I am removing the original barely-still-there insulation in my 1950 attic (S. Cal.) and then sealing and then placing R 30 fiberglass batting. A problem I have is that about 5%-10% of the attic is covered with plywood nailed to the joists.
I have been advised by a professional to not lift up the plywood for fear that tension between the joists and plywood would be released potentially cracking the drywall ceiling below it. To take a stab at insulating the plywood areas I'm thinking of adhering panels of rigid foam to the top of the plywood. It would probably be only R-7. Is it worth it and am I asking for any problems like condensation between the layers?
Assuming any insulation under the plywood is the same as the exposed areas it is so thin it almost just paper. The smallest plywood area is about 3' x 4'. And I do not think condensation is a big issue here.
I have thought about pushing blown insulation under the plywood by hand and also sliding in 14" wide slices of rigid foam.
Best Answer
Condensation should not be a problem in SoCal. IS there insulation under the plywood now? If so, but is has compressed or something, or if not, you could drill holes in it and use blown-in insulation under there.If you put the foam on top, you eliminate the option of walking on it, in which case you may have well as removed it.