Vaulted Ceiling Insulation Rigid Foam

The roof rafters are 2 x 6 i was planning to do 2 inch rigid polyiso super tuff r back to back in the rafter bays with foil facing the interior.

Vaulted ceiling insulation rigid foam. While it is possible to use a permeable insulation open cell foam fiberglass or cellulose in an unvented cathedral ceiling it is risky. We re roofed our house this summer and found a lot of damage over our family room with a vaulted ceiling. Vented ceiling across rafters. We are planning to use r30c insulation which is denser for cathedral ceilings.

Rigid foam on roof sheathing with air permeable insulation between the rafters. Do no use a vapor barrier under the. Use closed cell spray foam closed cell foam board extruded polystyrene such as dow styrofoam or foil faced iso board. Seal the insulation or the ceiling surface below against air leakage.

How to attach rigid insulation to ceilings. You don t want moist air leaking into the roof cavity. The roof has a roof ridge vent and ventilation holes in the soffits. Vaulted ceilings require venting as well as insulation.

Polyiso provides one of the highest r values per inch of any rigid insulation r 6 at 1 inch. When applied to the. Johns manville aptm foil faced insulation sheathing board is an excellent choice for insulating attics and cathedral vaulted ceilings. I bought an old ranch on long island climate zone 4 with no insulation and i vaulted the living room and den ceiling they are next to each other.

We are creating on site baffles with 1 rigid foam boards. Attics and cathedral vaulted ceilings. The terms refer to whether the foam bubbles burst during curing making the foam soft like a sponge or remain intact and firm like those in the rigid foam panels at home centers. In this case the rigid foam can be thinner than when it s used alone.

Thin metal or rigid foam the baffles. Rigid foam also can be installed above the roof sheathing in tandem with air permeable insulation between the rafters. Place the insulation between the rafters or below them. Code specifies the minimum r value of the rigid foam layer.

Most local building codes require that rigid foam boards made from polyurethane or polystyrene be covered with a 15 minute fire rated thermal covering if they are used on the inside of the house. Rigid foam boards used in ceiling insulation are often made of either cellulose fiber fiberglass polystyrene or polyurethanes. I have a dilemma. This approach relies on a near perfect air and vapor barrier on the house side of the ceiling cavity to keep moist household air and water vapor out of the roof cavity.

Regular ceilings are likely to be under. About the only time you are likely to add rigid insulation to a ceiling is in a retrofit of a cathedral ceiling.