Unvented Cathedral Ceiling Insulation

A poorly detailed cathedral ceiling can lead to energy losses and rotted roofing.

Unvented cathedral ceiling insulation.

Insulating an unvented cathedral ceiling. Yes unvented roof assemblies can be insulated with fiberglass a wufi post and not just in climate zones 2b amp. Martin s post focuses on the marketing of owens corning 039 s propink unvented attic insulation system. Worries about the hot roof un vented cathedral ceiling designs how to.

Regarding the roof insulation closed cell foam is the best product to use for an unvented cathedral ceiling. 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. Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. 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.

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. 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. How to avoid condensation leaks attic mold insulation mold structural damage to roof framing when roof venting is not possible cathedral roof and knee wall insulation venting air path options in older homes hot roof designs. Our summers in northern california can be pretty hot amp i am looking to add more insulation to my attic the attic floor is insulated already there is a ridge vent there are 2 gable vents 1 has a fan there are 2 between rafter vents.

Cathedral ceilings provide a majestic crown for many a great room but insulating them can be tricky. If you choose sistering 2x10 s then they have a net depth of 9 1 4. Suggestions for un vented or hard to vent building roof cavities. 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.

An unvented assembly can perform well but it s important to get the details right to avoid sheathing rot.