An insulation sheath for a pipe in a furnace is provided. The sheath has excellent insulation properties together with adequate resistance to the corrosive environment and thermal shock conditions. A pre-formed, substantially C-shaped, elongate member shaped to conform to the pipe over a portion of its circumference, the member comprising an inner layer of bonded insulating material integrally-bonded to a protective outer layer of refractory material. The inner layer is preferably formed of bonded ceramic fibre.
