Vaulted Roof Ventilation

Is the radiant barrier in a useful place.

Vaulted roof ventilation.

In my proposed cathedral ceiling detail sketch at left i want to use a reflective foil between the insulation and the roof sheathing to double as a radiant barrier and a cathedral ceiling ventilation space liner. Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation evenly split between intake and exhaust for every 300 square feet of attic floor space. In the case of a cathedral vault where the interior ceiling is parallel to the exterior roof line installing skylights is a simple process. A ridge vent features an open strip along the length of the ridge where the air that enters the soffit can escape.

Proper ventilation even with the attic bypasses sealed and effective vapor retarders installed proper ventilation is essential to prevent moisture problems in cathedral ceilings. When renovating an older home whose roof rafters are only 2x6 really 5 1 2 x 1 5 in dimension the available space for insulation and ventilation is limited therefore limiting the options for a combination of good under roof ventilation and high insulation r values in the cathedral ceiling. Depending on your house interior and roof framing design cathedral ceiling ventilation can be treated as an independent or attic ventilation related condition. Vent the roof deck.

Proper attic ventilation consists of a balance between air intake at your eaves soffits or fascias and air exhaust at or near your roof ridge. In a vaulted roof a ridge vent serves as the outtake or exhaust vent. You ll want a tight ceiling air barrier with no air leakage into the cathedral ceiling a critical detail for all cathedral ceiling designs. That is create a vent channel above the insulation with low and high 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. If the attic space is going to be conditioned either for living or mechanical purposes or if a home design calls for a vaulted ceiling provision r806 3 in the international residential code calls for the roof deck above the space to be vented continuously from the eave to the ridge. Without an attic baffle there will not be any air space for fresh air to enter the attic from the soffit vents. A balanced system of soffit and ridge ventilation provides continuous ventilation of hot moist air at the hottest point of the roof.