we are doing a roofing job and I noticed the siders did a full tear off. However, there is no plywood or sheathing,just fiberglass between studs then of course Sheetrock on interior. They are nailing siding directly into studs and I asked the guy about it. He said since he's using Insulated siding it's ok..is this true. I souls still worry the insulated siding could still warp due to the voids.