Nate R
Member
Have a sloped ceiling in my bathroom that follows the roofline. The house is only 20 feet wide, and has 2X4 rafters at about an 11/12 slope. I've pulled most of the plaster ceiling out of the bathroom, and the rock wool insulation. Real, brand name Rock Wool.
Anyway, once I'm done, I want to reinsulate of course. Because I only have a 4" cavity (Actually 4", not 3.5) I'm thinking of 2 layers of 2" rigid foam board, giving me an R20 insulation value in the cavity. Otherwise with fiberglass I'm looking at R13, plus R3 1/2" foam board as well.
So,
Drywall
Vapor Barrier
Rigid Foam board (2 layers)
Roof sheathing
1. Anything wrong with that assembly?
2. Is there any reason I should not or can not use the rigid foam board on the interior side? I'm thinking of possibly using it in the walls in some spots, too.
3. How would you fasten it to the exterior sheathing? Or would you just Glue it to the rafters on each side? I'm worried if I use it in a wall, glue it to the sheathing, and someone pulls off a piece of sheathing that they'll be ripping the insulation out with it. Or am I worrying too much?
Anyway, once I'm done, I want to reinsulate of course. Because I only have a 4" cavity (Actually 4", not 3.5) I'm thinking of 2 layers of 2" rigid foam board, giving me an R20 insulation value in the cavity. Otherwise with fiberglass I'm looking at R13, plus R3 1/2" foam board as well.
So,
Drywall
Vapor Barrier
Rigid Foam board (2 layers)
Roof sheathing
1. Anything wrong with that assembly?
2. Is there any reason I should not or can not use the rigid foam board on the interior side? I'm thinking of possibly using it in the walls in some spots, too.
3. How would you fasten it to the exterior sheathing? Or would you just Glue it to the rafters on each side? I'm worried if I use it in a wall, glue it to the sheathing, and someone pulls off a piece of sheathing that they'll be ripping the insulation out with it. Or am I worrying too much?