Insulating Cathedral Ceilings and Vaulted Ceilings

As all insulation contractors know, not all attic spaces are created equal. The insulator’s idea of the perfect attic would be above a level ceiling with lots of headroom. However, this is not always the case. Many builders and homeowners use vaulted and cathedral ceilings as part of their home designs. In order to properly insulate these areas, the most important step is correctly identifying the ceiling type. 

A cathedral ceiling is part of the roof system and thermal envelope. The underside, or sheetrock facing, is directly exposed to the living area of the home. The outside, or roof cladding, is exposed to the outdoor environment. These two components run parallel to one another and are separated only by the roof rafters. To properly insulate a cathedral ceiling with cellulose insulation, Fiberlite recommends completely filling each rafter cavity. Ventilation is not necessary for this application.

A vaulted ceiling is not part of the roof system. The ceiling does not usually run parallel to the roofline, and is not attached directly to the roof rafters. This type of construction is treated as a standard attic space. To proper insulate a vaulted ceiling, a backer board should be installed at the bottom ends of the vault as well as on the sides. This effectively creates a box to contain the insulation so that it remains in place. If the peak of the ceiling rises above the level of insulation, additional containment measures may be necessary.

As you can see, while these two ceiling types may have similar appearances inside the home, they are vastly different in construction. They cannot be insulated in the same way and still be thermally efficient. If you have any questions about how to identify vaulted and cathedral ceilings or how to properly insulate them using FIBER-LITE Cellulose Insulation, please give us a call.

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