Vaulted Ceiling Insulation Rigid Foam

Vented ceiling across rafters.

Vaulted ceiling insulation rigid foam.

About the only time you are likely to add rigid insulation to a ceiling is in a retrofit of a cathedral ceiling. We replaced the plywood and are now redoing the underside. In this case the rigid foam can be thinner than when it s used alone. Closed cell foam ceiling insulation in a vaulted ceiling offers substantial advantages over open cell.

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. How to attach rigid insulation to ceilings. We re roofed our house this summer and found a lot of damage over our family room with a vaulted ceiling. Johns manville aptm foil faced insulation sheathing board is an excellent choice for insulating attics and cathedral vaulted ceilings.

Place the insulation between the rafters or below them. I have a dilemma. Vaulted ceilings require venting as well as insulation. Regular ceilings are likely to be under.

Do no use a vapor barrier under the. While it is possible to use a permeable insulation open cell foam fiberglass or cellulose in an unvented cathedral ceiling it is risky. 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 also can be installed above the roof sheathing in tandem with air permeable insulation between the rafters.

Use closed cell spray foam closed cell foam board extruded polystyrene such as dow styrofoam or foil faced iso board. Code specifies the minimum r value of the rigid foam layer. Polyiso provides one of the highest r values per inch of any rigid insulation r 6 at 1 inch. 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.

When applied to the. We are planning to use r30c insulation which is denser for cathedral 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. 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.

The roof has a roof ridge vent and ventilation holes in the soffits. Rigid foam boards used in ceiling insulation are often made of either cellulose fiber fiberglass polystyrene or polyurethanes. You don t want moist air leaking into the roof cavity. Rigid foam on roof sheathing with air permeable insulation between the rafters.

We are creating on site baffles with 1 rigid foam boards. Seal the insulation or the ceiling surface below against air leakage.