Unvented Cathedral Ceiling Insulation

Insulating an unvented cathedral ceiling.

Unvented cathedral ceiling insulation.

So your choices are 3 1 2 thick batt insulation for an r value of about r 11 9 or rigid insulation board for a r 20 to r 30 depending on the type of board. A poorly detailed cathedral ceiling can lead to energy losses and rotted roofing. Worries about the hot roof un vented cathedral ceiling designs how to. Martin s post focuses on the marketing of owens corning 039 s propink unvented attic insulation system.

An unvented assembly can perform well but it s important to get the details right to avoid sheathing rot. 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. Therefore leaving about 1 for venting the net depth of insulation should be about 8 or so. These assemblies are created by eliminating ventilation openings and moving the thermal moisture and air control boundaries to the plane of the roof deck.

Air permeable insulation such as fiberglass batts dense packed cellulose or blown in fiberglass can t be used alone for an unvented assembly since these types of insulation can allow moist indoor air to reach the cold roof sheathing leading to condensation or moisture accumulation. If installed properly it will create an effective air and vapor barrier to keep interior moisture away from the roof sheathing where it can condense and cause problems. Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. If you choose sistering 2x10 s then they have a net depth of 9 1 4.

Cathedral ceilings provide a majestic crown for many a great room but insulating them can be tricky. To provide an unvented conditioned space for locating hvac equipment in the attic and or to provide a continuous thermal barrier for designs that have complex coffered ceiling planes and or numerous penetrations for lights speakers vents. Yes unvented roof assemblies can be insulated with fiberglass a wufi post and not just in climate zones 2b amp. Suggestions for un vented or hard to vent building roof cavities.

Regarding the roof insulation closed cell foam is the best product to use for an unvented cathedral ceiling.