Insulation Fundamentals and Principles

Heat-Transfer Mechanisms

It is no secret that a house will lose heat in the winter and allow heat in during the summer. Heat, or thermal energy, flows continuously through materials and space, taking the path of least resistance and flowing from the warmer object to the colder object. Insulation attempts to keep thermal heat where it is wanted. To understand how thermal insulation works, it helps to understand the three mecha­nisms of heat energy transfer: convection, conduction, and radiation.

In winter, the heat in a family’s living room invariably flows by air movement to spaces that are not heated, such as the basement, attic, or garage. This is an example of heat flowing through moving air, known as convection. Another example is when heat is transferred from hot coffee, through the cup, to the hand holding the cup. This is known as conduction, or the process by which heat transfer takes place in sol­id matter. A third example can be found when a rooftop is warmed by the energy of the sun. This an example of the transfer of heat through space via electromagnetic waves (radiant energy), known as radiation.