be addressed up front to avoid condensation problems down the road. A cathedral ceiling is typically constructed utilizing 2 x 8 rafters on 16" or 24" centers; plywood roof decking on top of the rafters; and drywall, which becomes the ceiling of the room below, on the bottom of the rafters. Since this rafter space becomes the only separation between living space and outside temperatures, many builders want to install as much insulation as possible in this space. This causes a problem by restricting the airflow capability from soffit (intake) to ridge (exhaust) within these rafter spaces. This usually shows up in the form of condensation. The following are tips to follow when designing or installing Roll Vent for use in cathedral/vaulted ceilings:   Be sure to properly “balance” the Roll Vent total net free area with soffit vent total net free area. Strip soffit vent with a net free area of at least 9 sq. in. per linear foot is necessary. Install Roll Vent and soffit venting continuously along the ridge and eave overhang, respectively. Each rafter space must have airflow. Install “vent chutes” between the rafters from the soffit to the ridge. This assures at least 1 1/2" of unobstructed air space between the bottom of the deck and top of the insulation. Install a vapor barrier on the “warm” side of the insulation to provide a block against living area moisture migrating into the rafter spaces. Following the above procedures will minimize the potential for condensation-related problems in cathedral or vaulted ceilings.

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