Cathedral Ceiling Attic Ventilation

Bliss points out in the original q a on cathedral ceiling ventilation the risk of forming a vapor barrier sandwich around fiberglass ceiling insulation foil faced insulation above and poly vapor barrier below is that any moisture entering the insulation will be trapped risking future mold or rot problems.

Cathedral ceiling attic ventilation.

Knee walls at the outer thirds cathedral ceiling in the middle thirds and a vented attic in the middle third with a ridge vent a common situation with finished attics at least around here. Without an attic baffle there will not be any air space for fresh air to enter the attic from the soffit vents. Cathedral vaulted or any ceiling that has insulation blocking the airflow from the soffit vents to the attic needs an attic baffle in each rafter bay. Proper ventilation is necessary in order to address water vapor that cannot be blocked to allow it to escape rather than allowing it to accumulate until it causes problems.

Each slope of the roof is divided roughly in thirds by 3 different situations. Even with the attic bypasses sealed and effective vapor retarders installed proper ventilation is essential to prevent moisture problems in cathedral ceilings. Depending on your house interior and roof framing design cathedral ceiling ventilation can be treated as an independent or attic ventilation related condition.