polyurethane foam materials are produced and used in batt form , and therefore are substitutes for insulation batts previously made of fibreglass insulation the polyurethane batts are preferably made of a flexible , and compressible foam material , such that the batts can be compressed and placed within a shipping container , and so that the compressed batt will form a friction fit in an opening , when in use an alternative insulation material and format are provided .