When elements of differing temperatures come into contact, heat flow becomes an inevitable consequence. Thermal insulating products provide a ‘layer’ of insulation in which thermal conduction is reduced or thermal radiation is reflected rather than absorbed by any lower-temperature element of construction.

The insulating capability of a material can be measured by its thermal conductivity (k). Low thermal conductivity is equivalent to high insulating capability (R-value). Other important properties of insulating materials are product density (ρ) and  specific heat capacity (c).