Abstract: Porous ceramic materials based on oxide fibers, which have lower specific density and thermal conductivity, are able to function at temperatures exceeding 1000°C, including in an oxidizing atmosphere, which allows this class of materials to have a wide range of applications in various industries. The disadvantage of such materials is the hydrophilicity caused by the chemical composition of the fibers and the highly developed porous structure, which severely limits their use, particularly in arctic and subarctic climates characterized by high humidity. The authors have investigated and proposed a method of hydrophobization using the technology of low-temperature postradiation graft polymerization of tetrafluoroethylene molecules. The technology makes it possible to apply polymer coatings to oxide fibers, providing high hydrophobic properties, which is manifested in the increased value of the contact angle of wetting the surface of the material, which in turn substantially improves their operational characteristics and expands the possibilities of practical application as heat-shielding and heat-insulating materials.