A thermal insulator is an industrial material characterized by its high thermal resistance. Establishes a barrier to the passage of heat between two media naturally they tend to equalize in temperature, preventing the heat transferred separators system.

In general, all materials offer resistance to the passage of heat, are thermal insulators. The difference is that the insulating materials have a very large resistance, so that small material thicknesses have enough resistance to the use we want to give. One of the best thermal insulators is vacuum, in which heat is transmitted by radiation only, but due to the great difficulty in obtaining and maintaining vacuum conditions is used rarely. In practice is mostly used air with low humidity, which prevents the passage of heat by conduction, due to its low thermal conductivity, and by radiation, due to a low absorption coefficient.