Has anyone had any experience with the polyisocyanurate foam sheathing boards ? I'm considering using one of the R4 rated .6" boards over a standard rigid wafer type sheathing before attach the fiber cement planked siding. Would a exterior wrap such as Permawrap also be helpful ? Can a wavy effect in the siding occur when applied to a foam based board ?

Hi...
The pink rigid foam boards won't compress enough to cause that "wavy" effect, but the white styrofoam ones will. So you should be OK there.

My only comment on your permawrap question is, every little bit helps, no? If I can save up the money, I think I'll use house wrap and foam when I do my big siding project. Ahhh, some day!

:)

I just replaced wooden siding with vinyl this summer. I did not go through the trouble of attaching "R4 rated .6" boards over a standard rigid wafer type sheathing". Not even sure what a 'standard rigid wafer type sheathing' is.

However, three of use replace old siding, soffets and fascia in three days. This included removal to the dump all the old wooden siding. We just popped the old stuff off, tar papered the bare plywood walls, put on the trim and on the siding went. Why spend so much extra time for so little gain (R4). Are your heating bills that bad?

Also, if its on a southern wall you may get expansion buckling that you're concerned about (because the siding may be attached too tight and stick to the insulation boards)!