The energy efficiency of ceramic thermal insulating used at high temperatures is mainly associated to the thermal conductivity (K) of the material. The basic mechanisms of heat transfer, which are conduction, radiation and convection, are in this text, related with the main microstructural parameters aiming to attain thermal insulating with suitable thermal conductivity values in a wide temperature range. It was possible to conclude that the thermal conductivity of porous ceramics is a function of the solid fraction composition and its microstructure. Moreover, the porosity and the pore size are key variables, where the higher the pore volumetric fraction, the lower the thermal conductivity. It was also shown that pores with sizes in the range of 0.5 and 4 µm are the most efficient towards the reduction of K, due to the lower permeability and high scattering capacity given to the microstructure. It is also stated that the presence of opacifier materials can significantly reduce the radiation, a fact that could be observed by the coupling theories involving conduction and radiation, as such materials increase the optical thickness of the insulating products. Finally, a study relating the main types of commercial ceramic insulating and their microstructural characteristics that lead to their usual characteristic properties was carried out.
energy saving; thermal insulating
