Here’s what I’ve found:
2" foam is R10
1" foam is R5
2" foam w/ aluminum facing 2-sides (“thermal sheeting”) is R14.4
1" of the same thermal sheeting is R7.2
I’m thinking of using 1" thermal sheeting (aluminum faced) R7.2 on the back of the door, plus 2" regular foam (unfaced) R10 over the stair hole.
Remember I have a standard solid door at the bottom, then a fixed flight of stairs that go up to the attic floor.
I like the 1" aluminum on the door b/c it’s thinner. But I have to look at a piece to see if aluminum is durable enough to hold up.
I like the 2" unfaced over the hole b/c it’s pretty heavy, and thick enough to (hopefully) not sag over the hole. One reason I’m thinking of not using the aluminum here is that this piece will be slid over the floor a lot and I imagine the aluminum tearing.
The last thing I’m wondering is if there’s any problem creating these stagnant air pockets: (1) big triangular pocket in stairs between door & floor, and 6 very small pockets on the back of door b/c of recessed panels.
I’m not inviting mold & mildew am I? And this is a reasonably effective way of insulating?
As you know, I haven’t been to school in this stuff. :mrgreen: