 Cathedral ceilings can add an element of charm and grandeur to any new home, but it is important to use the proper building techniques to manage moisture and energy performance issues. Condensation in the insulated cavity space can lead to wood rot and mold, which can compromise the durability of the roof, the efficiency of the home, and health of the homeowners.
The bulk of moisture moving into any insulated cavity is driven primarily by air. The best practice for building insulated cathedral ceilings is to create an airtight roof assembly. There are two options: vented batt insulation and unvented spray-applied insulation.
Considering the first option, cathedral ceilings built using 2 x 12 roof rafters allow enough space for the fiberglass batt insulation and a 1.5" gap for ventilation. 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.
By using spray foam insulation, the second option, air movement through the insulated space is stopped, so venting is not needed. This option can save the homeowner the cost of the soffit and ridge vents. The sealing nature of spray foam insulation works to make the ceiling cavity airtight. This will help keep moisture-laden air from entering and condensing within the insulation or forming on the underside of the roof sheathing, and is our preferred application at SDI Insulation Inc. In non-vented ceiling applications, we are proud to offer
Spray Foam as a tool.
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