Roof Venting Vaulted Ceiling

These assemblies pose unique ventilation problems.

Roof venting vaulted ceiling. Properly insulated cathedral ceiling assemblies incorporating air and vapor retarders can function without ventilation. Cathedral ceilings built using 2 x 12 roof rafters allow enough space for the fiberglass batt insulation and a 1 5 gap for ventilation. The only way to do that are gable vents for intake and ridge for exhaust. Sketch above showing venting in a steep slope cathedral ceiling roof is courtesy of carson dunlop associates.

Sealing bypasses the first line of defense. Ventilating cathedral ceilings step 1. To understand the necessity of proper ventilation it helps to have a basic. Only the air space that exist at the peak if any needs venting.

How to vent a vaulted roof vaulted roof elements. Now here is the contradictory part. This type of roof assembly is designed so the air can flow up the soffit vent through an insulation baffle pass through the 1 5 gap between the insulation and roof sheathing then exit through a ridge vent. Vaulted ceilings sometimes referred to as cathedral ceilings occur in steep slope roof assemblies in which there is no attic space between a ceiling and roof deck.

In buildings where there is no roof venting anyway and where ventilation is difficult or impossible to achieve an un vented well insulated hot roof can provide a high r value ceiling and may be the second best alternative to preventing ice dam related leaks in cold climates. Click to enlarge any image. A vaulted roof features angled rafters that rest on wall plates and connect at the top to a ridge. Vented cathedral ceiling assemblies incorporate soffit or eave vents adequate open air space between insulation and roof deck sheathing and ridge vents.

Cathedral ceiling ventilation insulation if properly installed between the rafters on top of the ceiling material drywall plaster paneling sheets etc there should be approximately 2 of space left above it which allows air to flow between the bottom and top of the roof. If you fill a bay in a vaulted ceiling no vent is required. Foam filled cathedral ceilings may make sense in some cases. The question and answer article below paraphrases quotes from updates and comments an original article from solar age magazine and written by steven bliss.

The flow of water vapor. The bottom of each rafter cavity ends at the soffit which is the horizontal plane that lies just beneath.