Vaulted Ceiling Insulation Rigid Foam

Insulating a vaulted ceiling is similar to insulating exterior walls with one notable difference.

Vaulted ceiling insulation rigid foam.

Rigid foam on roof sheathing with air permeable insulation between the rafters. Polyiso provides one of the highest r values per inch of any rigid insulation r 6 at 1 inch. How to attach rigid insulation to ceilings. 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.

Vaulted ceilings require venting as well as insulation. Regular ceilings are likely to be under. We are planning to use r30c insulation which is denser for cathedral ceilings. Place the insulation between the rafters or below them.

We re roofed our house this summer and found a lot of damage over our family room with a vaulted ceiling. Code specifies the minimum r value of the rigid foam layer. Rigid foam also can be installed above the roof sheathing in tandem with air permeable insulation between the rafters. 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.

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. Do no use a vapor barrier under the. 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. I have a dilemma.

We replaced the plywood and are now redoing the underside. Johns manville aptm foil faced insulation sheathing board is an excellent choice for insulating attics and cathedral vaulted ceilings. When applied to the. 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.

Seal the insulation or the ceiling surface below against air leakage. Vented ceiling across rafters. Rigid foam boards used in ceiling insulation are often made of either cellulose fiber fiberglass polystyrene or polyurethanes. Use closed cell spray foam closed cell foam board extruded polystyrene such as dow styrofoam or foil faced iso board.

While it is possible to use a permeable insulation open cell foam fiberglass or cellulose in an unvented cathedral ceiling it is risky. You don t want moist air leaking into the roof cavity. About the only time you are likely to add rigid insulation to a ceiling is in a retrofit of a cathedral ceiling. Closed cell foam ceiling insulation in a vaulted ceiling offers substantial advantages over open cell.

In this case the rigid foam can be thinner than when it s used alone. Thin metal or rigid foam the baffles.