Whenever there is a temperature difference between two objects heat transfer will take place. There are three methods of heat transfer:

• Conduction is where heat moves through a solid object.
• Radiation where heat is transferred between objects by electromagnetic waves (primarily infrared).
• Convection where heat is moved around in a fluid or gas, for example water or air.

With regard to insulation, all three of these methods of heat transfer are important. Insulation can reduce heat conduction by slowing the rate that heat is passed from the source to the receiving medium.

Convection can be reduced by slowing the movement of the air or liquid to slow the rate of heat movement. An example is stopping draughts.

Radiation can be decreased by changing the nature of the radiating surface. This is why many surface insulation coverings have a shiny surface. The property of the surface that affects this is called emissivity.