Conduction is heat transfer by means of molecular agitation within a material without any motion of the material as a whole. If one end of a metal rod is at a higher temperature, then energy will be transferred down the rod toward the colder end because the higher speed particles will collide with the slower ones with a net transfer of energy to the slower ones. For heat transfer between two plane surface, such as heat loss through the wall of a house, the rate of conduction heat transfer is:

Calculation = heat transferred in time = = thermal conductivity of the barrier = area = temperature = thickness of barrier