A thermal break is an element of low conductivity placed between any two materials in an effort to stop or slow down the transfer of heat from one to the other. The principle is based on the second law of thermodynamics formulated by Irish physicist, William Thomson, Lord Kelvin. All matter will transfer heat, and the transfer naturally moves from the warmer material, or area, to the cooler. Any material that impedes this transfer is a thermal break. It may be an actual material, such as insulation, or it may be trapped dead air; the function remains the same.
The scientific principle, which existed before it was identified, is demonstrated in everyday life. When someone picks up a potholder, he or she is employing a thermal break. The quilted pad prevents the transfer of heat from a hot pot handle to the cooler hand of the cook and prevents a nasty burn. Layering clothing is layering thermal breaks, which is why several thin layers can feel cozier than one thick one. Between each layer of clothing is an air space that acts as a thermal break to prevent the person bundled up under those layers from losing his body heat.
When outside air is cold in winter, homes and offices with old windows are chilly and hard to keep warm because the interior heat passes through the glass of the windows. Newer, more energy efficient windows have two panes of glass separated by a small space filled with air or an inert gas. Air or gas will not transmit heat as quickly as a single pane of glass, so rooms will stay warmer longer with less strain on the heating system. The air pocket between the glass panes is the thermal break.
Uninsulated houses and buildings suffer tremendous heat loss through their walls and roofs during winter months. Modern structures are built with insulation in their walls and between their ceilings and roofs. Spray-on foam is the newest insulation material that provides a thermal break between the inside and outside of a house or office, but other less expensive options are available.
Concrete, the most widely used construction material in the world, is very dense and heat does not pass through it quickly. Modern concrete buildings feature double concrete walls with a thermal break between them — usually a type of foam. This construction method gives the building both strength and great insulation qualities.
In areas where heat is more of a problem than cold, the system works the same way, only in reverse. Placing foam, fiberglass bats or blown-in cellulose between interior and exterior walls and in attic spaces provides thermal breaks and conserves energy. Thermal break windows and doors also help keep hot air out and lower utility bills.