I believe you are referring to polyisocyanurate foam, and if I remember correctly (can't be sure of that!), the International Building Code requires it be treated the same as polyurethane or polystyrene foam. It does burn-check manufacturer's data sheets, e.g., Johns Manville. It is available in sheets.
Dante
Polyiso foam is similar to polyurethane foam, except that is does not require the fire breaking of sheetrock. I have not seen it in sheet form, but it is used in spray(new) or injection(existing) construction. I suspect the cost may be higher than polyurethane sheets.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
Pursuant to an article that appeared several issues ago in MR, I am curious if anyone has done anything with a product called "Poly-Iso foam". I am in the process of planning my layout (not my first, but do not want it to be a disaster, either), and am entertaining several media options. Any feedback as to its working nature, applications, and reliability would be much appreciated.
It will be basically a seaport theme with docks, carfloat facilities, and associated environs.
Rich