My house has the old lapboard siding (partially rotted about 2' up) under the newer vinyl siding. Not sure what the stuff is, because it looks like old fiberboard (glued sawdust). there is no sheathing behind it, and the vapor barrier the previous homeowner used has disintegrated. So, what I have basically is stud, lapboard, plastic/aluminum wrap, vinyl.
I know that I should take the old siding all of the way down, sheath with OSB, then a layer of rigid foam insulation to seal the air leaks (I live in Louisiana), and then hang the vinyl. But since I am having to do this a little each week, are there any suggestions to mitigate the air loss while I do this? someone suggested using 0.5" rigid foam behind the siding (added from the inside) while I am already putting in new fiberglass insulation because there are major voids in the walls, and just replace the bad lapboard with the OSB. Would this work?