Unvented Cathedral Ceiling Insulation

Worries about the hot roof un vented cathedral ceiling designs how to.

Unvented cathedral ceiling insulation.

Unvented roof assemblies such as conditioned attics and unvented cathedral ceilings are becoming common in north american construction. Suggestions for un vented or hard to vent building roof cavities. Yes unvented roof assemblies can be insulated with fiberglass a wufi post and not just in climate zones 2b amp. 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.

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

Install insulation along the underside of the roof deck of an unvented attic rather than on the ceiling deck of a vented attic for either of two reasons. 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. If you choose sistering 2x10 s then they have a net depth of 9 1 4. An unvented assembly can perform well but it s important to get the details right to avoid sheathing rot.

Cathedral ceilings provide a majestic crown for many a great room but insulating them can be tricky. 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. 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. Therefore leaving about 1 for venting the net depth of insulation should be about 8 or so.

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.