The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer.

Heat energy can be transferred by conduction, convection, radiation or when undergoing a phase change. For the purposes of this discussion only the first three mechanisms need to be considered.

The flow of heat can be retarded by addressing one or more of these mechanisms and is dependent on the physical properties of the material employed to do this.