A polymeric composition for insulating fluid and/or gas transport conduits, such as off-shore oil and gas pipelines operating at temperatures of 130° C. or higher in water depths above 1,000 meters. The outer surface of the conduit is provided with at least one layer of solid or foam insulation comprising a high temperature resistant thermoplastic having low thermal conductivity, high thermal softening point, high compressive strength and high compressive creep resistance. The high temperature resistant thermoplastic is selected from one or more members of the group comprising: polycarbonate; polyphenylene oxide; polyphenylene oxide blended with polypropylene, polystyrene or polyamide; polycarbonate blended with polybutylene terephthalate, polyethylene terephthalate, acrylonitrile butadiene styrene, acrylonitrile styrene acrylate, or polyetherimide; polyamides, including polyamide 12 and 612 and elastomers thereof; polymethylpentene and blends thereof; cyclic olefin copolymers and blends thereof; and, partially crosslinked thermoplastic elastomers, also known as thermoplastic vulcanizates or dynamically vulcanized elastomers.