There is provided an insulation foam in a tubular form, comprising at least one seamless layer of crosslinked polyethylene (PEX) closed-cell physical foam. The tubular foam can favourably be used to thermally insulate tubes that convey water, refrigerants or other fluids, in particular, copper tubes for Heating, Ventilation, Air-Conditioning and Refrigeration (HVAC&R) applications, as well as plastic tubes for use in domestic plumbing systems, hydronic radiant heating and cooling systems. There is also provided a method for manufacturing a crosslinked polyethylene (PEX) closed-cell physical foam in seamless tubular form, an insulation foam material using the same and a polymer blend for its manufacturing.