Insulating a Cathedral Ceiling
Vented or unvented roof assemblies can work, but failure carries a heavy price
Cathedral ceilings provide a majestic crown for many a great room, but insulating them can be tricky. A poorly detailed cathedral ceiling can lead to energy losses and rotted roofing. In this article, senior editor Martin Holladay describes eight ways to get a cathedral-ceiling roof to R-45 or better using both vented and unvented processes. Holladay says that vented cathedral ceilings can be difficult to insulate well, so it’s important to place the vent baffles and insulation properly. He also says that unvented cathedral ceilings have a mixed track record, but can work when the details are managed correctly. This article includes cross-section diagrams showing four ways to prepare a ceiling from above (if the roofing is going to be replaced) and four ways to access the ceiling from inside. A sidebar outlines various roof-venting myths.